Rupture disk 3

[gguliye]

Dear All,
the datasheet says that the forward acting rupture disk (grooved one) can handle high level of vacuum, where i dont agree with it. I can understand that this grooved rupture disk will explode according to the predetermined pattern, along the grooves if excess pressure exists in the inlet, however the thing is that if the vacuum exists in the inlet, the rupture disk will be sucked towards the inlet thus will have irregularities on the surface. I believe those irregularities will have negative effect on the operation(can lead to fragmentation if extreme vacuum exist) am I right?

 

[monkeydog]

Ask your supplier for test data.
Extreme vacuum is a pressure differential of 14.7 psid.
Are you thinking of a downstream pressure of a much higher pressure and the inlet pressure at ambient creating a pressure differential much higher than 14.7 psid?

 

[gguliye]

monkeydog, yes, -5 barg, -10 barg for example

 

[monkeydog]

Then I would agree with you, the burst disc is probably not the correct application for this system. Industrial pipe experts on this forum can probably direct you to a better solution such as relief valve.

 

[RVAmeche]

Sometimes rupture discs are used on reactors and the like where there are both vacuum and pressure operating conditions depending on what they're doing in the vessel. The rupture disc may be saying it can tolerate high vacuum (not cave in to the process reactor) but its purpose is to relieve pressure. If you need a vacuum break or something, that may be a different device (such as a vacuum relief valve).

 

[gguliye]

RVAmeche,
I mean suppose, i have set this rupture disk to 10 barg. Unexpectedly, the pressure in the inlet is -5 barg, what would happen? Would this rupture disk sucked inside the pipe?
regards,

 

[RVAmeche]

The disc is mounted in a disc holder so the disc won't get sucked in. You'll have to discuss the worst case vacuum dP with the vendor to ensure it can withstand it.

Note full vacuum (0 psia) is -1.055 barg so I'm not sure where -5 barg is coming from? -5 bar would be -72.5 psi which doesn't make sense unless you have full vacuum inside the vessel and high pressure outside the vessel.

 

[Compositepro]

Qulu, the situation you describe should never occur. Rupture discs protect vessels from over-pressure and must relive pressure to atmosphere. If there is any possibility of positive pressure on the downstream side of the disc, it cannot protect the vessel. Vacuum is -1 barg. It cannot exceed this value.

 

[gguliye]

Thank u all really for ur huge help. I though there is no limit in vaccuum, that wasnt true..
Thank u

 

[RVAmeche]

Be sure to have a senior engineer review any designs or quotes. Process safety equipment is important.

 

[gerhardl]

First thing you have to define the necessary design and operating pressure limits based on the operation you have, both for safety devices and for the vessel.

Pressure differences on both sides of a safety device might vary, but for a single-shell vessel placed in atmosphere the outer pressure can by definition never be greater than the atmosphere.

A bursting disc can be made to withstand a negative pressure, but the whole balance of bursting pressure value and tolerance is limited to material choice, type and brand ability of the bursting disc.

A vacuum protection and pressure relief combined valve could be an alternative choice to your problem.