Lube oil system compressors

Packing/cylinder lubrication can be provided from a forced feed compressor lube oil system. For very cold installations, immersion heaters and special lube oils must be considered. If the lube oil temperature gets too cold, the oil becomes too viscous and does not flow and lubricate properly. 

Monitoring should include the usual parameters worthy of surveillance in high-speed turbo machinery the temperature of journal bearings, vibration and axial position of the pinions, inlet and discharge temperatures combined with discharge pressure from the individual compressor stages, and various lube oil system devices. Competent manufacturers make sure all measurement locations are completely prewired on the machine and made available at predefined interfaces or in terminal boxes for connection at the plant site. 

In this cycle, approximately 30% of the fuel consumed is available as power output. In addition, approximately 30% is used to drive the air compressors, 30% is contained in the hot exhaust gases, and 10%> is lost to radiation and the lube oil system. 

Compressors, together with related lube-oil systems. 

Eventually, the fouling deposits on the rotor will become so thick that they start to break off, especially if you shut the compressor down for a few hours for minor repairs to the lube-oil system. When the compressor is put back on line, bits and pieces of grayish salt break off, and unbalance the rotor. At 8000 rpm, the high-vibration trip cuts off the fuel to the gas turbine, and the machine is taken off line for repair. 

Cooling water failure. The loss of cooling water is one of the more commonly encountered causes of overpressurization. Two examples of the critical consequences of this event are the loss of condensing duty in column overhead systems and the loss of cooling for compressor seals and lube oil systems. Different scenarios should be considered for this event, depending on whether the failure affects a single piece of equipment (or process unit) or is plantwide. 

Other fouiing problems in a reformer will be the lube oil system on the hydrogen recycle compressor and the cooling water systems. The fuel lines on the furnaces will also eventually foul. 

Carbon contamination of the produced sulfur can result from liquid hydrocarbon droplets in the feed gas or by condensation of feed gas hydrocarbons. This problem is besr avoided by operating the process about 10°F above the feed gas hydrocarbon dew point and by removing any hydrocarbon aerosol in the feed gas (compressor lube oil, etc.) with a coalescing filter (Allen, 1995). Yet another potential form of sulfur contamination can occur when the feed gas contains a significant amount of mcrcaptans. Any disulfides formed will lend to coat the surface of the sulfur particles. If the sulfur is to be recovered as a salable product, special attention needs to be paid to the design of the overall system to avoid production of low-quality, disulfide-contaminated sulfur. Elimination of mercaptans and heavy hydrocar-... 

Space needs to be provided for the auxiliaries, including the lube oil and seal systems, lube oil cooler, intercoolers, and pulsation dampeners. A control panel or console is usually provided as part of the local console. This panel contains instmments that provide the necessary information for start-up and shutdown, and should also include warning and trouble lights. Access must be provided for motor repair and ultimate replacement needs to be considered. If a steam turbine is used, a surface condenser is probably required with a vacuum system to increase the efficiency. AH these additional systems need to be considered in the layout and spacing. In addition, room for pulsation dampeners required between stages has to be included. Aftercoolers may also be required with knockout dmms. Reference 8 describes the requirements of compressor layouts and provides many useful piping hints. 

The oldest of the various systems was commissioned when the plant first opened in 1985 it has been operating continuously 24 hours a day. The turboexpander-compressor set has proved its durability, requiring only lube oil skid maintenance prior to its first overhaul after many years of operation. 

Probably the biggest single advantage of dry gas seals is getting rid of the seat oil. The seal oil system, even when part of a combined lube and seal system, is a complex assembly. With the dry gas seal, the lubrication oil system is all that is needed to service the compressor train bearings and, on turbine driven units, to also supply turbine control oil. As. ui aside, it makes feasible the dream long held by the compressor vendor of having a standardized lube system line. 

Figure 8 4. Lube oil block diagram used for a compressor lube system with a control system and a seal oil system.

Forced coolant systems using a mixture of glycol and water are the most common for natural gas compressors. Normally, the compressor cylinder cooling system and compressor frame lube oil cooling system is combined. A single pump is used to circulate the coolant through the cylinders and the lube oil heat exchanger and then to an aerial cooler where the heat is dissipated. 

There are two types of seal oil systems.- gravity and pressurized. The gravity-feed seal oil system reservoir is mounted above and in view of the compressor, whose elevation is set by the compressor vendor. The sour oil traps can be integral with the lube oil console skid or located on a separate skid. The pressurized seal oil system is a pump-around facility whose components are integral to the lube oil console skid or mounted on a separate d. If components are mounted on a separate skid, placement must accommodate seal oil console operation and maintenance,... 

The deposits found here are primarily inorganic and usually are iron sulfide, iron bisulfide, or iron oxides. Quite often a combination of all three is found. This can be the most fouled part of a hydrofiner, as the metals are of lower alloys and there will be very little instrumentation on these systems. One refiner found his problem when he could not close his valves to bring down the unit. Considerable iron bisulfide also may be present. The compressors will have lube and seal oil systems that will also require cleaning. 

A very important part of a cracking unit consists of the lube and seal oil systems. In addition to the pumps and boiler uses, a cracking unit will have large systems for the air compressors and cyclone separators, which these units contain. Systems of up to 6000 gal (22,710 L) are not uncommon. 

The contact seal can be used under 1,000 psig. It is more complex, but has the advantage of not leaking while shut down. The contact seal is used extensively in refrigeration service where the compressor is part of a closed loop, and the shutdown feature is desirable. As mentioned, the seals must have a source of cooling and buffer fluid. In many cases, this fluid is lubricating oil. If contamination is not a problem, a combined lube and seal system can be used. 

The hydrostatic testing is the first test used on the lube system. The system is tested while assembled or partially assembled, based on the particular system. A test pressure of VA times the maximum allowable working pressure, a minimum of 20 psi for the oil side, is used for the test. For the oil-wetted parts, the test fluid should be light oil, which is normally the recommended lubricant for the compressor train. The test period is the length of time needed to inspect for leaks, or a minimum ol thirty minutes. Acceptance is based on the lack of leaks as visually observed or the lack of a drop in the test pressure. 

The specification must recognize this very important auxiliary part of the compressor. API 614 is a very complete specification and should be used when applicable. When direct use is not applicable, it makes an excellent guide. The seal system in many cases is combined with the lube system. When separate, many of the seal system components are fundamentally the same, with some specifics, such as operating pressure and control, being unique. For those applications where the sealant is other than lubricating oil, the particular fluid will need discussion. The system basic components, on the other hand, will probably be quite similar. General items that must be considered include ... 

Poor maintenance of lubrication-system components, such as filters and strainers, typically causes premature failure. Such maintenance is crucial to reciprocating compressors because they rely on the lubrication system to provide a uniform oil film between closely fitting parts (e.g., piston rings and the cylinder wall). Partial or complete failure of the lube system results in catastrophic failure of the compressor. 

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