Danlap
Mechanical
- Sep 17, 2013
- 311
Dear Valve Expert,
Need your suggestion of the following condition:
In regards with API 521 and TR 3001 Re: Leakage through 2 check valves in series, quote unquote “Where no specific experience or company guidelines exist, one may estimate the reverse flow through series check valves as the flow through a single orifice with a diameter equal to one-tenth of the largest check valve’s nominal flow diameter. A lower value may be used if a condition-monitoring system for the check valves (e.g. pressure indicators with appropriate volumes between the check valves) is installed…”
Which also interpreted in TR3001 that “With two check valves in series the standards indicate that a reasonable design rate for the PSV can be calculated using the flow from a single orifice with a flow area of 1% of the total flow area of the largest check valve. Using a smaller flow area, minimum 0,1% of the total flow area of the largest check valve can be allowed if an automatic system for condition monitoring of the two check valves is installed…”
The question that I would like to inquire is as follow:
Case: Single Nozzle check valve is installed right after compressor (distance approx. 15 meters), afterwards the pipeline is branched to one with PSV (to the flare) and the other one is to Gate Valve (which followed by similar system with higher pressure: Scrubber --> Compressor --> Check valve and so on).
I understand yes, we could installed another Check valve in series and put pressure transmitter in between (alarm system, etc.) shall latent failure occurred. However from my opinion, that’s only if latent failure (backflow occurred and exceedint its Allowable Preesure). Whereas how should I design the monitoring system to update the Check valve condition in 6 month basis (let say partial shutdown), as from my understanding that it would be hard purge the valve from compressor side (due to check valve configuration would allow it to be open) and from the downstream side (due to PSV branch and its Setting Pressure and also large volume required) in order to determine its leakage rate (during pressure testing).
Please correct me shall I missing something here. And also kindly disregard the common assumption that Nozzle Check Valve is considered Maintenance and leakage free for a while.
Appreciate a lot for you inputs.
Regards,
Adi
Valve rookie
Need your suggestion of the following condition:
In regards with API 521 and TR 3001 Re: Leakage through 2 check valves in series, quote unquote “Where no specific experience or company guidelines exist, one may estimate the reverse flow through series check valves as the flow through a single orifice with a diameter equal to one-tenth of the largest check valve’s nominal flow diameter. A lower value may be used if a condition-monitoring system for the check valves (e.g. pressure indicators with appropriate volumes between the check valves) is installed…”
Which also interpreted in TR3001 that “With two check valves in series the standards indicate that a reasonable design rate for the PSV can be calculated using the flow from a single orifice with a flow area of 1% of the total flow area of the largest check valve. Using a smaller flow area, minimum 0,1% of the total flow area of the largest check valve can be allowed if an automatic system for condition monitoring of the two check valves is installed…”
The question that I would like to inquire is as follow:
Case: Single Nozzle check valve is installed right after compressor (distance approx. 15 meters), afterwards the pipeline is branched to one with PSV (to the flare) and the other one is to Gate Valve (which followed by similar system with higher pressure: Scrubber --> Compressor --> Check valve and so on).
I understand yes, we could installed another Check valve in series and put pressure transmitter in between (alarm system, etc.) shall latent failure occurred. However from my opinion, that’s only if latent failure (backflow occurred and exceedint its Allowable Preesure). Whereas how should I design the monitoring system to update the Check valve condition in 6 month basis (let say partial shutdown), as from my understanding that it would be hard purge the valve from compressor side (due to check valve configuration would allow it to be open) and from the downstream side (due to PSV branch and its Setting Pressure and also large volume required) in order to determine its leakage rate (during pressure testing).
Please correct me shall I missing something here. And also kindly disregard the common assumption that Nozzle Check Valve is considered Maintenance and leakage free for a while.
Appreciate a lot for you inputs.
Regards,
Adi
Valve rookie