Compressors damage

As vapour bubbles tend to damage pumps, so do liquid inclusions tend to damage compressors suction systems must avoid any possibility of liquid build-up or carry-over. 

Example case history 7. For a damaged compressor blade ... 

Filtration and water-knockout systems are used to clean up the gas before it enters a compressor. Cooling systems are sometimes required to maintain compressor discharge temperatures below 54°C to avoid damage to the pipeline s protective coatings. Automated compressor stations are typically staffed by maintenance and repair personnel eight hours per day, five days per week. Other stations are staffed on a 24-hour basis because personnel must start, stop, and regulate compressors in response to orders from the dispatch office. 

Indoors, a few tens of kilograms are sufficient for an explosion that can destroy the building. Outdoors, a few tons are necessary for serious damage. A roof over equipment such as compressors is acceptable, but walls should be avoided. (If leaks of toxic gases are liable to occur, it may be safer to locate the plant indoors, unless leaks will disperse before they reach the public or employees on other units.)... 

Any downtime of an expander results in significant lost revenue. When this particular damage occurred, the user no longer obtained power from the process to drive the equipment. Instead, the user was forced to buy electricity to drive the axial compressor. Depending on the power capability of the expander, losses of 300,000 per month or greater may be experienced. 

Damage to the labyrinth requires replacement of the expander heat barrier or compressor shaft seal. A replacement design (Figure 5-6) uses a replaceable stainless-steel labyrinth mounted on the shaft. Because the seal is not tapered, axial movement of the shaft has little or no measurable effect on seal gas flowrates. Each labyrinth has an integral oil slinger incorporated into the design. Also, each rotating... 

It would appear obvious for startup, and in some cases full-time operation. that a suction strainer or filter is mandatory. The reason for ilic strainer is to keep Junk and pipe scale out of the compressor. Fines from pipe scale and rust will make short work of the internal bore of a cylinder and are not all that good for the balance of the components. In some severe ca.ses, cylinders have been badly damaged in a matter of a few weeks. The strainer should be removable in service for cleaning, particularly when it is intended for permanent installation. Under all circumstances, provision must be made to monitor the condition of the strainer. Much frustration has been expended because a compressor overheated or lost capacity and no one knew if the strainer had fouled or blinded. 

The rod drop monitor is recommended for all non-lubricated compressor applications, because there is no lubricant to act as a buffer to prevent piston-to-cylinder contact on the loss of the wear band. Lubricated com pressors handling gases with traces of water or gas components that can degrade the local lubricant are candidates. Hydrogen compressors should be considered for monitors because hydrogen is a difficult gas in it sc It and may contain trace quantities of water. While sweet gas compressor-, as are found in pipeline service, would normally not be considered a problem, the rod drop monitor may be used to signal a loss of lubricant anti the compressor can be shutdown before damage can occur. 

These are locations where condensation can accumulate. If allowed to accumulate, at some time it will enter the compressor as a slug of liquid and cause damage. If the piping configuration must contain a loop, the lower portion of the loop should be instrumented to detect the presence of liquid accumulation. Both for the drums and for the piping loops, pro vision must be made to drain any liquid that may be present. 

Check valves are required in the piping system at any point where backflow of gas after a shutdown has the ability to restart the compressor, running it backwards or, for that matter, even in the normal direction. Reverse rotation is totally bad, as many components of the various compressor types are not designed for reverse rotation, and there is some possibility, generally remote, that the compressor could reach a destructive over speed. Forward rotation is bad primarily because the intent was to stop the compressor, and it is now operating out of control. This is a problem, particularly if the shutdown was caused by a compressor failure indication, and the need to stop was to prevent further damage. In this mode, it is unlikely that the compressor can attain an overspeed condition. An application with a high potential for backflow is the parallel operation of two or more compressors. 

The explosion and fire (May 1,1990) caused eight deaths (including a vice-president and site manager), 120 injuries, extensive damage to buildings in the area, and evacuation of an entire small town. The cause of the explosion, at the Angus Chemicals Plant, was the blowout of a compressor line on the nitroparaffin unit. 

Satisafactory compressor installations many times depend on how well the foundation or support structure was designed. An inadequate foundation design can result in equipment damage due to excessive vibration. The money saved by cutting comers on foundation design effort may be spent many times in costs associated with high maintenance and lost production. 

When specifying compressor packages to API 1 IP, it may be necessary to specify certain sections of API 618 to ensure satisfactory installations. An example of this would be the supply of multiple compressors to be located in pipeline booster stations. In this case, an analog or digital pulsation and vibration study per API 618 Section 3.9 would be advisable to improve reliability and to minimize system problems and potential damage caused by gas pulsations and interaction between the individual compressor packages. 

An ethylene compressor was shut down for maintenance and correctly isolated by slip-plates. When repairs were complete, the slip-plates were removed before the machine was tried out. During the tryout, some ethylene leaked through the closed isolation valves into the machine. The ethylene/air mixture was ignited, either by a hot spot in the machine or by copper acetylide on the copper valve gaskets. The compressor was severely damaged. 

Fires have often occurred when air is compressed. Above 140°C, lubricating oil oxidizes and forms a carbonaceous deposit on the walls of air compressor delivery lines. If the deposit is thin, it is kept cool by conduction through the pipework. But when deposits get too thick, they can catch fire. Sometimes the delivery pipe has gotten so hot that it has burst or the aftercooler has been damaged. In one case the fire vaporized some of the water in the aftercooler and set up a shock wave, which caused serious damage to the cooling-water lines. 

Damage to Feed compressor Capital loss, Provide spare... 

End view showing male and female rotors and slide valve on an 85-ton intermediate compressor. The robust design of the Series R compressor can ingest amounts of liquid refrigerant that would severely damage reciprocating compressor valves, piston rods, and cylinders. (Used by permission Cat. RLC-DS-2, Aug. 1995. The Trane Company.)... 

Figure 12-42. Results of internal chlorine gas fire and extensive corrosion in centrifugal compressor. Middle section of shaft with extensive damage to loss of center compression wheels. Note that ferric chloride is present.

---