PSV vs rupture disc 1

[nihili]

Hi everyone!

Recently I have been involved in the design of a hydraulic circuit with heavy pumps. The prblem came when we studied the shut off case. In case of shut off the piping were not able to stand the pressure so we decided to install PSV valves. Normally, this is not a problem, but in this case, the flow to evacuate was so high that we (advised by several suppliers) had to install 8 PSV valves.

The question is, if it is possible to use rupture discs when if using PSV it is needed so many of them taking into account we are talking about big flows.

Flow l/min 174440
Set pressure barg 19
Back pressure barg 10

Is it ok regarding ASME?

Thanks in advance

 

[don1980]

Using a disk is perfectly acceptable from an ASME perspective, but it's definately not good solution from an operability perspective. In liquid-filled systems a disk has a high risk of premature failure, caused by brief pressure spikes which are inevitable in liquid systems. You also have to consider where to send this stuff when/if the relief device opens. That's expensive if it requires more equipment and more instrumentation, which it commonly does. For cases like this I'd use a HIPPS that trips the pump when the pressure exceeds the limiting value. HIPPS are typically more expensive than relief devices, but in this case it's just the opposite.

 

[LittleInch]

That's some flow rate, over 10,000 m3/hr. What is this?, a tanker loading system?

Burst disc is only normally used when encountering something which has a very very low probability of occurring but high consequence. If this happens any time you come to a sudden halt, burst discs are not the answer. They are probe to accidental rupture, cannot be tested, degrade with age/corrosion and if the break need a shutdown to refit new ones.

You needed to look at all the options including up rating the pipework or using HIPPS or other instrumented systems, other surge relief devices such as accumulators before you determine which odds the best for your particular system.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[nihili]

Thanks a lot. I have been having a look through the web and:

- I apparently ASME VIII allows the use of this kind of systems for vessel protection. Do you know if ASME 31.3 and 31.1 allows the use of HIPPS???

- In all cases I have found in the web, the final elementis a valve. Do you know if the final element can be a pump motor?? The idea is that if I have an overpressure, I switch off the pump.

Once again, thanks a lot.

 

[don1980]

The ASME authorization for HIPPS is found in ASME Sec VIII (UG140). There's no similar provision written into B31.3, but one doesn't need such authorization in to use HIPPS to protect piping systems (B31.3) from overpressure. That's because the Sec VIII and B31.3 requirements are different. By default, Sec VIII requires active protection against overpressure (typically a relief device) for all pressure vessels. Piping (B31.3) doesn't have this default requirement. Relief devices are installed on piping systems by exception rather than by default. If there's a credible cause of overpressure then the piping system must be protected by a relief device, but it's the users responsibility to determine what is and what isn't a credible risk of overpressure. Thus, the user is empowered to rely on a HIPPS, rather than a relief device, to protect piping system from a potential cause of overpressure.