What are the hazards of low inlet pressure in a reciprocating compressor?
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This post was last edited by WQC on 2009-5-28 at 13:40. Generally, reciprocating compressors are equipped with an alarm for low inlet pressure, but the exact hazards associated with this condition have not been fully understood. Let’s discuss it. Here are the points I can think of for now; I welcome any corrections or additional information from those who know more – thank you very much: 1. Low inlet pressure results in insufficient suction volume, which in turn leads to low exhaust pressure. 2. The inlet pressure is low, resulting in insufficient intake volume; however, since the compression ratio remains constant, the clearance volume within the cylinder increases. As a result, some of the gas inside the cylinder is compressed repeatedly, which leads to an increase in exhaust temperature and can cause damage to the valve components. 3. When the inlet pressure is low and the compression ratio remains constant, the exhaust pressure decreases; as a result, the opening degree and duration of the gas valves are reduced, which can cause valve flutter and accelerate wear. 4. If the suction pressure is too low, it is possible that the suction valve cannot open, causing the compressor to work uselessly.
This post was last edited by rmxg on 2009-5-27 23:53. OP, what you said is incorrect. The purpose of the low inlet pressure alarm is to prevent an increase in the compression ratio, as a low inlet pressure can lead to such an increase (it should be emphasized that for reciprocating compressors, the compression ratio is not constant), since the outlet pressure of reciprocating compressors is primarily determined by the system backpressure rather than the inlet pressure. An increase in the compression ratio leads to an increase in piston force, the compressor has to do more work, and the outlet temperature also rises sharply.
I encountered the fourth situation mentioned by the original poster during the test drive. The suction pressure is too low, preventing the suction valve from opening, causing the compressor to work uselessly.
If there is a container in front of the reciprocating machine, it is possible to create a negative pressure in that container, thereby damaging the equipment； If the medium is oil, it’s even more dangerous; once air gets in, the consequences can be disastrous.
Too low an inlet pressure affects the compressor’s ability to do work, increases energy consumption; as a result, the compression ratio rises and the outlet temperature increases, which in turn affects the lifespan of the transmission equipment, lubricating oil, and exhaust valves； Too low an inlet pressure can also lead to negative suction, which may damage the equipment located before the inlet. If the compressed medium is flammable or explosive, the introduction of air due to negative pressure can result in an explosion, which is extremely dangerous.
When the inlet pressure is low, the gas entering the cylinder gets compressed repeatedly; the amount of gas discharged is too small to carry away heat energy, resulting in a sharp rise in temperature inside the cylinder, which can damage the piston or the cylinder itself
Too low an inlet pressure is very dangerous; it’s easy to experience negative pressure. Last year, our factory’s gas scrubber was deflated due to this, and it almost led to a serious accident – it’s extremely dangerous.
A low inlet pressure in a reciprocating compressor causes the suction valve to open prematurely, which affects the volume of gas discharged. As a result, some gas is not expelled in time, impacting the efficiency of the unit; meanwhile, the repeated compression of this gas leads to an increase in the unit’s temperature. If the inlet pressure is too low, the unit will have to exert more effort when faced with a certain backpressure, which causes its components to not operate under their rated conditions; as a result, components such as bearings, pistons, and piston rings are prone to wear. If the inlet pressure is low, measures such as pre-compression or improving the inlet conditions to reduce resistance can be considered in order to increase the inlet pressure.
Too low an inlet pressure can lead to an increased compression ratio, which puts excessive stress on the piston rod and may cause it to break. In addition, low pressure can result in a too small reverse angle, leading to poor lubrication between the crankshaft and the bearing shells, and this may also cause the bearing shells to burn out.
I’m in contact with reciprocating compressors; I can start learning now
All the instructors explained things very well; what I learned has been extremely helpful to me. Thank you :hug: