Inlet and Bypass Valve Positioners - Ingersoll Rand …manualarchive.ingersollrandproducts.com/manuals/manuals/...INLET AND BYPASS VALVE POSITIONERS TP0011B 1992, 1999 Ingersoll-Rand

INGERSOLL-RAND�

AIR COMPRESSORS

CENTAC�

Inlet and Bypass Valve Positioners

INLET AND BYPASS VALVE POSITIONERS

TP0011B� 1992, 1999 Ingersoll-Rand Company

Date of issue: 22 April, 1999 Supersedes: 24-Feb-93, 8-Feb-94

Copyright Notice

Copyright 1992, 1999 Ingersoll-Rand CompanyTHIS CONTENTS OF THIS MANUAL ARE PROVIDED “AS IS” AND WITHOUT ANY IMPLIEDWARRANTIES WHATSOEVER.

Ingersoll-Rand air compressors are not designed, intended, or approved for breathing airapplications. Ingersoll-Rand does not approve specialized equipment for breathing airapplications and assumes no responsibility or liability for compressors used for breathing airservice.

Disclaimer

The information contained in this manual is general in nature and is meant to be used forwidespread application in training on Centac products. The Operation Manual, diagrams,blueprints and other information developed for individual Centac machines must be consultedfor specific or detailed information, specifications, and data applicable to specific machines. Theapplication of any information contained in this manual carries no implied or expressedwarranties. The user assumes the entire risk of usage.

Trademark Acknowledgments

Centac is a trademark of Ingersoll-Rand CompanyBELLOFRAM Type 80 is a trademark of Rexnard Company

BRAY Series 64 SR/CCK is a trademark of Bray International, Inc.




Table of ContentsIntroduction.............................................................................................................................. 1

Part I: The BELLOFRAM Positioner....................................................................................... 1

I/P, positioner, actuator and valve relationship ................................................................. 1

BELLOFRAM TYPE 80 Principles of Operation ..................................................................... 2

Feedback Spring................................................................................................................... 3

Zero and Span Adjustment .................................................................................................. 4

BELLOFRAM Positioner Stroking Procedure..................................................................... 5

BELLOFRAM Positioner Output Pressure Balance Setting Procedure............................ 6

Maintenance of the BELLOFRAM Positioner...................................................................... 6

Part II: The BRAY Positioner .................................................................................................. 7

I/P, Positioner, Actuator and Valve Relationship ............................................................... 7

BRAY SERIES 64, SR/CCK Principle of Operation............................................................. 8

Zero and Span Adjustment .................................................................................................10

Maintenance of the BRAY Positioner.................................................................................12

Part III: Actuators ...................................................................................................................13

Bray Actuator.......................................................................................................................13

Vane Type Rotary Actuator .................................................................................................14

INLET AND BYPASS VALVE POSITIONERS 1



IntroductionPrior to the introduction of the Ingersoll-Rand standard Inlet and Bypass valve assembly,the BELLOFRAM Type 80 Universal Valve positioner and the BRAY series 64 SR/CCKtype positioner were used extensively in the Centac inlet and bypass valve control system.The purpose of this manual is to provide a technical information reference source forservice personnel who may encounter the BELLOFRAM or BRAY Positioners whenservicing Centacs.Information in this manual has been taken from the BELLOFRAM Installation instructiondated 12/84 and provided by Rexnord Company under form R215-19. Informationconcerning the BRAY positioner is taken from the BRAY International Inc., BRAY controlaccessory modules, Series 64 for rotary actuator's publication. Information and datarelative to how these devices are used in the Centac control system are provided in thismanual.

Part I: The BELLOFRAM PositionerI/P, positioner, actuator and valve relationship

The purpose of the valvepositioner is to receive a controlsignal, amplify it, and send apower air-operating signal to avalve actuator. The actuator is thedevice that physically drives thecontrol valve open or closed. Thecontrol signal provided to thepositioner is a small air signal. Thiscontrol signal is, normally, avariable 3 to 15 PSIG. This controlsignal is varied by a milliamp (mA)to air pressure transducer (I/P).The transducer receives its mAsignal from the MP3 or otherprocess system controller.Figure 1 illustrates the relationshipbetween the I/P, the BELLOFRAMpositioner, the actuator, and thevalve being controlled. Theactuator illustrated in Figure 1 is aBRAY device. Centac has usedBRAY actuators in combinationwith BELLOFRAM and BRAYpositioners. Other type actuatorsare also used.

Butterfly valve

Transducer (I/P)

Actuator

Air in

Air in

BELLOFRAMpositioner

Figure 1. Valve control with BELLOFRAM positioner


CST-TP0011B� 1992, 1999 Ingersoll-Rand CompanyDate of issue: 22 April, 1999 Supersedes: 24-Feb-93, 8-Feb-94

2

Normal supply air pressure to the BELLOFRAM positioner is 80 to 100 PSIG. The supplyair by specification is instrument grade air. At pressures less than 80 PSIG there may beinsufficient power available to move the valves being controlled.

BELLOFRAM TYPE 80 Principles of OperationThe Type 80 double acting positioner controls the position of the valve actuator andthereby the valve by providing air pressure in the correct direction to move the valve. UseFigure 2 to follow the description of operation. A chain and stem connector arm are linkedto a feedback (Range) spring. The feedback spring system causes the valve motion to stopat a specific control signal dictated position. A force balance condition is initially establishedat set-up between the feedback spring and the force developed by the signal pistonassembly for the range of instrument signal pressures. In the case of Centac, signalpressures between 3 and 15 PSIG are nominally used. Any change in this force balancecondition either because of a change in control signal pressure or a change in valve stemposition caused by external forces, immediately produces a change in the clearancebetween the signal piston and the pilot nozzle.

Figure 2. Functional cutaway diagram of BELLOFRAM Type 80 positioner

Range spring

Zero adjustment

Stem connector arm

Output chamber No. 2 Output chamber No. 1

Servo diaphram No. 2Servo chamber No. 2

Signal piston chamberPilot nozzle

Servo chamber No. 1Servo diaphram No. 1

Restriction

Output valve No. 1Output valve No. 2

OUTPUT No. 2 OUTPUT No. 1

Locking seat

Signal pressure

Output pressure 1Output pressure

Range adjustment spring seat

Signal pressureBalance pressureadjusting screw

Instrument airsupply


CST-TP0011B� 1992, 1999 Ingersoll-Rand Company


3

Air from output chamber 1 is fed to the servo chamber through a restriction with the pilotnozzle serving to control the servo chamber exhaust rate. Any change in clearancebetween the nozzle and signal piston produces a corresponding change in servo chamberpressure.The servo diaphragms 1 and 2 are designed to produce 1:1 inverse operation of outputvalves 1 and 2. An increase in servo pressure opens valve 1 and closes valve 2 andexhausts output chamber 2. A decrease in servo pressure closes valve 1, exhausts outputchamber 1, and opens valve 2.The combined and simultaneous action of increasing pressure from valve 1 and decreasingpressure from valve 2, entering the actuator from opposite ends causes a "push-pull" effectand moves the actuator shaft, stem connector arm and feedback spring to the new positionthat satisfies the previously described force balance condition.The working or balance pressure in the actuator can be adjusted by means of the balancepressure adjustment screw. Turning the screw clockwise increases the spring force actingto open valve 2. This produces an increase in output pressure of valve 2 that isimmediately balanced by an increase in output pressure of valve 1 in satisfying the originalforce balance condition. A decrease in balance pressure is accommodated by turning theadjustment screw counterclockwise.

Feedback SpringThe feedback (Range) spring adjustment disks are named springseats. These seats have a threaded center hole. The zeroadjustment is screwed into the center hole after the seats arepositioned on the spring. To assemble the range spring to thepositioner, first assemble the two spring seats to the spring byinserting the spring wire (end opposite the hook) through the hole

in the top of thedisk and thenscrew the seat onto the spring.Figure 3 shows the top (closed) side ofthe seat. This top side is where the springwire is inserted. The closed side of thespring seat should face the hook end ofthe spring. There are two spring seats.The first spring seat should be screwedon approximately 3 turns, the second isscrewed on 2 turns. See Figure 4.After the spring seats are installed, attachthe feedback spring hook to the positionerclevis. The next step is to screw the zeroadjustment screw through both seats.

The chain is attached to the valve stemcollar as illustrated in Figure 5.

Figure 4. Feedback spring and attachments

Figure 3. Spring seat



4

To achieve proper operation, the positioner output from the feedback spring side of thepositioner (Output chamber 1) must be attached to the actuator in such a way that, whenoutput pressure from chamber 1 increases, the valve stem will move in the direction thatstretches the feedback spring.

Zero and Span AdjustmentAdjustment of the positioner to the stroke zero or valvestem starting position, for the corresponding desiredminimum input signal, is made by means of the zeroadjustment screw. The zero stroke position of the inletvalve is just fully closed when a 3 PSIG signal is fed tothe positioner from the I/P. The zero stroke position ofthe bypass valve is just fully open with a 3 PSIGsignal. In either case a 4 mA signal is being fed to theI/P at the zero stroke position.Adjustment of the positioner for signal span or fullvalve stem travel for the corresponding desiredmaximum input signal is made by changing the springrate of the feedback spring. This rate change isaccomplished by changing the number of spring coilsbetween the spring seat and the positioner. The fulltravel position of the inlet valve is just fully open whena 15 PSIG signal is sent to the positioner from the I/P.The full travel position of the bypass valve is just fullclosed when a 15 PSIG signal is fed to the positioner.Regardless of which compressor control valve is beingstroked, the first step in the stroke adjustmentprocedure is to properly stroke the I/P.

0 160

80

TYPE 80

0 160

80

15

0 30510 20

25

Valve stem collar

Zero adjust screw

Positioner clevis

Spring attachment

Figure 5. Attachment of spring

Valve Stroke Specifications

MP3 output

I/P input signal4 mA 20 mA

I/P output signal

Positioner input3 PSIG 15 PSIG

Inlet valve position Just full CLOSED Just full OPEN

Bypass valve position Just full OPEN Just full CLOSED




5

NOTE

The Centac standard electro-pneumatic control system uses a common pressurecontrol signal from a single pneumatic controller for both inlet and bypass valves. Theprocedure for stroking the positioner is the same except that there are differentvalues for the zero and full travel (span) pressures. The nominal signal strokingvalues are:Inlet Valve:

� OPEN = 15 PSIG� CLOSED = 7 PSIG

Bypass Valve:� CLOSED = *10 PSIG� OPEN = *3 PSIG

* These values will vary with ambient conditions.

BELLOFRAM Positioner Stroking Procedure 1. Check the inlet valve and assure it is fully in the mechanically closed position. The

bypass valve is checked in the fully open position. Check the spring seats and assurethey are separated (unlocked) by approximately 1 spring wire turn. Use of the I/P outputis recommended for setting the signal pressure to assure compatibility between the mAcontrol signal and resultant valve motion.

2. With full supply pressure (instrument air) to the positioner input (80 to 100 PSIG), setthe input signal pressure at the low end of the span (3 PSIG).

3. Adjust the zero adjusting screw until the desired valve stem position is obtained. I.e.Inlet = Closed, Bypass = Open.

4. Set the input signal pressure to the maximum span pressure; 15 PSIG.

5. Hold the feedback spring with one hand and with the other hand grasp and turn bothspring seats together until the desired valve stem position is reached. i.e. Inlet = Open,Bypass = Closed.

6. Recheck and adjust the low end span as per step 1 and 2.

7. Repeat steps 3 through 5 until the desired stroke versus signal is obtained. Span iscorrect when a very light touch on the feedback spring in either the zero or full strokesignal condition causes the valve to start to respond. Response is detected by valvemotion and air exhaust sound from the positioner.

8. Lock the spring seats in position by holding the spring seat nearest to the positionerand turning the other spring seat clockwise until both seats are locked together.



6

BELLOFRAM Positioner Output Pressure Balance SettingProcedure

1. Ensure no external forces are being exerted on the valve or valve stem.

2. With full supply pressure (instrument air) to the positioner input (80 to 100 PSIG), setthe input signal pressure at the mid point of the span (9 PSIG, 12 mA to I/P).

3. Adjust the balance adjusting screw so that the output pressures are approximatelyequal and the output pressure is 50% to 60% of the supply pressure. As an example,the balance pressure with 80 PSIG supply should be between 40 and 48 PSIG.Balance pressure at 100 PSIG should be between 50 and 60 PSIG. For properoperation, a minimum of 10 psi differential should be allowed between supply pressureand the balance pressure setting.

Maintenance of the BELLOFRAM PositionerMaintenance other than calibration is required if the positioner is supplied withcontaminated instrument air. Routine maintenance consists of cleaning the two installed 40micron filters. Access to these filters is gained through the chrome plated hex bolts on theback side of the mounting plate. Remove filters and clean or replace as required by on siteconditions. Contaminated supply air can damage diaphragms and clog internal passages.Corrective maintenance (overhaul or replacement) is required in the event of damage orcontamination. Ruptured diaphragms are indicated by an excess amount of air exiting fromthe exhaust ports.




7

Part II: The BRAY PositionerI/P, Positioner, Actuator and Valve Relationship

Figure 6 illustrates the relationship between the I/P, BRAY positioner, and actuator for theinlet valve. The configuration for the bypass valve is the same except for cam and powerhose connection. The initial valve position control signal originates from the MP3Microcontroller or other process controller. This signal is in the control span of 4 to 20 mA.The mA signal activates the I/P where the mA signal is converted to an air signal pressure.The air signal pressure provides the control feed to the valve positioner. The process ofvalve control when using the BRAY positioner is the same as when the BELLOFRAMpositioner is used.

Figure 6. Inlet Valve control configuration (BRAY)

Normal supply air pressure to the BRAY positioner is 80 to 100 PSIG (max. 150 PSIG).Supply air by specification is instrument grade. At pressures less than 80 PSIG there maybe insufficient power available to move the valve actuator under some conditions.



8

BRAY SERIES 64, SR/CCK Principle of OperationUse Figure 7 in following the description of the principle of operation of the BRAYpositioner. The SR/CCK positioner consists of a diaphragm (1), that is activated by the airsignal pressure from the I/P, a feedback spring (2), that acts in opposition to the signalpressure, a double action spool valve (3), a stem (4), that connects the spool valve to thediaphragm and cam (7), that moves with the controlled valve to provide valve positionfeedback. An increase in air signal pressure on the diaphragm (1) causes a movement ofthe spool valve (3), the spool valve motion allows supply air to pressurize output (F) andexhaust output (E). The output and exhaust functions power the controlled valve motion.Valve shaft rotation is transmitted to the feedback spring (2) through the cam (7), camroller (6), and the lever (5). The force of the feedback spring (2) balances the signalpressure on the diaphragm(1).

When the feedback spring and the signal forces acting on the diaphragm are in thebalanced state the spool valve is in the neutral position. The controlled valve will remain ina stationary position as long as the feedback spring's force is equal to the signal air forceon the diaphragm.

6

8

7

9

Signal from I/P

Supply pressure(Instrument air)

Exhaust Exhaust

Output to actuator (F)

Output to actuator (E)

Cam

Lever

Cam roller

Pointer

Zero adjustment ring nut

Range adjustment ring nut

Feedback spring

Diaphragm

Stem

Spool valve Spring

Spring cap

Spool valve cap

1

2

3

45

R

Figure 7. Representative functional cutaway diagram of the BRAY SR/CCK positioner




9

A decrease in signal air pressure upsets the balance and the feedback spring causes thespool valve to move in the opposite direction. Output (F) will exhaust and output (E) willpressurize. The controlled valve will move, the cam will move in response to the valvemotion and the feedback spring will balance the signal air pressure. Under balancedconditions, the spool valve returns to the neutral position.The cam has three lobes. Each lobe is designed to serve a specific signal pressure andlinear range. One side of the cam is used for a direct action valve and the other for areverse action valve. The inlet valve is direct acting since it opens as the signal rises. Thebypass is a reverse acting valve since it closes as the signal rises.The cam is marked D for direct use and R for reverse use. The lobes are also lettered withtheir linearity and signal pressures. The lobe that is used for both inlet and bypass is theone marked 0 - 90�, 3 - 15 psi. The inlet valve uses the side of the cam marked D and thebypass uses the side marked R. Figure 8 illustrates how the cam is configured for inlet orbypass valve use.

Proper connection of the power air hoses to the actuator is required for correct valverotation. In the case of the inlet valve (direct acting), view the positioner from the side, camfacing up with the plastic cover to the left. The power outlet fitting in the positioner body isthe right hand fitting and the left fitting is for the gauge. The power hose goes from thepower outlet to the left inlet connection on the actuator. Figure 6 illustrates the inlet valveconnections.In the case of the bypass valve, the power connection from the positioner is made to theright inlet connection on the actuator.

D

Bypass valve cam configurationInlet valve cam configuration

R

Cam shown in inlet valve closed position Cam shown in Bypass valve open position

Valve rotationValve rotationopen Close 3-15 psi, 0 - 90

3-15 psi, 0 - 90

Figure 8. Positioning of cam for Inlet or Bypass valve configuration



10

Zero and Span AdjustmentThe zero and span adjustments are made in a manner similar to the BELLOFRAM. Thecoils of the feedback spring are tensioned to achieve zero and the number of active coils isadjusted to achieve the range. An Allen wrench is provided to make the zero and spanadjustments. It is stored on clips within the covered area. The zero adjustment nut isenclosed by the spring. The Allen wrench is positioned between spring coils and inserted ina hole provided in the nut to turn the zero adjustment ring. The range adjustment nutclamps to the spring with an Allen screw in the handle of the range adjustment nut. Therange adjustment nut is made out of a plastic material. The tab on the range adjusting nutwhere the Allen screw is placed can easily be broken off if excessive tightening force isapplied to the screw. Do not attempt to take an extra tightening turn on this screw becausethe tab will crack or break away.Figure 9 illustrates the major components used in setting the zero and span of the BRAYpositioner.

Figure 9. Zero and span adjustments

D

Zero adjust ring nut

Wrench attachment holes

Allen wrench

Range adjusting ring

Allen set screw

Pointer Pointer hold down screw

Active coils




11

Inlet Valve Calibration1. The inlet valve must be in the fully closed position and the cam positioned with the D side

up, on the 3 - 15 PSIG, 0 - 90� lobe with the cam roller at the lowest point on the lobe(bottom of the stroke). See the inlet valve configuration in Figure 7. If it is necessary tomove the cam, loosen the recessed screws around the cam and the pointer hold downscrew from the center of the cam. Rotate the cam and align with the "0" indication withthe contact point of the roller. Then align the pointer along the direction of the zeroindication mark that is on the see-through cover.

2. Instrument air must be turned on. Use a 4 - 20 mA source and apply a 4 mA signal to theI/P. Hold the spring and range adjust nut to prevent them from turning and rotate thezero adjust ring-nut until the inlet valve is just at the fully closed point. Rotation of thezero adjust ring-nut towards the roller support (clockwise rotation) decreases the zerostart point. Rotation in the counterclockwise direction – zero adjust away from the rollersupport increases the start point.

3. Apply a 20 mA signal to the I/P. Loosen the Allen screw in the range adjust nut and holdthe spring to prevent it from turning while the range adjustment is being made. Rotatethe range adjustment nut without turning the spring until the inlet valve is just fully open.Gently retighten the Allen hold down screw. Motion of the range nut toward the rollersupport decreases the range span. Movement away from the roller support increases thespan.

4. Apply a 4 mA signal. If the valve goes to the “just at the closed point”, the valve iszeroed. If the valve is not at the “just closed point”, repeat steps 2 and 3 until both thezero and span conditions are met.

5. Replace the Allen wrench in its holder and reinstall the see-through cover. The pointershould be aligned to the “0” mark when the inlet valve is closed and to the “90” mark onthe cover when it is open.

NOTE

The positioner exhausts into the area covered by the see-through cover. Holes areprovided in the bottom of the cam housing to vent off this exhaust to the atmosphere.If these vent holes are blocked by a bracket or other structure, a provision must bemade to vent the exhausting air to the atmosphere; i.e., notch the cover, drill smallhole, etc. A tight cover with vents blocked will cause a back pressure in the positionerand it will not function properly. The positioner must be able to exhaust.



12

Bypass Valve Calibration1. The R (Reverse) side of the cam is used in the bypass valve configuration. See Figure 7

for cam configuration. The bypass valve is just full open at 4 mA and just fully closed at20 mA. Zero and span are set accordingly using the same general procedure as for theinlet valve. Refer to the inlet valve procedure if details are necessary.

2. Adjust zero: 4 mA, just open.

3. Adjust span: 20 mA, just closed.

4. Repeat steps 2 and 3 until bypass valve position matches requirement.

5. Pointer at “0” when full open, “90” when closed.

Maintenance of the BRAY PositionerMaintenance other than calibration is required if the positioner is supplied withcontaminated instrument air. Routine maintenance for cleaning consists of cleaning thespool valve. To clean the spool valve, remove the hex head bolt (spool valve cap) on theback side body of the positioner. Remove the valve and clean with solvent. The spool valveis inserted long end first. Use care not to drop the spring when the cap is removed.

CAUTION

A constant rush of air, in excess of normal exhaust venting, from under thesee-through cover indicates a diaphragm rupture. Overhaul or replacement isrequired in the event of diaphragm damage.




13

Part III: ActuatorsBray Actuator

Figure 10 is a functional diagram of the BRAY rotary actuator. Power air from the positioneris supplied to move the pistons in the CCW or CW direction. No routine maintenance isrequired. Travel limit is set with the travel adjusting screws. Both travel screws are adjustedto limit travel of the pistons. The pinion is connected to the valve stem with a collar. O ringsprovide for air tight sealing of caps and pinion.

Piston (2)

Pinion (1)Stop nut (2)

Travel adjusting stop screw (2)

Cap (2)

Cap hold down screw (8)

Air in to move CCW Air exhaust

Upper bearing with O ring

Lower bearing with O ring

Reverse flows cause CW rotation

* *

*

Figure 10. BRAY rotary actuator functional diagram



14

Vane Type Rotary ActuatorFigure 11 is a functional diagram of the vane type of actuator. No routine maintenance isrequired. A thin coat of silicone grease on the vane seal may release an actuator that issticking due to contaminated air supply. Keep instrument air clean and free of moisture.

Figure 11. Typical vane operated rotary actuator

TOP VIEW

SIDE VIEW

* Reverse flows cause CCW rotation

Air in to move CW

Air exhaust

Vane

Shaft

*

*

Vane seal

Actuator body

Shaft

Vane

Vane seal

Travel stop padsSelf lubricating bushing

Positioner coupling end

Valve drive coupling end

SIDE VIEW

Inlet and Bypass Valve Positioners - Ingersoll Rand …manualarchive.ingersollrandproducts.com/manuals/manuals/...INLET AND BYPASS VALVE POSITIONERS TP0011B 1992, 1999 Ingersoll-Rand

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