Optimizing Reciprocating compressor performance: Reveal Critical Insights Into Cylinder Valves Issues

Continuing the previous article on reciprocating compressors—one of the crucial components is the cylinder valves, essential for efficiency and power. These valves are the first components facing the process gas, making them vital. However, they are the first to be affected when operating parameters deviate from the design.

Their role and working principle seem simple—opening and closing based on pressure differences. Yet, the timing and swiftness of these motions are critical.

So, why do cylinder valves fail? What causes maintenance and operational headaches? It's not always one cause but can be a combination of many.

Firstly, let's rule out design flaws. If the compressor initially runs smoothly as per specs, any change may lead to different problems. If we notice a reduction in lifetime, we have to think in other directions and detect the changes.

If you missed the first article, please go through it; it takes 2 minutes. We explained the possibility of losing history and not noticing the small gradual changes happening in the operational side or compressor overall health condition due to incorrect maintenance philosophy.

Remember our talk about gradual changes over time? Valve lifetimes drop from the expected 8000 running hours annually to 4000 or even 3000 hours. This leads to frequent unexpected and costly shutdowns.

Let's dive deeper into what affects cylinder valve performance:

Gas Composition: Yes, this is one of the main possible causes—gas composition, gas molecular weight, corrosiveness (critical elements such as H2S, HCL, CO2, O2, etc.). If these elements' percentages may change over years and were not considered during design, they may impact the valves' lifetime and be a source of cracks leading to failure of different components later on.

Molecular Weight: Even tiny changes stress valve elements differently, potentially increasing the loads and wearing rate, causing early wear and reducing lifetime.

Dealing with different Process gas type: Handling H-C gases with pressure and temperature shifts is tough. The gas might be pushed into a saturated phase (a mix of gas and liquid). Detecting and proving that partial gas turned into liquid is quite challenging because once the pressure and temperature returns to normal atm condition, it goes back to its original form (gas). Most maintenance and mechanical engineers lack the chemical experience part and understanding. Therefore, it may be wise to involve a chemical expert if required and check the pressure enthalpy curve.

Gas Quality: Dirt in the gas harms parts, increasing wear. Solid particles, impurities in the gas—killers for all wear parts no matter how good the design. Certain valve types will have longer lifespans than others, but they are significantly impacted, and lifetimes reduced due to increased wearing rates. Solid particles may be more detrimental in lubricated applications. Instead of forming an oily layer to reduce wear, they mix with the particles, resulting in an abrasive sticky paste that increases wear rates, delays valve actions, and stresses internal components.

However, changes in gas composition or quality may not be fully controlled by end-users and operation teams. This is a fact we must acknowledge. In such cases, re-looking into the valve design and material becomes essential. It's not because the as-built design is bad but because this valve type, design, and material might not be suitable anymore for the current conditions and parameters.

In lubricated systems: excessive oil injection inside the cylinder can cause wear and sticking.

Other factors such as condensation and liquid carryover, chemical reactions, pressure changes, or prolonged unloading of suction valves affect valve life.

Valve maintenance or repairs: It is always advisable to repair valves in certified service centers following OEM standards. Standard valve repair isn't complicated; it might appear simple, but it entails numerous details, knowledge, know-how, and hands-on experience.

These are essential to achieve a repaired valve that performs equally to a newly purchased one but at a lower cost. It is also crucial to test the valve using air to obtain measurable leakage results through restricted testing criteria by a certified and calibrated leakage test equipment to ensure the final repair quality.

An important note: Standard valve repairs or purchasing new valves will not increase valve lifetimes if we are facing any of the issues mentioned above. Without understanding the root causes, improving the situation becomes challenging.

Valves are vital; eliminating or reducing factors affecting them will boost compressor performance and availability.

In upcoming articles, we'll explore more wear parts and potential solutions. Stay tuned!