centrifugal pump (4521)

8/3/2019 Centrifugal Pump (4521)

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CENTRIFUGAL PUMPCENTRIFUGAL PUMP

P-4521A

MAKE: WORTHINGTON CENTRIFUGAL PUMPSERVICE: AMMONICAL WATERMIN. OPERATING TEMP: 40 C

MAX. OPERATING TEMP: 70 CSUCTION PRESSURE: 16.0 Kg/cm2

DISCHARGE PRESSURE: 30.07 Kg/cm2

DIFFERENTIAL PRESSURER: 14.7 Kg/cm2PUMP MATERIAL: CAST IRON AND CARBON

STEEL


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PUMPPUMP

Pump is a machine which adds energy into liquid to move it fromlow elevation to higher elevation or low pressure to high pressure.

Pumps are divided into two main groups:y Centrifugal pumps

y Positive displacement pumps

Within these two main groups there are many different types of

pumps.


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y Between bearings: Impeller/s supported between two

sets of bearings.

y Overhung Impeller: Impeller overhungs a bearing

support bracket.

Mechanical ConstructionMechanical Construction


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Introduction of PIntroduction of P--45214521

Two stage centrifugal horizantal with radially split casing with casted

top top flanged.

Casing Specification:

The first and second stage single volutes are opposed to reducehudraulic radial thrust and shaft deflection.

The liquid is conveyed from one to other stage by and an intergral

casted crossover. The inter stage diapharagm too is integrally casted

with casing. All the flow passages are accurately designed to

minimize efficiency losses. We will discuss the clearances ofdifferent bushes and sleeves further.


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Impellers, wear rings & intermidate bushing.Impellers, wear rings & intermidate bushing.

Std. impellers with single suction closed type which werekeyed to shaft and secured by lock washer and nut, mounted face

to face to balance hydraulic axial forces. Impeller first and then

complete rotor are dynamically balanced to avoid vibrations and

assure long trouble free life to seals and bearings.

y Wear rings and intermidate bushing. Thecasing and the impeller front are fitted with replaceable wear rings

of cast iron placed with grab screws. Intermidate bushing is

provided to reduce the flow leakage from second to first stage thus

minimizing efficiency losses. Clearance b/w wear rings is 0.46mm.and clearance b/w intermidate bush and shaft sleeve is 0.43mm.


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Shaft and SleeveShaft and Sleeve

Shaft made of C.S with first critical speed atleast 20% higher thanthe maximum rotational speed. The bearing span is the shortest

possible to minimize deflection.

Sleeve made of Cast Iron fitted on shaft with an interfarence of0.02mm.


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Bearing AssemblyBearing Assembly

Pump is fitted with standard anti-friction bearings lubricated by meansof an oil slinger. Double row self alligning type and thrust bearing isdual single row angular contact type. Constant level sight feed oilersare provided for easy inspection and refilling.

y

Single row angular contact ball bearings can support axial forcesin one direction and high radial forces. They must be axially adjstedagainest a second bearing fitted in a mirror arrangement. Axial loadcarrying capacity is dependent on contact angle. The larger the anglethe higher the load bearing capacity. Contact angle of 40 Deg. Cansupport high axial loads. Mounted on out board end in back to back(X) arrangement. Bearing No. 7308 B tvp

y Self aligning double row ball bearing operating under normalconditions can swivel approx. 4 deg misalignment about their centerposition. As a result they permit skewing between the inner and outerring and can thus compensate misalignments, shaft deflections andhousing deformations.


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Angular contact ballAngular contact ball

bearingbearing

Double Row selfDouble Row self

Aligning Ball bearingAligning Ball bearing


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Mechanical SealsMechanical Seals

y Two multi spring balanced mechanical seals in tendum arrangement

on both inboard and outboard side with O ring and backup ring.

Material of balance faces CARBON and seat is of SILICON

CARBIDE.

API Flushing Plan for sealsAPI Flushing Plan for sealsy API plan 22 for process seal and API plan 52 for buffer seal.

Why doubleWhy double mechanical seals are used?mechanical seals are used?y Double or tandem mechanical seals are typically used in services

involving toxic, flammable, or hazardous liquid to prevent the liquid,

or its vapor, from leaking into the environment due to a leak or seal

failure.


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Double seals arrangementsDouble seals arrangements

y

Double sealsA double mechanical seal is a combination of two seals mountedback-to-back with a non-hazardous barrier liquid injected betweenthe two seals at pressure greater than service pressure. The barrierliquid comes from an external source such as a pressurizedreservoir in a closed loop piping system connected into, and out of,the seal gland.

Tandem seals

A tandem mechanical seal arrangement is also a combination oftwo seals but they are mounted in the normal position, as opposedto the back-to- back position of a double seal. A barrier liquid isalso injected between the two seals from an external reservoir in aclosed loop piping system but it is not pressurized. The barrier fluid

is circulated by the centrifugal force effect of a pumping ring inthe seal. The pressure in the stuffing box is higher than in thebarrier chamber so when the inner seal fails the process liquidenters the barrier chamber and forces the buffer reservoir level torise. The process liquid is piped out from the of the reservoir into asafe disposal area.Double and tandem seals are usually flushed using API Plan 52 or

Plan 53.


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Maintenance of PumpMaintenance of Pump

y

Dismentling Procedur.1. Remove all flanged connection, flusing of seal piping and drain piping.2. Drain oil from both bearing housings and remove oilers.

3. Remove coupling spacer piece b/w coupling hubs.

4. Remove coupling hub from pump shaft.

5. Remove outer bearing cover and outer water shied and lock nut and lock

washer.6. Remove oil slinger ring.

7. Unbolt bearing housing and remove it.

8. Remove mech. Seal sleeve locking arrangement.

9. Unbolt and remove hard face adapter plate.

10. Gently remove mech. Seal retainer assembly and sleeve.

11. Remove impeller lock nut and washer and finally remove impeller from shaftof inboard side.

12. Repeat these steps from outboard side but dont remove or loosen impellerand impeller lock nut.

13. Pull the shaft with 2nd stage impeller gently.

14. Remove pump base bolts from foundation plates.


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Maintenance of PumpMaintenance of Pump

Work Done:1. Dynamically balanced the shaft with impellers assembled.

2. New impeller and casing wear rings were

installed.(interfarance=_____ Clearance= 0.46mm ).

3. New intermidate bushing and shaft sleeve were

installed.(Interfarance=_____ Clearance= 0.43mm)

4. New mech. Seals were installed.

5. Inserting of bushing in bearing housing to maintain clearance with

bearing housing and bearing OD. Clearance= 0.025mm.

6. New set of bearings were installed.

7. Old casing were replaced with new one.

8. All material of w/rings, bushing and sleeve was CAST IRON.


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Installation procedure of bearingsInstallation procedure of bearings

There are two methods in use for mounting a bearing on

a shaft.

1. Heating the bearing to expand the inner race and

shrinking it on the shaft.

2. Forcing the bearing onto the shaft.

the first method is preffered. Heat the bearing in an oil

bath or on induction heater to a uniform temperature

of 108 C. when heated quickly mount it on the shaft.


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Checks for MECH. SEAL installation.Checks for MECH. SEAL installation.

y Check the od of sleeve and id of retainer must be with in tolerance

of + 0.05mm and ovality must not exceed 0.025mm.

y Check the surface finish of sleeve ensure that there are no sharp

edges or burrs.

y

Check that the leading edge of sleeve last shoulder over which theseal must passed is chamfered at 10 deg. For a length of 3 mm.

y Ensure the flatness of seat and blance face.

y Ensure the sleeve material must be corrosion resistant and with

sufficient hardness.

y Any elastomeric seal component made of ep rubber must nevercome into contact with mineral oils and or greese.


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Assembling of Mechanical Seal.Assembling of Mechanical Seal.y Locate springs in the holes in the seal retainer.

y Assemble the thrust ring into the retainer taking care to line up thenotches on the outside diameter with the dimples in the retainer.

y Assemble the back up and o ring into the seal face.then fit this faceassembly onto the thrust ring already in the retainer, taking care toline up the grooves on the face outside diameter with the dimplesin the retainer.

y Using mechanical seal assembling fixture gently compress thesprings and locate the lock ring into its groove, with the ends b/w 6to 12 mm(depending on the seal size) from the small hole or slot inthe retainer.

y Allow the seal to extend to its free length and check the grub

screws are fitted and are clear of the bore of the retainer.y There are two circumferential lines cut into the outside wall of the

seal retainer. One goes through the tapped holes for grub screwshave metric threads. The other line serves as a visible guideshowing whether or not the seal has been correctly set to itsworking length, if it is correct the thrust ring should line up with

this second scribed line when the seal installation is complete.


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ALLIGNMENTALLIGNMENT

alignment means that the centerline of the pump is aligned with the

centerline of the driver. it is critical with sealed pumps especially ifwe are using rotating seal designs where the springs or bellows

rotates with the shaft.

A little misalignment at the power end of the pump is a lot of

misalignment at the wet end, and unfortunately that's where the

seal is located in most pump applications.Misalignment will cause many problems:

y The pump bearings can become overloaded.

y The misalignment could be severe enough to cause contact

between stationary and rotating seal components:

y The wear rings can contact.

y The shaft or sleeve can contact the stationery face of the

mechanical seal.

y The impeller could contact the volute or back plate.


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ALIGNMENTALIGNMENTRegardless of the alignment method we select,

we should also check the following:

y A straight shaft that has been dynamically balanced.

y Good wear rings with the proper clearance.

y The correct impeller to volute, or backplate clearance.

y The elimination of "soft foot".

y Eliminate all pipe strain.y Good bearings installed on a shaft with the proper finish and tolerances.

y A good mechanical seal set at the proper face load. The closer the seal is to the

pump bearings the better off you are going to be.

y we must level the pump and driver. If the pump is aligned without being level, the oil

level will be incorrect and we will develop bearing problems.

y we then take a series of radial and axial measurements to see where the pump islocated in respect to its driver (motor).


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centrifugal pump (4521)

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