KC-03-040
OPERATION & INSTRUCTION MANUAL FOR
PNEUMATIC ACTUATOR (POWER CYLINDER)
KC-03-040
KERALA STATE ELECTRONICS DEVELOPMENT CORPORATION LIMITED KELTRON CONTROLS DIVISION AROOR – 688 534 ALAPPUZHA DIST., KERALA Phone: (0478) 872323-6 (4 Lines), Gram: “Electronic” , 872322 , e-mail:
[email protected]
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Fax: (0478)
KC-03-040
CONTENTS
Sl #
Description
Page #
1.0
INTRODUCTION
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1.1 1.2 1.3 1.4 1.5
GENERAL OPERATION POSITIONER ACCESSORIES MOUNTING
3 3 3 4 4
2.0
OPERATING PRINCIPLE
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3.0
CONTROL ADJUSTMENTS
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4.0
MAINTENANACE
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5.0
DRAWING NO: KC-03-040
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KC-03-040
OPERATION AND MAINTENANCE MANUAL FOR PNEUMATIC ACTUATOR
1.
INTRODUCTION
1.1.
GENERAL KELTRON double acting pneumatic actuators accurately operate and position regulating devices such as dampers, fan inlet vane, variable speed drive lever, rheostats, butterfly valves etc. Owing to the proper selection of materials and components the actuator can operate in any corrosive, dusty, outdoor environment.
1.2
OPERATION The pneumatic actuators mainly consist of a double acting power cylinder in which a piston slides and through which the necessary force is transmitted to the final control element. Actuator without positioner is used for ON / OFF control of a regulating device in which air supply is given to the cylinder through a solenoid / pilot operated valve. Actuator with positioner can establish any desired relationship between pneumatic input signal and piston displacement. To match the regulating device characteristics with the system requirements linear, interchangeable cams are provided with the positioner.
1.3
POSITIONER All regulating type actuators are integrally mounted with a highly sensitive pneumatic positioner that sets the piston position accurately with reference to the pneumatic input signal. The positioner is suitable for direct or reverse loading. Change of direction can be easily obtained by reversing the air supply connections and reversal of the mounting of the cam.
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KC-03-040
1.4
ACCESSORIES
The actuator is provided with the following standard accessories:1.4.1 Pneumatic Positioner. 1.4.2 Air Lock Relay (ALR) (Optional) 1.4.3 Air Filter Regulator (AFR) (Optional) 1.4.4 Electronic Position Feedback Transmitter (EPFT) (Optional) 1.4.5 Limit Switch Assembly (Optional)
For details of the accessories, please refer to the Data Sheet enclosed separately.
1.5
MOUNTING The actuator is provided with supporting stand or with an end tru-union swivel base with axle suitable for mounting on platform. For details of the mounting, please refer to the GA drawing enclosed separately.
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KC-03-040
2.
OPERATING PRINCIPLE The operating principle is shown in the drawing KC-03-040 enclosed herewith. The Positioner controls the cylinder piston position according to the control signal pressure.
When signal pressure increases, the Bellow moves the Balance beam towards its high stop. The movement of the beam moves the pilot stem out of the pilot valve (slide relay). This causes an increase in the modulated air pressure at C1 and a decrease in the modulated air pressure at C2. As a result of this the Piston rod of the power cylinder assembly moves out of the Cylinder. As the Drive lever of the actuator pivots at its pivoting point, the cam turns clock-wise and acts on the Positioning Spring. The force exerted by this spring is opposed to the force exerted by the bellow. When the two forces are equal, the balance beam returns to its balanced position, pressures C1 and C2 become equal and the cylinder piston stops moving, thereby stopping the cam from rotating. The cylinder piston thus reaches a position by the control signal pressure.
When the signal pressure decreases, the spring moves the balance beam towards its low stop. The movement of the beam moves pilot stem (slide) back into the pilot valve (slide relay). This causes a decrease in modulated air pressure at C1 and an increase in pressure at C2. The Piston rod moves into the Cylinder. The Cam turns counter-clockwise and this decreases the tension of the spring. When the forces exerted by the spring and the bellow are equal, the balance beam balances the pressures at C1 and C2 again and the cylinder piston reaches a new position.
The operating principle applies to a direct acting control drive where the piston rod comes out of the cylinder when the signal pressure increases. To obtain the reverse operation i.e. to have a piston rod go into the cylinder when the signal pressure increases, simply reverse the air supplies C1 and C2 on the cylinder and reverse the Cam
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KC-03-040
3.
CONTROL ADJUSTMENTS There is no real adjustment of the control drive cylinder. When the cylinder is used with a positioner, it is the position that is adjusted. These adjustments concern the following operations: 1) 2) 3) 4) 5) 6)
Mechanical adjustment Pilot stem (slide) Zero Stroke (span) Cam Operating speed.
Before making any adjustments, disconnect the control drive from the controlled unit. Off (disconnect) the supply and signal pressure. Connect a pressure gauge to each of the tubes connecting the pilot valve (slide relay) to either end of the cylinder.
3.1
Mechanical Adjustment
Manually position the piston at mark zero on the cam (piston rod completely IN for direct acting control drive or piston rod completely OUT for reverse acting control drive operation). Adjust the drive rod connecting the positioner to the control drive so that this mark on the cam is tangent with the cam follower (bearing) of the spring beam. Tighten the lock nuts to set the rod length.
3.2
Pilot Stem Adjustment Switch ON the positioner. Apply the supply pressure. Apply enough signal pressure to set the cylinder rod between the two stops (positioner cam around 50%). The pressure indicated on the two pressure gauges connecting the pilot stem to the cylinder must be half the supply pressure ± 0.14 bars (± 2 psi). If the pressure is less than this value, tighten the adjusting screw on the pilot valve. If it is greater than this value loosen this adjusting screw until the desired pressure is obtained. Then lock the adjusting screw with a lock nut.
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KC-03-040 3.3
Zero Adjustment
Apply a signal pressure corresponding to the start of piston displacement and set the spring tension with the knurled nut for zero adjustment so that a slight increase in the signal pressure causes the piston to start and the cam to rotate.
3.4
Stroke Adjustment Apply signal pressure corresponding to 100% of the scale and adjust the stroke (position of slider on spring beam) to let the cylinder piston reach the end of its stroke or the desired stroke.
3.5
Speed Control Adjustment (Optional) To adjust the operating speed external speed control valve (speed muffler) is provided. Desired speed can be obtained by using its knob and it can be locked with check nut.
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KC-03-040
4.0
MAINTENANCE For correct control drive operations the air supply must be clean and free from dust, oil or moisture.
4.1
Cylinder
4.1.1
Every Three Months Lubricate the clevis (fork axle) pin and the bottom pin with a few drops of SAE 30 or SAE 40 oil.
4.1.2
Every Two Years Remove the cylinder. Clean the inside of the cylinder and the piston rod with a trichloro-ethylene type solvent. Check all O Rings and if necessary replace them with new ones. Lubricate the inside of the cylinder with a fine coat of grease as per the following specification using a clear brush.
Recommended Grease a) VULCAIN 939 Mo (imported) b) BALMEROL LICOM-3M c) SERVOGEM HTXX
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KC-03-040 4.2
Positioner The Positioner requires very little maintenance. Nevertheless, be careful with the following points:
4.2.1
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All the tubes must be kept perfectly sealed. A leak in any tube can give the impression of incorrect operation. Check all connections for leakage, while under pressure, with a soapy solution.
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The air supply to the pilot valve (slide relay) must be kept perfectly clean. Although the positioner has a filter, the repeated presence of dust, oil or moisture may lead to faulty operation.
Once in a year: -
Remove the pilot valve stem (slide) and inner liners (sleeves) of the pilot valve (slide relay) and clean with a trichloroethylene type solvent. Never use files, reamers or abrasives. If liners stick in valve body upon removal, push them free with a wooden stick or pencil: NEVER use a metal rod for this purpose.
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Remove the valve block after removing the valve handle.
Use a coin as a screwdriver to remove the filter plug and to replace the filter if necessary. Using a 17mm wrench, loosen the valve nut, pull out the valve body and lubricate it with special valve grease. Important Note: The valves are not interchangeable with valves in other positioners.
4.2.2
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Put a few drops of light oil on the positioning spring pivot pin.
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Check the adjustments.
Once in every three years -
Change the grease in the drive arm gear case. Fill the gear case about half full with high consistency grease and turn the drive arm to work the grease into the gears. The gear case volume is approximately 70 cm3.
Recommended Grease a) PAIX 858 Mo. (imported). b) Special wheel bearing grease – BHARAT UNIVEX RB or equivalent. c) CASTROL multipurpose.
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KC-03-040 4.3
Air Filter Regulator (Optional) The standard bowl capacity is 130 cc, which do not require daily draining under normal working conditions. In plants where the compressed air carries more than the normal limit of moisture it is recommended to drain often. However, this depends upon the concerned plant operating conditions and the frequency of opening the drain valve has to be fixed in view of the above. In order to avoid operation of the adjusting screw by unscrupulous persons it is recommended to use the check-nut provided for locking the top screw.
4.4
Air Lock Relay (Optional)
4.4.1
Every 3 months See whether air is bleeding thro' small hole provided on the tapered top cover. If not, clear the hole with a steel pin.
4.4.2
Every 3 years Replace all rubber items with new one.
4.5
Position Feedback Transmitter (Optional) Every 3 months Lubricate the 2 ends of connecting linkage with lube oil. Apart from the above no maintenance is required for the EPT.
4.6
I/P Converter (Optional) The I/P converter is a maintenance free item.
4.7
Limit Switch (Optional) Every 3 months Lubricate the 2 ends of connecting linkage with lube oil. Apart from the above no maintenance is required for the Limit Switch.
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