Our Guide to Condition Monitoring Reciprocating Compressors
Reciprocating compressors are essential for several production processes, especially in the oil and gas, petrochemical, and chemical industries. As a result, they are used extensively and often operate like perpetual motion machines, 24/7 and 365 days per annum, while retaining an incredibly high degree of efficiency.
However, as with equipment that runs frequently, breakdowns occur, which have severe consequences. This includes risks to plant safety, production loss, environmental damage, costly consequential damages, and so on.
Therefore, one of the easiest and cheapest ways of resolving this issue is via condition monitoring. This prevents consequential damages due to machine breakdowns.
What is Condition Monitoring?
Condition monitoring refers to the process of checking out the parameters of a machine. This includes:
- Temperature
- Noise
- Vibration
- Alignment
- Oil, etc.
Condition-based equipment health monitoring systems are critical additions to machinery in order to monitor the entire system. This ensures the reciprocating compressor runs remarkably well at peak efficiency. It also helps prevent catastrophic failure by discovering issues on time and schedule maintenance accordingly.
In many cases, condition monitoring systems are used in combination with a wide variety of sensors. This makes it easier to predict precisely when service will be required for different wear components while keeping the reciprocating compressor running optimally.
An excellent prediction of machine health is usually accompanied by analyzing and measuring different vital parameters and accurately detecting when the critical parameters deviate from specified values.
Why is Monitoring a Reciprocating Compressor So Important?
Reciprocating compressors enjoy specific capabilities such as interstage cooling, broad capacity control ranges, incredibly high compression ratios, as well as the flexibility to compress gas irrespective of k value and mole weight.
Therefore, this makes them a perfect fit for selected applications such as hydrogen compression in the popular de-sulfurization process of refineries as well as part of the production of low-density polyethylene production processes, just to name a few.
However, reciprocating compressors have one major drawback: extremely high maintenance costs. Reciprocating compressors can easily consume as much as 5 times the amount of maintenance dollars compared to centrifugals of similar size.
A conditioning monitoring system is primarily designed to cover the most frequent – and essential – causes of routine wear and failure in compressors. Such conditioning monitoring systems can help close the gap, considerably minimizing maintenance costs to levels linked with centrifugal compressors.
Implementing Condition Monitoring
The effective implementation of condition monitoring into reciprocating compressors requires the consideration of several critical factors. These essential factors must be observed with unwavering resolve to prevent severe damage to the driver and the compressor.
The inlet and discharge pressures and temperatures are vital in this regard. The power draw of the driver can also help influence failure onset. Whenever the power draw increases, the compressor’s losses start building up or accumulating. This makes the driver start working harder in order to have similar performance outputs from the compressor.
A highly effective method of implementing condition monitoring is by making use of a PNN (probabilistic neural network). For example, you can make use of unhealthy and healthy compressor data to create a probabilistic neural network of a compressor.
The overall health of a particular reciprocating compressor can be predicted via the results obtained from making use of a probabilistic neural network if implemented in real-time applications.
Identifying the Defects
A condition monitoring system for reciprocating compressors must consider the types of malfunction and failures that may occur. It must then provide precise measurements for detecting these issues.
Some of the most critical malfunctions associated with reciprocating compressors include:
- Worn rider bands
- Excessive piston rod flex
- Leaky pressure rings
- Excessive crosshead clearance
- Leaky pressure packing case
- Excessive combined rod load
- Excessive bushing/pin clearance
- Excessive cylinder and crankcase vibration
- Excessive crosshead clearance
- Faulty cylinder discharge valves
These are just a few defects typical of reciprocating compressors.
Challenges Influencing the Monitoring of Reciprocating Compressors
- Using Portable Vibration Analyzers Instead of Online Monitors
Reciprocating compressors are essential and always require critical handling. However, many cases abound in which no condition monitoring specialists observe them.
For instance, portable vibration analyzers are used routinely on rotating equipment. But they are not too suitable for reciprocating equipment and have monitored compressors for several years without success.
Hence, the machine’s overall health is ignored and misdiagnosed until severe damage occurs. At this point, saving the machine from critical failure becomes highly unlikely.
Portable vibration analyzers are only helpful for non-critical equipment that go long periods between failures. The best way to condition monitoring reciprocating compressors is via the use of online monitors. The latter is most beneficial for critical units and machines with short point-to-failure time frames.
Conventional vibration analyzers are only well suited for detecting faults early in other types of machines but have severe limitations with reciprocating compressors.
- Uneven Forces
Reciprocating compressors mostly generate uneven forces with typically intermittent processes. This is why the overall vibration amplitude is mostly unaffected and provides little to no warning of serious equipment failure while severe damage may exist.
Moreover, mechanical looseness produces very impactful short-duration waves and high amplitude spikes that require continuous monitoring on crossheads for early detection. Only online monitoring systems offer this kind of observatory power.
- Valve Problems
Lost valve springs (earlier opening impacts) and sticky valves (delayed opening impact) are some common valve problems to contend with. These issues call for a crank-angle tracking system for detecting faults.
In addition, wear in rider bands, compressor piston rings, as well as other operational failures or malfunctions can be pretty difficult to detect by conventional analyzers.
They demand special continuous monitoring via the use of internal sensors.
Online Monitoring Systems
The primary intent of installing online monitoring systems is to ensure the general safety of assets, personnel, and the environment. However, it also offers critical data that engineers and operators can utilize to assess the machine’s condition, determine the equipment’s availability, and make informed decisions.
In a few cases, this critical data may even be employed in order to maximize machine health and operating efficiency.
Conclusion
Investing in close monitoring of your reciprocating compressor is vital. It ensures every aspect of the equipment is functioning optimally and makes it easy to detect early malfunctions in machines quickly. Ignoring its use may result in ineffective machine operation and costly downtimes.
The best way of monitoring compressors is via online monitoring systems. This ensures the safety of operators and assets while making it easier to detect faults in reciprocating compressors.
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