Answer / instru

Bigger size actuator are required whenever thrust required
for control valve is higher. Thrust required is higher
whenver control valve has to open against high differntial
pressure. Also whenver type of packing is Graphite , large
size actuators are required because packing friction is
higher compared to PTFE.

Answer / ku

Normally the selection of the actuator is governed by the
maximum dp shutoff for any service, You have find out what
could be maximum possible inlet pressure to the control
valve and minimum possible downstream pressure, which will
provide you maximum delta P that your actuator should
handle, for example you have a column operating at pressure
P1 and a pump is taking suctionfrom this column and the
control valve is at outlet of the pump, the pump is
discharging this material to a drum with certain pressure,
in this case you will take the shutoff pressure of the pump
as inlet pressure and minimum pressure that can be at the
drum. This will automatically result in an actuator sizing
and selection suitable for this service. I am not sure why
you mentioned bigger size actuator as actuator should
be "big enough" to handle the maximum delta P across the
control valve.

Answer / rakesh kumar .n be

for high pressure application we use the the bigger actuator is wrong concept, mostly in the early days days we used this kind of actuator, mostly used for diaphragm and piston type actuator , if u use diaphragm type then u need big cascade, for high pressure , but we should change the cascade for regular intervel. in our company we control the 220 kg/cm2 of pressure in the small actuator only, bigger actuator is disturbance only large space is needed and difficult to calibrate. thanks

Answer / rahul

when valve size is more,
mostely for control valve

Answer / joby

if the valve is in higher size ,we have to go for higher
actuators for operating the valve.
FOR ESD VALVES
if the valve size is more than 18" mostly the suppliers
prefer hydraulic systems for operating the actuator
instead of air.The pressure required to operate the higher
size actuator will not be sufficient ,if you are using
plant air.

What is the purpose of valve positioner. Explain 4 uses.

2 Answers   SRACO,

What is difference between radial vibration and axial vibration explain in detail .

0 Answers   Emerson,

I have a orifice installed in plant which is design for 0~100 inH2O for 0~80MMSCFD, now due to process change the maximum flow is change to 120 MMSCFD so for this new process value what will be the DP across orifice.

1 Answers  

What are the charecterstics of control valve.

2 Answers  

what is the difference between plc & DCS?

5 Answers   Cheminova, NGIL, Siemens,

sir i m preparing for BARC but i am not getting any papers to prepare for this exam so please send me some sample papers to my i.d for the preparation of barc.

0 Answers  

explain level transmitter working

1 Answers  

I am pujita completed Electronics and Instrumentation Engineering.As a fresher i am going to attend the interviews.Could anybody guide the topics/questions covered mostly in interviews.

11 Answers  

In a gas over oil actuator, after the opening/closing of valve, how the gas is vented out? How does the hydraulic/gas circuit function?

0 Answers   Reliance,

what are the documents(Construction point of view for a process plant) submitted by contactor initially entering in to new site for client?

0 Answers   NTPC, PSU,

what is difference between E/P positioner and I/P positioner. Why E/P fixed in below actuator and why I/P fixed in other place

1 Answers  

How a rtd work, and what volts/current goes to a RTD to measure the resistence?

1 Answers   DVC,