I recently came across a test paper in which the answers to some true/false questions puzzled me, so I’m posting those questions here in the hope that everyone can discuss them

The original poster has posted this in the wrong place; it should be posted in the Chemical Machinery section

This statement should have a premise; without one, it is not precise. When a compressor starts under no-load conditions, that is, when it operates without a load, a certain amount of gas is still required, but the volume of gas used is at its minimum. If pressure is increased and the compressor is loaded, the gas consumption will rise; as a result, the gas consumption of the other compressors connected in parallel will decrease accordingly. This, especially during the production process, can affect fluctuations in the production load.

Our factory uses hydrogen-nitrogen compressors; if they are started under load, it is easy for them to shut down, which affects production and is also detrimental to the compressor’s lifespan. In addition, when operating without a load, it is necessary to check the condition of the main moving parts before applying pressure. Also, before applying load, the gas flow rate must be increased. It seems that the answer to this question isn’t very accurate.

It should be correct. In our plant, the hydrogen and nitrogen compressors are first operated at no load for a certain period of time; only after the preceding units, such as the gas generation gas holder and the desulfurization system, are operational can the load be increased gradually to start production. Otherwise, the level of the gas holder will drop sharply until it reaches a negative level, which is very dangerous

There probably isn’t a clear answer; it’s likely just an exam question created by your own organization This situation can only be determined based on the operating conditions of the equipment; when starting with a light load, it is done to avoid exceeding the equipment’s capacity, as starting under load may lead to accidents.

This answer is incorrect; generally, running the compressor without a load is done to protect the compressor and the motor (prime mover).

This answer is incorrect; generally, running the compressor without a load is done to protect the compressor and the motor (prime mover).

In my humble opinion, it should be to prevent impacts on the system...

The valves that are integrated into the system at startup should be closed, right? Open the discharge valve before starting, and then close them one by one after startup. When the pressure is roughly equal to the system pressure, open the valves that integrate into the system… This helps to mitigate any impact on the system and prevents the medium inside from flowing back. So I think this answer is correct…

I checked our factory’s operating procedures, and it indeed is done that way. As for the exact reason, I asked a few senior employees, but they weren’t very sure either! It’s probably really designed for specific situations! !

The question you mentioned is a bit implicit. Because operating the equipment under no-load conditions is necessary to ensure that it can properly enter normal operating mode. The hazards of large units operating under load have been discussed above. It is to prevent equipment failures caused by excessive motor load and unstable initial operation of the unit. Therefore, when in use, it is necessary to consider operating at no load first and then gradually connecting to the grid. Because even if it is connected to the grid too quickly or too slowly while in operation, it will definitely have an impact on the process system. By the same logic, if the equipment is in good condition and operating at full capacity, how can the pressure in the process system be maintained at that moment? So I think the answer to this question is correct, but there is a flaw in this reasoning itself.

To reduce the motor starting current, protect the equipment, and buffer the material feeding time and process, which facilitates a smooth loading of the system: lol

It can be said that this answer is one of many; combining everyone’s answers above results in a standard answer.

It’s just that the current is high at the moment of startup; there’s nothing unusual once it returns to normal

Everyone should not discuss the original poster’s question on a broader scale; it has its own limitations, as these are determined by the characteristics of their own factories, and there is nothing wrong with that. If the discussion is left open, any answer has room for scrutiny. The so-called “no load” can be vividly described as putting down one’s burdens, or staying in the same place without moving forward. Its so-called impact mainly pertains to the impact on production systems. As long as the device is operating, it will inevitably have an impact on the devices connected to it. So the answer is correct.

That makes sense, right? It’s easier to understand this way. Perhaps there’s no absolute truth regarding these things, but it’s still useful to discuss them; at least it will help us be more careful in future operations! I’m also very grateful for your answers!