Difine flashing , Cavitaion & Noise?
how to minimize these effects
- 3 Answers
- 7911 Views
- L&T, I also Faced
- E-Mail Answers
Answer Posted / www.islamqa.com
# Flashing: it's formation of vapour bubbles in liquid
stream as valve cause pressure drop to the liquid below its
vaporization pressure.
# Cavitation: it's formation and collapse of vapor bubbles,
collapse occures due to pressure recovery at valve
downstream which cause bubbles to implode, giving microjets
and very high pressure waves (in range 100000 psi).
# Noise: is a result of turbulent fields generated through
the flow stream caused by many parameters:
- pipeline restrictions (orifice, valves, ..)
- pressure fluctuation
- unstable flow and very high flow velocity
and the noise radiation depends on pipeline material and
diameter and thickness.
# Here is the main guidelines to avoid flashing and
cavitation:
# 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
| Is This Answer Correct ? | 6 Yes | 0 No |
Post New Answer View All Answers
wich is coming the first HAZOP OR SIL
what is IEC code in cables & how to selecting cables?
How to Calibrate Level Troll in field
Which type of pressure can be measured by primary elements?
principle of automatic votage regulator
sir,would you please send me the Hindustan petroleum corporation limited papers(HPCL).my e-mail ID is ujjwal_sharma1983@yahoo.com
what are the documents(Construction point of view for a process plant) submitted by contactor initially entering in to new site for client?
Can anybody tell me which type of question are asked in the interview for the FORMULATION(Pharma) as a instrumentation engineer, & question in building managment system.
what is insdustrial vibration.who it works. give atleast 2 types of insdustrial vibration
Tr. Wiring for calibration.
What is the difference between modbus,fieldbus & profibus
how to work static pressure sensore how to work dpt
What is the advantage of using locally fabricated hook ups over Pre fabricated hook ups in process instrumentation?
Please can anybody help for control valve sizing step by step procedure?
䑰ҕ䔈ҕ䖠ҕ䘰ҕ䛀ҕ䝐ҕ䟐ҕ䢐ҕ䥐ҕŹ
