15.10 Actuators for Valves
15.10.1 Wherever required, valves shall be provided with actuating gear for remote operation. All actuators with complete assemblies shall be included in the Bidder’s scope. Isolating and remote manual regulating valves shall generally be provided with electrical actuators.
The power supplies for electrical actuators for regulation duty shall be provided with solid state reversal facility and shall be mounted in separate panels near respective control cabinets. All actuator motors shall be suitable for 415 V, 3 phases, 4 wire supply. All motors shall be suitable for voltage variation of ± 10 % and frequency variation of ± 5 %. Actual selection of voltage level will be decided during detailed engineering.
Each actuator shall be provided with sufficient sets of independent position operated adjustable limit switches each for open and close position for signaling, interlocking etc. In addition, two numbers torque limit switches (one for fully open position and the other for fully closed position) and space heater shall be provided in case of ;regulating actuators, provision shall also; be made for suitable two numbers position transmitters for remote position indication . In case two position transmitters are not available suitable single sharing arrangement shall be provided.
For hydraulically operated valves/dampers/vanes the bidder shall furnish all required equipment and accessories such as power cylinders, positions, position transmitters of approved design, pressure gauges, filter, pressure regulator, hydraulic piping solenoid valve, 4 nos. limit switches (2 nos. for open and 2 nos. for close position) and other requisite accessories. Hook up diagram for each type of hydraulic operated valves shall be furnished for owner’s approval. All actuators shall be stay put type both for failure of signal as well as failure of power (electric, pneumatic). For certain cases, open/close fail safe positions may be necessary which shall be decided during detailed engineering.
Solenoid valve shall be Electromagnetic type 3 ways having !/4 NPT ports . Body shall be made from ss bar stock whereas trim shall be AISI ss-316 materials.
15.10.2 Electro-Pneumatic converters
Electro pneumatic converter having 4-20 ma current input shall deliver 0.4 to 1kg/sq. cm output air to drive the final control element like control valve etc. This shall have all required accessories like Air filter regulator, air lock relay, isolating cock, mounting accessories cable gland etc. On loss of control signal the last set point pressure shall be maintained so that the associated control valve remain in stay put condition without any additional Solenoid valve. the allowable drift rate shall be +-2% of set point/hour maximum.
15.10.3 Air filter Regulator
Air filter regulator shall have filter element of size 5 microns and to have continuous adjustable output pressure from0to 2kg/sq.cmor oto7 g/sq.cm.All accessories like 2dial size output pressure gauge and proper bowl (metallic or transparent poly carbonate)shall be provided.
