Why the Air Tank Accumulators required for the single acting
actuators SDV's or BDV's as I see in some Schematic diagrams
of ROTORK ??
- 2 Answers
- 9708 Views
- L&T, Siemens, I also Faced
- E-Mail Answers
Answer Posted / carl_ellis
Similar to Valtek's fail-safe "air spring":
Where service conditions exceed the capabilities of the
standard fail-safe spring to drive the valve to its failure
position, and where specially designed, extra-strong failure
springs may be both mechanically and economically
unfeasible, air spring fail-safe systems on Valtek control
valves provide the thrust necessary to drive the plug to its
failure position. An air spring provides a pressurized
volume of air to drive the actuator piston in the failure
direction.
The volume of air is sometimes provided within the actuator
itself, or where the cylinder volume is insufficient, a
separate external volume tank is provided. Air spring
systems are used primarily to close valves upon air failure.
And sometimes they must open valves upon air failure. A
fail-closed Valtek valve is customarily operated with the
flow direction over the plug. Thus, with the plug on the
seat, the upstream pressure acts to hold the valve closed.
Fail-open Valtek valves customarily operate with the flow
direction under the plug. Thus, when a general system
failure occurs, the upstream pressure will keep the plug off
the seat and the valve open.
Air springs on Valtek valves are practical because the
locked-up air is used only at the instant of air failure to
drive the valve to the fail position. Line pressure will
insure that the valve stays either closed or open.
Occasionally, service conditions require that the valve
remain in the last operating position upon loss of air
supply. For such applications, Valtek valves can be
equipped with a fail-in-place lock-up system. If air
failure occurs, the system activates two pilot-operated
lock-up valves that trip and lock the existing cylinder
pressures on both sides of the piston, thus maintaining the
last throttling position.
Carl Ellis
Measure First
| Is This Answer Correct ? | 0 Yes | 0 No |
Post New Answer View All Answers
key exchanges in wpa,wpa2,tls
what is instrument philosophy
What is the function of solenoid valve in on/off & shutdown valve and why it is not used in control valve normally?
Draw block digram for well head from well to shipping pump?
how u calibrate pneumatic n motorized c/v?
hiii.... can any one provide me previous years question paper of hindustan petroleum for instrumentation engineering???
what is the PC interface and software for connection to ABB logic module “ LM011-CE18RAC “ ( for Programming ) ??
how pressure transmitter work, what is its principal to measure and how its generate signal. for pressure transmitterinstallation which precautions must be taken ??
Turbidity analyzer working principle ?
what is the electrical operation procedure for switching on 27.6MVA electric furnace.
HI friends.I am Surya a BTech in Electronics and Instrumentation Engineering.I am going to appear Relince Industries Ltd all India writen test very soon. so plz help me by sendind the probable questions about my subject.My mail ID is surya.barik@gmail.com.
what does it mean an active front end in vfd plz explain it briefly
How to calibrate the flow transmitter
How d.p. Transmitter can be applied to open tank?
1.what is controller proportional gain 2.what is the controller intergral action time. 3.A proportional plus derivative controller that has a proportional band of 20% and a derivative action time of 0.1 minutes. Construct the shape of the output waveform for the triangular input if the input rises and falls at the rate of 4 units per minute.
