baylor 7838

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RIG/PLANT

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REFERENCE

Model 7838 REFERENCE DESCRIPTION

Eddy Current Brake This document contains proprietary and confidential information which belongs to National Oilwell Varco; it is loaned for limited purposes only and remains the property of National Oilwell Varco. Reproduction, in whole or in part; or use of this design or distribution of this information to others is not permitted without the express written consent of National Oilwell Varco. This document is to be returned to National Oilwell Varco upon request and in any event upon completion of the use for which it was loaned. National Oilwell Varco

National Oilwell L.P. 500 Industrial Blvd. Sugar Land, TX 77478-2898 United States Phone: +1 (281) 240 6111 Fax +1 (281) 274-0426

DOCUMENT NUMBER

165-31591 REV

G

Installation, Operation and Maintenance Instructions

Model 7838

Baylor Eddy Current Brake

Document number 165-31591 Revision G of 68

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REVISION HISTORY

G 18.01.2006 Updated to New Template G.K.A. L.S. L.P. Rev Date (dd.mm.yyyy) Reason for issue Prepared Checked Approved

CHANGE DESCRIPTION Revision Change Description

G Updated MS word in new template.


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SAFETY FIRST! Before placing this equipment in operation, certain basic rules of safety should be observed. It should be noted that no safety rules and no amount of safety equipment will make operating this equipment safe, unless the operator enforces the rules and proper uses of the equipment.

MACHINE OPERATION

1. Only responsible persons, trained to do so, should operate this equipment. 2. Any person operating this equipment should be thoroughly familiar with the

manufacturer's recommended operating instructions.

CLEANLINESS AND SERVICE

1. Periodic cleaning of the equipment may reveal potential mechanical trouble spots such as loose or missing bolts, fittings, etc..

2. Keep the area around the equipment clear of loose tools, trash, extraneous matter, etc.. 3. Shut the equipment down before servicing or cleaning unless the service work requires

the equipment be operating. 4. Allow only an experienced mechanic to service the equipment. 5. If a mechanical problem or deficiency is found, correct or report it before continuing

operation. 6. Before working under or between components that are suspended by hoists or slings,

securely block or crib them. 7. When working in an area of potential head injury, wear an approved safety helmet.

CAUTION! MANY PARTS ARE HEAVY OR DIFFICULT TO HANDLE.

PLAN LIFTS AND MOVES CAREFULLY TO AVOID SEVERE PERSONAL INJURY. PROVIDE SAFE SUPPORTS FOR DISASSEMBLED PARTS.


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TABLE OF CONTENTS MACHINE OPERATION.............................................................................................................. 3

CLEANLINESS AND SERVICE .................................................................................................. 3

1 INTRODUCTION AND DESCRIPTION............................................................................. 6

1.1 Scope of Manual..................................................................................................... 6

1.2 General Description of Equipment .......................................................................... 6

2 SUMMARY OF SPECIFICATIONS EDDY CURRENT BRAKE........................................ 7

2.1 Specifications ......................................................................................................... 7

3 INSTALLATION................................................................................................................ 9

3.1 General................................................................................................................... 9

3.2 Radial Bearing Clearance..................................................................................... 15

3.3 Brake Alignment ................................................................................................... 15

3.4 Shaft Alignment .................................................................................................... 15

3.5 Cooling Water Quality........................................................................................... 17

3.6 Cooling System Capacity...................................................................................... 20

3.7 Brake Field Coil Polarity ....................................................................................... 23

3.8 Certification for Hazardous Location..................................................................... 29

4 THEORY OF OPERATION ............................................................................................. 36

4.1 General................................................................................................................. 36

4.2 Brake Operation on Rig ........................................................................................ 36

5 ACCESSORIES AND OPTIONS .................................................................................... 39

5.1 General................................................................................................................. 39

6 MAINTENANCE AND SERVICE .................................................................................... 41

6.1 General................................................................................................................. 41

6.2 Maintenance and Repairs..................................................................................... 45

6.3 Electrical Problems and Troubleshooting ............................................................. 50

6.4 Mechanical Problems and Troubleshooting.......................................................... 51

6.5 Inspection and Maintenance Schedule ................................................................. 53

6.6 Evaluating Conditions of Brakes in the Field ........................................................ 57


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7 PARTS AND SUPPLIES................................................................................................. 61

7.1 General................................................................................................................. 61

8 DRAWINGS .................................................................................................................... 62

8.1 Drawing List .......................................................................................................... 62


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1 INTRODUCTION AND DESCRIPTION

1.1 Scope of Manual This manual provides a source of important reference information regarding the installation, operation, and maintenance of the BAYLOR Eddy Current Brakes and should be given careful consideration and study before operating the BAYLOR brake. It is impossible to anticipate every kind of problem or condition that may be encountered in the use of the brake, but compliance with the instructions and suggestions set forth in this operating manual will assist the operator in successfully operating this equipment. Failure to operate and maintain the brake in accordance with this operating manual may void the warranty covering this equipment. The information contained in this operating manual shall not in any way relieve the operator of the responsibility for exercising reasonable care and prudence in the operation of this equipment.

WARNING!

Failure to comply with the instructions in this operating manual could result in serious property damage, severe injury, or death! Any alteration or unauthorized repair work to the brake or control system will VOID ANY WARRANTY expressed in the terms and conditions of sale and will void the HAZARDOUS AREA CERTIFICATION. All applicable schematics, flow diagrams, and major assembly drawings are contained in SECTION 8 of this manual.

1.2 General Description of Equipment The BAYLOR Eddy Current Brakes are auxiliary braking devices for the Drilling Rig Drawworks. This braking is produced entirely electrically without the aid of friction brake devices, slip rings, or other wearing elements. The brakes are water cooled.


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2 SUMMARY OF SPECIFICATIONS MODEL 7838 EDDY CURRENT BRAKE

2.1 Specifications

General Specifications Principal of Operation Induced Eddy Current Braking Torque-Maximum @ 150 RPM, lb-ft (n-m) 117,000 (158,631) Torque @ 50 RPM, lb-ft (n-m) 96,000 (130,159) Number of Magnets 2 Number of Coils per Magnet 2

13.4-13.9 Coil Internal Resistance @ 68° F (20° C), Ohms 11.0-11.5 (Prior to July 1985) 3.9-4.1 Total Brake Input Resistance @ 68° F (20° C), Ohms 2.8-2.9 (Prior to July 1985)

Brake Excitation Voltage, volts DC 250

74.07 Current-Coil Temperature @ 68° F (20° C), Amps DC 89.29 (Prior to July 1985)

18.5 Power Input @ 68° F (20° C), kW 22.3 (Prior to July 1985) Cooling Water Requirements

Flow @ 100° F (38 Deg. C) At Brake Inlet, gpm (lpm) 150 (568) pH 7.0-7.5 Maximum Discharge Temperature, oF (oC) 165° (74°)

Cooling Water Piping Inlet (2) 2’’ NPT Outlet (2) 4’’ NPT Overflow (2) 1 ¼’’ NPT

Overall Sizes Height, in (mm) 78 (1,981) Width, in (mm) 38 (965) Weight, lbs (kg) 28,000 (12,701) Inertia (WK2)-Shaft and Rotor, lb-ft2 (kg-cm2) 37,938 (15,987,118) Weight-Shaft and Rotor, lbs (kg) 6,458 (2,929)

Diameter, in (mm) 7.5’’ (190.5) Shaft Size (Oilfield Standard) Taper per foot, in (mm) 1 ¼’’ (31.75) Average Rotor Radial Clearance (Air Gap) Over Magnets (Without Paint or Other Build up), in (mm) 0.055-0.065 (1.397-1.651)

Maximum RPM 600


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3 INSTALLATION

3.1 General The BAYLOR Brake should be cradle mounted on the drawworks structure. The drawworks manufacturer furnishes the adapter mounting components as well as the disengaging coupling between the brake and the drum shaft of the drawworks. The necessary shifting mechanism and related accessories should be furnished by the customer.

CAUTION! Heat removal from the rotor in the BAYLOR Brake is accomplished by cooling water. The movement of the rotor through the water is necessary to keep the rotor and magnet from overheating. To avoid damage to the brake, use a coupling that allows rotation of the rotor in either direction at all times. DO NOT USE AN OVERRUNNING TYPE CLUTCH. A standard mounting flange on the outboard bearing cap is provided by National Oilwell Varco for mounting water and/or air tube assemblies. The required tube assemblies are furnished by the drawworks manufacturer and should be installed in accordance with their instructions. Electrical control wiring and cooling system water piping should be installed in accordance with the drawings contained in this section. A minimum of five-thread engagement shall be maintained on all threaded connections. Figure 3-1 illustrates a standard Brake cooling configuration without a heat exchanger. Figure 3-2 illustrates a standard Brake cooling system with a heat exchanger. A closed loop cooling system provides the greatest and best degree of protection against corrosion / erosion with adequate flow and temperature protection for the BAYLOR Brake. These closed loop systems are manufactured to provide proper cooling for the particular size BAYLOR Brake and can also be capacity sized to cool other portions of the drawworks drive. Figure 3-3 shows the electrical connections for the magnet coils and power input to the junction box.

CAUTION! The water outlet(s) at the bottom of the brake should not be hard piped or otherwise restricted. This should be free-flowing, gravity drain. A funnel-type drain as illustrated in Figure 3-4 is preferred. Do not plug, pipe, connect hoses to, or otherwise obstruct the water overflow outlets, located on the brake just below the shaft centerline. These overflow outlets provide a warning of improper water flow conditions.


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Removal of heat from the Brake is most important. Absence of proper cooling water flow could damage the rotor. Proper cooling water flow at all times will prolong Brake life for many years. As illustrated in Figure 3-4 the BAYLOR Eddy Current Brake allows cooling water to flow over the lower sections of the magnets and rotor before it exits at the bottom. If the cooling water outlets are restricted, the water level inside the Brake will increase to a level which could damage the Bearing grease seals and permit water to enter the bearing cavity with ultimate damage resulting to the bearing.

CAUTION! The BAYLOR Eddy Current Brake is not designed to operate with the cooling water internal of the brake at other than atmospheric pressure. For proper brake operation insure that brake cooling water flows unrestricted through the brake with gravity discharge and unrestricted flow back to the cooling water reservoir.


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Figure 3-1


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Figure 3-2


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Figure 3-3


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Figure 3-4 Drain


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3.2 Radial Bearing Clearance Measuring radial bearing clearance upon receipt of a new or factory rebuilt brake is a method that will allow the prediction or verification of bearing failures. This is not a foolproof method, but when done as a part of a routine maintenance program this measurement can be very helpful. In order to carry out this measurement, the brake must be uncoupled from the drawworks. A dial indicator is placed at the top dead center of the shaft’s vertical centerline, and the shaft is lifted. Care must be taken not to apply more force than one half the combined weights of the rotor and shaft. This weight information can be found in Section 2 of this manual. Care must also be taken to insure the dial indicator is perfectly vertical and properly zeroed. As with any lifting operation, all lifting apparatus must be properly sized, and qualified personnel must perform the lift. The radial clearance data should be recorded for future use. This information can be used later to predict bearing failure. The bearing manufacturer will indicate that a bearing that is in the process of failing will undergo microscope surface failures prior to a complete failure. When this begins to happen it is impossible to observe these surface failures with a radial clearance measurement, but a large deviation from the original measurement will indicate the failure process is well underway and a bearing replacement should be planned.

3.3 Brake Alignment The Brake should be aligned to the drum shaft in keeping with good machinery practice and in accordance with the recommendations of the drawworks manufacturer. NOTE: If the Brake is correctly aligned on the drawworks, the only loading on the bearings is the weight of the shaft and rotor assembly since the magnetic attraction when the brake is energized is radially equal in all directions. Improper alignment results in bearing wear and premature failure.

3.4 Shaft Alignment Angular misalignment and offset misalignment between directly-connected shafts often cause increased bearing loads and vibration, even when the connection is made by means of flexible coupling. Shaft alignment is especially critical if the coupling is to be operated at high speed.


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3.4.1 Angular Misalignment Angular misalignment should not exceed 0.010 inch (0.0025 mm) total indicator reading. Refer to the illustration in Figure 3-5.

3.4.2 Offset Misalignment Total indicator run out of offset misalignment should not exceed 0.010 inch (0.0025 mm). Refer to the illustration in Figure 3-6. NOTE: When conditions make it impossible to check alignment with a dial indicator, a rough check can be made with a straight edge and feeler gages. Check angular misalignment by inserting feeler gages between the faces of the coupling hubs at four equi-distant points. Check offset misalignment by placing a straight edge across the machined diameter of both coupling hubs.

Figure 3-5 Angular Misalignment


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Figure 3-6 Offset Alignment

3.5 Cooling Water Quality

3.5.1 Scope In order to function properly, the cooling water used in BAYLOR Eddy Current Brakes must meet four basic requirements: It must adequately transfer heat energy from the rotor to the heat exchanger used for cooling. It must not form scale or sludge deposits in the Brake or in the cooling system. It must not cause corrosion in the Brake or cooling system. It must not deteriorate any of the seals or gaskets used in the Brake or cooling systems. These requirements are normally met by combining a suitably demineralized water with a reliable corrosion inhibitor. Under extreme operating conditions it may be necessary to use an antifreeze coolant. In this case the cooling liquid should be a mixture of the ethylene glycol type antifreeze, de-mineralized water, and an adequate corrosion inhibitor.


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3.5.2 Water Quality Standards The water used in BAYLOR Eddy Current Brakes should meet the following requirements:

1. No undissolved particles such as sand, grit, or silt. 2. A ph level between 7.0 and 7.5. 3. A maximum dissolved chlorides content of 40 parts per million. 4. A maximum dissolved sulfates content of 100 parts per million. 5. A total dissolved solids content of 340 parts per million. 6. A total hardness of 170 parts per million. Water that does not meet these

standards should be treated by softening, de-mineralization, or de-ionization before being used to cool the Brake.

3.5.3 Corrosion Inhibitor Standards The use of "home made" type inhibitors are not recommended. The ready availability of suitable commercial products makes these "home made" formulations impractical and unnecessary. The use of soluble oil type inhibitors is also not recommended due to the effect they have on ethylene glycol type antifreeze additives and the fact that they are detrimental to efficient heat transfer. Commercially available corrosion inhibitors are generally of three types; chromate based, borate-nitrite based, and silicate nitrite based. Of these, the chromate based and the borate nitrite based are the most common. It is important to note that there are environmental restrictions on the disposal of these types of inhibitors due to the chromium and boron content. Chromate type rust inhibitors are not recommended for use because the mixture forms sludge with the recommended antifreeze, ethylene glycol. See Section 3.5.4 and the note on the following page. The silicate nitrate inhibitor is basically non-polluting. Be sure to check with national, state, and local authorities before disposing of any water treated with inhibitors. Also be sure to follow the manufacturer's recommendations for applying the inhibitor, both for new untreated water and for maintenance of already treated water.


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Due to the successful use in Baylor Eddy Current Brakes, the following corrosion inhibitor is recommended for use: NALCOOL 2000 Nalco Company 3720 W. Alabama St. #5318 Houston, TX 77027 Tel (713) 626-8113 Fax (713) 626-8120 (Previously called Pencool 2000) It is recommended that this inhibitor be purchased through a local distributor so that proper field support in its use is available.

NOTE! If a glycol anti-freeze is used, then NALCOOL 3000 is recommended due to possible interaction with the glycol, causing sludge. NALCOOL Inhibitor Startup, Maintenance, and Testing Standards Water Quality Standards with NALCOOL:

1. Insure water quality meets the water quality standards in Section 3.5.2. 2. Coolant has a PH level of 8.3 after corrosion inhibitor is added. (Coolant solution

turns pink.) 3. Recommended nitrite level of 1500 parts per million.

Startup of NALCOOL with fresh water:

1. Insure water quality meets the water quality standards in Section 3.5.2.

2. Add a 4-1/2% concentration of NALCOOL. (Approximately 28 gallons for a 630 gallon tank.)

Testing: Coolant Testing should be done weekly for PH and Nitride levels. PH and Nitride test kits can be purchased from National Oilwell Varco in Sugar Land, Texas or from Nalco directly.


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WARNING!

IF THERE IS A RAPID NITRIDE LOSS OVER TIME, THEN A BACTERIA IS SUSPECTED TO BE PRESENT. TO GET A BACTERIA TEST KIT, OR OTHER PRODUCTS, PLEASE CONTACT NALCO.

3.5.4 Usage of Antifreeze Standards Only ethylene glycol type antifreezes are to be used in BAYLOR Eddy Current Brakes due to the operating temperature generated. NOTE: Chromate type rust inhibitors are not to be used with ethylene glycol antifreezes. The resulting mixture forms a sludge. It is recommended that the Brake cooling fluid not exceed 68% ethylene glycol. Levels of ethylene glycol higher than this will lower the freezing point of the Brake cooling fluid, but will not provide adequate heat transfer. If the antifreeze contains corrosion inhibitors, it is not recommended to add additional inhibitors to the original mixture or for maintenance of a used mixture. This practice can actually cause corrosion of the Brake. If the corrosion inhibitors in this type of solution are no longer effective the entire content of the cooling system should be replaced by a fresh mixture. National Oilwell Varco does not recommend the use of antifreezes containing anti-leak compounds. These compounds can cause plugging of water passages and reduction in effective heat transfer rates, resulting in a Brake that fails from overheating. Be sure to dispose of used antifreeze mixtures according to the manufacturer’s recommendations and the applicable environmental authority’s recommendation.

3.6 Cooling System Capacity National Oilwell Varco recommends the use of treated coolant in a closed loop cooling system for cooling all Eddy Current Brakes. A closed loop cooling system generally consists of, at minimum, a circulating pump, a water-to-water heat exchanger or radiator and a reservoir tank. Cooling an Eddy Current Brake is much more difficult then cooling other frequently used equipment in the oilfield.


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This is true for two reasons. The Eddy Current Brake can absorb thousands of horse power as heat that is rejected to its cooling water. Therefore, the Eddy Current Brake is putting more heat into its coolant than most other equipment. The other reason cooling Eddy Current Brakes requires generally large heat rejection equipment is the required inlet water temperature is very close to the ambient air temperature. This means diesel engine radiators will not properly cool an Eddy Current Brake. As a result of these factors, water to water heat exchangers are generally more cost efficient and much more compact. If a radiator is to be used it will generally be extremely large. Any heat rejection equipment selected must be sized to supply the rated coolant flow at the rated inlet temperature. If due to high ambient conditions the inlet temperature of the cooling water is in excess of 100 degrees F (38 degrees C) the flow of the cooling water to the Brake must be increased. See figure 3-7. It is important to note there is a maximum amount of cooling water flow that may be passed through the Eddy Current Brake. The curves indicated in Figure 3-7 are extended to the maximum flow rate capacities of the brakes. If ambient conditions do not permit the operation of the brake on its indicated curve, then the brake must be derated for this application. Contact National Oilwell Varco for performance curves that will indicate reduced cooling capabilities.


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Eddy Current Brake Coolant Flow

Required to Maintain Outlet Temp of 165° F.

Curve No. 1

Curve No. 2

Curve No. 3

Curve No. 4

Curve No. 5

Curve No. 6

Model 15050

EC Brake

Model 7838 / 9650 EC Brake

Model 19RD130 EC Brake*



Model 7RD150

EC Brake* Note for 5032 / 3550:

BASED ON MAX TORQUE @ AVG SPD 250 RPM OUTLET TEMP OF 165° F. ONE-THIRD DUTY CYCLE

* Model’s 19RD130 & 7RD150 calculations based on average speed of 1000 R.P.M.

Curves are extended only to maximum GPM flow rate capability of the specific brake model water housing. If higher flow rates are required, contact National Oilwell Varco with specific coolant requirements.

Figure 3-7


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3.7 Brake Field Coil Polarity Correct field coil polarity is extremely important in obtaining maximum torque from the BAYLOR Eddy Current Brake. There are a number of methods for determining correct field coil polarity. None of these methods are totally accurate. However, if the following instructions are closely followed, good results may be obtained. The best method is utilized by National Oilwell Varco during coil manufacture. During the coil winding process, the start of the winding and the end of the winding are tagged. At final assembly of the Brake, knowing the start and finish of each coil permits accurate determination of how to tag each coil lead to insure proper Brake polarity. It is very important to maintain the coil lead tags during any period of maintenance or parts replacement in the field to insure proper polarity after all work has been accomplished. In the field, the following tests may be performed to determine correct Brake polarity:

1. If Brake polarity is not correct, the Brake will appear weak and not as responsive to actuation of the Driller’s Control. To obtain a reference point as to the Brake’s holding capacity, raise the traveling block into the derrick so that three joints of drill pipe are visible. Turn the Brake Driller’s Control “full on” and allow about 5 seconds for full saturation of the Brake magnetic circuit. Then, with the Eddy Current Brake fully energized, release drawworks friction brake and allow pipe to descend into the bore hole. As the second joint of drill pipe starts through the rotary table, time the interval of time it requires for this second joint to progress into the bore hole.

Next, turn off electrical supply to BAYLOR Brake. Lock out circuit breakers to insure safe conditions while performing work in and around Brake and Control System. Remove cover of Brake Junction Box. Mark present position of coil leads F7 and F8. Reverse the position of these two coil leads, that is, disconnect F7 and F8, and then reconnect F7 where F8 was connected and F8 where F7 was connected. Turn electrical power on and re-test by timing length of time for second joint of drill pipe to pass through rotary table. Compare the results of these two tests. If polarity was correct initially, the drill pipe would have taken longer to enter bore hole during first test. On the basis of these two tests, choose correct junction box coil lead connection for correct polarity.

2. Second method of determining correct Brake coil polarity is the procedure as follows:

a. Turn off electrical supply to Baylor Brake. Lock out circuit breakers to insure safe conditions while performing work in and around Brake and Control System. Remove Brake junction box cover. Record the location of each coil lead on terminal block in Brake junction box. Disconnect all coil leads from Brake junction box terminal strip.


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b. Check resistance of inboard field coil of inboard magnet as illustrated in Figure 3-

14. Set multimeter to lowest resistance scale (200 ohms or less) and connect meter leads to F5 and F6. Reading should approximately agree with those listed in Figure 3-15. If meter readings are lower by 30% or more, a coil problem may exist. Troubleshoot coil problem before proceeding to next step.

Figure 3-14 View of Brake from Junction Box Side

c. Remove meter leads from coil leads F5 and F6. Reconnect coil lead F5 to

positive (+) lead of Control DC in Brake junction box terminal strip. Reconnect F6 to negative (-) lead of Control DC in Brake junction box terminal strip.

d. Observing meter lead polarity, connect meter leads to a pair of Field Coil Leads

as indicated in Table I.

F1F2F3F4

F7F6F5

F8

OUTBOARD MAGNET INBOARD MAGNET


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Brake Model Coil Internal Resistance

at 68°F (20°C) 15050 10.8 OHMS TO 11.2 OHMS

*7838 13.4 OHMS TO 13.9 OHMS

9650 15.5 OHMS TO 16.4 OHMS

7040 13.0 OHMS TO 13.5 OHMS

8350 13.0 OHMS TO 13.5 OHMS

6032 5.9 OHMS TO 6.3 OHMS





19RD130 6.7 OHMS TO 7.1 OHMS

9RD130 6.7 OHMS TO 7.1 OHMS

7RD150 4.4 OHMS TO 4.8 OHMS *NOTE: For Model 7838 brakes manufactured prior to July 1985, coil resistance will be 11.0-11.5 ohms.

Figure 3-15 e. Set meter scale as indicated in Table I for specific Field Coil Leads selected.

Table I

Field Coil Leads F1 - F2 F3 - F4 F7 - F8

Meter Lead Polarity

F1 - F2 + -

F3 - F4 + -

F7 - F8+ -

Meter Scale 1 – 10 VDC

1 – 10 VDC

1 – 50 VDC

Meter Deflection

Positive Positive Positive


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f. Insure that disconnected coil leads not being tested are not in contact with each

other or surrounding surfaces. Unlock circuit breakers for Brake Control and energize the Control circuit. Move the Driller’s Control handle to a position as indicated below:

• For the following Brake Models, move the handle “half way” through its total

travel:

3630 3550 5032 5250 6032 19RD130

• For the following Brake Models, move the handle “full on” position:

7040 15050 8350 7RD150 7838 9RD130 9650

NOTE: Those brakes requiring only half on position of Driller’s Control have coils which are connected series-parallel and therefore require only half value of applied control voltage for full saturation. Reference drawing D56772, sheets 1 and 2.

g. Observe positive meter deflection. If in agreement with Table I, move Driller’s

Control handle to “off” position. Turn off AC power to Brake Control System, lock out circuit breakers. Remove meter leads and move to next pair of Field Coil Leads. If not in agreement, with Table I, move Driller’s Control handle to “off” position. Turn off AC power to Brake Control System, lock out circuit breakers. Swap Field Coil identification tags on Field Coil being measured, and connect meter leads to another pair of Field Coil Leads for polarity test per Table I.

h. Repeat steps d, e, f, and g until all Field Coil Leads have been tested and are in

agreement with Table I.

i. Turn off AC power to Brake Control System, lock out circuit breakers. Reconnect Field Coil Leads to junction box terminal strip per drawing D56772, sheets 1 and 2.


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3.8 Certification for Hazardous Location The Factory Mutual Certification of BAYLOR Eddy Current Brakes is reproduced on the following pages. Note that if a Factory Mutual Approved Installation is required, a water flow alarm system must be installed to monitor water cooling flow in the Brake inlet line in accordance with drawing B46765 and drawing D47915 sheets 1 and 2. Copies of these Drawings are included at the end of this section.


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12


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4 THEORY OF OPERATION 4.1 General

When the steel rotor rotates through the stationary magnetic field, currents are induced in the rotor. These currents, commonly called “eddy currents”, produce a magnetic field which interacts with the stationary field. This field interaction produces a force, which opposes rotor rotation, and provides the braking torque for the BAYLOR Brake. The braking torque of the Eddy Current Brake is dependent on the strength of the stationary magnetic field, rotor speed, and rotor temperature. Torque increases with magnetic field strength and with rotor speed. Torque decreases as rotor temperature rises and the rotor expands which widens the air gap. The strength of the stationary magnetic field is controlled by the field coil in proportion to the braking requirements. The eddy currents induced in the rotor produce heat. This rotor heat must be kept within acceptable limits or braking torque will be reduced. To maintain rotor temperature within acceptable limits, a cooling system is required. A steady flow of water is directed into the area containing the rotor, as illustrated in Figure 3-4. The movement of the rotor through this water as it turns provides uniform cooling of the rotor surface. If the flow of cooling water fails while the brake is in operation, the rotor will become overheated. In this state, the rotor will be damaged if a safe cooling procedure is not followed. Consult Section 6 of this manual for the proper procedure to use.

4.2 Brake Operation on Rig When a BAYLOR Eddy Current Brake is installed on a rig its response may vary depending upon the following items:

• Brake torque capacities may vary + or – 5% between individual units.

• When the brake becomes overheated it will lose some of its torque capacity.

• Normal reaction time for the brake to reach maximum braking torque is approximately 2 seconds. This may vary depending upon the Brake Control System employed.

• Normal reaction time for the brake to decay to zero braking torque is approximately 1-2 seconds. This may vary depending upon the Brake Control System employed.

• As the brake ages, the air gap between the rotor and the magnets may increase due to rust or erosion which will cause a decrease in brake output torque.


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With all these factors in mind, the operator must learn and get a feel for the brake response time during the early stages of tripping when the loads are lighter. When the load exceeds the brake capacity, note that the brake will not be able to control or properly decelerate the load. Proper operation of the brake is to apply the Eddy Current Brake before releasing the main drawworks friction brake when tripping into the bore hole.

CAUTION! When the brake is being used close to its Maximum torque capacity, apply the Eddy Current Brake before releasing the main drawworks friction brake when tripping into the bore hole.

4.2.1 Drill Assist Operation If the brake is used for “drill assist” where the rotor speed is very limited, it is recommended that no more than half of full rated DC voltage be applied to the field coils continuously. The brake’s primary purpose as an auxiliary brake is to dissipate the energy of drill pipe or casing being lowered into the bore hole. For this specific purpose, the field coils are designed to accommodate a duty cycle of full DC voltage “on time” of 20 seconds out of every 60 seconds. Increasing the duty cycle to 100%, or an “on time” of 60 seconds out of 60 seconds will create excessive heat buildup within the individual conductors of the field coils. As the electrical insulation system of the field coil has excellent dielectric characteristics, it also is an excellent thermal insulator. The heat produced internal of the field coil due to the DC current passing through each conductor will continue to rise until, within a short period of time, the insulation system will de-grade and turn-to-turn shorting will occur with ultimate failure of the field coil. It is also interesting to note that the torque curves for BAYLOR Eddy Current Brakes all have a similar characteristic. The torque produced at very low drum shaft speeds (0-20 r.p.m.) is approximately the same for various excitation values. In other words, the brake torque produced at 15 r.p.m. is about the same, at full applied excitation, as the torque with 50% applied excitation. Therefore, the brake, utilized for “drill assist”, will perform at the low speed drum requirements of feed off at 1/2 of excitation as well as performance at full excitation. This can reduce the excitation to the larger capacity brakes from 21 kW to 7 kW with the reduction of thermal load of field coils.


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Operation of the brake at very low speeds during drill assist, with full excitation, will also contribute to excessive wear to the I.D. of the rotor and the O.D. of the magnets. At very low rotor speeds, with full excitation to the field coils, the magnetic attraction between magnets and rotor is greater than the collapse strength of the rotor material. Pull over will occur where the outer circumference of the rotor drum will pull down and contact the O.D. of the magnet. The resultant contact, at slow speed, will gall and gouge the surfaces of rotor and magnets. This mechanical contact will increase the air gap between the rotor I.D. and the magnet O.D. such that maximum torque of the brake will be reduced. In conclusion, to utilize the BAYLOR Eddy Current Brake in the drill assist mode requires specific attention to how much excitation is applied to the field coils. Continuous operation at full excitation can significantly shorten the life of the field coils and increase the air gap dimension such that reduced torque output will result.

NOTE! National Oilwell Varco manufactures several different types of Control Systems for use with the BAYLOR Eddy Current Brakes. Each Control System design incorporates a different method of supplying reduced voltage to the brake during drill assist operations. Consult your Brake Control System Manual to determine the proper operational technique for drill assist conditions.


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5 ACCESSORIES AND OPTIONS 5.1 General

In striving to satisfy the needs of all customers, National Oilwell Varco offers the following accessories and options.

5.1.1 Brake Controller Each Eddy Current Brake requires a brake controller which supplies voltage to the field coils. The brake controller is a variable DC voltage power supply which controls the amount of excitation delivered to the brake field coils as a function of the position of a driller’s control lever. A complete controller system consists of an isolated power transformer, a power control unit, and a driller’s control.

5.1.2 Special Brake Shafts Certain applications may require an optional special shaft on the brake. Double-ended shafts and special coupling features have been manufactured in the past. If the brake is required to operate in highly regulated areas such as the North Sea, then special shafts may be required to conform to low temperature requirements. One of these may fit your needs; if not, a new “special” can be designed to your specifications.

5.1.3 Brake Cooling Packages Each Eddy Current Brake needs a cooling system to remove the heat from the brake while the brake is being used. National Oilwell Varco builds brake water cooling systems to meet a variety of operational and regulatory requirements. In addition to cooling water for the BAYLOR Eddy Current Brake, extra capacity can be designed into the system for the main drawworks friction brake, top drives, electric drive motors, and other rig cooling requirements.

5.1.4 Cooling Water Alarm A cooling water alarm system is available to monitor flow and temperature of the coolant to the brake. This system warns the operator whenever cooling to the brake has been impaired. It can prevent the need for expensive repairs. This is also required to maintain the hazardous area certification on the Brake.


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5.1.5 Safety Monitoring Device A safety monitor system manufactured by National Oilwell Varco which signals the potentially dangerous loss of control of brake excitation is available for BAYLOR Brakes. If there is a need for further information about any of the aforementioned items, or if you have other special requirements, please contact National Oilwell Varco Sales Department or Service Department. Telephone Number in the U.S.A. (281) 240-6111 Fax Number (281) 274-0426 These Numbers are in operation 24 hours/day, 7 days/week

5.1.6 Parts and Service Parts and service are available from the factory: National Oilwell Varco 500 Industrial Blvd. Sugar Land, Texas 77478-2898 Phone: (281) 240-6111 Fax: (281) 274-0426

Factory Sales and Services personnel may also be directly contacted at the following e-mail address:

[email protected]

Factory Engineering personnel may also be directly contacted at the following e-mail address: [email protected] For a list of worldwide National Oilwell Varco locations and Service Centers go to www.nov.com and click “Contact Us”


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6 MAINTENANCE AND SERVICE

6.1 General An Inspection and Maintenance Schedule is provided at the end of this section.

6.1.1 Lubrication To maintain the lubricant volume, add approximately 2 ounces of grease to each bearing cavity each 24-hour period, or before each trip into the hole with pipe. There is a grease fitting for each of the two bearings, and each must be independently lubricated. (See Figure 6-1). The recommended grease is a NLGI No.2, water resistant (Lithium base) grease. A good grade of lithium base ball and roller bearing grease may be used. The bearings and seals will not be harmed by excess grease. It will simply enter the cooling water stream by momentarily lifting the seal lip to relieve pressure. Drawworks manufacturers and users may connect the grease inlet holes in the bearing caps to lubrication header blocks with tubing to facilitate lubrication from a remote point. This is satisfactory if the tubing is regularly inspected, and it is determined that the required amount of grease is actually reaching the bearing.

6.1.2 Breather Figure 6-1 shows a breather on the upper and / or lower exterior face of each magnet assembly. These breathers should be inspected periodically to insure that they are clean and have free access to air to minimize condensation and to prevent any accumulation of moisture in the coil cavity. They should be removed and cleaned with kerosene at least once a month.

CAUTION! The accumulation of moisture in the coil cavities caused by plugged breathers will result in early deterioration of the coils. These breathers should be cleaned as outlined above and must always be pointed downward for proper drain.


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Figure 6-1 Inboard Side

6.1.3 Air Gap If there is erosion/corrosion in the air gap between the rotor I.D. and the magnet O.D. due to the use of poor quality cooling water, this gap distance may gradually increase to a point where rated torque will be reduced. In making any field check of this air gap, it is necessary to allow for any pitting and for any scale build-up to determine the effective gap distance. Any scale present does not provide an effective magnetic path so it must be deducted from the gap distance measurement. This air gap should be checked monthly. The effective air gap is the average of all measurements taken. Measurements should be taken at each air gap inspection hole (both inboard and outboard) and recorded. Then rotate rotor assembly 90 degrees clockwise. Again record all readings. Rotate rotor assembly 90 degrees clockwise and record all readings. Rotate rotor 90 degrees clockwise and record readings. Finally, rotate rotor assembly 90 degrees clockwise. This will bring you back to original position and readings should agree with first position readings. Normally, a 50% increase in the air gap will produce a 70% decrease in rated torque. For original air gap dimensions see SECTION 2 of this manual.


GREASE FITTING(TYPICAL BOTH SIDES)

BREATHER / VENTTOP & BOTTOM OR MAY BE BOTTOM ONLY ON SOME MODELS (TYPICAL BOTH SIDES)

AIR GAPINSPECTION PORTS(TYPICAL BOTH SIDES)


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6.1.4 Overflow Outlet Located on both sides of the brake, just below the centerline of the shaft and to one side is a 90 degree elbow for water overflow. This elbow should always be pointing down and be clear of any obstructions. Should the cooling water level, internal of the brake, rise to the point that water could penetrate into the shaft bearings, this overflow outlet would allow the excess water to run off. If the drains are partially blocked or piped with too much resistance to flow, the water level in the brake could rise above the shaft height and get into the bearings. In normal operation, there should never be any water coming out of these overflows. These overflows should be checked daily.


6.1.5 Water Outlet Drain Located underneath the brake are one or two NPT threaded water outlet drains. The preferred method of installation is use of an open, free-flowing funnel on each water outlet as indicated in Section 3.1. Check these funnels daily for any obstructions. The water should flow freely back to the supply reservoir.


OVERFLOW(TYPICAL BOTH SIDES)

DRAINS


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6.1.6 Preparation of Brake for Storage If a brake is to be stacked, stored, or inactive for any long period, proper precautions should be taken to prevent the rotor assembly from becoming stuck to the magnet assemblies because of scale, rust, or salt growth. As an initial step, both bearing cavities should be pumped completely full of grease to protect the bearings during storage. If water of doubtful nature had been circulated in the brake before being inactivated, it should first be flushed with good clean water. The interior of the brake should then be sprayed with a fluid which will inhibit rust and/or salt growth. A solution of 50% clean water and 50% Nalcool is recommended. Spraying the interior of the brake can be accomplished by inserting a spray gun nozzle into each of the air gap inspection holes which are equally spaced in each of the end rings at the rotor diameter, as illustrated in Figure 6-2.

CAUTION! Do not remove coil breather / vents and introduce any fluid or substance into the coil cavity. This could attack the coil insulation and greatly reduce the life expectancy of the brake coils. See Figure 6-1. Plug all ports, including both water inlets and outlets as well as both overflows, and continue to spray until the rotor is well coated with the preserving fluid. Rotate the shaft once each month to distribute the bearing grease and preserving fluid internal coating. Spray more preserving fluid into the brake air gap inspection holes if necessary. Additionally, all exposed surfaces of the shaft should be coated with Rust-Ban 373 or an equivalent rust preventative.

6.1.7 Removing a Brake from Storage If a brake has been in storage, either after field use or as shipped from the plant, for more than three months, it will need a through inspection to make sure it has not been damaged in any way and all parts are properly in place. Failure to observe the following points can result in serious damage.

1. Remove all plugs and drain preservative fluid from the brake. 2. Rotate shaft and verify that the rotor turns freely. 3. Check the bearings and seals. 4. Replace seals if they have been in place for more than three years.


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5. Check and tighten all the bolts. 6. Grease the bearings and seals. 7. Remove clean magnet breathers and re-install. Replace if unable to clear

breather obstructions. If the brake has been in storage for approximately one year or more, megger the windings and check coil internal resistance before energizing the coils. Coil internal resistance values may be obtained from values listed in Section 3, Figure 3-15. Coil resistance to ground should not be less than 5 megohms (tested with 500 VDC megger and with all interconnecting wires disconnected from coil leads). Note: Coil leads will normally read low due to humidity or other moisture which can accumulate in the brake junction box. If readings are low enough to cause concern, use heat source such as hair blow drier to reduce moisture in leads. If this process does not help resistance readings, contact National Oilwell Varco as indicated in Section 5.1.6.

6.2 Maintenance and Repairs

6.2.1 Water System Problems If the cooling water supply fails while the BAYLOR Brake is being used, the heat generated in the rotor may build very quickly. The rotor will expand if the heat is not properly carried away. As a result, the braking action will be below normal due to this expansion and the consequent widening of the air gap between the rotor and magnet assemblies. If the rotor overheating continues beyond a short period of time, the rotor may suffer severe distortion and require replacement. The presence of any cooling water at all and the temperature of the water will affect the length of time before which irreversible damage occurs. It can be simply said that a sufficient flow of cool water will yield a long operating life for the Eddy Current Brake. If overheating of the rotor occurs, do not immediately turn on or increase water flow to the brake. First, let the rotor air-cool to 200 to 250 degrees F. The driller should then run the drawworks so that it turns the brake rotor at a uniform slow speed as the cooling water supply is slowly reintroduced into the brake. In this way the rotor will be cooled evenly, and any out-of-round condition or eccentricity of the rotor may possibly be avoided. However, once a rotor becomes severely overheated, permanent warping of the rotor cylinder is a distinct probability, even if the above steps are taken to cool it. On many rigs, the cooling water systems of the BAYLOR Brake and the drawworks mechanical friction brake are paralleled from a common source of adequate capacity for the two systems. Any failure of the cooling water supply then becomes noticeable promptly.


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NOTE! Do not connect the two brake cooling systems in series; that is, where the outlet from the friction brake system is fed to the inlet of the BAYLOR Brake System.

6.2.2 Bearing Removal and Replacement Initially, before attempting to remove the old bearing, remove any external components which have been added to the basic brake on the side from which the bearing is to be removed. This would include such items as the hub of the disengaging coupling, any components of a drill feed control drive, any water/air tube components, guards, brackets, etc., which may have been added by the drawworks manufacturer or user and which would interfere with the removal of the bearing involved. In addition, it is necessary to move the brake out of position on the drawworks if an inboard bearing is to be removed, but it is often possible to change an outboard bearing with the brake in place. Refer to the assembly drawing showing the cross section of the brake included in Section 8 of this manual for a better understanding. To remove a bearing, proceed as follows:

1. Remove the bearing cap: Loosen and remove the cap screws which fasten the bearing cap to the inner seal retainer.

2. Remove the retaining ring or locknut and lockwasher.

(Note: To remove the inboard bearing on a model 7838 brake, reverse the order of steps 1 and 2 above.)

3. Remove the center plate: Loosen and remove the cap screws which fasten the

center plate to the inner flange of the magnet assembly. Insert four pusher bolts into the threaded holes located at four equidistant positions about the outer edge of the center plate. Screw in these (4) pusher bolts, evenly, to remove the center plate.

NOTE!

Care should be taken to exert even pressure on the four pusher bolts. This will move the plate out evenly and avoid damage. The model 6032 brake center plate is cast iron. Be especially careful not to exert uneven pressure on the pusher bolts or the center plate may crack due to its brittle, cast iron, construction. The bearing is now clear and may be removed by conventional procedures.


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Figure 6-5 Bearing Assembly

Item No. Description 1 Rotor with Shaft Installed

2 Cylindrical Brake Housing

3 One of the two Magnets

4 End Ring

5 Center Plate with Jacking Screws

6 Inner Seal Retainer with all threads installed

7 Bearing Cap

8 Spherical Roller Bearing

9 Bearing Lock Nut and Lockwasher

10 Grease Seal

11 Machined areas requiring sealant when assembling

12 Sleeve, Seal


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The inner race of the bearings has an interference fit with the shaft, and hydraulic pulling equipment is usually required to remove the bearing when cold. If the bearing is to be discarded, it may be removed by other methods if proper care is taken to insure that the shaft is not damaged. The outer race may be cut off and the rollers removed. The inner race may then be heated and removed. Any time a bearing is replaced, it is recommended that the related seal be replaced as well as its seal sleeve in order to provide adequate protection for the new bearing. To remove a bearing, proceed as follows:

1. Install new seal sleeve on shaft. Note: never heat seal sleeves or bearings with heating torch. The point source of heat of a heating torch is in the range of 6000 degrees F. This high temperature small area contact with bearing tempered alloy steel will cause a micro structure change to occur which will greatly reduce the life expectancy of the bearing or seal sleeve. Heat bearings and seal sleeves in an oven or a container of clean oil. Heat range is 200-250 degrees F. After heating the seal sleeve and installing on the shaft, place a good quantity of clean bearing grease on the seal sleeve. Before installing the seal retainer with the seal over the seal sleeve, also hand-coat the seal with clean bearing grease. Install retainer and seal over seal sleeve. Insure that seal lip is turned in right direction with respect to bearing cavity. (If in doubt, look at assembly drawing in this manual. Some brake models have more than one seal.)

2. Heat and install new bearing. 3. Install the snap ring or bearing lockwasher and locknut.

Note: The tightness of the locknut should be checked after the bearing has cooled.

4. Prior to replacing the center plate, hand pack the bearing and seal with clean bearing grease. Screw guide pins into two of the tapped holes in the inner seal retainer to align the corresponding through holes in the center plate and bearing cap.

5. Thoroughly clean the machined mating surfaces between the inner seal retainer

and the center plate, and the inner flange of the magnet assembly. Apply a coating of Part No. 1885-11-0015, non-hardening, silicone sealant to these surfaces. No gasket is used here since the cavity is not pressured and a sealer serves quite satisfactorily.


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6. Install the center plate and pull it firmly into position by tightening the cap screws

which hold it to the inner flange of the magnet assembly. Care should be taken to insure that the center plate is drawn up straight and evenly. The rotor shaft should be supported while the center plate is replaced. A “cheater pipe” may be used with a hoist to support it.

7. Install the bearing cap and position the cap screws which hold the bearing cap in

place. Tighten these cap screws firmly. Remove the (2) guide pins and replace with the remaining (2) cap screws and tighten firmly.

NOTE!

Care should be taken to insure that the pilot diameters of the inner seal retainer and the bearing cap have entered the bore of the center plate straight and both of these parts are straight and firmly affixed to the center plate. Prior to replacing external parts, remove air gap inspection plugs (Figure 6-2) and check the air gap at all three inspection holes. Rotate rotor 90 degrees and take three more readings (this is to check concentricity of rotor). Compare air gap readings. If center plate O.D. and/or magnet pilot diameter is worn, gap at vertical top of brake will be less than (2) gap readings at lower quadrant of brake. If difference is greater than 0.010" (0.25 mm), then it will be necessary to shim between O.D. of center plate and I.D. of magnet assembly. This can be accomplished by loosening the cap screws which retain the center plate to the magnet by two full turns. Using the “cheater pipe” mentioned in 6.2.2.6 lift weight of shaft and rotor assembly such that shim may be inserted between center plate O.D. and magnet pilot diameter (at bottom vertical center line). Tighten cap screws which retain center plate to magnet assembly. Remove “cheater pipe”. Recheck air gaps as outlined previously. Shimming should correct concentricity between magnet O.D. and rotor I.D. and insure equal magnet attraction and reduce rotor pull over. 8. Add sufficient grease to the bearing cavity with a grease gun to insure that the

cavity is at least two-thirds filled. The external parts which may have been removed can be replaced after it is determined that the shaft and rotor assembly rotates freely. If it was necessary to move the brake from its position on the drawworks, it should be reinstalled and aligned with the same care as when initially installed.


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6.3 Electrical Problems and Troubleshooting All electrical problems must be in one or more of these components.

1. Interconnect cables and wiring. 2. Brake (coils, lead wires, or terminations). 3. Control System (Refer to Control System Manual).

Experience has shown that about 90% of all problems can be traced to interconnect cables and wiring, therefore it is suggested that these be checked first. With power removed, use a 500 VDC megger to check for grounds. Wiring and interconnect cables should be a minimum 1 megohm to ground. Individual magnet coils should be a minimum of 5 megohms to ground. An ohmmeter should be used to check the coils for open or short circuits. Coil resistance is listed in the specifications summary in Section 2. There is no difference in the inboard and outboard magnets. The leads are numbered for convenience in wiring and to assist in proper coil lead connection to insure proper coil polarity. Outboard magnet leads are F1, F2, F3, and F4. Inboard magnet leads are F5, F6, F7, and F8. If there is a need to convert an inboard magnet to outboard or vice-a-versa the following table should be used: Leads F1 = F8, F3 = F6 F2 = F7, F4 = F5 Therefore, the inboard and outboard magnets are mechanically and electrically interchangeable. Refer to Figure 3-3. Most problems can be solved with the preceding information. Additional checks which may be useful are included in the voltage and resistance checklist in the BAYLOR Brake Control System Manual.


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6.4 Mechanical Problems and Troubleshooting

All mechanical problems eventually lead to noticeable loss of braking. There are four generalcategories of mechanical problems which result in braking loss. These categories and theirone or more causes are listed in the following pages. Troubleshooting Chart

Symptom Trouble Shooting Hint Rotor is dragging on the magnet or the bearings are noisy Water coming out of the overflow piping. Gradual loss of torque capacity due to increase of magnet / rotor gap

1. The brake shaft may be misaligned with the drawworks or automatic feed shaft. If this is the case, align the shafts correctly. Check for damage to the bearings before tripping.

2. The bearings may be worn because of poor grease maintenance. If this is the problem, replace the bearings and maintain the proper bearing grease service.

An incorrect water level may have been maintained inside the brake housing causing an overflow. This may result in seal and bearing failure. 1. If the output water flow rate is excessive, then limit the flow

rate as shown in the brake specifications.(Section 2) 2. If the water outlet is restricted, check for any restrictions.

NOTE: Do not reduce the pipe size of water outlet (s). 3. If the outlet water back pressure is excessive, the water

tank is not sufficiently below the brake water outlet level or a long return line does not have a sufficient increase in pipe diameter to allow the flow to pass. NOTE: Allowing the water to drain into a funnel not mechanically connected to the brake prevents backpressure problems.

The surface of the magnets and rotor may have an accumulated layer of rust and scale due to a cooling water system with a high salinity content or low pH factor. This build-up will eventually decrease the brake torque capacity. 1. If the brake is cooled with saltwater, the life expectancy of

the brake may be as short as 3 years. It is recommended not to use saltwater for cooling, but to maintain a clean fresh water system.

2. If the brake cooling water is shared with other remote machines, freshwater should be added to prevent acquiring too much acid content. Also add corrosion resistant chemical as recommended by a water treatment specialist.

3. If iron oxide flakes off the magnet and rotor, the air gap is increased. This decreases the brake torque capacity. The


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Air Gap measurement at the 12 o’ clock position is consistently larger than the air gap measurements at the other two locations

Loss of torque capacity due to overheating the brake.

No cooling water to brake – cooling on overheated rotor.

Torque not at full capacity due to incorrect coil polarity Torque reduced due to loss of one or more coils

air gap should be as listed in the specifications. Remember to remove rust and scale before measuring the air gap. NOTE: Life of the brake with proper cooling system care can be as long as 15 years.

The bearing on that side of the brake is wearing. The bearing internal clearance is increasing and the rotor is sitting lower in the brake assembly. This condition should be monitored. In extreme cases the bearing condition should be checked or the bearing replaced. See Section 3.2 for more details.

Overheating the rotor will increase the magnet / rotor gap. This decreases the brake output torque. Overheating the magnet will increase the coil resistance. This decreases the coil current, and this reduces magnetic flux. This will also reduce the torque. 1. If the water flow rate is below the recommended level, then

raise the input GPM to the specified level. 2. If the amount of cooling water is not sufficient to maintain

the system at or below 165°F maximum brake discharge temperature, then the cooling system should be inspected. NOTE: In extremely hot working areas, additional volume may be required.

3. If no water is applied to a brake that is full on, damage to the coils or rotor will occur.

If this happens, the rotor will be overheated in a matter of minutes. If cold water is turned on an overheated rotor the rotor will distort and may lock up on the magnets. To cool an overheated rotor: a) Let the rotor air cool to 200 to 250°F. b) Then turn the water on while turning the rotor slowly. This

procedure may salvage the rotor. If coils are connected incorrectly, refer to Section 3 of this manual. Check for coil polarity and connections. 1. If an over-voltage is applied to a coil, see electrical

troubleshooting in brake controller manual. 2. The coils may have an insulation failure due to

condensation in the coil cavity. To prevent condensation from becoming a problem, remove the coil cavity drain plugs and/ or breather plugs and clean them periodically.


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6.5 Inspection and Maintenance Schedule

NOTE! Below is a list of daily, weekly, monthly, and quarterly maintenance checks. Many clients are using maintenance systems based on usage instead of timed schedules. The use of equivalent usage (eg. Ton - Miles) is acceptable as long as it can be demonstrated that maintenance done in these type maintenance systems is at least equivalent to the below schedule.

6.5.1 Daily Inspection

6.5.1.1 Cooling Water Flow Rate Inspection Observe brake water overflow vent while lowering drill string into hole. If constant flow is observed coming from vent, slowly begin to reduce rate until constant flow is no longer observed coming out of vent. If cutting back on flow rate results in too high temperature on brake water at outlet (165 degrees Fahrenheit), check on brake discharge water line to see if it has become restricted. Flow rates from brake should be unrestricted.

6.5.1.2 Lubrication Grease each brake bearing with 2 ounces of lithium base ball and roller bearing grease (See page 6-1 paragraph 6.1.1) Each brake has two grease fittings, one on inboard bearing cap and one on outboard bearing cap.

6.5.1.3 Electrical Wiring Inspection Inspect control system wiring with visual inspection for cut wires, snags, or other accidental damage. Turn off main power, unplug any in-line disconnects, and inspect for oxidation, moisture, and signs of arcing. Clean as required and return to service.


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6.5.2 Weekly Inspection

6.5.2.1 DC Voltage Check Check DC voltage to brake under full load condition (electrical full load, Driller’s Control in FULL ON position). See Section 2, Summary of Specifications.

6.5.3 Monthly Inspection

6.5.3.1 Drain/Breather Inspection Remove brake magnet coil cavity drain and brake junction box drain from fitting. Clean with kerosene. This drain / breather should be open for passage of air or liquid. Replace drain/ breather into fitting after inspection.

IMPORTANT! To protect the full life of the coils the condensation that may form in coil cavities must be drained. To assure free flow, these drain / breathers must be inspected every month and cleaned if necessary.

6.5.3.2 Air Gap Inspection

NOTE! Disengage brake shaft from drum shaft by using disconnect clutch before making any air gap measurements. Inspect and record brake air gap. Remove 1 ¼ inch N.P.T. pipe plugs from end rings. Using feeler gauges which are a minimum of 12 inches long, insert gauges into the air gap between the brake magnet and the rotor.

NOTE! When checking Eddy Current Brake air gaps, the correct measurement is the thickest stack of feelers that can be inserted completely into the air gap by hand without getting stuck. There will be drag on the feeler gauges. Contrary to most feeler gauge measurements, this is not a measurement taken with only light drag on the feeler gauge.


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Air gap measurements should be taken as far in on magnet as feeler gauge length will permit. Try to approximate the thickness of any scale, (Rust and Calcium) if cleaning is not possible. This figure must be added to basic feeler gauge reading. If rotor is pitted, an additional pit estimate must be added to air gap measurement. Remember, at least two sets of measurements 90° apart are required to get meaningful results.

6.5.3.3 Disconnect Clutch Inspection While the brake shaft is coupled to the drum shaft and while the brake is being slowly rotated (preferable under loaded conditions) observe the brake disconnect clutch. Verify that if fully engaged the clutch hub on the brake shaft does not move with respect to the shaft. Check that the clutch is being properly lubricated. (Refer to drawworks manufacturer for lubrication specifications.)

6.5.4 Quarterly Inspection

6.5.4.1 Voltage and Resistance Check Check brake coil voltages at brake junction box as described in voltage check. After voltage check is complete (see 6.5.2), turn off main supply voltage to brake control system. Disconnect each coil from the electrical control system by removing coil leads from their installed position in brake junction box. The coils should read 5 megohms or higher to ground when checked with a 500 Volt DC megger electrical insulation tester.

NOTE! Remove only one set of leads at a time, for example, F1 and F2. Mark their position carefully; check the coil and then return the leads to their exact same position. Failure to return all leads to their correct position could result in incorrect polarity which would seriously decrease the braking effort. Readings for the individual coils should be as listed under coil resistance in summary of specifications. See Section 2.


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Cut here and place near Maintenance area Cut here and place near Maintenance area

BAYLOR Eddy Current Brake Maintenance Schedule

DAILY SCHEDULE 1. INSPECT COOLING SYSTEM.

2. LUBRICATE BEARINGS.

3. INSPECT ELECTRICAL

WEEKLY SCHEDULE 1. DC VOLTAGE CHECK

MONTHLY SCHEDULE 1. DRAIN / BREATHER INSPECTION

2. AIR GAP INSPECTION

3. DISCONNECT CLUTCH INSPECTION (IF APPLICABLE)

QUARTERLY SCHEDULE 1. VOLTAGE AND RESISTANCE CHECK


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6.6 Evaluating Conditions of Brakes in the Field Baylor Eddy Current Brakes are complex electro-mechanical pieces of equipment. They are generally located in potentially hazardous areas, and they are usually considered critical safety equipment. As such, no single check is ever sufficient to accept or reject the condition of one of these brakes in the field.

NOTE! The following checks and testing is only based on determining the condition / performance of the Eddy Current Brake. It is assumed that the brake has been properly installed and commissioned as indicated in Section 3 of this manual. These checks are intended for brakes that are on a properly executed maintenance program. It is assumed the prescribed daily, weekly, monthly and quarterly maintenance as indicated in 6.5 of this manual is being done. The following data should also be taken as reference or baseline information on new brakes to have a starting point to compare future evaluation against.

• Remove breathers and verify they are clean and free of debris or obstructions as indicated in Section 6.1.2 of this manual.

• Check air gaps as indicated in Section 6.1.3. of this manual.

• Verify the internal rotor and magnet surfaces are clean and freshly primed.

• Check radial bearing clearance as indicated in Section 3.2 of this manual.

• Meggar brake coils as indicated in Section 6.3 of this manual

• Check brake coil resistance and compare to values indicated in Figure 3-15 of this manual.

• Verify the brake is wired as indicated in Figure 3-3 of this manual.


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It is expected that all these checks will result in expected results and the brake is acceptable for installation. If these checks are not satisfactory as indicated in the referenced sections contact National Oilwell Varco. After the brake is installed in its cradle the following check should be performed:

• Verify Brake Alignment as indicated in Section 3.3 of this manual. It is the responsibility of the operator to align the brake to the drawworks if the brake is provided separately. If the brake is provided as part of a drawworks skid it is aligned at the factory. It is the responsibility of the party commissioning the drawworks to verify this alignment during commissioning. These checks must be performed with the brake connected and ready for use.

• Verify the brake is wired properly as indicated in the applicable Brake Control Manual.

• Verify the rated coolant flow as indicated in Section 2 of this manual is being supplied to the brake.

• Verify the coolant meets the water quality standards in Section 3.5 of this manual.

• Verify there is zero volts when the Driller’s Control is in the “off” position.

• Verify the rated voltage is applied to the brake as indicated in Section 2 when the Driller’s Control is in the “FULL ON” position.

• Verify the rated current is supplied to the brake when the brake coils are “cold” (68ºF or 20ºC).

• Verify the existence and functionality of Drill Assist and/or manual Power Selection Switch on the Brake Control System.

All results from the above checks should be to the specification indicated in the referenced sections of this manual. If problems are found in the Closed Loop Brake Water Cooling System or Brake Control, consult those manuals for remedial actions. If all the above checks indicate a set of normal conditions, then the brake can be assumed fit for its rated duty cycle. If discrepancies are found then they must be immediately corrected if possible.


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6.6.1 Evaluating Brake Performance of Brake Out of Specification It is impossible to remediate the following items:

• Increased airgap and corrosion of internal surfaces of the brake

• Damaged coils indicated by low resistance to ground or out of spec. coil resistances

• Damaged bearings

All of these items will deteriorate over the brakes life cycle. The rate of deterioration is solely a function of preventive maintenance. It is absolutely essential to understand that just because a brake is out of the specification range for a new brake, does not indicate that it will not function properly in a given application. In order to maximize the life cycle of the brake it is important to understand the principle causes for the above conditions. The biggest contributor to loss of airgap and damage to internal surfaces is water treatment. It should be noted that an airgap measurement that is below the specified range after the brake has been in the field usually indicates rust or scale build up. Both of these are detrimental.

NOTE! There is no way to remediate a bad air gap or bad internal surfaces in the field. A factory repair is required. The best way to test the performance of an Eddy Current Brake when the air gaps are out of tolerance is by conducting Time / Travel Testing as indicated in the National Oilwell Varco Technical Bulletin #201. These procedures will indicate actual brake performance at one point on the performance curve. The use of the brake in any application must be evaluated based on this testing IN ADDITION TO assessing the coil and bearing condition and conducting all the checks indicated in above Section 6.6. Damaged coils are indicated by a low resistance to ground or out of spec coil resistance. The low resistance to ground is the direct result of improper maintenance on the brakes breathers. When the breathers are not maintained, condensate will accumulate in the coil cavity. Over time the water breaks down the coils insulation system and a short to ground will eventually occur. Out of spec coil resistances are generally caused by turn to turn shorts. Turn to turn shorts are the result of overheating of the coil caused by improper use of Drill Assist or power selector switch features.


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There is no way to remediate a bad coil. A replacement brake will eventually be required. A brake may run at reduced capacity on three coils. Consult the Brake Control manual for details. There must be allowances in the reduced capacity operation of the brake for the event of another coil failure. It should be noted that if a single coil fails due to internal shorting it is due to overheating as indicated above. Since all the coils in a single brake are subjected to the same amount of power, one failed and overheated coil usually indicates other coil failures are eminent. If a coil failed due to a short to ground, it is probably due to poor breather maintenance as indicated above. In brakes with two coils per magnet, both coil cavities are drained through a single breather, so it is reasonable to assume the failure of the second coil in a magnet some time after the failure of the first coil.


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7 PARTS AND SUPPLIES

7.1 General The recommended spare parts and supplies for the 7838 BAYLOR Brake are provided in the following table:

Recommended Spare Parts BAYLOR Eddy Current Brake

Qty. Part No. Description 1 1030-20-0003 Bearing, Inboard 1 1030-20-0004 Bearing, Outboard 2 1555-10-0021 Seal, Inboard 1 1555-10-0005 Seal, Outboard 2 07626 Sleeve, Seal, Inboard 1 07370 Sleeve, Seal, Outboard 1 1420-20-0044 Locknut, Inboard 1 1420-20-0036 Locknut, Outboard 1 1690-20-0044 Lockwasher, Inboard 1 1690-20-0036 Lockwasher, Outboard 5 1075-10-0003 Breather/Drain 4 06614 Housing, Breather


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8 DRAWINGS – 7838 BRAKE

8.1 Drawing List

31591 Assembly – Model 7838 Eddy Current Brake B/M31591 Bill of Material – 7838 Eddy Current Brake Assembly 56168 Outline and Mounting – 7838 Eddy Current Brake


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