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.

how to caluculate flow by using transmitter?tell me plz I am eagerly waiting for your reply..

2 Answers   Agi Glaspac, Reliance Power,

How to make position transmitter feedback reverse i.e at valve close i want 20ma output and at full open 4ma.for the NELES positioner,model:ND8261/TS1.

3 Answers  

What are the type of bonnets in the control valves?

0 Answers   CCIE,

Why we use the double acting control valve in flow line?

3 Answers  

why we use by pas on a positioner? When can a by pass be not used on a positioner ?

1 Answers  

what is axial shift n what is differential expansion in turbine? how many sensor probes r mounted for this n how it works?

2 Answers   Apple,

What is DCS?

5 Answers   Adani,

What is the difference between ROM & RAM .

1 Answers   Sabic, SPIC,

generally transmitter power supply having some range(12v to 35v) but the out put(4-20 mA) must same for given input.If we vary the power supply voltage then output mA also to be change according to V=IR. Is there any voltage regulator in the transmitter ?

1 Answers  

please any body have most important data for study for saudi aramco test of instrument QC thanks email shahnaveedullah@gmail.com

0 Answers  

detail of mass flow meter pricipal

0 Answers  

In RTU Panel we are having several Analogue & Digital Inputs /Outputs. We are recently facing some problems over Analog inputs , which are not updating properly (But Digital Input are updating normally) Can any one tell me from where the problem is creating , we have checked PLC CPU card, Analog Input card & we reconfigured ,But still the issue is there. Issue : 1. Sometimes Analog values are updating & sometimes not. 2. Analog values are not updating normally , showing some wrong Values 3. Total dead (0 value) Analog values are Level & flow measurement from the field instruments. (But in field the instruments are working normally & Displaying the values normally in local display unit) This problem we are facing in our Water Plant. If any one experienced this same problem or having any ideas related to our issue PLS send your valuable Answers/Replies...

6 Answers   L&T,