Answer / carl_ellis

I seen 10 to 20 causes for each of these categories, but
I've only listed one as an example.

Reasons for valve not closing or opening:

intentional or unintentional
- lack of energy - air/electric/hydraulic (Fuse blown)
- insufficient energy - (supply air regulator turned down)
- control system issue (control signal interlocked)
- positioner or I/P issue (locked in manual)
- actuator crippled (punctured diaphragm)
- positioner-to-actuator linkage/plumbing issue (tubing failed)
- actuator-to-valve linkage issue (sheared roll pin)
- valve trim damage
- foreign object blocking movement (how does all that junk
get in the piping in the first place?)
- change in design process conditions (actuator can't close
against increased line pressure)

Not all failures to actuate/move are faults - a valve could
be intentionally locked in place for safety reasons - access
to the piping/tank.

Tell 'em Carl sent you.

Why we use 4 to 20 mA, (This is International Standard) instaed of this can we use 4-16, or 4-24 or 3- 15 or any other range

13 Answers   ONGC,

---

Coriolis flow meter coil supply is 24vdc but why still we given 230ac for this transmitter let me explained detailed review please

1 Answers   Shell,

---

how to explain PID?

2 Answers   Jindal,

---

how its work inductive proximity sensor explain briefly?

1 Answers  

---

how to rectify the problem ,if we erected the DPT instrument wrongly of hp on lp side and lp on hp side?

5 Answers  

---

Can all intrinsic safe transmitters are provided with inbuilt zener barriers? why

2 Answers  

---

what different types of problems do occur while doing instrumentation commisioning and how to solve them? please explain in detail

0 Answers   Process Control Technologies,

---

What is 3 element control system

0 Answers  

---

if a tank is contaning oil and water than how can we measure the oil and water level seperately

3 Answers  

---

can we copy the software from a transmitter using hht(hart 275) ?

0 Answers  

---

how do we commission inergen system?

0 Answers  

---

what is the approximate cost of U tube manometer having range 1000mmwc to 1000mmwc?

1 Answers  

---