Some issues regarding the start-up and shutdown of centrifugal compressors
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I would like to ask some questions regarding the start-up and shutdown of centrifugal compressors: 1. In the initial stage of operation of a process system, when the pressure in the system has not yet been fully established and the pressures at the compressor’s inlet and outlet are roughly the same, it is necessary to increase the pressure gradually using the compressor. How should the compressor be operated during this phase, and what are the states of the inlet and outlet valves, as well as the bypass valve? How to increase voltage gradually. What is the difference between constant speed control and variable speed control? 2. According to the performance curve, when the pressure difference is very small (the difference between inlet and outlet pressures), the flow rate can be quite high; could this lead to overloading? Or, by using a throttle valve, the outlet pressure can be adjusted so that the flow rate remains within the limits permitted by the compressor. Generally, what is the throttling pressure difference that can be achieved with a throttle valve? Especially for systems that have just been put into operation, are there any specific requirements regarding the selection of this control valve? 3. For a normal process system where the system pressure has already been established, what are the procedures for starting and stopping the compressor at this point? How are various valves adjusted, and what are the considerations for selecting valves? 4. During the shutdown process, how should the compressor be operated? Thank you!
Your question is too broad; it should be a device user manual. It would be better to go to the reference room and find a set of targeted, standard instructions and precautions. Additionally, for the first use after the equipment is installed, there should also be a \"commissioning plan\" that can answer all your questions. As a supplementary note, operations must be carried out within the rated range of current; under no circumstances should overcurrent occur. Before starting up/shutting down, it is essential to bring the equipment to its minimum load before proceeding with the operations.
1. There is an anti-surge valve; during startup, you need to open the anti-surge valve fully first. Once pressure has been established, then open the outlet valve, and gradually close the anti-surge valve to stabilize the pressure. The inlet valve should remain fully open (this does not apply to air compressors)； 2 It is recommended that you first learn about centrifugal compressors, as well as the piping system and operation manual.
When driving the machine, first open the guide vanes and then close the anti-surge device; use the anti-surge system to control pressure. Under normal conditions, ensure that the anti-surge valve is fully closed as indicated by the corresponding line. When stopping the machine, increase the opening of the anti-surge device to reduce pressure; increase the opening of the anti-surge device and decrease the opening of the guide vanes. Eventually, leave the anti-surge device fully open, while reserving about 10% opening for the guide vanes
I am mainly referring to centrifugal air compressors; after the manufacturer has completed the commissioning process and the unit has been operating for 72 hours, the user can shut it down to prevent any oil leakage. After shutdown, the centrifugal unit automatically controls the inlet and exhaust valves, without the need for manual intervention； Before cold starting, it is necessary to ensure that the auxiliary oil pump is operating properly, that the oil temperature and pressure are stable, and that the oil level in the tank is within the normal range. Only after all these startup conditions are met can power be supplied to start the machine (usually high-voltage power is applied, while low-voltage power should be available continuously, unless under special circumstances). Centrifugal air compressors are not suitable for frequent starting; there are usually requirements regarding the number of times a high-voltage motor can be started, typically once every 4 hours.
Thank you all. My question might be quite complex – it relates to designing pipeline systems. The inlet pressure is currently 4 megapascals, and the outlet pressure needs to reach 20 megapascals in the end. However, the entire system operates at 4 megapascals from the start; it stops when the pressure is raised to 20 megapascals, but the required target pressure is 20 megapascals. The drive mechanism is a gas turbine with variable speed. According to the performance curve, the pressure at the lowest rotation speed must also reach 6 MPa; so I’m not sure how to proceed
This should be the entire startup procedure for the unit: a comprehensive pre-startup inspection of the unit → establishment of the oil circuit → low-speed warming up of the unit → adjustment of the operating conditions so that the unit can increase its speed from low to high → normal operation of the unit, with pressure being generated and the compressing medium connected to the grid. The steps for starting up the unit are outlined in both your commissioning plan and the unit’s operation manual; please check those documents
Different media require different driving methods!