9 replies to this topic

[Questions34]

Hi All,

 

Long time reader, first time poster.

 

On the weekend we had a rupture disc fail on a liquid nitrogen storage vessel (100T capacity, 25% full, 11.5 bar), resulting in the entire vessel contents being lost to the atmosphere.

 

The plant trends showed the vessel pressure was being controlled by a vent valve at 11.5 bar at the time of failure. 

 

The vessel is fitted with a PSV and RD in parallel, with the SP of the PSV 12.5 bar and the RD 13.75 bar. The PSV was not activated before the RD failure.

 

What could be some possible causes of a premature RD failure? 

 

 

Thanks in advance!

[Bobby Strain]

Many are possible. Most likely cause is corrosion on the atmosphere side. You will only know when you inspect the disk. Depending on your location, you may be able to install a block valve so you can prevent loss of the tank contents, and make disk replacement easier.

 

Bobby

[Questions34]

We initially suspected corrosion on the atmosphere side due to the presence of acid vapours in the air surrounding the storage vessel, however, after removing the RD and inspecting, there appears to be no signs of corrosion present.

[breizh]

Hi ,

It might be fatigue which leads to rupture . How long this unit has been in service ? PM program may help.

Hope this helps.

Breizh

Edited by breizh, 23 January 2017 - 09:34 PM.

[Questions34]

Hi ,

It might be fatigue which leads to rupture . How long this unit has been in service ? PM program may help.

Hope this helps.

Breizh

 

Vessel has been in service for less than a year, approximately 9 months.

[fallah]

 

On the weekend we had a rupture disc fail on a liquid nitrogen storage vessel (100T capacity, 25% full, 11.5 bar), resulting in the entire vessel contents being lost to the atmosphere.

 

The plant trends showed the vessel pressure was being controlled by a vent valve at 11.5 bar at the time of failure. 

 

The vessel is fitted with a PSV and RD in parallel, with the SP of the PSV 12.5 bar and the RD 13.75 bar. The PSV was not activated before the RD failure.

 

What could be some possible causes of a premature RD failure? 

 

 

Hi,

 

Lack of info about type and material of RD... also about the operating temperature of the vessel...

 

Anyway, as appears the operating temperature of the vessel to be very low, brittle fracture due to low temperature can be the reason of premature failure of RD...
 

[Saml]

Is 13.75 the actual stamped pressure? or it is the P&ID value?. What is the manufacturing range?  

What is the operating ratio by manufacturer spec? You were operating at 80% ratio. However there are disks (ie: Fike P) that require 70%.

Also, mounting of the disk in the holder is critical regarding bolts torque and bolting sequencing.

[Questions34]

 

 

On the weekend we had a rupture disc fail on a liquid nitrogen storage vessel (100T capacity, 25% full, 11.5 bar), resulting in the entire vessel contents being lost to the atmosphere.

 

The plant trends showed the vessel pressure was being controlled by a vent valve at 11.5 bar at the time of failure. 

 

The vessel is fitted with a PSV and RD in parallel, with the SP of the PSV 12.5 bar and the RD 13.75 bar. The PSV was not activated before the RD failure.

 

What could be some possible causes of a premature RD failure? 

 

 

Hi,

 

Lack of info about type and material of RD... also about the operating temperature of the vessel...

 

Anyway, as appears the operating temperature of the vessel to be very low, brittle fracture due to low temperature can be the reason of premature failure of RD...
 

 

 

Material is 316L stainless steel.  

 

Is 13.75 the actual stamped pressure? or it is the P&ID value?. What is the manufacturing range?  

What is the operating ratio by manufacturer spec? You were operating at 80% ratio. However there are disks (ie: Fike P) that require 70%.

Also, mounting of the disk in the holder is critical regarding bolts torque and bolting sequencing.

 

13.75 +- 5% is the stamped pressure on the RD.

 

Operating ratio is not mentioned anywhere.

[Adodic1]

What relieving conditions was the RD sized for? If the RD was sized to relieve at the conditions in the tank then it is possible that heating by ambient air and sunlight warmed the RD to the piint whee it failed at a lower pressure. Plot the relieving pressure of the RD against temperature and you may see that it failed at a higher temperature not pressure.

Please let me know the results.

[shvet]

1. Pressure increase in past? Lets imagine that once before pressure rised up to 13-13.5 bar and PSV relieved and lets say it was a pike pressure rise. RD has not opened but anyway metall has changed and real SP of RD droped up to operating pressure. Anyway instrument trends in control station can give you a possible answer.

2. Manufacturer's defect. Unlike PSV, RD manufacturers can't check their devices on pressure test bench.

Edited by shvet, 23 March 2017 - 11:29 PM.