Motor-Operated control valves??? it's proper??
Motor-Operated control valves??? it's proper??
(OP)
Dear All
I'm a mechnical engineer in the power plant. I'd like to know that if i can use motor actuator for the control valves (regularing purpose, not on-off purpose).Normally we use the pneumatic actuator for this kind of control; such as desuperheater, feed water system and so on. Even though I know the motor actuator of which technologies have highly been developed but I'm not quite sure that whether it's proper for regulating purposes or not, you guys are electrical engineers and i do hope that there would be someone making me for clarity of this my concern.
Thanks indeed and best regards
I'm a mechnical engineer in the power plant. I'd like to know that if i can use motor actuator for the control valves (regularing purpose, not on-off purpose).Normally we use the pneumatic actuator for this kind of control; such as desuperheater, feed water system and so on. Even though I know the motor actuator of which technologies have highly been developed but I'm not quite sure that whether it's proper for regulating purposes or not, you guys are electrical engineers and i do hope that there would be someone making me for clarity of this my concern.
Thanks indeed and best regards





RE: Motor-Operated control valves??? it's proper??
http://www.gemu.com/Opening.htm
David Baird
mrbaird@hotmail.com
Sr Controls Engineer
EET degree.
Journeyman Electrician.
RE: Motor-Operated control valves??? it's proper??
RACO makes a extremly rugged line of electric actuators but they cost a bunch. I think they are doing some valve stuff also.
Barry1961
RE: Motor-Operated control valves??? it's proper??
RE: Motor-Operated control valves??? it's proper??
RE: Motor-Operated control valves??? it's proper??
Its probably not important, but electric acutators operate slower than pneumatic.
RE: Motor-Operated control valves??? it's proper??
In fact, I thought like what you suggested, what I'm concerned is we cannot do fail safe operations if power has gone as well as the life time of the motor actuator over the frequently-regulating operation but i really have no idea why the main contractor who is being awarded the project really wants to supply this type of actuator since, in my view, the cost of motor actuator is probably higher than the pneumatic actuator!!?? (I might be wrong) i'm not sure that if we consider overall an instrumentation-compressed air system (Higher capacity of compressors, piping and pneumatic actuators), we might need more investment for pneumatic system than power lines and motor actuators, don't we?
Regards
RE: Motor-Operated control valves??? it's proper??
It may pay to consider the environmental conditions that the intended actuator is going to be installed in and if the presence of electrical energy is ok. Recently we had an actuator explode, through an insufficent IP rating for process environmental conditions, ingress of moisture and some other nasties caused a build up hydrogen gas, sparking ignited the gas, and KARBOOM!, actuator cover in a million bits. Although the actuator itself did not fail and continued to operate fine, the safety risk was unacceptable. Some actuators can be confrigured to fail open or closed (for signal loss) depending on your process requirements and depending on process conditions have in-built mechnical redundancy (for power loss) to facilitate this. A 0-20mA control loop could be utilised where 4-20mA operates the 0-100% control and 0-4mA simulates broken wire/signal loss and will drive the valve to a fail safe position. Depending on the scope of works, instrument air can be expensive, only an indepth study of process requirements, operating conditions, process environmental conditions, safety targets, area/location regulatory requirements, long-term maintenence goals...etc will give an idea of pro's and con's vs cost/eff. between pneumatic/electrical control systems.
Kensea
RE: Motor-Operated control valves??? it's proper??
RE: Motor-Operated control valves??? it's proper??
2)For your application (Power Plant)Relaible supply of instrument air is always available in the power plant.
3) For desuperheater and feed water control valve, the duty is severe than the furnce draft and other application.
4) Electric actuators are being used for the regulating duty as well. However,due to the speed(gear box), torque, power supply and safety considerations the selection of the actuator is a difficult task. They are available in all voltage frequency, speed range.