Must a hydrogen buffer tank be equipped with a fixed nitrogen purge line?

Here are a few points from my personal experience for reference: Regulatory requirements: The GB50177 \"Code for Design of Hydrogen Stations\" specifies that hydrogen equipment must be equipped with an inert gas displacement system, with nitrogen purging being a common method. However, for buffer tanks specifically, it is necessary to determine whether to install them separately based on the process pressure, volume, and the interaction between upstream and downstream equipment ； Risk considerations: If the buffer tank is located in a location where explosive mixtures can form, such as at the compressor outlet, it is recommended to install a fixed purge line. For small-volume tanks operated intermittently, mobile nitrogen cylinders can be used as a substitute ； Additional note: Would it be possible to provide details on the specific operating conditions of the tank (such as operating pressure, and whether frequent start-up and shutdown operations occur)? This way, everyone can provide more targeted suggestions.

In accordance with the requirements of GB50177, it is indeed important for hydrogen equipment to be equipped with an inert gas displacement system. Regarding whether a separate fixed nitrogen purge line is needed for the buffer tank, I would like to share some practical experience: We have encountered similar situations in our projects; when the volume of the buffer tank exceeds 2 m³ or the operating pressure is greater than 1 MPa, a separate fixed purge line is usually installed, primarily to ensure efficient gas displacement and safety. It is recommended to pay special attention to the frequency of shutting down the buffer tank; in cases where it needs to be turned on and off daily, fixed pipelines will be much more convenient and can also reduce operational risks. If space is limited, shared systems can also be considered, but it is necessary to ensure that the purging pressure and flow rate meet the requirements; it is best to specify this clearly in the PID. Specifically, it is necessary to evaluate based on your process flow diagram; if possible, it is recommended to have a design institute review the plan.

"After reviewing everyone’s discussions, it is clear that GB50177 sets specific requirements for the inert gas purging of hydrogen equipment. Based on our factory’s practical experience, a few additional points: although fixed pipelines require a higher initial investment, they are safer and more reliable in the long run. We had a minor incident earlier with one of our buffer tanks due to poor sealing at the temporary connection; after switching to fixed pipelines, no problems have occurred since then. If cost factors are taken into consideration, fixed purge ports should be installed preferentially in the following locations: near the drain port at the bottom of the tank (to facilitate the removal of residues), at the top of the gas phase space (where sampling ports are usually located), and at the flanges connecting to the process pipelines. It is important to note that the effectiveness of the purge system should be tested regularly; we conduct nitrogen displacement efficiency tests on a quarterly basis, and any issues related to insufficient pressure must be addressed promptly. It would be more reliable to have the design institute carry out calculations based on your process parameters to come up with specific suggestions~"