9 replies to this topic

[anjan.paul]

I have 1,3 butadiene storage tank in my current project. Design pressure of storage tank is 7 bar(g). As a safety device we have provided PSV with rupture disc at the inlet of PSV on tank. PSV set pressure is 7 bar(g) i.e same as tank design pressure. And Rupture disc set pressure also i kept as 7(g) as per API-520,PAGE N0-16,SECTION- 2.3.2.2.2.

 

Now my question is-  can the rupture disc set pressure is same as PSV? or Rupture disc set pressure will be lower than PSV set pressure? As per my understanding i can keep the same set pressure. Please guide me.

 

Regards,

Anjan Paul

Process Engineer

 

[flarenuf]

Anjan
You can set the Rupture disk pressure = set pressure or marginally below it.

The code says
The stamped (certified) burst pressure of the rupture disk must be between 90% and 100% of the relief valve set pressure. Also, the bursting of the rupture disk and the opening of the relief valve must be essentially coincident with each other.

 

hope this helps

brian

[fallah]

Anjan Paul,

 

There are variuos guidelines (ASME Sec.VIII, API 520, EN ISO4126-3) on your request regarding set pressures of RD/PSV combination which are slightly different but with the same basic...

 

Keep the specified burst pressure of the RD same as set pressure of the PSV at nominal value. Obviously, in special cases you should evaluate the system to ensure the above approach wouldn't affect the system performance adversly...

Edited by fallah, 17 June 2013 - 06:29 AM.

[anjan.paul]

Thnx Brian & Naser........i appreciate your reply.

 

So its clear to me now. So its not mandatory to keep lower set pressure of RD than PSV. I can keep set pressure same as PSV. So my understanding was correct. Thnx u all guys.

[jrtailor09]

Anjan

 

As per the OISD guideline RD can be set at 5 % below the safety valve set pressure.

 

It can be set at 6.65 barg pressure in your case. Please don't forgot to provide the Pressure guage in between these 2 safety device for to indicate health of rapture disk.

 

Regards,

Jatin Tailor

[anjan.paul]

Hi Jatin Sir,

Thnx for your reply. Ya i have already considered pressure gauge between RD & PSV as per API guideline.

 

Regards,

Anjan

[karthik.kattupalyam]

haii ,

 

I have a question what should be set pressure of  Rupture disk and safety valve pressure (after rupture disk safety valve is there) when design reactor pressure is 22 kg/cm2

Existing :In my plant they are kept rupture disk at 17 kg/cm2 and safety valve at 16 kg/cm2.

[fallah]

Hi,

 

If your system is governing by ASME or API you are not allowed to set the RD burst pressure higher than PSV set pressure. If the governing code is EN-ISO4126 you would have no problem because the maximum limit of RD burst pressure could be 110% of the PSV set pressure; and you are within the range...

[Malek]

Karthik,

 

According to API 520, it's preferred to keep the PSV set pressure equal to the reactor design pressure but any way if the PSV set pressure is 16 Kg/cm2, the burst pressure of the combined rupture disk shall be 16 Kg/cm2 not higher.

[karthik.kattupalyam]

thaks Mr.Fallah and Mr.Malek for giving clarity