Gate valve + TRV 1

If you read the description, this is simply for internal valve cavity relief, NOT for the pipe relief requirements.

It does not replace TRVs.

What you buy is up to you, but this looks like a foolish option to me.

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The fluid in long pipe segments expands and needs pressure relief. 1/2x3/4" or 3/4x1" liquid TRVs are pretty inexpensive compared to bursting pipes or breaking things.

Not sure where you have seen a “gate valve” which has a built-in TRV, similar to the picture?
It looks like a customer made speciality item and won’t be cheap.

My idea is clear. The design and function are simple and well known, nothing but readily available on the market on demand. All I need is to find manufacturers offering cheap replicas.

You can pipe the outlet of a TRV to the other side of a valve to avoid long runs of drain pipe.

I repeat, the valve will only relieve the cavity within the valve when closed, NOT the pipe it is connected to.

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Also: If you get a response it's polite to respond to it.

I repeat, the valve will only relieve the cavity within the valve when closed, NOT the pipe it is connected to.
See the screen attached above - TRV relieves from piping, not cavity.

This system performs the same function as the DTR system as well as protecting the piping system. When the DAN-EX valve is closed, piping is subject to thermal pressure buildup.

Click to expand...

That's even worse. Your isolation valve won't isolate if the is more than 25 psi across the valve.

Just fit some TRVs and pipe them into the upstream side. No need for fancy valves.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Your words sound like I am doing something bad. I disagree, there is a need for "fancy valves".

What is wrong with a combined device providing shut-off and overpressure protection both? My idea is still clear - I do not want to use a supplemental feature that is able to be combined. Less cost, less weak spots, less cost, more foolproof, less space occupied. Sure some disadvantages can be found, but should one discard such options because these have some disadvantages or should one compare pros&cons and find a benefit at the bottom of the line?
All we here at this forum know that thermal expansion is biased. There is no an exact "red line", boundaries are blurred and every user/operator/designer/authority creates and implements own rules&practices regarding this phenomenon. Is this fact a sound reason to ignore options available in piping design? Why a small bypass valve integrated in a gate valve for pressure equalizing is ok while a spring loaded valve having very similar features at the same position is not ok?

May be references I have used for explanation above found confusing but I intended to share major design - how those look like, but not how those work. Again, my point is - I do not ask for a design/operability /safety or whatever, I ask for a manufaturer.

shvet,

"What is wrong with a combined device providing shut-off and overpressure protection both?"

IMO, you want an isolation valve to isolate and an over pressure protection device to provide over pressure protection in all shut in circumstances.
Your valve may not do either as there is a leak path from one side to the other. yes there are isolation valves, but the whole purpose is that they are providing over pressure protection.

I personally don't agree that these combined things are less cost or more foolproof or that their benefits outweigh their disadvantages. But that's just me.

you will find many / most valve suppliers will provide tapped plugged connections on the valve body, then just pipe up between them.

Up to you to get this through a HAZOP. You seem to have found a few suppliers already?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I agree with LittleInch. This feels very similar to relying on a PD pump internal relief because its relief! its there! we're fine....

Yeah...until the system breaks.

LittleInch said:

You seem to have found a few suppliers already?

Click to expand...

Not, but I have not tried much yet.

This Omniseal valve is an integral double block and bleed with integral body relief for the inventory in between the 2 integral gates. Agreed it will provide thermal relief for the valve and piping when it is open. But after you've closed the valve, you've lost the capacity for overpressure relief for the connected piping, since the TRV is in between the 2 gates. That will not be what you want, I suspect.
In my experience in my old OpCo, Operations have moreover stopped using integral DBB such as these many years ago, especially in high pressure service. They prefer to install two separate ball valves with manual bleed in between.