Interested to Buy Any Domain ? << Click Here >> for more details...
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
- 11179 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
If a control valve is hunting means means if we are giving 50% to the cv, the cv will open at 51% then slowly slwoly it will reaches 49% , so what to do for solve this problem. The cv is double acting and mounted for anti surge operation, it having 4 nos. volume booster, one sov, one positioner, etc..?
How works weighfeeders in cement industry? what is the working principle?
what is effect of specific gravity in differential level transmitter , explain formula related with this .
WHAT IS MEANT BY PROJECT MANAGEMENT STRATEGIES IN INSTRUMENTATION?
Name different types of bourdon tubes.
Explain bernoulli’s theorem.
hey any one got the papers of SAIL and HPCL plz do help me by posting them to my mail ID's naren07_87@yaho.co.in, surenarendra@gmail.com
Why does a pressure gauge installed on reactor, doesn't have any vent line below to release the pressure? Is it any kind of designing mistake or it actually does not require any vent line? And if it does not require any vent line below it then how we are gonna release the pressure built inside the pressure gauge?
what does it mean an active front end in vfd plz explain it briefly
Why the ammonia and Nitric Acid level indicators is with millimeter ? and What is the conversion form millimeters that level indicator indicate to weight ?
What is the difference between ff transmitter and non ff transmitter
how to tune siemens sipart electro pneumatic positioner..plz tel me..
how pressure transmitter work, what is its principal to measure and how its generate signal. for pressure transmitterinstallation which precautions must be taken ??
How flow can be measured with dp?
what are procedure of sox-nox calibration
