How to adjust the 110% flow rate of a motor-driven reciprocator
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One in use and one as backup, driven by a motor with a fixed speed; the compressor is certainly designed for 100% flow rate. So how is 110% flow rate adjusted? Does the backup unit operate at reduced load, or is 110% taken into account during the design of the reciprocating pump and the motor, so that the maximum exhaust volume corresponding to the motor’s speed is 110%?
This is a fixed-frequency motor; its speed cannot be adjusted. If only one compressor is operating, the exhaust flow rate can increase only if the back pressure is too low. Clearance, unloading, rotational speed, backflow, and so on are all designed to reduce flow rate.
So I’d like to ask how this 110% flow adjustment is achieved? All the other adjustment methods result in a decrease
Some insights on reciprocating compressors: http://bbs.hcbbs.com/thread-1001423-1-1.html (Source: Haichuan Chemical Industry Forum) You can take a look at this post. Back pressure decreases, and the exhaust volume increases slightly.
Three ways to increase flow rate: 1. Reduce back pressure； 2. Increase stroke length ； 3. Reduce the spring force of the valve spring ；
I can tell you with certainty that the compressor is designed for the maximum flow rate specified. If the adjustment range is 60–120%, then the compressor is designed to handle a flow rate of 120%; during operation, the amount can be adjusted accordingly
1. Reducing back pressure has some effect in single-stage compression, but no effect in multi-stage compressors. 2. Increasing the stroke means replacing the compressor. 3. Spring force implies a new design for the gas valves; these are not methods to increase flow rate in reciprocating compressors.
Do you mean that if the air volume required by the process is 40,000 m3/nh, and the desired adjusted flow rate is 60–120%, then the rated flow rate of my compressor should be set at 40,000*1.2=48,000? But during normal operation, the operating flow rate is maintained at 40,000 through backflow or unloading – is that correct? Also, what is the purpose of this 20% margin in the manufacturing process?
Compressors often need to adapt to various operating conditions, with a margin provided to cover incomplete operating conditions upstream and downstream of the compressor as well as other scenarios. This is my understanding; I work at a compressor manufacturing factory, not in the process engineering department of a design firm.
1. Its effectiveness is indeed limited. 2. Increasing the stroke does not necessarily mean replacing the compressor; the stroke of a compressor can be adjusted. 3. The spring force is also not fixed and can be adjusted as well. 4. Additionally, to account for design margins, if the process requires 40,000, then a safety or margin factor is needed – that is the margin. The design must take into account special conditions that may occur occasionally during operation, such as process fluctuations, slight overloads, equipment aging, and performance degradation, among others. Just like a motor, with a rated current of 100A, it is designed to be able to handle at least 120A – that’s what it means