Reciprocating compressor flow control methods

Reciprocating compressors are widely used in various industries to compress gases. The flow rate of these compressors depends on the speed, the cylinder size, the clearance volume, and the valve characteristics. In this post, I will discuss some of the methods to control the flow rate of reciprocating compressors and their advantages and disadvantages.

One of the simplest methods to control the flow rate is to vary the speed of the compressor. This can be done by using a variable frequency drive (VFD) or a throttle valve. The advantage of this method is that it maintains a constant compression ratio and efficiency. The disadvantage is that it may require a broad range of speed variation and may affect the lubrication and cooling of the compressor.

Another method to control the flow rate is to use a suction valve unloader. This is a device that holds the suction valve open during part of the compression stroke, reducing the effective cylinder volume and the flow rate. The advantage of this method is that it can provide stepless flow control and can operate at low speeds. The disadvantage is that it reduces the compression ratio and efficiency and may cause valve wear and noise.

A third method to control the flow rate is to use a clearance pocket. This is a chamber that can be opened or closed to increase or decrease the clearance volume of the cylinder. The advantage of this method is that it can provide stepless flow control and can operate at low speeds. The disadvantage is that it reduces the compression ratio and efficiency and may cause pressure pulsations and vibrations.

These are some of the common methods to control the flow rate of reciprocating compressors. Each method has its pros and cons and should be selected based on the specific application and operating conditions.