mechanical seals module

Mechanical Seals Course Manual

IHRDC

GRADUATE ENGINEERDEVELOPMENT PROGRAMME

MECHANICAL DISCIPLINE

MECHANICAL SEALS

Total Pages: 91

IHRDC MS- M– 01 (Rev.0) 02 – 2 - 1999 Page- 1


Mechanical Seals

Graduate Development Programme Module (M – 01 ) 5D This Module is designed for AFPC existing Mechanical Graduates, to provide understanding and hands-on experience on mechanical seals and packing.

This Module focuses on the principles of operation, seal components and function, circulation, measuring run outs of shaft sleeve and stuffing box, troubleshooting, practical exercises on mechanical seal and packing.

Principles of operation. Circulation system. Optional features. Seal types and function. Installation/ practical exercises. Causes of seal failure.

Audience :Prerequisites :Location :Format :

Mechanical Graduates. English comprehension and communication.AFPC Training Center, D. Z.Lecture, discussion and OJT workshop practices.

This module is one of thirteen modules, which together cover the theoretical aspect of the Technical Training for the AFPC Mechanical Graduates Development Programme. This programme has been developed specifically for AFPC Graduate Development to enhance the dynamic Nationalization drive adopted by the company.



SAFETY REQUIREMENTS

1.GENERALParticipant must become thoroughly familiar with the following safety requirements and first aid procedures, and must observe the safety requirements at all times. Maximum safety of personnel is of primary importance, followed closely by protection of equipment from damage. Careful observation of these safety requirements will minimise hazards or injury to personnel and equipment.

There are three types of Safety Requirements: Warning, Cautions, and Notes, which are intended to emphasize critical information. Safety Requirements also include procedures to be observed in the event of certain operating malfunctions and important precautions to be observed when personnel are working in a special environment (such as in an explosive atmosphere) or with a special substance.

Warnings, Cautions, and Notes are listed in order of significance as follows:

WARNING

A WARNING points out a procedure, practice, condition, or precaution which, if not heeded, could result in personal injury or loss of life.

CAUTION

A CAUTION points out a precaution which, if not observed, could result in damage or destruction of equipment.

Note

A Note highlights information necessary to understand or follow a procedure, practice, condition, or description.

2. COURSE SAFETY REQUIREMENTS

Participant has to use the following safety precautions during this course:



-Coverall. -Safety helmet. -Safety shoes/boots. -Leather gloves.

Course Content

Page

1. Objectives. 5

2. Course Outline. 6-9

3. Equipment/ Resource. 10

4. Course Manual (Handout of the Participants) 11-58

5. Training Aids. 59

6. Lesson Plan. 61 - 73

7. Course Final Test. 77

8. Appendix-A 81-92

Installation instructions for double seals.

IHRDC MS- M – 01 (Rev. 0) 02 – 2 - 1999 Page- 4


Course Objectives:-

Upon completion of this course, participant should be able to:-

Lesson 1: Technical Aspects of Mechanical Seals. Explain the Seal function, components and operation. Explain the circulation system for Mechanical Seal. Understand the optional features for Seals.

Lesson 2: Flexibox Seal Types. Identify balanced and unbalanced Seals. Explain double and tandem Seals.

Lesson 3: Installation. Demonstrate stuffing box, shaft and shaft sleeves

measurements.

Lesson 4: Causes of Seal Failure. Understand the causes of Seal Failure. Understand the symptoms, causes and remedy of Seal

Leakage.

Lesson 5: Hand on Exercises at Workshop. Remove, inspect and install Tandem Seal. Remove, inspect and install Single Seal. Remove, inspect and install packing Seal. Measure shaft, shaft sleeve and stuffing box runouts. Perform lapping of carbon ring.



Course Out Line:-

Course Period (5 days) Classroom (12 Hrs)W / S (12 Hrs)Final Test (6 Hrs)

Day – 1 (6 Hrs)

Time Hrs Activities Location

1

1. Technical Aspects Of Mechanical Seal.1.1 Principles of Operation.

1.1.1 How do they work.1.1.2 Hydraulic balance.

1.2 Importance of fluid film stability.

Classroom

1.30

1.3 Circulation. 1.3.1 Circulation in single seal. 1.3.2 Circulation system for double/ Tandem seals.

Classroom + W. S

1.30

1.4 Optional Features. 1.4.1 safety Bush. 1.4.2 Auxiliary Sealing Device. 1.4.3 Quench. 1.4.4 Circulation. 1.4.5 Impeller. 1.4.6 Multi point injection. 1.4.7 Flushing.1.5 Use of ancillaries.

Classroom + W. S

1

2. Flexi Box Seal Types2.1 Single Seal – unbalanced.2.2 Single Seal – balanced.2.3 Bellow.2.4 Multiple Seal.

Classroom

30 3. Revision. Classroom30 4. Assessment. Classroom



Day – 2 (6 Hrs)


2

3. Installation.1.3.1 Shaft run out.1.3.2 End play.1.3.3 Concentricity of sleeve.1.3.4 Concentricity of stuffing box.1.3.5 Squareness of the stuffing box.

W / S

14. Causes of seal failure.5. Checklist of identifying causes of seal

leakage.Classroom

2.30

6. Hands- on Exercises at W/ S1.6.1 Remove, inspect and install Mechanical Seal.

A. Mechanical Seal Data Sheet.B. Sequence of assembly of the seal.

W / S

30 Assessment Classroom



Day – 3 (6 Hrs)


5

6.Hand-on exercises in W/S.C. Measurement and check prior to

mechanical installation.D. Installation of Mechanical Seal.

6.2 Practical Exercises/ single seal.A. Removal.B. Inspect all parts of Mechanical Seal.C. Installation.

W. S

1 AssessmentW. S



Day – 4 (6 Hrs)


2

6.3 Practical exercise (soft packing).A. Soft packing gland.B. Repacking a soft gland.C. Function Test.D. Calculation for packing rings.

W/S

26.4 Practical exercise/ stuffing box shaft measurement. W/S

2

6.5 Practical exercise Disassemble/ assemble single seal.6.6 Practical exercise Disassemble/ assemble Tandem seal.

W/S

Day – 5 (6 Hrs)

- Final Assessment (Classroom).

- Final Assessment (Practical at W/ S)



3 - Equipment and Resources

Single Spring Mechanical Seal.

Double Seal.

Tandem Seal.

Single stage Centrifugal Pump.

Multi Stage centrifugal Pump.

Submersible Pump.



4 - Course Manual

Hand Out For Participants



1. Technical Aspects of Mechanical Seals

1.1 Principles of Operation

Flexibox mechanical seals are the answer to the problem of preventing leakage between rotating shafts and their housings.

The old method of using soft packing has many disadvantages, for example, the packing must be regularly inspected and tightened down to take up wear, and it must also be replaced frequently. In time, the pump shaft or sleeve becomes worn, necessitating expensive renovation. Since the packed gland relies for its successful operation on lubrication of the packing material by the fluid being pumped, it can never entirely stop leakage, unless a costly liquid sealing system is introduced.

Flexibox face-type seals overcome these disadvantages. There is a wide range of seals available, differing in design and application, but all applying certain basic design considerations.

1.1.1 How Do They Work?

To illustrate the principle of operation of the mechanical seal, the simplest type, five components, are illustrated .The five basic parts are:

1 Stationary seal ring2 Stationary seal ring packing 5 Rotary seal ring6 Rotary seal ring packing7 Spring

Sealing action is obtained by intimate contact between the opposing faces of two rings, one of which is held resiliently (stationary seal ring) in the gland housing while the other (rotary seal ring) rotates with the shaft As the rubbing surfaces are extremely flat- they are lapped within two light bands-leakage of the fluid being handled is prevented.

Rotary Seal RingThe rotary seal ring rotates with, and is driven by, the shaft In Flexibox mechanical seals, the rotary seal ring is normally the hard face. A flexible 'O' ring (rotary seal ring packing) effectively prevents leakage between the rotary seal ring and the shaft while allowing the ring sufficient freedom of movement to maintain full face contact with the stationary seal ring. The shaft must be smooth and free from flaws.



Stationary Seal Ring

The stationary seal ring, usually made from a specially compounded grade of carbon, is resiliently mounted on a second flexible 'O' ring (stationary seal ring packing). This prevents leakage between the stationary seal ring and the gland housing and, at the same time, provides a cushion for the former, to allow it to take up a fair degree of 'out-of-squareness.The stationary seal ring is provided with a slot to enable the ring to be positively located in the seal housing, thus preventing its rotation.

Spring Drive

Initial seal face contact is maintained by a fifth component the spring. An interference fit between the spring and the shaft at one end and the neck of the rotary seal ring at the other provides a positive resilient drive. The spring is available with either a right hand or left hand coil.The handing of the coil is arranged so that in operation, the spring will tend to increase its grip. Spring drive also helps to make the fitting of a Flexibox seal a comparatively simple matter, since access to the back of the seal, to locate and fix it is unnecessary. In addition, the use of heavy gauge wire, normally stainless steel, eliminates what can be serious operational drawback when a number of smaller springs of lighter gauge are employed.



Single Mechanical Construction

Mechanical Seals



1.1.2 Hydraulic Balance

The term hydraulic balance, when applied to mechanical seals, is used to denote the relationship between the pressure being sealed and the seal face contact pressure. Seals are classified as balanced or unbalanced but within each classification there is a variation of degree of balance. In both types of seal, the initial face load is provided by the seal spring. The fluid pressure then acts on radially disposed areas in such a way as to increase face pressure in proportion to fluid pressure. In the case of an unbalanced seal, the face contact pressure may be a hundred per cent or more of hydraulic pressure. In the case of balanced seal, close control of the radially disposed areas enables the face contact pressure to be maintained at a value less than pressure being sealed. This lowering of seal face pressure allows a thicker fluid film between the faces, thus reducing the friction and consequent heat generation. Because of this, a balanced seal is able to handle more arduous duties and higher fluid pressures than an unbalanced seal. Normally, a balanced seal is designed to operate with the lowest face pressures that will effectively prevent leakage between the faces.

Variations of seal balance are illustrated in Fig. 1.1.2. Here S, the diameter of the seal sleeve shoulder, represents the effective sealing diameter, which may also be referred to as the hydraulic or sliding diameter since all thrust loads would be computed about this surface 'A' represents the hydraulic piston area of the sliding seal ring and 'B' represents the contact face of the sealing faces.

In arrangement a, all the contact face area B is disposed outside the effective sealing diameter S and the hydraulic piston area A is equal to the contact face area B. This, therefore, represents a condition of one hundred per cent balance, which also indicates that the average face contact pressure will be exactly one hundred per cent of the hydraulic pressure sealed.

In arrangement b, all contact face area B is disposed outside the effective sealing diameter S and the hydraulic piston area A is greater than the contact face area B. In this instance, the seal is more that one hundred per cent balanced, in accordance with the ratio of area A to B. The unit contact face loading will be higher, by an equivalent percentage, than the hydraulic pressure being sealed. This is a condition existing in most unbalanced seals.



Arrangement c, shows the relationship of most balanced seals, here part of thecontact face area B, designated as B1, is disposed outside the effective sealing diameter S. Area B1 is, therefore, equal to the hydraulic piston area A Since the rest of the face area B2 is located inside the effective sealing diameter S, the total seal face area B will equal the sum of B1 + B2 and the unit face loading will be less than the pressure sealed in accordance with the ratio of the two areas, ie

B1 A

B1 +B2 B

This value, expressed as a percentage, indicates the degree of balance of the seal.



Step design balanced seals, shown in figure below, where the rotating members has a step design on its front edge. This step allows a certain amount of pumped fluid to counter act the force on the back of the seal element.

This force relieves some of the pressure on the seal, Thus producing lighter contact pressure between the rotating and stationary elements. This contact pressure increase seal life and ensure adequate lubrication on the contact surface, by increasing oil film thickness.

Balanced Seals



1.2 Importance Of Fluid Film Stability

It is known that for the seal to work efficiently, it is necessary for a stable fluid film to exist between the faces. In the majority of cases this film is a liquid, although in certain special applications a gas film may be induced between the faces. If this film stability is destroyed, excessive wear takes place leading to rapid seal failure.

Vaporisation Due to Excessive Heat or Dry Running:

The most common cause of premature seal failure arises from the loss of the liquid film between the seal faces. Just before this occurs, the seal emits a puff of vapour every few seconds and there is local boiling off of the liquid film. This causes the seal to open and tilt temporarily. This allows more liquid to enter between the seal faces, giving a temporary cooling effect When the frictional heat generated at the seal faces has built up sufficiently to vaporise more liquid, another puff of vapour is emitted and the cycle is repeated. At this stage, the only damage suffered by the seal is the chipping of the edges of the carbon seal face, caused by the tilting of the rotary seal ring.

This is the prelude to complete loss of the liquid component between the seal faces and dry running with resultant heavy face wear occurring. Carbon and metal seal ring surfaces are then heavily grooved, somewhat like a gramophone record.

Figure 1.2 Seal Face Liquid film (Exaggerated)



1.3 Circulation

As already discussed, the use of mechanical seals inevitably involves the removal of generated heat from the immediate seal area. The most practical and efficient method of achieving this is to arrange for a flow, of the product being pumped, to pass over the seal. This transfers the local heat generated to the main flow in the equipment. It is this arrangement of flow which is covered by the term circulation.

The main purpose of circulation is the removal of heat from the seal area. Other benefits include the prevention of sediment deposits; control of the flow temperature by means of coolers or heaters and the facility of cleaning the flow by the use of separators or strainers. By full use of these facilities the conditions at the seal can be modified to provide longer seal life.

1.3.1 Circulation In Single Seals

The main requirements of heat removal by the circulation flow can only be achieved efficiently if the flow passes around or over the seal faces. With most of the standard range of seals the circulation flow is directed onto the seal faces, efficiently removing the heat from its source. With seals in the high duty range, the circulation flow can be passed through the spring pockets, in order to prevent sediment deposition, and then over the seal faces.

Cooling Circulation to Mechanical Seal: (A) Internal Circulation Plug Port, (B) External Circulation Plug Port



1.3.2 Circulation Systems For DoubleAnd Tandem Seals

A double or tandem seal circulation system should possess each of the following characteristics:

• A means of circulating the sealant• A means of recharging the system to make up leakage.• A means of cooling to remove the heat generated by the seals.• Systems for double seals, and occasionally tandem seals, also need a

means of pressurising the system.

1.3.2.1 Circulation Of Sealant

A By using a pump working against a relief valve, the circulation generally being returned to an open tank on the suction side of the pump.

B. Thermo-syphon Circulation, which, by means of height and differential temperature in the two vertical legs, causes a circulating flow between the seal chamber and a header vessel.

C. By using a small pump in a pressurised circulation system.D. By using an impeller or pumping ring, fixed to the rotating sealing ring or

pump shaft inside the seal housing. In this case, the impeller is generally made integral with the seal and is known as a W feature.

1.3.2.2 Charging Means

A charging means is necessary in order to make up for any barrier liquid loss, to change contaminated sealants, or to ensure completely automatic operation.

1.3.2.3 Cooling Means

There are four principal ways of cooling:

A By using a water cooler in the system, passing the sealant through the cooler coil.

B. By using an air cooler.C. By cooling a closed header tank by means of an integral cooling coil.



1.3.2.4 Pressurising The Seal Unit

There are four ways of pressurising.

A. By vapour from the sealed product which means vaporising the product by means of ambient temperature.

B. By pressurising a small header vessel by a neutral gas from an outside source.

C. By using a pressure controller, which will pressurise the sealant by using product pressure.

D. By using a pump both to pressurise and circulate the sealant.

1.3.2.5 Barrier Liquid Conditions

There are two basic considerations affecting the choice of barrier liquid.

1. The barrier liquid, or sealant between the seals must be a stable liquid and should preferably have lubricating properties. The following liquids are preferred as sealants.

Temperature Range Sealant-120 deg C to;-90 deg C Propanol.- 90 deg C to -30 deg C Methanol or Propanol.- 30 deg C to 20 deg C Kerosene or

Hydraulic Oils20 deg C to 200 deg C Light Oil or Gas Oil.

2. In either the double or tandem seal arrangement there will be mixing of the product and barrier liquid; these must, therefore, be compatible.

For double seal systems, the barrier liquid pressure should always be above the liquid being sealed (ie product pressure at the inner seal), thus ensuring that a film of the sealant, essential for the correct operation of the seal, is introduced at the inner seal faces. This film replaces the major part of the product film which would normally be present.The pressure to produce, this should be at least 2 bar greater than the sealed pressure.

For tandem seals, the barrier liquid pressure should be lower than the product at the inner seal. This ensures that there will be no barrier liquid contamination of the product



1.3.2.6 Testing Double And Tandem Seals

It is essential that double seals are assembled correctly and that they are leak free from startup; otherwise a pressure drop and loss of barrier fluid could be the result Because the design of a double seal is contained in a housing or stuffing box, it should be possible to put a static pressure on the seal before proceeding with the complete assembly of the seal into the equipment

The pressure between the seals should hold for at least 30 minutes; any pressure drop over this period suggests a possible leak path from one or both of the seals and should be investigated.

Because the inner seal operates against the pumped liquid, it is not usually practical to test tandem seals until the pump is pressurised, when the pump is installed. Tandem seals should be tested by pressurising both the pump and the seal chamber after fitting the seal. The pressure should be at least that of the barrier fluid pressure.



Double Seal Installation with axial- flow pumping ring (Johan Crane- Houdialle, inc.)



1.4 Optional features

1.4.1 'B' Feature (Safety Bush)

Balanced or unbalanced seals can be fitted with a throttle bush to conform to the requirements of specification API 610. This gives extra protection in the event of a sudden seal failure and takes the form of a close clearance safety bush. The bush is pressed into the seal plate from the inside to prevent it being blown out and functions by considerably reducing the pressure of the escaping product and directing the leakage to drain. In the event of a pump bearing failure, whereupon the shaft could run eccentric and to eliminate any possibility of sparking, the bush is manufactured from a nonferrous material and connections are provided for quenching and draining the space contained by the bush.

In the event of the bush having to be replaced, the diametrical clearance between the bush and shaft or sleeve should be 0.025 inch/0.63mm as specified by API 610.

1.4.2 'P' Feature (Auxiliary Sealing Device)

To prevent or control the leakage of the quenching medium from between the outer end of the seal plate and the pump shaft, it is necessary to incorporate an additional 'P' feature in the form of a special lip seal or a labyrinth bush, or even an auxiliary packed gland. Controlling the quench medium leakage could be for safety reasons, or to aid the efficiency of the seal and to prevent the leakage from entering the pump bearing housing.

1.4.3. ‘Q’ Feature (Quench)

The quench feature is standard on all balanced seals and may be specified on unbalanced seals. The feature provides for the admission of a quenching medium e.g. water, LP steam or methanol, through a threaded connection to the outer or atmospheric side of the seal, flowing freely around the annulus to drain.

The feature is mainly used to improve the function of the seal by preventing a product build up on the atmospheric side of the rotary or sliding packing which causes the seal to hang up or stick on the sleeve, thus preventing face contact. There could be occasions where the quench could be used to neutralise seal leakage for safety reasons or to satisfy environmental controls.To improve the efficiency of the quench feature and to reduce or prevent the quench medium from leaking between the safety bush and sleeve, lip seals or auxiliary packings can be incorporated in the design. This also prevents the medium from entering the pump bearing housing.



NOTE: The pressure of the quench medium entering the seal plate, should not exceed 1 bar (15 psi) and should enter the plate from above the centre line and be drained away from the bottom to prevent a build up of liquid; also it is essential that the drain hole is clear to prevent a blockage.1.4.4'C' Feature (Circulation)This is a feature on standard Flexibox balanced seals and of unbalanced seals which are supplied with a seal plate. They are provided with threaded connections into which a calculated or recommended flow of the product is directed from a point of higher pressure, around the stationary and rotary seal rings, back to a point of lower pressure in order (a) to remove generated frictional heat; (b) to prevent the settling of sediments, abrasives or polymers; (c) to keep seals handling hot products cooler in the line, if necessary.This method of providing circulation is generally applicable to single stage pumps. In the case of multistage pumps, the circulation would come from first or second stage because of the high differential across a group of stages.A close clearance neck bush may be used in a general purpose process pump to restrict the circulant, and build up of a pressure in the stuffing box on light hydrocarbon duties Where the application demands an external injection of less aggressive product, for example on hot, abrasive or corrosive duties, the neck bush can isolate the seal faces and products from the pumped fluid. The low volume, higher pressure, injection flow under the neck bush, from the stuffing box to the pump impeller, prevents this from happening.1.4.5 ‘W’ Feature (Impeller)An impeller is added to a seal so that it can generate its own circulation flow, providing a means of heat removal which is more thermally efficient than normal circulation cooling. Another case where the 'W' feature can be used is where a seal is operating at pump discharge pressure, and the seal requires cooling below the product temperature. Further applications are to generate circulation in a double or tandem seal system, or on a single seal where there is little or no pressure differential across the seal.The Flexibox 'W' feature essentially consists of an open impeller mounted on one of the rotating parts of the seal, generally the rotary seal ring. 1.4.6 'M' Feature (Multi-Point Injection) The circulation system for seals on liquified gases is of paramount importance. The usual injection of product at a single point will sometimes cause localised hot spots resulting in unequal thermal expansion, or contraction of the seal rings and deformation of their faces. With light hydrocarbons, vapour bubbles may form an insulating blanket on the seal rings, greatly reducing the heat transfer to the circulation liquid. The Flexibox multipoint injection feature supplies the circulation evenly around the seal faces to provide symmetrical cooling and break up the bubble blanket, thereby enhancing heat dissipation.



1.4.7 Flushing

The flushing of the mechanical seal is the fluid flow from the stuffing box through the neck bush to the pump impeller.

The flushing is used when the pumped fluid is abrasive or corrosive product, to prevent the settling of sediments, abrasive or polymers on the seal faces.

The flushing fluid should be of low volume and high pressure.Procedure For Flushing.

Bring clean liquid (not steam or gas), from an outside source (not the pump discharge) into the stuffing box at a rate of 1-2 gallons (4-8 liters) per hour.

The liquid is brought in 15 Ibs. ( 1Bar) higher than stuffing box pressure.

Regulate the flow with a meter.

A restrictive bushing (usually carbon) is placed into the bottom of the stuffing box to restrict the flow and keep the liquid clean in the stuffing box.

Bushing length - At least 3/8: (10 mm) Bushing Clearance - Close as possible - .008” (0, 25 mm) on the diameter

This bushing must be chemically compatible with both the product and flushing fluid. (Refer to Feature ” circulation”)

The flushing fluid can be any clean compatible liquid:

a. Finishing product.b. Solvent.c. An additive normally added downstream.d. Water.e. Compatible liquids.



1.5 Use of ancillaries

Many ancillary devices are used in seal circulation systems to modify the product conditions and to give the best seal performance. Ail ancillaries will have an influence on the flow to the seal, and this must be given due consideration to ensure adequate circulation rates are maintained.

AIR OR WATER COOLERS

Coolers are used in circulation lines to modify the temperature of the product and ensure correct seal performance. Careful selection of a cooler will often eliminate the need for a more sophisticated shaft sealing arrangement.

FLOW CONTROLLERS

A flow controller is an adjustable orifice and is used to regulate the product circulation to the seal. Flow controllers must be designed so that circulation cannot be completely cut off.

STRAINERS

Strainers are generally fitted in new lines to protect the seal from pipescale, dirt or other solids that may be initially present. They are usually removed, or the element withdrawn, when the plant is fully operational and considered clean.

CYCLONE SEPARATORS

Cyclone separators are fitted as permanent devices in circulation circuits to remove solids continuously. The product entres the separator, where centrifugal force extracts the denser solids and flushes these away through the dirty outlet. The dirty outlet is usually piped to pump suction. The product carried over through the clean outlet is supplied to the seal, through the circulation connection. As this is only a portion of the original flow to the separator, this must be taken into account when considering the circulation requirements of the seal.

MAGNETIC FILTERS

Magnetic filters are used to remove ferritic solids continuously from circulation lines. They are used principally on boiler feed applications where the problem is due to abrasive black iron oxide particles.



2. Flexibox Seal Types

2.1 Single Seals –Unbalanced

2.1.1 Single Spring Unbalanced Seals

The unique single spring feature gives a flexible drive whilst maintaining intimate contact of the two seal faces. The drive is achieved by shaft rotation which makes the spring grip both the shaft and rotary seal ring, thereby eliminating the need for extra keys or pins. In the reverse direction, the spring releases its grip on the components, easing assembly and dismantling. Secondary seals are generally 'O' rings selected for product compatibility and they provide resilient mountings for the seal rings.

2.1.2. Multispring Unbalanced Seals

The multi- spring unbalanced seals are designed for applications where seal length

is critical and for dual rotation.

The multi- spring seal design include a set screwed spring sleeve.

A Single Spring Unbalanced Seal Multi- Spring Unbalanced Seals



2.2 Single Seals-Balanced

2.2.1 Single Spring Balanced Seals

In this design, a single robust spring provides a flexible drive from the shaft sleeve to the rotary seal ring, whilst maintaining contact of the two seal faces. Shaft rotation makes the spring grip the shaft and the rotary seal ring, eliminating the need for extra keys or pins. In the reverse direction the spring releases its grip on the components, easing assembly and dismantling. Secondary seals are generally '0' rings, selected for product compatibility and they provide resilient mountings for the seal rings.

2.2.2 Multi-Spring Balanced Seals

A multi-spring version of the balanced seal range, which includes a set screwed spring sleeve. The multispring design makes the seal bi-directionai for applications where the reverse rotation is anticipated.



2.3 Bellw Seals

GENERAL PURPOSE BELLOWS SEAL

The general purpose metal bellows seal is designed with a very spring rate giving very low specific face and excellent misalignment capabilities. The seal is available to offer a wide range of chemical and mechanical operating capability.

Bellow Seal



2.4 Multiple Seals

DOUBLE SEALS

Double seals are often used when a single seal cannot give satisfactory performance on the pumped products, or where any product leakage is unacceptable for economic or hazardous reasons.

In the double seal configuration two single seals are arranged back to back to maintain a liquid barrier between the pumped product and barrier fluid. The inner seal operates on the barrier fluid which is kept at a pressure higher than the product, and therefore anyleakage is of the barrier fluid and not the pumped product. The product and pumped liquid must consequently be compatible. Most Flexibox single, mechanical seals have been successfully used in double seal configurations and Fexibox also have specific ranges of integral double seals available. In designing these double seal ranges a short axial length has been achieved by using components which are common to both inner and outer seals.

TANDEM SEALS

A tandem seal is defined as an arrangement, using two seals, where the pressure between the seals, i.e. the barrier fluid pressure, is less than that of the product pressure at the inner seal.

Tandem seal arrangements are used to solve a variety of sealing problems and are particularly useful when contamination of the product by a barrier liquid must be avoided. In a tandem arrangement, single seals are arranged in line and the inner seal operates on thepumped product. Any leakage which may occur will be from the pumped product into the barrier fluid, thereby avoiding contamination of the product.



TANDEM SEALS



3 Installation

An analysis of seal failures reports show that a large proportion of failures are caused by pumping or equipment problems, i.e. operational, vibration and eccentricity. The next section deals with equipment checks that should be car-ried out to ensure long and continuous service from your mechanical seals.

Misalignment

Alignment between equipment and driving unit is very important in order to obtain maximum running efficiency, to reduce maintenance and ultimately break-downs. Although normally referred to as coupling alignment, it is actually the alignment of the shaft centre lines. Correct alignment between the driving and driven shaft is equally important to obtain the maximum life from your mechanical seals. Bad alignment puts lateral, angular and axial load on the shafts which excessive errors which in turn puts extra load on the bearings. This results in excessive wear and bearing failures allowing the shaft to move in an orbital fashion or to become eccentric, causing swash and track run out at the seal faces.

Eccentricity

Here again, swash and tracking at the seal face can be caused by eccentricity. Another serious fault arising from eccentricity, which fortunately does not apply to Flexibox seals using a spring drive, is wear on drive pins and slots. The conclusion to be drawn is that the seal with the maximum amount of flexibility built into it must be considered the best, hence the name 'Flex-in-box' or' FLEXIBOX’.

Hot Alignment Check

After the initial alignment check, equipment handling hot Products should be given a further alignment check; this is normally carried out ofter several hours running at working temperature. Due to the conditions, the job is hot and arduous and should be carried out as soon as possible after shut down. If it is found from readings taken that the driving or driven unit has expanded outside the permitted limits then the alignment shims should be adjusted to allow for the amount of movement.

Some equipment manufacturers give an expansion growth to a given temperature, e.g. 0.016 inch at 400 degrees centigrade, but to be safe the above method is recommended.IHRDC MS- M – 01 (Rev. 0) 02 – 2 - 1999 Page- 38


Pipe Strain

Where repeated alignment has to be carried out to correct a fault it may be that there is a strain on the equipment from the pipework attached to it. The suggested method to correct this is to unbolt the pipework and carry out the alignment in the usual manner leaving the dial indicators in position whilst the pipe flanges are re-connected, observe any variation in the dial that the pipe strain is severe and other corrective methods must be carried out, i.e. cutting pipework and re0welding.

Limits

A recommended allowable limit of 0.05 mm between the coupling faces and 0.10 mm TIR on the peripery may be worked to when aligning couplings on medium speed applications. Other applications are treated on their own merits i.e. turbine and high speed applications could be as low as 0.02 mm.

Pump And Equipment Checks

To ensure maximum service life, we advise that the following dial indicator checks to be carried out on equipment to pin- point any excessive errors which may have prevented the seals from running concentric (within limits). These checks are also good maintenance practice and can only contributed to reduced down- time and running costs.

3.1 Shaft Run Out, Deflection Lift

If possible, mount two indicators locating the stems as shown in Fig. A rotation of the shaft could show radial run out at the seal end whilst observation of bothindicators would show whether or not the shaft was bent. Lightly lifting the shaft may show a greater reading than shaft run out, which would indicate wear in the bearings. These faults can result in fretting and wear of seal components and variation in the fluid film, which shortens seal life, also eccentricity which can result in bearing failure.

On multi-stage and split casing pumps the shaft should be removed from the pump and taken to the workshop where it should be checked between centres, taking readings at several points. This will show whether or not the shaft is bent. The maximum TIR at any point should not exceed 0.05mm (0.002")

3.2 End Play Or Shaft Float

With the dial indicator mounted on the pump housing and the stem located against the shoulder of the shaft, sleeve or deflector ring, attempts should be made to move the shaft from end to end.



This is normally done by tapping it lightly with a hide mallet. End play should normally be less than 0.05mm (0.002"), although with some types of bearings, for instance 'Michell' type, there could be as much as 0.20mm.

The excessive end play causes fretting and wear between the point of contact of the rotary seal ring packing and the shaft or sleeve.



3.3 Concentricity Of Sleeve

Having checked the shaft for run out it now remains for the sleeve to be checked, locating and locking it into position before doing so. Allowing for tolerances the total run-out of the sleeve should not exceed 0.05mirn (0.002") TIR. If found to be more than this, then the fault should be corrected. Here again, the effects are similar swash and tracking at the seal faces, variation of the fluid film thickness (which is very important on light hydrocarbons) setting up vibration and possibly causing bearing failure.

3.4 Concentricity Of Stuffing Box

To carry out this check it may be necessary to make available an adaptor to fit onto the indicator stem to enable readings to be taken between the box bore and shaft TIR should not exceed 0.1 Omm (0.004"). Effects of this fault are track-ing and swash at the seal face resulting in uneven wear on the carbon face and eventually breakdown.

3.5 Squareness Of The Stuffing Box

With the pump completely assembled, including the thrust bearing but without the seals, mount the dial indicator on the shaft with the stem located on the stuffing box face. (it may be necessary to make a special adaptor if space is restricted.). When the dial indicator is rotated TIR should not exceed 0.08mm (0.0OW). If the stuffing box face is not normal to the centre line of the shaft the stationary seal face will also not be square, causing the problems associated with washing or wobbling of the rotary faces. If the run-out is excessive contact may not be maintained between the seal faces and fretting may occur under the rotary seal ring packing.



4. Causes Of Seal Failures:

An indication of the type of failure can be gained by a visual inspection of the running characteristics and nature of the leakage etc. Precise identification of a fault can only be achieved by close examination of the seal components during the removal of the seal, from which it may possible to determine the leakage paths.

4.1 Vaporisation

Occurs when heat generated at the faces is not removed effectively and local boiling of the interface film takes place, indicated by a popping or puffing noise.Occasionally (nearly always on water) a seal will blow open and remain open.

4.2 Dry Running

Dry running occurs when no,or insufficient, liquid exists between the two seal faces.

4.3 Abrasives in Product

If the product being pumped contains any abrasive matter then this will tend to penetrate the seal faces leading to rapid wear and seal failure.



4.4 Sludging/ BondingSludging is associated with the sealing of high viscosity liquids. The wear stresses between the seal faces can exceed the ruptive strength of the carbon and particles are pulled from the face of the stationary seal ring. The problem can be particularly acute on pumps sealing hydrocarbon liquids at temperatures above ambient. When shut down the viscosity of the liquid and interface film increases as the temperature drops and problems may arise on re-starting the pump. Another possible cause of sludging occurs when the interface film partially carbonises due to overheating.

BondingA similar type of phenomenon to sludging is bonding. In this case a bond is formed between the two seal faces usually crystallisation after the pump has been standing for a long period. On starting particles are pulled from the carbon face and leakage occurs.

4.5 CokingCoking is a type of failure that frequently occurs when the product is hydrocarbons at high temperatures.Minute quantities of film ;leakage tend to carbonise on the atmosphere side of the seal, causing the sliding member (the rotary seal ring) to jam up and preventing it from following up any face wear. This type of seal failure would be indicated, on stripping down for inspection, by the rotary seal ring having no sliding action after removing the seal plate.

4.6 Carbon Ring Erosion

Occurs when the differential of the circulation to the seal between the point of take off and entry to the seal is too great, or when circulation flow contains abrasive matter.

4.7 Face DistortionIn some cases leakage can be due to face distortion.

4.8 Broken Carbon Seal Rings

This problem mainly arises on seals fitted with PTFE ‘O’ rings when the pin sleeve has been omitted on re-assembly. Due to the low coefficient of friction on of the PTFE ‘O’ rings the carbon ring may on occasions tend to spin, allowing the side of the slot in the carbon ring to come into sudden contact with the pin.This can also happen occasionally on seals fitted with synthetic rubber ‘O’ rings on high viscosity duties.



4.9 ‘O’ Ring Extrusion

Extrusion occurs when parts of the ‘O’ ring is forced through close clearance gaps.Extrusion can be caused by the use of excessive force when fitting and assembling components. Operational extrusion is generally caused by excessive pressure combined with overheating and incompatibility. It can Also be caused when seal parts have been reconditioned on site and size are beyond their limits, creating larger clearance between the components.

4. 10 ‘O’ Ring Overheating

Overheating of the packing is generally caused by adverse conditions at the seal faces causing excessive heat generation.

4.11 Sleeve Damage, Preventing Follow Up Of Rotary Seal Ring

Vibration

Severe vibration of the shaft or pump will cause the close clearance of the landings, on either side of the ‘O’ ring grooves in the rotary seal ring, to come into contact with the nose of the sleeve, resulting in fretting and marking into which foreign matter lodges, thus preventing the sliding member from moving.

4.12 Spring Distortion Or Breakage

In most single spring seals, the drive is unidirectional. In operation the spring should always grip the sleeve and rotary seal ring. If, for any reason, the wrong hand spring is fitted, or the pump shaft is rotated in the wrong direction, e.g. turbined backwards, the spring will tend to uncoil, slip and distort or crack the spring may even break. However, this type of failure occurs more frequently when springs are fitted incorrectly on high viscosity duties, where excessible torque at the seal faces may be caused by sludging or boding. On multi-spring seals, a build-up of solids around the springs can make some of them inneffective and overload the remaining springs, causing failure.



4. 13 Checklist of Identifying Causes of Seal leakage

Symptom Possible causes Corrective proceduresSeal spits and sputters (face popping) in operation

Seal fluid vaporising at seal interfaces

Increase cooling of seal facesAdd bypass flush line if not in use Enlarge bypass flush line and/or orifices in gland plate

Seal drips steadily Faces not flat Carbon graphite seal faces blistered Seal faces thermally distorted

Check for incorrect installation dimensionsImprove cooling flush linesCheck for gland plate plate distortion due to overtorquing of gland boltsCheck gland gasket for proper compressionClean out foreign particles between seal faces; relap faces if necessaryCheck for cracks and chips at seal faces; replace primary and mating rings.

Secondary seals nicked or scratched during installationO rings overaged Secondary seals hard and brittle from compression setSecondary seals soft and sticky from chemical attack

Replace secondary seals Check for proper lead in chamfers, burrs, etc.

Spring failureDrive mechanism corroded

Replace parts

Seal squeals during operation

Amount of liquid inadequate to lubricate seal faces

Add bypass flush line if not in use Enlarge bypass flush line and/or orifices in gland plate.

Carbon dust accumulates on outside of gland ring

Amount of liquid inadequate to lubricate seal faces Liquid film evaporating between seal faces

Add by pass flush line if not in use Enlarge bypass flush line and/or orifices in gland plateCheck for proper seal design with seal manufacturer if pressure in stuffing box is excessively high



Seal leaks Nothing appears to be wrong

Refer to list under “seal drips steadily”Check for squareness of stuffing box to shaftAlign shaft, impeller, bearing, etc., to prevent shaft vibration and/or distortion of gland plate and/or mating ring

Seal life is short

Abrasive fluid Prevent abrasives from accumulating at seal faces Add bypass flush line if not in use Use abrasive separator or filter

Seal running too hot Increase cooling of seal faces Increase bypass flush line flowCheck for obstructed flow in cooling lines

Equipment mechanically out of line

AlignCheck for rubbing of seal on shaft



5. Hands on Exercises at Workshop

Objectives:

On completion of the hands-on exercises, trainee should be able to:

1. Remove, inspect and install Tandem Mech. Seal.

2. Remove, inspect and install Single Mech. Seal.

3. Remove, inspect and install Soft Packing.

4. Measure shaft, shaft sleeve and stuffing box runouts.

5. Perform lapping of Carbon ring.



5. 1. Practical exercise: (Tandem Seal)

Mechanical seal removal, inspection, servicing and installation for:Crude oil shipping pump ( P 124 A/B EL ISBA, 4” x JTC/10) “TAYSSEN Pump”.

A -Mechanical seal data sheet:

Manufacturer : John Crane

Drawing : D/19603 A (N.D.E)

Mech. Seal type : 3 1/8 “ type 8 B1 2 7/8” type 8 B1Flushing according to API plan 31/52

Condition of servicing

Liquid: Crude oil

Flushing fluid process: crude oil from cyclone separator API-plan 31

Flushing fluid (atmospheric): Methanol from vessel through pumping ring (API-plan 52)

Pressure at mech. Seal max.: 28.2 barSuction pressure max. : 9.4 barViscosity : 2.0 cpTemperature max. : 77 CDischarge pressure : 47 barVapor press. : 0.24 barPump speed : 2960 rpm.

Circulation system of the seal: API-plan 31/52 include orifice, flow controller, cyclone separator and other fittings.Main parts of the mechanical seal:(A) A cover with stationary ring (seal face ring)(B) The shaft sleeve with the rotating seal face ring.

Notes: The seal must not be operated dry, even for a few revolutions. The Teflon rings are often hard, so they can be heated in boiling water at

100C and then plunged into cold water. Having been treated in such a way, their behavior will be quite normal.



B- Sequence of assembly of the seal

First of all, the stationary ring is pushed with its seal ring into the seal cover. To this end, the seal ring can be - slightly lubricated. Care must be taken to fit the stationary ring into the cover such that after pushing in the tappet will fit exactly into the recess provided. The rotating ring can be used as a means for pushing in. It is placed with its sliding face against the sliding face of the stationary ring. A piece of wood is placed onto the rear of the rotating ring for protection during pushing in. During pushing in tilting of the stationary ring must be prevented. It is appropriate to use a press or drill.

Now the Completely Assembled Shaft sleeve - with spring and rotating ring is pushed carefully onto the shaft and in case a seal of larger dimension is used, screwed into the correct position by means of a shank spanner. Care must be taken that threads, which are opposed to the direction of rotation of the shaft can be fitted. Thus one seal will have a right-handed thread and the other will have a left-handed thread.

The shaft sleeves can be finally adjusted to the dimension required only after complete assembly of the bearings and adjustment of the pump rotor. The shaft sleeve is then secured by means of the tappet ring and its threaded pins.

If a separate disk has been provided on the seal cover to facilitate the adjustment of the spring pretension, the disk must be taken out prior to start-up of the pump.

C- Measurements and checks prior to mechanical seal installation:

(A) Shaft bearings must be in good condition and shaft run out should not exceed .002 total indicator reading. Shaft endplay should not exceed .004 on radial ball type thrust bearings.

(B) Clean stuffing box bore and stuffing box face thoroughly. Be sure that stuffing box face is sufficiently smooth to make a good basket joint and that it is at right angles to the shaft within .001 total indicator reading per inch of bore diameter up to .005 maximum.

(C) Clean shaft thoroughly. Break or radius all sharp corners on shaft steps, threads and keyways over which shaft sleeve gasket must pass. Shaft concentricity to stuffing box bore should be within .001 total indicator reading per inch of shaft diameter.

(D) All gasket surfaces must be smooth and free on nicks and scratches, which can cause leakage.



(E) Driven shaft to be in alignment with driver shaft within .002 total, or within manufacturer's recommended tolerances.

(F) In ease in installing rubber gaskets and to help avoid cutting of gaskets, lubricate prior to installation with lubricant compatible with media and gasket material.

(G) Lapped seal faces joints must not be scratched or nicked during handling. Dirt and dust particles left on faces can scratch and cause unsatisfactory seal performance.

Note: Lubrication of he seal faces and lapped surfaces is not recommended.

D- Installation Of Mechanical Seal:

(A) Install the cover with stationary seal face ring.(B) Install the cartridge mounted shaft sleeve.

Install seal on shaft sleeve complete with seal flange, shaft sleeve and drive collar, being sure that shaft sleeve gasket is in place. Install cartridge assembly over shaft in position.

Hold seal setting dimension between collar and seal flange within tolerance shown assembly drawing. (If tolerance not give, use 1/16.) Lock sleeve and collar firmly in position.

Bolt up seal flange progressively, tightening bolts using uniform torque. Be sure gasket is in place and that pipe taps are in position as shown on the applicable assembly drawing.

(C) Installation of circulation system as per API- plan 31.



5. 2 Practical Exercise (Single Seal).

Removal, inspection and installation for mechanical seal for Wilson-Snyder, submersible pump.

A. Removal

(1) Disconnect electrical leads from motor.(2) Loosen mechanical seal from shaft.(3) Disconnect pump shaft from driver.(4) Lift driver of the pump.(5) Loosen seal cover and remove seal housing.

B. Inspect all parts of mechanical seal as follows:

- Lab carbon ring if necessary and clean.- Clean the seal cavity.- Check circulation lines and flush.

C. Installation

- Install the mechanical seal, if its cavity keeping seal faces, seal housing and seal housing cover clean from burrs.

- Adjust the mechanical seal after adjusting the impeller.- Tighten seal housing cover and rotate the pump shaft by hand.



5. 3 Practical Exercise (Soft Packing)

Removal, replacement of packing rings and adjustment for union pump (single

stage, centrifugal) gland packing.

A- SOFT PACKED GLANDS

Soft packed glands (sometimes known as stuffing boxes) are used on reciprocating and centrifugal pumps and on valve spindles.

B- Re-packing a Soft Gland

(1) Remove gland nuts and withdraw gland follower.(2) Remove old packing with a packing extractor and the lantern ring by means of

the lantern ring extractor. (Refer Fig. 4)

Fig. 4 Tools (3) Examine studs and nuts for correct material, corrosion, and damage, e.g. bent

studs etc. Run down the threads or renew as necessary.



(4) Check that the gland follower is not bent, if it is, it is necessary to remove and straighten or renew it. (Refer Fig. 5)

Fig. 5 Bent Gland Follower

(5) Check that the gland follower is a good fit in its housing, and that the clearance between the follower and spindle is not excessive. If worn, the gland follower must be renewed.

(6) Examine neck bush, if fitted, is not worn, renew as necessary.(7) Examine shaft for wear and corrosion in way of gland and neck bush. renew

shaft if necessary.(9) Cut the first turn of packing to length, making sure that the ends are cut at 45

(scarfed). This may be done by wrapping the length of packing around the shaft and marking it. Try this turn for fit and if correct the remainder of turns may be cut using the first turn as a guide.

(10) Place the first turn of packing in the stuffing box, pushing it to the bottom by means of the packing followers supplied with the unit. Fit the remaining turns below the lantern ring making certain that the scared joints are staggered, using the packing followers to push each turn home.

(11) Fit lantern ring in place ensuring it is correctly positioned and follow up with the remainder of the packing as above. The gland follower should enter the box about 1/8” (3 mm), and is parallel. (Refer Fig. 6)



NOTE:

Check that packing is not overflowing the stuffing box as this will cause jamming of the follower.

(12) If the studs and nuts are steel, coat them with anti-seize grease and pull up the gland follower using calipers to ensure it is square.

C- Functional Test

When a pump is run up for the first time after the gland has been repacked, a careful watch must be kept to ensure that the gland does not overheat. The gland must be adjusted as necessary to give a few drops of leakage every minute.

D- Calculations for Packing Rings

a Diameter Of stuffing box =Diameter of shaft =

Size of packing required =

b Depth Of stuffing box = Length of lantern ring =

No of turns of packing required behind lantern ring =No of turns of packing required in front of lantern ring =



5.4 Practical Exercise Stuffing Box/ Shaft Measurements:

Carry out the following checks and measurements on the mechanical seal and stuffing box for single stage centrifugal pump “union”, and compare with maximum allowable limits.

No. Measurements ActualMax. Limits

Comments

1Pump shaft run out and deflection lift.

0.002”

2 Pump shaft endplay 0.002”3 Pump shaft sleeve concentricity 0.002”4 Stuffing box concentricity 0.004”5 Stuffing box squareness 0.003”

6Misalignment on pump coupling due to pipe strain

0.004”



5. lapping, Carbon Ring

Hand lapping and polishing with a manual plate can be successfully accomplished by anyone if the simple steps in this section are carefully followed.

The sealing face surface must first be examined to determine whether it is repairable. If wear is 1/32in. (0.8mm) or more into the sealing surface or if there is evidence of heat cracking on the sealing surface, the seal face should be discarded and replaced.

Carbon Ring:

1. Prepare a slurry of one part coarse- grit abrasive and two parts mineral seal oil.

2. After shaking the slurry, apply a small amount to the plate working surface with a sweeping Motion, to distribute slurry evenly across the entire surface.

3. Work the part in figure- eight pattern across the plate. Use the entire plate surface to minimum plate flatness. Apply maximum down pressure with the palm of the hand.

4. Continue working the part until the wear pattern has been removed.



Transparencies

Transp. Description Page

T-1 Course objectives 5

T-2 Parts, mechanical seal 13

T-3 Parts, mechanical seal 14

T-4 Single mechanical seal construction 15

T-5 Hydraulic balance (1) 17

T-6 Hydraulic balance (2) 18

T-7 Seal face liquid film 19

T-8 Cooling circulation in mechanical seal 20

T-9 Testing double & Tandem seals 23

T-10 Double seal installation with axial flow

pumping ring.

24

T-11 Optional features for seals 28

T-12 Tandem mechanical seal 30

T-13 Bellow seal 34

T-14 Double & Tandem seal 36

T-15 Tandem mechanical seal parts 37

T-16 Installation of mechanical seals 40

T-17 Possible leakage paths in seals 46

T-18 Tandem seal for Tayssen pump 50

T-19 Piping schematic API plan-31 51

T-20 Single mechanical seal (John Crane) 53



6. Lesson Plan

Trainer to follow these instructions:

- During the introduction, talk to the participants.

- Gauge their technical knowledge and ability to follow your language.

- Adjust your speed to match them.

- Pay individual attention in classroom and workshop.

- This course shall be conducted in five working days (30 Hrs), four

lessons to be Processed in four days as listed in lesson plans and course

final test shall be Conducted in fifth day.



Lesson One (6.0 Hrs)

Objectives: Explain the seal function, components and operation. Explain the circulation system for Mechanical Seal. Understand the optional features for Seals.

Contents Activity

A

Lesson (1_): Technical aspects of Mechanical Seals.1.1 Principles of operation.

1.1.1 How do they work -----------------------.1.1.2 Hydraulic balance --------------------.

1.2 Importance of fluid film stability ----------.

Show T2 & T3 & T4

Show T5 & T6

Show T7

B

C

1.3 Circulation 1.3.1 Circulation in single seal --------------. 1.3.2 Circulation in double/ Tandem Seal. 1.3.2.1 Circulation of sealant. 1.3.2.2 Charging means. 1.3.2.3 Cooling means. 1.3.2.4 Pressuring the seal unit. 1.3.2.5 Barrier liquid condition. 1.3.2.6 Testing double/ Tandem Seals.

1.4 Optional Features 1.4.1 Safety bush. 1.4.2 Auxiliary sealing device. 1.4.3 Quench. 1.4.4 Circulation. 1.4.5 Impeller. 1.4.6 Multi- point injection. 1.4.7 Flushing.1.5 Use of ancillaries

Show T8

Show T9

Show T10

Show T11

Show T12

D Lesson briefingE Free discussionF Assessment Allow for 30 minutes



Lesson One Assessment

(Part- A)

1- What is the function of the mechanical seal?

2- What is the function of the rotary seal ring packing (O-ring)?

3- How does the rotary seal ring packing (O-ring) maintain full-face contact

between the rotary and stationary seal ring?

4- Name the mechanical part which provides a cushion for the stationary seal ring

to maintain its squareness.

5- What is the function of the spring in the mechanical seal?

6- Define the hydraulic balance.

7- What is the relation between the face contact pressure and the fluid pressure in

the unbalanced mechanical seal?

8- Why is the seal face pressure is less than the pumped fluid pressure in a

balanced mechanical seal?

9- What is the effect of excessive heat on the liquid film stability in mechanical

seals.

10- What will happen if a mechanical seal run dry.




(Part- B)

11- What are the causes of circulation in the mechanical seals?

12- Why does the neck bush have a close clearance with the shaft?

13- What does thermo- syphon circulation means?

14- What is the difference between a double seal and a tandem seal.




(Part- C)

15- What is the function of a throat bush in a pump?

16- Why is the safety bush (throttle bush) manufactured from nonferrous

metal?

17- What is the use of an auxiliary sealing device?

18- What is the main function of a quench feature?

19- How much pressure of the quench medium is entering the seal plate?

20- What is the function of the eyclone separator?



Lesson Two (6.0 Hrs)

Objectives: Identify balanced and unbalanced seals. Explain double and Tandem Seals.

Contents Activity

A

Lesson (2): Flexibox Seal Types.2.1 Single seals- unbalanced 2.1.1 Single spring- unbalanced seal. 2.1.2 Multi spring- unbalanced seal.2.2 Single Seals- balanced 2.2.1 Single spring- balanced seal. 2.2.2 Multi-spring- balanced seals.2.3 Bellow Seals.2.4 Multi Seals.

- Double Seals.- Tandem Seals.

Demonstrate on seals at workshop.

Show T13

Show T14 & T15

B

C

Demonstrate at work shop.

Lesson Briefing.

Explain types of seals

Review main topics

D Free Discussion.E Assessment. Allow for 30 minutes.

FHouse Keeping the workshop, to be left clean and tidy.



Lesson Two Assessment

1. What is the multi-spring unbalanced seal designed for?

2. What is the general purpose metal below the seal designed for?

3. What is the multi-spring balanced seal designed for?

4. What is the relation between barrier fluid pressure and product pressure in the

double seals?

5. Which is higher in tandem seals, product pressure or barrier fluid pressure?

6. Explain why there is no contamination for the product in tandem seals.

7. Explain the double seal configuration.

8. Why does the barrier liquid have to compatible with the product in a double

seal?



Lesson Three (6.0 Hrs)

Objectives: Demonstrate Stuffing Box, shaft and shaft sleeve measurements.

Contents Activity

A

Lesson (3): Installation.3. Introduction.

Misalignment. Eccentricity. Hot alignment check. Pipe strain.

3.1 Shaft run out, deflection left. 3.2 End play or shaft float. 3.3 Concentricity of sleeve. 3.4 Concentricity of stuffing box. 3.5 Squareness of stuffing box.

Show T16

B

C

Hands-on Demonstration

Lesson Briefing.

Workshop

D Free Discussion.E Assessment.F Workshop Housekeeping.



Lesson Three Assessment

1- What are the causes of seal failure during installation?

2- How can you check pipe strain?

3- How can you check the end float of the shaft?

4- What is the disadvatange of concentricity of the sleeve on the shaft?

5- What is maximum allowable run out of the seal sleeve?

6- What is maximum concentricity of a stuffing box?

7- How can you check the squareness of the stuffing box?

8- What is the maximum allowable limit for squareness?



Lesson Four (6 Hrs)

Objectives: Understand the causes of Seal Failure., Understand the symptoms, causes and remedy of Seal Leakage.

Contents Activity

A

Lesson (4): Causes of Seal Failure 4.1 Vaporization -----------.4.2 Dry running.4.3 Abrasive in product.4.4 Sluding/ bonding.4.5 Coking.4.6 Carbon ring erosion.4.7 Face distortion.4.8 Broken carbon sea ring.4.9 o-ring extrustion.4.10 o-ring overheating.4.11 Sleeve damage.4.12 Spring distortion.4.13 Check list identifying causes of seal leakage.

Show T7

B

C

Lesson Briefing.

Free Discussion.

Review the lesson in brief.

D Assessment.



Lesson Four Assessment

1. What is vaporization?

2. What are the symptoms of dry running seals?

3. What is the cause of carbon ring erosion?

4. What are the causes of O-ring failure?

5. What is the result when the gland ring bolt tightens excessively or

unequally?

6. What is the effect when installing an improper seal gasket?



Lesson Five (6.0 Hrs)

Objectives: Remove, inspect and install tandem Mechanical Seal. Remove, inspect and install single Mechanical Seal. Remove, inspect and install soft packing. Measure shaft, shaft sleeve and stuffing run outs. Perform lapping on carbon ring.

Contents Activity

A

Lesson (5): Hands-on Exercise at W/ S

5.1 Practical Exercise (Tandem Seal)A. Mechanical Seal Data Sheet.B. Sequence of assembly.C. Measurements and checks prior to seal

installation.D. Installation.

5.2 Practical Exercise (Single Seal)A. Removal.B. Inspection.C. Installation.

5.3 Practical Exercise (Soft packing)A. Soft packed gland.B. Re-packing.C. Function Test.D. Calculation for packing rings.

5.4 Practical Exercise: Stuffing Box and Shaft Measurement.

Lapping Carbon ring

Demonstrate on multi-stage pump.Show T18 & T19

Demonstrate on sub-miserable pump.Show T20

Demonstrate on single stage centrifugal pump.



Answers:

Lesson One (Part-A)

1- Prevent leakage between the rotating shaft and the housing.

2- Prevent leakage between the shaft (or shaft sleeve) and the rotary seal ring.

3- Because it allows sufficient freedom of movement to the rotary seal ring.

4- Stationary seal ring packing (O-ring)

5- Maintain the initial seal face contact.

6- The relationship between the pressure being sealed and the seal face contact

pressure.

7- The face contact pressure is greater than the fluid pressure.

8- To allow a thicker fluid film between the faces, thus reducing wear.

9- Excessive heat may destroy the liquid film stability and leads to vaporisation.

10- Excessive wear.

Lesson One (Part-B)

11- 1- Removal of heat from seal area.

2- Prevent sediment deposits.

3- Control the flow temperature.

12- To increase the pressure in the stuffing box.

13- Circulation flow between the seal chamber and header by means of height

and deferential temperature.

14- For double seal:-

Barrier liquid pressure is greater than the product pressure.

For tandem seal:-

Barrier liquid pressure is smaller than the product pressure.



Answers

Lesson One (Part-C)

15.Protect against sudden seal failure.

16.To prevent sparking with the shaft in case of bearing failure.

17.Prevent leakage of the quenching medium from between the outer end of the

seal plate and the pump shaft.

18.To improve the function of the seal, by preventing a product build up on

atmospheric side of the seal. Also, to neutralise seal leakage for environmental

control or safety reasons.

19.One bar.

20.The cyclone separator is a device used to remove solids continuously from the

circuits, using the centrifugal force.

Lesson Two

1- For application where seal length is critical and for dual rotation or when

reverse rotation is anticipated.

2- An excellent alignment capabilities.

Very low specific face loads.

3- For application where the reverse rotation is anticipated.

4- Barrier fluid pressure higher than product pressure.

5- Product pressure.

6- Because the leak-if occurs- form the product to the barrier fluid.

7- The double seal arranged back to back, to maintain a liquid barrier between the

pumped product a barrier fluid.

8- Because the leak-if occurs- will be from barrier liquid to the product.



Lesson Three

1. Misalignment, Eccentricity, Thermal Groth and Pipe Strain

2. Mount to dial indicators on the coupling at 12 & 3 o’clock as a preparation of

for alignment. Zero dial indicators. Unbolt the pipe work and observe the

movement of dial. If more than 0.1 mm, you have to adjust pipe work.

3. Using dial indicator at the shaft shoulder axially, push shaft as for as it will go

and zero dial indicator. Push to the other side again and record the reading

should not exceed 0.05mm.

4. It develops wash and tracking at he seal face which causes variation in fluid

film thickness.

5. 0.05 mm.

6. 0.1 mm.

7. Attached a clamp on shaft and dial indicator axially on stuffing box. Rotate

shaft and record dial indicator reading.

8. 0.08 mm.



Answers

Lesson Four

1- Vaporisation occurs when heat generated at the faces is not removed effectively. The stable interface liquid film change into vapour condition.

2- 1- Severe wear and grooving of stationary seal ring.2- Metal seal ring shows scoring.3- O-ring hardened and cracking.

3- When differential pressure across mechanical seal is too great.

4- Extrusion and over heating.

5- Distortion which leads to seal face leakage.

6- It will affect the seal setting, and the spring load imposed on the seal, thus liquid film thickness.



Final Assessment (Classroom)

Question:

1. Identify the basic components of a single mechanical seal, and explain the

function for each.

2. Define the hydraulic balance.

3. Define the unbalanced mechanical seal.

4. Define vaporization in mechanical seal.

5. List the types of pumping for circulating the sealant in Tandem seals.

6. Explain the Thermo- syphon circulation method in Tandem seals.

7. What is the difference in operation between double and Tandem seals.

8. Explain two of the safety features:-

- Safety Bush – Quench – Impeller - Flushing

9. What is the function of cyclone separator in circulating system.

10.Explain how to correct pipe strain to avoid mechanical seal problems.

11.Explain the cause and remedy for the seal drips steadily.



Answers:

1. a. Stationary seal ring: The seal face of the Mechanical Seal.

b. Stationary Seal Ring Packing: Prevent leakage between stationary seal ring

and gland housing.

c. Rotary Seal Ring: The seal face.

d. Rotary Seal Ring Packing: Prevent leakage between rotary seal ring and

the shaft.

e. Spring: To maintain the initial seal face contact.

2. The relation ship between the pressure being sealed and the seal face contact

pressure.

3. The unbalanced seal is the seal in which the seal face contact pressure is greater

than the fluid pressure.

4. The case of loosing a liquid film between the seal faces. The vaporisation at the

stuffing box destroy the fluid film stability.

5. a By using a pump and relief valve.

b. Thermo-syphon circulation method.

c. By using an impeller or pumping ring, fixed to the rotating sealing ring or

pump shaft in side the sealhousing.

6. This Thermo-syphon circulation method depends on the height of the

circulating header and the differential temperature, to make the circulating

flow.



Answers:

7. Double seal barrier liquid pressure is greater than the pressure of liquid being

sealed.

Tandem seal barrier liquid pressure is lower than the pressure of liquid being

sealed.

8. Safety Bush: the close clearance of safety bush prevents severe leakage in the

case of seal failure.

Quench: This type of cooling, is used to:

- Prevent a product build up on the atmospheric side of rotary seal ring.

- Prevent leakage to atmosphere due to safety reasons.

Impeller: A feature used to circulate the barrier liquid in Tandem Seal. The

impeller is mounted on the rotating ring of mechanical seal.

Flushing: used to prevent settling of sediments, abrasives on the seal faces.

9. To remove solids continuously from the circulating system it uses a centrifugal

force to extract the dense solids and flushes it away to the dirty outlet.

10.Attach two dial indicators on a fixed foundation, and anvils on the coupling

hub of the pump at 3.00 and 12.00 O’clock.

Disconnect the suction and discharge pipings of the pump.

If there is a reading more than .002 inch on the dial indicators, you have to

correct the piping.

11.Cause Remedy

Faces not flat or thermally distorted Check installation improve cooling lines Check gland tightening Check gland gasket check seal faces for abrasive materials re-lap carbon ring

Secondary seal scratched ReplaceSpring failure Replace



Final Assessment (Practical)

1. Remove and install Single Mechanical Seal.

2. Remove and install Tandem mechanical Seal

3. Remove and install soft packing.

4. Measure shaft, shaft sleeve and stuffing box run outs, end play and

squareness.

5. Perform lapping for carbon ring.



APPENDIX _ A

Installation Instructions

For BW Seals Type Double UHT 5500-FNAN

BW Seals Order Number841182

Al Furat Petroleum CompanyOmarSyria

Plant Item No. 220 A/ B/ C/ D.



GENERAL

Prior to installing the seal make sure the pump is in a sound mechanical condition. Please refer to the general instruction leaflet and/or the pump manufacturers instructions for this purpose.

This seal can be assembled into a cartridge and be set by means of setting plates, a setting check is therefor not required.

The use of silicon grease is generally recommended to lubricate gaskets. If not compatible to the pumped product, substitute with suitable lubricant which is compatible with both gasket material and product. The lubrication of the seal faces is not recommended.

Use anti seize compound on all fasteners holding stationary components and Loctite TM retaining compound on all fasteners holding dynamic components.

Care must be taken when handling the seal faces so as to avoid damage and consequential excessive leakage.The following instructions refer to assembly drawing A1N00944 A

CAUTION

These assembly and installation instructions have been written by personnel with in excess of 20 years field experience. It should be noted however that the instructions were written without the actual seal being available for assembly.

It is therefore, in rare instances, possible that the assembly sequence arid/or method may differ slightly from that described below.

PREPARATION

Prior to undertaking seal assembly observe the following general rules.

1) Ensure all re-useable seal parts are thoroughly cleanedbefore commencing assembly.Shaft must be free of scratches and burrs.Remove sharp edges on steps, threads, relieves and key ways overwhich the shaft sleeve gasket must pass.

2) Check whether all required components are available.Leave parts in protective wrapping until needed, to avoid damaging.



3) Use lint-free tissue and quick drying solvent to clean seal faces.

4) Make sure piping is checked for cleanliness and/or blockage prior to (re)connecting.

Pre Assembly Of Stationary Components

(Inner flange) flange

1 Lightly grease and fit gasket (S71) to groove on outside diameter of adapter ring (S41).

2) Insert adapter ring into (inner) flange (S11) in such a way that the dimples in the adapter ring align with the threaded holes in the flange.

3) Insert (3 off) set screw (S57-1) into threaded holes in flange ensuring the dog point engages the dimples in the adapter ring. Set screws should not be over tightened (finger tight).

4) Insert (3 off) set screw (S57) into threaded holes in flange and tighten securely against set screws previously installed.

5) Place (12 off) spring (S16) into pockets provided in flange.

6) Lightly grease and fit backing ring (S44-1) into backing ring (S44).

7) Lightly grease and fit gasket (S53) to backing ring (S44) so that it rests against backing ring (S44-1).

8) Lightly grease and fit gasket (S13) to dove tail groove in backing ring (S44) and wipe off excess grease.

9) Place seal face (S14) onto backing ring in such away that slots in outside diameter of face align with holes in backing ring.

10) Carefully, so as not to damage seal face, lower lock ring (S124) over seal face/backing ring, engaging anti rotation notches into slots in face.

11) Lightly grease and insert (3 off) lock pin (S5) into holes provided in lock ring/backing ring.



12) Carefully introduce backing ring sub assembly into flange/adapter ring assembly ensuring gasket (S53) and backing ring (S44-1) are properly located and that heads of lock pins engage slots in flange.

Depress backing ring sub assembly several times to check for free movement. Protect face whilst doing so.

13) Insert inner ring (S140) into flange so that pin engages notch in (inner) flange.

14) Grease and fit (2 off) gasket (S18) to grooves provided in inner and outer faces of flange.

This completes the assembly of the inner flange. Set aside and protect from dirt and damage.

Assembly Of Seal Cartridge/Outer Flange

1 Fit flange bushing (S24) to recess provided in outer face of flange(S 11 -1)(S1 1-2) and secure by means of snap ring (S1 11).

2) Fit (3 off) setting plate (S103) to flange by means of cap screws (S40-2).Cap- screws may be left finger tight.

3) Place flange, inner face up on a clean work surface and insert (12 off)spring (S16) into pockets provided.

4) Lightly grease and fit backing ring (S44-1) into backing ring (S44).

5) Lightly grease and fit gasket (S53) to backing ring (S44) so that it restsagainst backing ring (S44-1).

6) Lightly grease and fit gasket (S13) to dove tail groove in backing ring(S44) and wipe of excess grease.

7) Place seal face (S 14) onto backing ring in such away that slots in outsidediameter of face align with holes in backing ring.

8) Carefully, so as not to damage seal face, lower lock ring (S 124) overseal face/backing ring engaging anti rotation notches into slots in face.

9) Lightly grease and insert (3 off) lock pin (S5) into holes provided in lockring / backing ring.



10) Carefully introduce backing ring sub assembly over shoulder on flange so that it rests against the springs whilst ensuring gasket (S53) and backing ring (S44-1) are properly located.

Depress backing ring several times to check for free movement. Protect face whilst doing so.

11) Place seal cartridge (S42) (S42-1) inner face down on a clean worksurface.

12) Grease and fit gasket (S18) to groove in outer face of cartridge.

13) Carefully insert flange/backing ring sub assembly into cartridge so that heads of lock pins engage groove in cartridge.

14) Secure cartridge and flange together by means of (2 off) cap screw (S40-1) whilst making sure that the various connection on flange and cartridge are correctly located in relation to one and other (see assembly drawing view 'A').

IMPORTANT NOTE:

The (outer) flange and cartridge are handed and care should be taken to bring the correct parts for drive- and non drive end seals together. Please consult the bill of material for the matching part numbers.

This completes the assembly of the (outer) flange/cartridge. Set aside and protect from dirt and damage.

Assembly of Complete Seal.

IMPORTANT NOTE:Like the (outer) flange and cartridge, the shaft sleeve is also handed and care should be taken to bring the correct parts for drive- and non drive end seals together. Please consult the bill of material for the matching part numbers.

1) Place shaft sleeve inner end down on a clean work surface.

2) Grease and fit gasket (S76) to dove tail groove in landing area for the(outer) rotating seal face. Wipe off excess grease.

3) Place (rotating) seal face (S15) into shaft sleeve ensuring drive pinsengage notches.



4) Ensure both faces of the outer seal are clean and invert (outer)flange/cartridge sub assembly so that seal face is facing down.

5) Very carefully introduce flange/cartridge sub assembly over shaft sleeve making sure the seal face does not contact the shaft

6) Once the faces are in contact depress springs slightly so that setting plates can be advanced into groove in shaft sleeve.

7) Secure setting plates by means of cap screws.

Note: in order facilitate easy assembly of the seal into the pump 4t is advisable at this stage to align the key way in the shaft sleeve with connection (B0) at the 12 o'clock position on the outer flange.

8) Carefully rotate flange/cartridge/shaft sleeve sub assembly and rest on clean work surface on outer end of shaft sleeve.

9) Grease and fit gasket (S76) to dove tail groove in landing area for the (inner) rotating seal face. Wipe off excess grease.

10) Place (rotating) seal face (S 15) into shaft sleeve ensuring drive pins engage notches. A small dot of grease applied to each of the three drive notches will keep the face in place during the next assembly step. Do make sure that none of the grease gets on the sealing face.

11) Place the outer flange/ cartridge/ shaft sleeve sub assembly with its centre line in a horizontal position and with the inner end of the shaft sleeve protruding over the work bench. Wedge the assembly so that it can not start rolling.

12) Ensure both faces of the inner seal are clean and hold inner seal sub assembly with its centre line in a horizontal position.

13) Very carefully introduce inner seal sub assembly over shaft sleeve making sure the seal face does not contact the shaft sleeve.

14) Secure inner seal sub assembly to cartridge by means of (2 off) cap screw (S40) whilst making sure that the connection on flange correctly located in relation to those on the cartridge/outer flange sub assembly (see assembly drawing view 'A').

15) Grease and fit gasket (S l g) to groove on inside diameter of shaft sleeve.



16) Insert (3 off) set screws into sleeve nut (S20) but do not allow them to protrude into bore of same.

17) Apply a thin coat of anti seize compound to thread at outer end of shaft sleeve and fit sleeve nut to shaft sleeve

The seal is now ready for installation in the pump.

Installation

1) Remove 2 off studs from stuffing box face 180* apart and fit 2 off guide bars (non BW supply) to stuffing box face.

2) Ensure stuffing box and shaft are clean free of sharp edges and otherdamage.Lightly grease or oil shaft and stuffing box bore to facilitate easyinstallation.

3) Rotate shaft with key in 12 o'clock position. Carefully bring seal assembly over shaft and onto guide bars. Bolt seal onto stuffing box face evenly and squarely.

Note I: ensure that each seal is fitted to the correct end of the pump

Note II : ensure the connections on the seals are correctly located in relation to the pump and the connecting piping.

4) Remove guide bars. Refit studs and tighten remaining 2 nuts.

5) Screw sleeve nut onto shaft sleeve until it comes to a stop (do not force).

6) Place “split ring retainer” (Weir Pumps supply) over shaft against sleeve nut and insert split rings (Weir Pumps supply) into groove in pump shaft at outer end of shaft sleeve.

7) Back off sleeve nut/retainer so far that split ring is retained but not fully confined.

8) Complete the pump build up in the normal manner.



9) When the shaft is held in its running position by means of the thrus bearing the setting plates locate the shaft sleeve in the correct position in relation to the stationary assembly.

10) "Unscrew" sleeve nut until it holds the retainer and split ring in position. Do not over tighten sleeve nut against retainer as this will warp the setting plates.

11) Tighten set screws in the sleeve nut securely to torque values shown on the assembly drawing.

12) Retract setting plates and secure in "disengaged position".

Piping

1) Connect piping as per separate instructions.

2) Always ensure piping is clean and unobstructed prior to installation.

3) Make sure seal cavity and piping are adequately vented prior to start up.

4) Always ensure the seal is pressurised before the pump casing and do not de-pressurise the seal before the pump casing has been depressurised and vented


mechanical seals module

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