Regarding the design pressure of pipes for safety valves and steam traps
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As the title suggests, I am facing a problem regarding the design pressure for the pipes connected to safety valves and steam traps in this design. First of all, when both the outlets of the safety valves and steam traps are connected to the atmosphere, it’s not clear whether to use the design pressure before the valve or simply the atmospheric pressure (plus the pipeline resistance and height)； Moreover, in the case of a medium-pressure pipeline with a diameter of 40 kilograms, it seems a bit excessive to design it based on the pressure in the pipeline ahead of the steam trap. Another important point is that pressure relief valves come equipped with bypass pipes. Let’s discuss this – are there any relevant standards or design experiences? Additionally, I found tables regarding the design pressure for pipelines online; see the attached figures. I’m not sure if there are any standards, and whether these tables are universally applicable ； Is this standard still applicable today? Are there SH marks or other alternatives?
A bypass for the steam trap doesn’t make any sense, and the HG/t standard is merely recommended by the Ministry of Chemical Industry
They are definitely necessary in key locations, for replacement and repair purposes. Although HGT is only a recommendation, in the absence of HG, it is generally followed as recommended, unless the design institute is very strong
There are shut-off valves and drain valves in front of each trap. Firstly, their replacement frequency is very low; it’s not easy for the static equipment itself to get damaged. Therefore, bypasses are rarely used – when a malfunction occurs, the trap can be disconnected and a temporary pipe connected using the drain valve in front of it
In key locations, for example, can a bypass be omitted for the drain valve in the flash tank after the heat exchanger?
I’m not in design, but I’m familiar with the site； It is common to install two sets of hydrovanes in critical locations as a backup for each other. For safety valves and steam traps, the outlets that lead directly to the atmosphere are almost always of PN25 standard; this is a fairly high pressure rating, but the cost isn’t that high either
The safety valve for venting air is designed with a pressure of 0.35 MPa, which should represent the minimum design pressure for pressure pipelines.
What is the minimum design pressure for pressure pipelines? 0.35mpa？ How to understand it