i have read that electro hydraulic convertors are of many types as servoguide, powerguide, dynaguide, etc. i need some understanding of these. Dynaguides are used in some steam control valves.
Dynaguide is the name of a jet pipe type servo valve which was manufactured by Nireco. Google "jet pipe servo valve" and you will find information from other manufacturers.
thankyou very much for giving the exact details of reading material.
i have some more issues regarding this. basic process is a jet pipe will guide pressure to two orifices equally, and in case of valve opening or closing required, then torque motor will be energized. please check this link:
in this link, we saw a page no. 4 figure 1C stabilized with current, that means there will always a current. and system is stabilized with one port opened to pressure side, and the other one opened to drain. i understand most of the concept. but if you may give some clarity, it will be helpful. because what i think is that jet pipe valve must regain its center position otherwise continuously oil will flow.
When current is being applied, after the initial shift, the jet pipe returns to center due to the feedback spring mechanism (stabilized condition), but the spool remains shifted. When the spool is shifted, oil will flow, even if the jet pipe is centered.
i am able to understand that but i need to share an application of the same.
Please check the SHARED three slides. you will find that first one is a line diag for steam control valve and last two are of a jet pipe servo valve. oil supply is at two places OEHC (oil for EHC) in blue line and OCVO (oil for Control valve-through PIVOT valve) in yellow line. Electro hydraulic converter is dynaguide. this construction works like this, oil from jet pipe servo is guided to power cylinder, and power cylinder gets lifted. lifting of power cylinder will shift pivot valve upwards and thus allows oil to flow in BFPT CV actuator.
but what we discuss is if oil will continously flow from jet pipe servo valve, power cylinder will continously charged by oil from one side. pilot valve will stay in upward condition and oil will keep on going in BFPT CV actuator. now comes the role of fulcrum provided in BFPT actuator shaft. when oil goes through the pilot valve to actuator, then actuator gets lifted. then through fulcrum pivot valve is getting a force downwards, and it will get closed as actuator gets opened. but what i think is still power cylinder is in pressurized condition so it will force pivot valve to stay for continous flow in actuator.
how this control valve holds its position if continous pressure is there in power cylinder.
one reason i think is: this fulcrum keep forcing pilot valve to get closed when control valve start opening more; and the force from power cylinder is less than the actuator force working opposite to keep the pilot valve in closed condition.
one thing more i want to ask. is there any specific term "on port valve position control" used in these systems?
i think this will explain my doubt. i have an idea how does our steam valve operates, but nobody approves it that i am correct or wrong. if i am wrong anywhere about its working, please correct me. i will provide more info if you need.
Keep in mind that the current signal input to the dynaguide determines if the spool is shifted, and therefore oil flowing to the power cylinder. It's not clear from the drawing, but I guess the LVDT provides feedback of the lever position, and the control then modulates the dynaguide coil current accordingly. I'm not familiar with this system, but would be surprised if the fulcrum arrangement is meant to limit the travel of the lever mechanically as you describe. The control system should be modulating the dynaguide electrically so that power cylinder movement stops when lever position attains setpoint.