PSV/ PRV Inspection Interval 1

[Vaione]

Hello guys,

I am chemical engineer and I am working as Reliability engineer in refinery. Right now i am preparing PSM program. I am working on PRV/PSV ispection interval frequency. In our plant its like 3 yreas, but I dont know why its 3 why not 1/2/5.?? I came across one thing we did inspection for all PRV's in 2005 and then did it in 2008. but in case of one PRV we did it in 2007. because it got burst. now i want to know do i have to revise inspection interval for this PRV.?? From history how can we find that frequency is right it or not?

 

[JLSeagull]

It depends. Start here:

https://sbms.bnl.gov/sbmsearch/subjarea/171/171_exh2.cfm?ExhibitID=7147

http://www.eng-tips.com/viewthread.cfm?qid=243699&page=1

BOILERS
ASME SEC VII SUBSEC C4 SAFETY VALVES
...
Testing, inspection, and repair should be performed at a
regular frequency determined by the valve’s maintenance
history. The application characteristics can vary for each
valve on a multivalve system and create a different cycle
for each valve. The normal cycle time is 1 year.
...

See ASME PTC 25 Pressure Relief Devices for the reports.
See API STD 527 for seat tightness.

Lots more …

 

[Vaione]

thank you for providing me an info for this. Can you let me know wat are the main key parameter I have to consider to make PRV inspection frequency.?? Why PRV failed?

 

[lizking]

You may look into risk-based inspection methodologies. See API 580 & 581. Companies sell software to utilize the techniques.

 

[Vaione]

ok thanks. I will look at that.

 

[JAlton]

Another Reference is National Board Inspection Code (NBIC), Part 2, Para. 2.5.8(f) on page 53. Available at

http://www.nationalboard.org.

SERVICE INSPECTION FREQUENCY
Steam Annual
Air & Clean Dry Gases Every 3 yrs
PRV in combo with Rupture Disk Every 3 yrs
Propane, Refrigerant Every 5 yrs
All Others Per Inspection History

JAC

 

[Mecha20]

If you have a PM scheme, you can use the past inspection data as well failure data to develop an inspection frequency.

Some PSV manufacturers give a 2yr inspection period, but again this may or may not be 'shelf' period. You may have to take into consideration the environment and operating conditions for developing an inspection frequency.
All in all, past data, operating & environmental conditions, OEM recommendations, present frequencies used, field experience of lead technicians, history of the particular PSV, would all play a crucial part in determining your frequency.

One of the world biggest oil and gas giants uses a 2 yr inspection frequency for their PSVs, well unless one has been lifted.

Hope this helps.

 

[Vaione]

hey thank you mecha20.

Hey i have two set of history for PRVS, both has goos comment not mechanical repair. so i decide to go with 3 yreas. But few PRVs have comments in history like light deposits at inlet out let and gasket cut or disc cut. i m plannin to go with 1 or 2 year depend up on service if H/C then thinking of 1 yr and if utility then thinking of 2. what u says??

 

[dcasto]

Use risk based inspection as outlined in API RBI. The table Jalton set forth is a good guide for maximum times.

 

[Vaione]

Thank you Dcasto. Well our company has inspection interval 3 yrs for PVS. I have 2 set of history for PRV, but for few PRVs test reports show that light deposits at inlet and outlet. and also some had mechenical repiar like disc lapped and gasket lapped. can anyone tell me should go ahead with 3 yrs or make it 2 becoz see it has been repaired already.?? please guide me?

 

[dcasto]

Because PSM requires documents and good engineering practices, you need these two. Because you have data points about deposites that could cause reduced capacities, I'd find the common cause of those deposites and then any PSV in the same service would have a 2 year inspection. The valve lapping is a leak and sealing issue left to your air emmissions people and risk analysis of venting gases/liquids.

We set up a matrix of questions about the process that includes temperature, pressure, material being contained properties and score the PSV. It's like the risk matrix you used in the PHA where the probability of failure is judged against the consequences. Then asign an inspection time period between .5 years and 5 years. the worsts or shortest time period send up on our dirty, sour, wet, ugly pumps, and the 5 year on LPG storage tanks, Cryo plant outlets, ect....