This must be the perfect place to ask this question as i see a lot of experience among the users.
What are the experience(pros&cons) with the different types of valves for emergency shut down? ( ball, gate (slab, expanding))
Thanks
Hi,
I am not to say if the valves are weird or not. I do agree with you that high pressure larger floaters are not suitable as a double sealing, not only will the force of the ball damage the seat, but it will also affect the integrity of the stem.
This is a 4" low pressure valve with a pipe OP...
Do have a few floating ball valves (with single piston seats) in our plant, with cavity drain. We use some as double isolationvalve, but to do so you need a cavity drain regulate the pressure in the cavity. It might not be a standard from any supplier, but they do exist. As long as the upstream...
It depends on the seat configuration. If you have floating seats, the pipeline pressure will push the upstream seat towards the ball and you will have a double isolation. Take a look at the valve drawing, or you can verify the tightness of the upstream seat through the cavityvalve. Both floating...
It is not a requirement to have pressure at both upstream and downstream seat, but a SPEXSPE will give only you a single barriere independent of which side the pressure is coming from.
The SPE seats are designed to reliev overpressure in the cavity (as Roberto1956 are stating).
My main point is...
Hi,
It does not seem very strict to me. We evaluate the neccesity for singel or double barriere according to the pipe pressure and medium. I do not see any reason for having a limit of 40 degrees C as we do have hazardious medium below this temp. By doing the correct valve choice you can easily...
The cavity relief is determined by the spring force of the seats(normally 7-10barg). If you pressurize the cavity of a closed ball valve with atmospheric pressure at upstream and downstream flange, the seats will relief the pressure when you reach the spring set point (more or less the same as...
To make this correct You need to discuss with both the valve and actuator supplier. Normally this is standard in the documentation delivery from the supplier.
It will also be dependent on the seat design of the valve, floating seats require different break-away torque than fixed seats, but as...
There are several european companies (e.g Petrolvalves, Pacson etc) that produce valves according to API 6A PR2 with 5000psi presure rating, depending on the size if it will be a special design.
Just out of curiosity, any reason for choosing an expanding gate?
Hi,
Be sure not to confuse DBB and DIB. For a DIB you need a second block ( e.g double piston downstream for trunnion ball).
You can choose to use a DPE x DPE or SPE X DPE dependent on what you need the barriere for.
A DBB valve has 2 seating surfaces to have seat sealing against pressure from...
Hi,
Not 100% sure excactly what you mean, but SPE X SPE seated valve is common and in use for many applications not requiring double barriere. Can also refer to it as a DBB.
To be able to give you a good answer i need to know the purpose of the valve
The main issue is the delta p, what is the max the valve will be open at? Not all valve manufacturers has a good seat design.
For a valve with sound softseat design, you should avoid opening the valve with more than 60barg DP. For higher DP you should use metalseat, or for high pressure a...
Hi,
We do not have systems requiring DPE X DPE. Always use SPE X DPE where the SPE seat work as a overpressure cavity reliev. Not necessary with a separate PSV from the cavity.
Not excactly sure what you mean by differential pressure test, but when i schock the valve i normally use 15-20barg...
Hi,
Yes, the valve was still leaking a bit after cleaning and lubrication of the seats.
To shock the valve you need to rapidly realive the cavitypressure through the cavitydrain valve. This might loosen the seat that still not loosened from the seatpocket.
Just note that it doesn't always work:)
I agree with littleinch.
We use the DIB2 valves to enable maintenence of equipment, but i always use the body cavity to monitor the first barrier(SPE) leakage as we do have a strict requirement for a double barrier. In addition i sometimes use the cavity drain to pump some pressure to the...
If you need a double block and bleed valve you have plenty of choices. Expanding gate valves gives you mechanical sealing, a slab gate can also do this as long as you have floating seats. Ball valves can also give you the correct sealing. Just be sure that you differentiate between double block...
