Requirements for the location of instrument pressure tapping pipes
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I encountered the following issue in the design and am seeking help. In the process pipeline under test, surface-mounted pressure switches are required; in the initial design, these two instruments were connected together using a single pressure conduit for measurement. Some people have suggested that this does not comply with the design specifications. Which specification requires this, and are all measuring instruments necessitated to have separate pressure lead pipes?
There’s no need to refer to specifications for this; it’s obvious even without thinking – since it’s a switch, it must be involved in interlocking. Won’t putting it together with a pressure gauge cause any problems?
In practical use, pressure switches are unstable; it is better to replace them with pressure transducers. It is fine for the pressure switch to be part of the interlock design, but in reality it poses a serious risk
As a newcomer to the job, there are inevitably some unreasonable aspects in the designs, and I would like to know what the standard requirements are. What are the relevant design standards? It’s worth taking a look as a reference; the senior colleagues in our unit design things based on experience, and there are no so-called standard guidelines. . .
It’s rare to see ones that share a pressure tap.
I don’t know the standards. But even in the absence of such regulations, separate design is still required. First, because the pressure gauges on site are usually of poor quality and often break down, either due to water ingress or a broken pointer. So it needs to be replaced frequently. How to replace it without removing the interlock? If removing the interlock happens to be the cause of an accident, well then, let the instruments go to jail! Second, since it is a mutual reference, what is there to refer to on the pressure pipes of the same origin? The pressure measurement points are the same, so they have no reference value. Thirdly, what if my pressure tapping tube gets blocked or leaks? Both pieces are useless. If designed separately, I can move the interlock instrument to the pressure tapping point of the on-site pressure gauge, ensuring production and safety!
You, it’s clear from your words that you’re not very convinced by the senior colleague. A quick glance at the design specifications for safety instrumented systems shows clear requirements that measuring instruments and sampling points should be installed separately.
Please refer to point 4.2.7 in the last item of the above standards
Agree with you; upvote.
If this pressure switch is used in interlocks or as a sensing element in a safety instrumented system, an independent pressure tap is required to ensure higher safety and reliability. This requirement is specified in the safety instrument design standards.