Answer / gk3000

Valve does not stop immediately, but of course, due to
cavity / flashing, there will be a great impact on the
valve body. This case, you need to consider some solution
to lessen this phenomena. One may be putting a restriction
on valve inlet, or changing the trim construction of the
valve, or using a high grade material.

Answer / www.islamqa.com

Actually the valve will not stop working, but as a result
of continous errosion it will be useless and you will need
to change the valve completely.

talking about solution need more details about the
situation but here is the basic guide lines:

# To avoid flashing:
====================

1 - valve selection with high Fl.
Fl:valve pressure recovery coefficient, and this introduced
by MASONILIAN as: Fl=(P1-P2/P1-Pvc)^.5 - and Fl max is 1.

where FISHER introduced Km =(P1-P2/P1-Pv) - and this is a
valve parameter presented by vendor and it's calculated by
lab tests, and usin Km we can get allowable(P1-P2) which
will not cause flashing.

2 - using anti cavitation trim, which generate multi vena
contracta points in the presuure profile, and this prevent
pressure drop below Pv.

3 - To cool down the process material to make Pv very low.

4 - To change the valve position to another place with high
pressure, to make pressure drop through the valve away from
PV.


And anyway if there is no escape from flashing, it's better
to sustain flashing within the valve to assure that we will
not have a cavitation when pressure recover, and liquid can
be recovered and bubbles can implode any other place away
from the valve.

and this can be achieved by heating up the process liquid
so we raise Pv, and a good indication for us to be sure
that flash will be sustained is p2, as we can know P2 at
downstream pipeline and make sure that it's below Pvc of
the process liquid.

Regards,

Ahmed Sabry
Control and Instrumentation Engineer
GPC - General Petroleum Company
ahmedsabry.online@gmail.com
CELL.: 00 2 0121367310

why we are using (-24VDC) and where we r using plz tell me

7 Answers  

---

what happen if i install my pressure transmitter below the elevation of pipe in natural gas service. Also support your answer

3 Answers   C2C,

---

what is the working principal of pribe

0 Answers  

---

what is commisioning procedure,2)what is is the main work in commisioning in the field tx to dcs, plz send me detail

0 Answers  

---

plz send me placement paper of ongc

0 Answers   ONGC,

---

---

in any transimitter (flow/level) there are three terminals for supply& test (+,-,+)in two wire,24VDC given to Tx.,but how 4-20 ma signal travels thru same wire (as it is for 24VDC input supply)?

1 Answers   Jindal, UltraTech,

---

tell me about the instrumentation,what is the actual need of it ?what are the characteristics of a IC engineer ?

11 Answers   L&T,

---

Any body have know try work calculation ???

0 Answers  

---

Which are all the commonly used Bordon tubes in the pressure gauges. Do any one use ASTM A 312 tubes for this purpose?

0 Answers  

---

My flow transmitter range is 0-1000mmwc.DCS range is 0- 100m3/hr.What is correspond out put in terms of milliamps if my flow is 65m3/hr

4 Answers  

---

tell about various protocols used in different plcs

3 Answers   Emerson, Samtel,

---

What types of Instrumentation Related Questions can an Interviewer ask in a Telephonic Interview ?

0 Answers   Cairn, Honeywell,

---