3 replies to this topic

[umeshr]

I have a vessel working at a pressure of 100 bar a. The inlet line is of 20" with a shutdown valve. This shutdown valve is provided with a 2" bypass line (with shutdown valve and Retriction orifice in series). During start-up the 20" Shutdown valve will be in close position. the 2" bypass valve will be open and will be it will equivalise the pressure across the 20" valve. After equivalisation the 20" valve will be opened. (the initial pressure at upstream is 100bar and downstream is 2bar)

This system will infact safeguard internals of the downstream separator plus the 20" shutdown valves internals during start-up.


I have the following points to get claried

1. sizing basis of the RO,

currently,

for gas i am sizing it in such a way that the mach no. of the gas in downstream of the RO is less than 0.8ma (on 2" line at downstream). Here my problem is to lower the mach i am trying to keep low flow rate. some time this will end up in a longer hours for equivalisation of pressure

For liquid i am keeping the flow rate in such a way the velocity through the pipe line is equal to max allowable velocity (max allowable velocity for liquid allowed by our engineering standard)

For two phase ??


2. Whether this RO is required at all required for this bypass line?

3. What is followed generally by HC industries for such kind of application

regards
Umesh.R

[JoeWong]

Umesh,

Bypass line with Shutdown valve & Restriction orifice (RO) is normally use for pressurization & equalization.

1. sizing basis of the RO,

currently,

for gas i am sizing it in such a way that the mach no. of the gas in downstream of the RO is less than 0.8ma (on 2" line at downstream). Here my problem is to lower the mach i am trying to keep low flow rate. some time this will end up in a longer hours for equivalisation of pressure

For liquid i am keeping the flow rate in such a way the velocity through the pipe line is equal to max allowable velocity (max allowable velocity for liquid allowed by our engineering standard)

For two phase ??

Since the objective is for pressurization & equalization, i think you will only consider gas for this service. You don't pressurize downstream system with liquid. Do you ?

2. Whether this RO is required at all required for this bypass line?

You can calculate the flowrate of the 2 " valve under full open position and check the momentum , potential surge, sudden cooling and pipe contraction, etc that your downstream system will experience. Your results will advise you if an restriction orifice if required. General we provide RO on the bypass line.

3. What is followed generally by HC industries for such kind of application

Not clear with this question. Please be specific.


JoeWong

[oomme]

Joe Wong,

Is it restriction orifice after the shutdown valve or throttling valve after the shutdown valve or both orifice and throttling valve? Also, what is the sequence in a manual blowdown senario?

Thanks

Obioma

[JoeWong]

Joe Wong,

Is it restriction orifice after the shutdown valve or throttling valve after the shutdown valve or both orifice and throttling valve? Also, what is the sequence in a manual blowdown senario?

Thanks

Obioma

RO can be upstream or downstream of throttling valve as long as the "safety distance" (e.g. 600mm) is provided (Read More in "Requirements of SDV Bypass Pressurization Line")