Manual 820-pp As

Pneumatic Positioner Series 820-PP Operation & Maintenance Manual

Pneumatic Positioner Model 820- PP This operation & maintenance manual corresponds to Forbes Marshall Arca make Pneumatic Positioner model 820-PP. If you experience any difficulty with the installation or operation of this equipment, please contact our Customer Support

Manufactured & Marketed by Forbes Marshall Arca Pvt. Ltd. A Forbes Marshall Company A 34/35, H Block, MIDC Estate Pimpri - 411018 Pune, India TEL. : +912027442020 FAX. : +022027442040

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Table Of Contents

1.General 2.Nomenclature/ Model No. 3.Salient Features 4.Specifications 5.Principle Of Operation 6.Block Diagram 7.Installation & Calibration 8.Auto/Manual switch 9. Seat adjuster 10.Maintenance and check 11.Caution and Handling 12.Trouble shooting

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1. GENERAL The pneumatic positioner is used in Control Valves with pneumatically operated actuators. The valve is operated by means of electrical controller or Control Systems (through I/P converter) with a control signal of 0.2~1.0 bar or split ranges of 0.2~0.6 bar & 0.6~1.0 bar. The 820-PP Pneumatic Positioner converts this control signal into a pneumatic output in proportion to the lift of the control valve. This manual contains the information required for the installation & usages of this equipment. It is addressed to technically qualified & trained person or having relevant knowledge of instrumentation & control technology. It must be used in the way described in this manual. Successful safe operation of this equipment is dependent upon the proper handling, installation, operation & maintenance.

2.Nomenclature/ Model No. –

8

2

0

-

P

P

82 SERIES POSITIONER 0 - NORMAL

ALWAYS "-"

PP - PNEUMATIC TO PNEUMATIC

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3. SALIENT FEATURES 1. There is no change in performance in the range of 5-200Hz of Vibrations. 2. Can be Used for Split Range Application 3. Easy to adjust zero and span & calibrate to the required travel of the valve. 4. Easy to convert from ATO (Air to Open) to ATC (Air to Close) action or vice versa. 5. Easy Feedback connection. 6. Fast and accurate response. 7. Low air consumption.

4. SPECIFICATIONS

Input Signal

0.2~1.0 barg (or SPLIT RANGE)

Supply Pressure

1.4~6 kg/cm2

Air Consumption

3 lpm at 1.4 bar

Air Flow capacity

80 lpm at 1.4 bar

Linearity

± 1% of FS

Hysteresis

± 0.2% of FS

Repeatability

± 0.5%

Air Connection

¼” NPT (F)

Gauge Connection

1/8” NPT (F)

Ambient Temp

-20 0C to +80 0C

Protection

IP 66

Weight

2.1 kg

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Pneumatic Positioner 820-PP

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5. PRINCIPLE OF OPERATION This equipment works on the force balance principle and uses a flapper/ nozzle & set of springs to bring the forces under equilibrium at the required valve position with respect to the signal/command given to it. When the input signal from the controller is applied, this pressure makes bellow to expand thereby exerting force on flapper to move away from the n o z z l e . T h e c l e a r a n c e b e t w e e n t h e N o z z l e & t h e F l a p p e r i n c r e as e s , d u e t o which, the back pressure in the Nozzle decreases.

As a result of the above, the exhaust valve of the Pilot Valve moves towards right and the Inlet Valve “A” opens, thereby the supply air goes to t h e a c tu a t o r t h r o u g h p o r t O U T 1 . T h e v a l v e S p i n d l e w i l l m o v e u p o r d o w n depending up on the actuator configuration (ATO/ATC) and the Feedback Spring will lengthen or shortens by the movement of Feedback Lever. When there is a force balance between Feedback Spring tension and the moment generated by bellow, the valve Spindle stays in it’s position. When the signal pressure decreases the operation is reversed.

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6. BLOCK DIAGRAM

BELLOW CHAMBER

INPUT SIGNAL (0.2~1.0 bar)

FLAPPER & NOZZLE MECHANISM

STABILIZER /COMPENSATION SPRING

FEEDBACK SPRING

PILOT VALVE

ACTUATOR

(OUTPUT ) VALVE STROKE

FEED BACK LEVER

7. INSTALLATION & CALIBRATION a. Check that the Pneumatic pipes/ tubing are properly flushed. b. Connect the pneumatic connections as per the diagram of point 7-e. c. Connect the Feedback lever to the Control Valve’s Link mounted on the Valve’s Lift Indicator. Apply 50% signal ( i.e. 0.6 barg) and position the Stroke Scanning Pin/ Positioner in such a way that that the Feedback Lever is at 90 0. 6

Positioner

5

Positioner Mounting Bracket

4

Stroke Scanning Lever

3

Threaded Pin

2

Link

1

Lift Indicator

Sr. No.

1

2

3

4

Part Name

8

5

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d. For best performance the movement of the Feedback Lever should be between +15~200 to –15~200 from the 900 (horizontal position set at 50% signal). Pl. check that, while setting the full stroking angle, the Feedback Lever should not foul with the stoppers, provided near the Feedback Lever Connection point on to the Positioner. e. Position the SPAN lever as per the actuator function i.e. ATO (Air to Open) or ATC (Air to close), as explained under ATC Actuator

ATO Actuator

ATC ACTUATOR

ATO ACTUATOR

SPAN Lever Fixing Screw SIGNAL AIR SIGNAL AIR Lock Screw

Lock Screw SUP AIR

OUT1

OUT2

OUT1

OUT2

SUP AIR

SPAN Lever Fixing Screw

For changing the position of SPAN Lever, the Lock Screw, should be loosened slightly, to avoid getting the Feedback Spring damaged. After re-orienting the SPAN Lever to the desired position, the Lock Screw should be tightened carefully. While changing the position of SPAN Lever, take care not to stretch the Feedback Spring. OUT2 port is not to be used, unless confirmed from works. f. Apply, starting signal (0.2 barg) and turn the Zero setting adjuster, to set the zero setting. (Clockwise rotation of the adjusting wheel will increase the pneumatic supply to the actuator, to decrease the supply to actuator rotate the adjuster in CCW direction). g. Then apply 100% signal (1.0 barg), if the valve is not taking 100% stroke then slightly loosen the Lock Screw mounted on the SPAN Lever, rotate the knob on the SPAN lever to achieve the full stroke position. After setting the SPAN, again check the Zero setting at 0.2 barg and set if found disturbed. After setting, carefully tighten the Lock Screw of the SPAN Lever. Note - The positioner can be set in Split Range also (i.e 0.2~0.6 barg or 0.6~1.0 barg), as described under Split Range 0.2~0.6 barg – Set ZERO at 0.2 barg & SPAN at 0.6 barg for 100% valve travel. Recheck ZERO after setting SPAN, correct, if found disturbed. Split Range 0.6~1.0 barg - Set ZERO at 0.6 barg & SPAN at 1.0 barg for 100% valve travel. Recheck ZERO after setting SPAN, correct, if found disturbed.

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8. By-Passing The Positioner/ ”A-M” Screw The Positioner can be by-passed, by the adjustment of “A-M” Screw. The factory setting is for AUTO mode, however to by-pass the positioner, rotate the “A -M” screw in counterclockwise direction slowly towards “M” marking on the Pilot Valve (Ref. fig. Under Point no.5) In by-pass mode, the full pr. of the supply air goes to the Actuator. Therefore, pl. be careful to check the air supply recommended for the actuator. After using the Positioner in manual mode, again rotate the “A-M” Screw in Clockwise direction towards “A” to go into AUTO Mode. It should be fully tightened for AUTO Operation.

9. SEAT ADJUSTOR – (Should Not be disturbed) This is set at the factory at fully tight position and should not be disturbed. Disturbing this screw may cause positioner malfunctioning. 10. MAINTENANCE AND CHECK 1. If the quality of the supply air is fouled, then the positioner may not operate normally. Moist air may damage the Pilot Valve/ Torque Motor and cause Positioner to malfunction/ defunct. The requirement for a quality air supply can be found in the instrument society of America’s “Quality Standard for Instrument Air” (ISA-S7.3) or BS 5967:Part 2. Basically, this standard calls for the following Particle Size – The maximum particle size in the air stream at the instrument should be no larger than 3 microns. Dew Point -

The dew point -at line pressure- should be at least 10 0C below the minimum temperature to which any part of the instrument air system is exposed at any season of the year.

2. The compressed air cleaning/de -humidifying system should be checked periodically. 3. When the fixed orifice is clogged with carbon particles or others, remove the pilot valve Auto/Manual changeover screw (built-in fixed aperture) and clean it by inserting a 0.2 wire (provided at the inside of the Positioner Cover) into the aperture. If it is required to be replaced with new one, stop the supply pr. and remove the Stopper Screw of the pilot valve. 4. Check the positioner once a year. If any abnormality is observed, contact our works. 5. There should not be any air leakage from the tubing. Use pipe sealant sparingly, only on the male thread of the tube fittings. A non-hardening sealant is strongly recommended.

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11. CAUTION AND HANDLING

1. Do not apply large vibration or impact to the positioner. It causes trouble to the positioner and it must be handled very carefully during transportation and operation. 2. If the positioner is used under temperature outside of the specifications, the sealing materials may deteriorate quickly and also the positioner may not operate properly. 3. Be sure that the body cover is put on during the operation. 4. If you leave the positioner at the operation site for a long time without using it, put a polythene cover on it so that the rainwater does not harm it in any way. 5. If the atmosphere is of high temp. Or high humidity, take measures to avoid condensation during shipment. 6. For proper functioning of the positioner, use only factory authorized replacement parts. Substitutions of components can impair the performance of the equipment.

12. TROUBLE SHOOTING

PROBLEM

CAUSE

WHAT TO DO

Too Low or None Supply Pr.

Check Supply Pr.

Damaged Bellow

Replace Bellow

Clogged Nozzle

Clean The Nozzle with the help of wire provided in the Positioner Cover.

Loose or Wrong Setting of Feedback Lever

Correct Setting/ Tighten

Wrong Orientation of SPAN Switch

Correct to the Required Position (Refer Point 7e)

“A-M” Screw is Disturbed

Fully tighten the “A -M” Screw (It has two ‘O- Rings)

Wrong Connection of OUT1 & OUT2 Ports

Correct the Pneumatic Connection w.r.t. the Position of SPAN adjustment Switch (Refer Point 7e).

No Response when Input Signal is Applied

Valve Operates Only for 0% & 100% Signal i.e. No Response for in between Signals and Actuator Operates Only to ON or OFF Position

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PROBLEM

CAUSE

WHAT TO DO

Leakage of A/M Switch

OUT PUT Pressure Raised and Stays, Does Not Come Down

OUT PUT Pressure is Operated by A/M Switch Only

Tighten or Replace ‘O’ Rings of A/M Switch

Wrong Orientation of SPAN Switch

Correct to the Required Position (Refer Point 7e)

Clogged Fixed Orifice

Clean the Orifice with the help of Wire, provided in the Positioner Cover

Clogged Nozzle

Clean The Nozzle with the help of wire provided in the Positioner Cover.

Disturbed Compensation/ Stabilizer Spring

Correct the Positioning of Stabilizer Spring

Clogged Fixed Nozzle

Clean The Nozzle with the help of wire provided in the Positioner Cover

Wrong Setting of Feed Back Lever

Readjust the setting of the Feed Back Lever (Refer Point 7c & 7d)

Wrong ZERO, SPAN adjustment

Readjust the ZERO & SPAN

Supply Pressure is unstable

Check the Air Leakage from the Pneumatic supply OR Replace the Air Filter Regulator

Loose Pneumatic connections in the Actuator or Positioner

Check & correct

Hunting is Occurring

Linearity is not Good

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