Questions about hydrogen compressors

I don’t understand; please advise. It should be that the greater the pressure after third-level compression, right?

The appropriate number of compression stages depends mainly on the compression ratio. You only mentioned that the outlet pressure is 12.5 MPa; you didn’t mention the inlet pressure, so it’s not possible to determine your compression ratio. If your inlet pressure can reach over 4.0 MPa, using two-stage compression is no problem; the compression ratio for each stage can be kept below 2. If the inlet pressure is below 3.0 MPa, it is recommended to use three-stage compression, with the compression ratio also kept below 2. Piston compressors employ a multi-stage compression process primarily to reduce the compression ratio. If multi-stage compression is not used, from the intake of air to the exhaust of gas, the compression ratio would be very high, the exhaust temperature would be extremely high, the materials required for the equipment would need to be of high quality, and lubrication and cooling would present problems as well. Moreover, a high compression ratio leads to increased energy consumption. To avoid these issues, a multi-stage compression process is adopted in the design of those compression processes where the compression ratio in a single stage is too high. The compressor motor should be of increased safety type; Jiamusi motors are good quality, you might want to check them out.

We are also working on things related to reciprocating compressors, and hope to learn more and exchange ideas with everyone

It depends on whether it is secondary or tertiary compression, based on the pressure required by the system; the compression ratio determines the pressure after each stage of compression. As for whether an increased-safety type or an explosion-proof type motor should be used, that doesn’t matter – it depends on the manufacturer

Thank you for your answer. I have another question: why isn’t an explosion-proof type of motor used?

Increased safety electrical equipment was invented in Germany and has a history of over 70 years. Approximately 80% of electrical equipment uses increased safety type devices, 15% uses explosion-proof types, and 5% uses other types. Compared to explosion-proof electrical equipment, the main advantages of increased safety type devices are lower cost, lighter weight, and easier maintenance due to their economic nature. These devices do not generate arcs, sparks, or dangerous high temperatures during normal operation, and additional protective measures are built into their design to enhance the safety of the equipment. During normal operation, flameproof equipment contains the components that can generate sparks or arcs within a flameproof enclosure. This enclosure is capable of withstanding the internal explosion pressures without being damaged, and it prevents the explosion from spreading outside the enclosure.   In theory, intrinsically safe types are safer than increased safety types, but for the operating environment of hydrogen compressors, increased safety types are sufficient, which is both economical and cost-effective. Of course, it’s better to choose the explosion-proof type, but the equipment cost will increase, as will the maintenance expenses.

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Thank you. I have another question: is it true that increased safety type is used for high voltage applications and flameproof type for low voltage applications?

I don’t know what the theoretical basis for this claim is. I recommend choosing the increased safety type based on considerations of safety and cost-effectiveness. All the main motors for hydrogen compressors that I have seen are of the increased safety type, that is, those equipped with water cooling.