Where should the three-valve assembly for the process pipelines of the inlet and outlet devices be installed?
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SH/T 3122-2013 \"Specifications for the Design of Process Piping in Refining Units\" states that \"at the inlet of the process piping to the unit, a shut-off valve, a check valve, a drain valve, an 8-shaped blind plate, and another shut-off valve should be installed in sequence.\" Additionally, \"at the outlet of the process piping from the unit, a shut-off valve, a check valve, a drain valve, an 8-shaped blind plate, and another shut-off valve should be installed in sequence.\" If that’s the case, I would like to ask everyone: for the three-valve assemblies related to the nitrogen and vent pipelines as shown in the diagram below, should they be placed inside the equipment frame or on the pipe rack, near the main nitrogen and vent pipes? What do you all think?
This post was last edited by Hansonwen on 2018-7-24 at 16:06. You might have a misunderstanding of the standards; clause 3.3 of SHT 3122-2013 applies to process pipelines, not utility pipelines. This requirement is consistent with clause 7.2.16 of the GB50160 petrochemical standards, which states that for pipelines carrying combustible gases, liquefied hydrocarbons, and combustible liquids entering or leaving a facility, isolation valves and tee blind plates should be installed at the boundary of the facility； Such valves should be placed as far away from the equipment as possible, so that in the event of a fire, it will be possible to approach them and cut off the feed and discharge, thereby preventing the fire from spreading further ； 1) For utility pipelines such as nitrogen/deionized water/fresh water entering and leaving the plant area, it is not required to install this set of valves; a shut-off valve is sufficient. However, at the connection points where utility systems meet process pipelines, valve assemblies shall be installed in accordance with Section 3.4 of SHT 3122-2013; this also complies with the requirements specified in Clause 7.2.7 of the petrochemical regulations. The valve assemblies are to be placed near the connection points of the process pipelines. Hard connections are provided for utility systems and process pipelines or equipment; such valve assemblies are installed at the connection points to prevent flammable, explosive, high-pressure, or toxic process media from leaking into the utility system. 2) There is no requirement to install such valve assemblies at the inlet and outlet of the vent piping into and out of the boundary area, and there is a risk of them being accidentally closed, which can result in poor pressure relief and venting as well as pressure buildup within the system.
Thank you for your advice. So, the three-valve assembly and control valve for the nitrogen line should be placed near the process pipelines it is connected to, right? As for why the bypass wire is designed in this way, I’m not quite sure either; I checked several standards and found no similar provisions
I’m asking for an explanation of this passage; I don’t quite understand why three valve assemblies need to be installed
Prevent hazards caused by failures in the single-cut-off valve