natural gas compressors and their lubrication

natural gas compressors and their lubrication

Natural gas is widely used to heat homes, generate electricity and as a basic material used in the manufacture of many types of chemicals. Natural gas, like petroleum oil, is found in large reservoirs underground and must be extracted from these underground cells and transported to processing plants and then to distribution centers for final delivery to the end user.

The gas is moved with the use of many types and sizes of compressors that collect, pressurize and push the gas though the distribution pipes to the various processing centers and points of use. The compressors that move the gas are located in ships and drilling fields, in chemical and process plants, and in the huge maze of pipes that makeup the distribution network, which brings gas to the market in a pure, useable form.

Natural gas and petroleum oil formed as a result of the decay of plants and animals that lived on earth millions of years ago. The decaying matter was subsequently trapped in huge pockets called gas reservoirs in rock layers underground.

These pockets may contain predominantly gas or they may exist together. It is estimated that the amount of recoverable natural gas within the United States alone is 900 to 1300 trillion cubic feet (Tcf).

The composition of natural gas at the well head is variable and often contains different compositions of volatile hydrocarbons in addition to contaminants including carbon dioxide, hydrogen sulfide and nitrogen. Commercial pipeline natural gas contains predominantly methane and lesser amounts of ethane, propane and sometimes fractional quantities of butane as shown in Table 1.

For transportation and storage, natural gas must be compressed to save space. Gas pressures in pipelines used to transport natural gas are typically maintained at 1000 to 1500 psig. To assure that these pressures are maintained, compressing stations are placed approximately 100 miles apart along the pipeline. This application requires compressors and lubricants specifically designed for this use.

Compressors can be classified into two basic categories, reciprocating and rotary. Reciprocating compressors are used for compressing natural gases and other process gases when desired pressures are high and gas flow rates are relatively low. They are also used for compressing air.

Reciprocating compressors compress gas by physically reducing the volume of gas contained in a cylinder using a piston. As the gas volume is decreased, there is a corresponding increase in pressure. This type of compressor is referred to as a positive displacement type. Reciprocating compressors are typically a once-through process. That is, gas compression and lubricant separation occur in a single pass.

Reciprocating compressors may be further classified as single-acting or double-acting. Single-acting compressors, also classified as automotive compressors or trunk piston units, compress gas on one side of the piston, in one direction. Double-acting compressors compress gas on both sides of the piston.

To consider the lubrication process, it is convenient to divide the parts that need to be lubricated into two categories, cylinder parts and running parts. Cylinder parts include pistons, piston rings, cylinder liners, cylinder packing and valves. All parts associated with the driving end (the crankcase end), crosshead guides, main bearing and wristpin, crankpin and crosshead pin bearings are running parts.

The lubricant is then fed directly to the cylinders and packings using a mechanical pump and lubricator arrangement. Single-acting machines, which are usually open to the crankcase, utilize splash lubrication for cylinder lubrication. Compressor valves are lubricated from the atomized gas-lubricant in the system.

Compared with cylinder part lubrication, the lubrication of running parts is typically much simpler because there is no contact with the gas. The equipment manufacturer specifies the required viscosity grade.

Because gas temperature increases with increasing pressure, if heat is not removed, the lubricant will be exposed to high temperatures and undergo severe decomposition. Therefore, compressor cylinders are equipped with cooling jackets. One of the most important roles of the compressor cylinder lubricant is as a coolant.

The coolant is usually water or a water-glycol refrigerant. Although the same lubricant can be used to cool both the cylinder and the running parts, there are many cases where different lubricants are used because the cylinder lubricant is exposed to compressed gas at high temperatures. Therefore, the lubricant should also exhibit thermal and oxidative stability. Table 2 compares compressor operating temperatures.

Rotary compressors are classified as positive displacement or dynamic compressors. A positive displacement compressor utilizes gas volume reduction to increase gas pressure. Examples of this type of compressor include rotary screw, lobe and vane compressors (Figure 1, Figure 2and Figure 3).

The rotary screw compressor illustrated in Figure 1 consists of two intermeshing screws or rotors which trap gas between the rotors and the compressor case.The motor drives the male rotor which in turn drives the female rotor. Both rotors are encased in a housing provided with gas inlet and outlet ports. Gas is drawn through the inlet port into the voids between the rotors. As the rotors move, the volume of trapped gas is successively reduced and compressed by the rotors coming into mesh.

These compressors are available as dry or wet (oil-flooded) screw types. In the dry-screw type, the rotors run inside of a stator without a lubricant (or coolant). The heat of compression is removed outside of the compressor, limiting it to a single-stage operation.

In the oil-flooded screw type compressor, the lubricant is injected into the gas, which is trapped inside of the stator. In this case, the lubricant is used for cooling, sealing and lubrication. The gas is removed from the compressed gas-lubricant mixture in a separator. Rotary compressors, such as the screw compressor, continuously recirculate (1 to 8 times per minute) the lubricant-gas mixture to facilitate gas cooling and separation as opposed to reciprocating compressors, which are once-through processes.

In a rotary screw compressor, the lubricant is injected into the compressor housing. The rotors are exposed to a mixture of the gas and lubricant. In addition to providing a thin film on the rotors to prevent metal-to-metal contact, the lubricant also provides a sealing function to prevent gas recompression, which occurs when high-pressure, hot gas escapes across the seal between the rotors or other meshing surfaces and is compressed again.

The lubricant also serves as a coolant by removing heat generated during gas compression. For example, for rotary screw air compressors, the air discharge temperature may be 80C to 110C (180F to 230F), accelerating oxidation due to turbulent mixing of the hot air and lubricant.

In addition to these functions, the bearings at the inlet and outlet of the compressor must be lubricated. With rotary screw compressors, the lubricant is in contact with the gas being compressed at high temperatures and it experiences high shearing force between the intermeshing rotors. These are demanding use-conditions for the lubricant.

The lubricant and gas mixture from the compressor discharge line goes into a gas/lubricant separator where the compressed gas is separated from the lubricant. After separation, the lubricant is cooled and filtered, then pumped back into the compressor housing and bearings.

A schematic diagram for a rotary lobe compressor is provided in Figure 2. The principle of operation is analogous to the rotary screw compressor, except that with the lobe compressor the mating lobes are not typically lubricated for air service. As the lobe impellers rotate, gas is trapped between the lobe impellers and the compressor case where the gas is pressurized through the rotation of lobes and then discharged. The bearings and timing gears are lubricated using a pressurized lubricating system or sump.

A rotary vane compressor is schematically illustrated in Figure 3. Rotary vane compressors consist of a rotor with multiple sliding vanes that are mounted eccentrically in a casing. As the rotor rotates, gas is drawn into areas of increasing volume (A) and discharged as compressed gas from areas of small volume (B).

As with reciprocating compressors, lubrication of rotary vane compressors is also a once-through operation. The lubricant is injected into the compressor casing and it exits with the compressed gas and is usually not recirculated. The lubricant provides a thin film between the compressor casing and the sliding vanes, while providing lubrication within the slots in the rotor for the vanes. The sliding motion of the vanes along the surface of the compressor housing requires a lubricant that can withstand the high pressures in the compressor system.

Energy from a set of blades rotating at high speed is transferred to a gas, which is then discharged to a diffuser where the gas velocity is reduced, and its kinetic energy is converted to static pressure. One of the advantages of this type of compressor is the potential to handle large volumes of gases.

In a centrifugal compressor, the lubricant and gas do not come into contact with each other, which is a major distinction from reciprocating, rotary screw and rotary vane compressors. The lubricant requirements are simpler and usually a good rust and oxidation-inhibited oil will provide satisfactory lubrication of the bearings, gears and seals.

The choice of a compressor lubricant depends on the type and construction of the compressor, the gas being compressed, the degree of compression and the final outlet temperature. Piston compressors provide the highest gas pressures and are among the most difficult from the standpoint of cylinder and valve lubrication and equipment reliability. However, R&O (rust and oxidation inhibited) oil is often sufficient for the crankcase splash lubrication of a reciprocating compressor.

Rotary compressors with final pressures below 1 Mpa (approximately 145 psi) are less difficult to lubricate. Because of the potential for vane to cylinder or lobe-to-lobe contact, rotary screw and vane compressors require the use of an antiwear (AW) oil. The selection of the proper compressor and application-dependent lubricant with the appropriate physical-chemical properties is vital to a successful process, and will be addressed fully in the second part of this two-part series of gas compressor and compressor lubrication issues.

mobil shc rarus 46

mobil shc rarus 46

Mobil SHC Rarus Series oils are supreme performance air compressor lubricants primarily intended for the lubrication of severe duty rotary screw and vane air compressors. They are particularly suited for severe service where synthetic oil-based products are not meeting expectations such as in severe applications subjected to high final compression temperatures or where extended oil drain intervals are desired. Mobil SHC Rarus Series formulation provides the potential to deliver up to 3 times oil drain interval versus a leading synthetic compressor lubricant.

Excellent water separability helps reduce carryover to downstream equipment, reduce sludge formation in crankcases and discharge lines, helps reduce blockage of coalescers, coolers and less potential for emulsion formation

Mobil SHC Rarus Series are primarily for rotary screw and vane air compressor, very effective in screw type compressors with oil injection cooling; compressors with a history of excess oil degradation, poor valve performance or deposit formation

Compatible with all metals used in compressor construction and with conventional mineral oil-based air compressor oils but mixture with other oils may detract from the total performance capability

oil flushing strategies for compressors

oil flushing strategies for compressors

The purpose of oil flushing is to clean the system in contact with the lubricant. Whether it involves a machine, storage container, lubricant line, hose or lubricant conditioning system, flushing is designed to eliminate or control contamination that can negatively affect the performance of the lubricant or machine.

The flushing strategy you choose should be based on the specific contaminant to be removed. Flushing must also be performed in conjunction with other maintenance activities, such as a machine repair or an oil change, in order to restore the machine and lubricant condition to a reliable state.

Several questions must be asked to determine the root cause of the contamination. Has there been a catastrophic machine failure? If so, it may be necessary to disassemble the system and remove chunks of metal that may be trapped in the lubrication system. Have sediment and moisture settled in the machine due to a long standby period? If this is the case, an oil drain and turbulent oil flow with fresh oil should be enough to remove the contaminants.

Is varnish deposited in the compressor's synchronizing gears or screws? Check with the equipment manufacturer as well as the oil manufacturer about using a detergent. When the varnish is soft or sticky, a detergent additive can be a good option.Several lubricant manufacturers offer these types of additives. However, if the varnish has been deposited for a long period of time and has become an enamel-like compound, no chemical or solvent likely will be able to remove it.

Although the use of solvents in oil is no longer common, an emerging technology involves adding 10 percent of an oil-miscible polyglycol that has high solvency. This strategy has been used in turbines, but be sure to check its suitability for your compressors.

If the contaminant concentration is high or risky for the application, first open the machine and clean it manually. After the machine has been reassembled, perform an oil flush. If you choose a high turbulent flush, isolate any sensitive components and ensure the affected area will have the necessary flow to remove the contaminants.

oil & gas - lubrication engineers

oil & gas - lubrication engineers

Engine oil, gear oil, hydraulic oil and other lubricant solutions for oil drilling and natural gas operations can help equipment combat an array of challenges, including wear, heat, heavy loads, contamination from water and dirt, oil leakage, foam, sludge and rust. Grease point problems, such as pound-out and wash-out, pose additional difficulties. If left untreated, these challenges can lead to increased downtime, decreased production, shortened engine oil lubricant and equipment life, and expensive parts replacement.Lubrication Engineersoffers an array of lubricant reliability solutions for oil and gas field operations, including high-performance lubricants for drilling equipment.

It is much easier and more cost-effective to put clean lubricant into your equipment and keep it clean and dry than it is to remove water, particulate matter and other contaminants after theyve gotten into the lubricant. The best way to prevent and remove contamination is a comprehensive lubricant reliability program that includes the right lubricants, the appropriate reliability tools and training for key personnel. LE has the expertise, products and services to create the right solutions for all of our oil and gas customers.

LEs high-quality, high-performance engine oils, gear oils, hydraulic oils, greases and other lubricant reliability solutions chosen wisely and cared for properly for each piece of equipment can protect expensive equipment, extend lubricant life, increase production and decrease downtime. By reducing the amount of waste oil and filters that require disposal, LE lubricants are also environmentally friendly.

LEs engine oils, gear oils, hydraulic oils, greases and other lubricant reliability solutions are appropriate for a wide range of oil and gas applications. Oil field operations encompass many processes, including drilling, completion, workover, stimulation, production, gathering and transportation of the product for the final stages of processing and refining. Our lubricants are put to work frequently within mobile work rigs, pumping stations, compression units and gathering fields.

LE offers an array of lubricants and lubricant reliability solutions appropriate for oil field equipment and applications. To learn how we can accommodate you with our engine oil lubricants, natural gas engine oils, and other products and services, pleasecontactus today.

lubricating your electric shaver - why you must do it & how to

lubricating your electric shaver - why you must do it & how to

If youre using a foil shaver, the more traditional type, one or more blades are hidden under extremely thin foils perforated by very small holes. When you press the shaver against your face, facial hair enters the holes and is sheared off, as with scissors.

This type of razor was invented by Jacob Schick. The motor on the original invention was so large that holding and using the trimmer required both hands, but after a few more iterations a truly handheld device was created, Schicks new invention flew off the shelves. The foil razor, however, is only one of two highly popular electric trimmers used today.

Both foil and rotary shavers are constructed to extremely high tolerances, which means the moving parts come into contact with other quite a bit. Any sediment (such as dry skin or hair) can increase the friction, which increases the heat building up in your razor.

When heat builds up, the dynamic parts of the razor can come under significant stress. Your razor could break down, become dull, or even injure you. Cleaning your razor and using electric shaver lubricant regularly is vital to helping maintain a close shave, keeping you comfortable, and protecting your electric razor.

How often you clean it is up to you. You should factor in how often you shave and how thick or long your beard is when you do shave. If you're rinsing your shaver every time you use it, you might not need to deep clean it as often. I recommend to clean it more often than not; taking a few minutes to do so once or twice a week saves time in the long run.

Another thing to consider is purchasing a self-cleaning shaver. Some have cleaning stations that clean, dry, charge and lubricate your shaver with just the press of a button. These can be more expensive, and you still have to keep an eye on them as theyre not foolproof, but if you hate spending the extra time on maintenance, you might love a shaver with this feature!

To clean your shaver, youll usually be able to pop off the head piece without needing to use any tools. Be very careful with the foil, if thats the type of razor your cleaning, and of course be careful with the blades, which can be very sharp! Some razors come with cleaning kits that include brushes for cleaning out the nooks and crannies of your device, but if not a toothbrush is a popular option. Since this is my face, I dont like using an old toothbrush that can breed bacteria; instead, I prefer to use a new toothbrush that is dedicated to this job.

When youre cleaning, make sure you pay careful attention to where everything goes--you dont want to struggle with putting your shaver back together! Be thorough and carefully dislodge as much sediment as possible. When youre finished, you should be able to pop all the pieces back together.

The final step is the actual lubrication. Its important to use the right kind of oil, and I should note here that cooling sprays that are popular (especially on trimmers used for hair) are not oils and do not act as lubricants. Oil is special for its viscosity or thickness. You need something with a good level of viscosity to be able to adequately cushion the friction building up inside your device.

You also do not want to use a heavy oil, such as WD-40, though oils for small machines, such as sewing machines, will work just fine. The amount of oil you use depends on the size of your trimmer, but do not use a lot. Too much oil is often as bad as too little and can drip, cause your razor to rust, or deaden the blade.

Typically, I recommend three drops of oil, one in the middle and one on each corner. Youll want to apply the oil while your trimmer is running, and then let it run for a few seconds to allow the oil to work into the gears. Thats it!

The con, however, is that the Shaver Saver has an overpowering smell. If youre planning on oiling your shaver daily, this will quickly saturate your bathroom. You will, at a minimum, need to make sure your fan is running on high. That said, this product has long been a favorite thanks to how easy it is to use!

My only concern is that sometimes the viscosity of an aerosol isnt as thick as you might hope. If Im putting my shaver through a lot, I want to make sure its getting a nice thick oil treatment. That said, this aerosol will work perfectly for most.

Using an electric shaver lubricant doesnt have to be difficult, but it does need to happen regularly! Regular cleaning and lubrication will keep your shaver in top condition, which will mean a great, comfortable shave for years to come.

heavy duty bearing oil externally cooled (i.e., water jackets)

heavy duty bearing oil externally cooled (i.e., water jackets)

Heavy Duty Bearing Oil is a non-grease lubricant for Rotary Kilns, Rotary Dryers and Ball Mills used in applications where support rollers / trunnions are cooled, usually with a water jacket. This oil is used in enclosed conditions, poured into housings as directed. Heavy Duty Bearing Oil provides excellent protection under severe conditions such as high load, shock load and reversed motion.

lubrication oil pumping by utilizing vane motion in a horizontal rotary compressor - sciencedirect

lubrication oil pumping by utilizing vane motion in a horizontal rotary compressor - sciencedirect

For a horizontal rotary compressor which utilizes reciprocating motion of the vane for oil supply into lubrication elements, an analytical study has been carried out on the oil pumping mechanism. Energy equation has been applied to the oil flow inside the oil-conveying pipe with oil feeding hole in the middle. Oil distributions into individual lubrication elements such as various bearing elements have also been analyzed by applying electric circuit network theory to the oil flow network. Fairly good agreement between calculations and experiments for the oil pumping rate has been obtained in a wide range of compressor speed.

honeywell lubrication & oil

honeywell lubrication & oil

An important tool for determining field performance, Honeywell Gas Depot offers both digital and analog differential pressure testers to measure pressure drop across meters, filters, valves, and other gas system components.

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