We would like to ask about equalizer pipe in gate valve. What are the functions of this pipe? Is there any standard that regulates the sizing of this pipe? What are the consideration for the sizing of that pipe?
For 20′ gate valve for HP steam valve, what shall the size be for the equalizer pipe?

Tanya – Alda Adrina

Dear all,

We would like to ask about equalizer pipe in gate valve. What are the functions of this pipe? Is there any standard that regulates the sizing of this pipe? What are the consideration for the sizing of that pipe?
For 20′ gate valve for HP steam valve, what shall the size be for the equalizer pipe?
Thanks before.

Tanggapan 1 – Crootth Crootth

Alda,

Imagine that you – alone – to open the 20′ valve which isolate HP system (says 1000 psig) and lower pressure system (says 100 psig), the differential pressure (900 psi) will inhibit you to easily open that valve. And you will ask for more manpower to help you out, as well as using any other tools (in some real case, a long stick of steel or even wood, which poses more risk to you), to open it. Three or more people stand on the vicinity of piperack – let assume this valve lies in 4 – 6 m high, will result in hazardous position.
That is the way people install a smaller valve to help you out – as well as to save your energy – during opening or closing the valve which has high differential pressure.
I don’t know if there any API Std or ASME Std regulate this condition, but for sure, some company have theirown regulation to address this.

Tanggapan 2 – Alda Adrina

Dear Gharonk,

Thanks a lot for the response, very helpful. Beside of operational reason, is it also for equalizing the entrapped steam pressure in bonnet cavity?
Otherwise the entrapped steam will be heated up which can result in a dangerous pressure rise.
Unfortunately, we don’t have our own regulation to address this matter.

Tanggapan 3 – Crootth Crootth

Alda,

Honestly I never dealt with any Steam Generation and Piping system, I have no idea with entrapped steam.

As far I know, for hydrocarbon processing, depends on the differential pressure, the common size for equalization line is 2′.

Tanggapan 4 – okto

Hi guys,

In my opinion, your gate valve is not the bubble tight class valve and your seats are metal seats (due to your HP steam fluid service-no soft seat could bear the pressure and temperature). If that is correct than you should not be worried about pressure rise up in the valve cavity because your steam will passing through, in very small rate.

If that is a bad guess than,

Fluids entraps in the valve cavity normally occurs on the bubble tight class valve (level 6). Where the fluids could enter valve cavity area due to high pressure on the upstream side could push the (ball, gate – depends on valve type) makes a passage that the fluids can go through but on the other side the sealing effect is getting tighter and it traps on the cavity.
The only way to release it is by providing pressure release device such as vent or drain or even psv installed on the valve body.