Reciprocating compressor pulsation

This standard could be adapted to the fuel compressor for the natural gas to be brought up to the injection pressure required for the gas turbine. Covers the minimum requirements for reciprocating compressors and their drivers used in petroleum, chemical, and gas industry services for handling process air or gas with either lubricated or nonlubricated cylinders. Compressors covered by this standard are of moderate-to-low speed and in critical services. The nonlubricated cylinder types of compressors are used for injecting fuel in gas turbines at the high pressure needed. Also covered are related lubricating systems, controls, instrumentation, intercoolers, after-coolers, pulsation suppression devices, and other auxiliary equipment. 

Cyclically transmitted torque. Pulsating or cyclic torque in reciprocating prime movers and load machines such as reciprocating compressors, pumps, and marine propellers. 

Nimitz, Walter, Pulsation Effects on Reciprocating Compressors, ASME 69-PET-2, New York, NY American Society of Mechanical Engineers, 1969. 1. 

Screw compressors of the dry type generate high frequency pulsations that move into the system piping and can cause acoustic vibration problems. These would be similar to the type of problems experienced in reciprocating compressor applications, except that the frequency is higher. While volume bottles will work with the reciprocator, the dry type screw compressor would require a manufacturer-supplied proprietary silencer that should take care of the problem rather nicely. 

Reciprocating compressor pulsations were covered in Chapter 3, but neeti to be mentioned with the discussions on reliability. Problems with reciprocating compressor pulsations and the potential for acoustic and mechanical resonances are very similar to those experienced with helical-lobe compressors. The significant difference is the frequencies are much lower and the number of discrete frequencies per compressor aie much less. However, piping vibrations can occur and there is always a... 

More recently, the Southern Gas Association s Gas Machinery Research Council and Pipeline and Compressor Research Council cooperated with Southwest Research Institute to develop a software package that enhances reciprocating compressor operation. Several major American and foreign compressor manufacturers (and some other interested companies) have cooperated with Southwest Research Institute or developed their own proprietary pulsation-reduction design computer programs. 

In many instances, the design of suction and discharge pulsation dampening drums (or bottles) for reciprocating compressors is based on piston displacement and volumetric efficiency, and this design normally will suffice to reduce peak pulsation to approximately 5% of the line pressure. In special or other cases, experience has shown that operational difficulties (vibrations, meter pulsations, etc.) may indicate that the peak pulse pressure of 5% line pressure is inadequate. Thus, the pressure in pulsation-reduction design selection is... 

Figure 13-1E. A computer facility performs dynamic simulation and analysis of reciprocating compressor installations such as this two-cylinder compressor. Interactive pulsation and mechanical analysis ensures trouble-free operation. (Used by permission Southern Gas Association s Gas Machinery Research Council.)...

Ehrich, R, Reduce Residual Pulsation in Reciprocating Compressors, Hydrocarbon Processing, V. 74, No. 7, p. 64 (1995). 

Reciprocating compressors deliver a pulsating flow of gas that can damage downstream equipment or machinery. This is sometimes a disadvantage, but pulsation dampers can be used to alleviate the problem. 

Pulsation can be problematic ancfdifficult to predict. Pulsations are also dependent on acoustic resonance characteristics. For reciprocating equipment, such as reciprocating compressors and pumps, in some cases, an analog (digital) study needs to be performed to identify the deficiency in the piping and pipe support systems as well as to evaluate the performance ofthe machine during operation. The study will also provide recommendations on how to improve the machine and piping system s performance. 

There are only two real problems with reciprocating compressors pulsation and mechanical reliability. But these problems are so intractable that, for most industrial applications, centrifugal compressors are pre-... 

For reciprocating compressors, if temperature rise < theoretical temperature rise, suspect problems with compressor valves or piston rings. For reciprocating consider downstream pulsation dampeners or accumulators to smooth out delivery volume and pressure, use variable speed drive, especially if load varies or unit may be oversized. To minimize vibrations for reciprocating equipment, the base should be 1.5 X mass of the machine. 

From the process standpoint, the major objection to reciprocating compressors would be their pulsating flow. Pulsation dampeners installed before and after a compressor help to rectify this. Tliese are carbon steel vessels whose basic purpose is to provide enough volume to reduce the amplitude of the pressure pulse to a satisfactory level, usually about 1-2% of the operating pressure. The pressure drop should be no more than 1% of the discharge pressure. On the suction side, the volume should be at... 

The action of the liquid-ring compressor gives a certain amount of pulsation in the delivered pressure. While this is not as severe as that encountered with reciprocating compressors, it should be recognized. The acid separator attached to the compressor provides some dampening on the outlet side. Some manufacturers will recommend a minimum volume on the inlet side, which is often only a length of expanded inlet piping. 

Reciprocating compressors (for air supply to air-diy a plant of small capacity) these are to be procured when substantially constant low volumetric capacity is required at higher discharge pressures. Vendor may be asked to indicate the type of capacity control being provided (variable frequency drive or by aity other means) as well as pulsation suppression device for the discharge side. This may be in the form of dampening pots. 

Reciprocating compressors have a history of chronic failures that include valves, lubrication system, pulsation, and imbalance. Table 8.3 identifies common failure modes and causes for this type of compressor. 

Reciprocating compressors are considered in the same light as pumps, with the exception that their outflow can be measured easily. Their higher speed and the compressibility of the fluid help to reduce pulsations. Control methods previously described for gear and vane pumps (Fig. 9.12) can also be used for reciprocating compressors. 

There are only two real problems with reciprocating compressors pulsation and mechanical reliability. But these problems are so intractable that, for most industrial applications, centrifugal compressors are preferred the exception is when dealing with low molecular weight gas. A low molecular weight gas, such as hydrogen, has a low density. Let s say that a compressor must develop a large differential pressure or AP. Recall Eq. (41.1) from the previous chapter ... 

Pulsation An acoustical phenomenon that causes a variable pressure inside the cylinder of a reciprocating compressor. 

Where pulsating discharge from reciprocating compressors results in pipe vibration so serious that piping and equipment may fail, the installation of additional pulsation dampeners may be warranted. 

Pulsation This is a unique problem for reciprocating compressor, not for centrifugal, OIS, or OFS compressQis. 

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