Centrifugal compressor wet seals high pressure seal oil circulates between rings around the compressor shaft oil absorbs the gas on the inboard side little gas leaks through the oil seal seal oil degassing typically vents methane to the atmosphere seal oil degassing may vent 40 to 200 scfminute. How to get clean, dry, oil free compressed air from any. However, different compressor duties require different packing ring designs and material selection. Dear all, please explain me whats the function of seal gas in compressor. Hofim hermeticallysealed motor compressor system 2 compressor inner casing upper half compressor inner casing lower half casing cover compressor outer casing motor. An example of a turbine control oil system is shown in figure 4. Once seal gas enter the compressor and it is vented to flare header. The seal oil is normally supplied from a combined lube and seal oil system, an example of one such system is shown in figure 1. Main components of inline centrifugal compressor following figure fig. These systems require auxiliary equipment such as pumps, regulators, filters, and so on for proper operation. Replacing wet seals with dry seals in centrifugal compressors. Centrifugal compressor 1 mechanical engineering in. Consult your seal vendor john crane burgmann flowserve etc.
Lubricated types are available in sizes ranging from 100 to cfm, with discharge pressure up to 10 bar. However, instead of oil, water is being used in these coke gas services. Since the pressure at each end of the compressor case is at or near suction pressure and. Basic seal oil systems engineering photos,videos and. However, oil becomes a detriment to system performance if present in large quantities in the evaporator. C101 seal oil system with both seal oil drainer outlets closed, the sight glasses on both drainers area observed for a level rise. Clean, dry, oil free compressed air unfortunately in the pursuit of oil free compressed air, the downstream air treatment system is often neglected or overlooked completely. Bps initial results show recovery of 99% of seal oil gas that.
Seals in many oil free rotary screw compressor applications, it is best to provide a sealing barrier between the process gas and the bearings. The oil is circulated at high pressure to form a barrier against compressed natural gas leakage. Most hydrogen cooled generator are incorporate the seal oil system, just because to avoid the contact between and air and hydrogen generally pressure of hydrogen in generator around 4bar. There are journal bearings outside the seal area, which are typically sleeve type hydrodynamic bearings. The lube and seal oil console may also provide control oil for turbine governors, compressor inlet guide vanes, process valve actuators, trip and shutdown devices on the equipment inlet, and nonreturn valves. The use of dry gas seals requires a system designed to supply sealing gas to the seal as a sealing and working fluid for the running gap. The circulated oil entrains and absorbs some compressed natural gas that may be released to the atmosphere during the seal oil recirculation process degassing or offgassing. In the singlestage compressor, air is drawn in from the atmosphere and compressed to final pressure in a single stroke.
Centrifugal compressors have lubrication systems designed as per api 614 consisting of an oil reservoir, pumps, filter, cooler and oil lines. These gas seal systems are normally supplied by the compressor oem mounted adjacent to the compressor. Recovery system that separates gas from the sour seal oil before being sent to the degassing tank recovered gas sent to various outlets. If the header pressure is low, the standby oil pump starts and maintains oil pressure during operation. Tutorial has a builtin quiz and comes with a learning management system lms.
For this reason, many users are disappointed to find that oil contamination and water are still present after the installation of their new compressor. The seal oil system works on the principle of pumping oil to the compressor seals and recycling back to the seal oil tank that doubles up as a heated degassing tank as well operating at 85 deg. On the inboard side of the rings, the seal oil mixes with the buffer gas. Therefore, it is necessary to control the distribution of oil within the system. Centrifugal compressor wet seals seal oil degassing and. Engineers modelled the hydrogen seal systems and used the simulated results to identify the case of their system trips. Bps initial results showed recovery of 99% of seal oil gas that would be otherwise vented to. The seal oil supply system must be capable of supplying higher seal oil pressure than the highest possible compressor process pressure inboard of the oil seal which may include settle out, or compressor discharge pressure.
A rise in the drainer levels ensures both cone seals are flowing oil and that they are no longer in metal to metal contact between the inner seal ring with the mating cone seal sleeve on. A seal oil ring is used to avoid the contact between and ai. Compressed air system bureau of energy efficiency 47. In a service situation a compressor with an oil cooler instead of a compressor without oil cooler can be used replacement of refrigeration systems. Pressure at the oil header creates starts the drive. The only essential difference is how the endsupply control is handled.
The use of four manual block valves in lieu of a transfer valve should not be. To isolate the rotor chamber from the bearing with an oil atmosphere, seals are furnished next to the rotor lobe on each end of the machine. Singlestage compressors are generally used for pressures of 70 psi pounds per square inch to 5 psi. The compressor seal oil system is designed and furnished with instrumentation similar to the lube oil system shown in figure 154. The seal oil circulation system is composed of a seal oil reservoir, pumps to pressurize the seal oil, filters to.
The seal oil system prevents gas from leaking out of the compressor case. Centrifugal compressor wet seals seal oil degassing. Dry gas seals are an integral part of modern centrifugal compressors. Worldclass oil free compression element unique z seal design guarantees 100% certified oil free air. Dry gas seal systems for centrifugal compressors page 3. Inboard of the dry gas seal is an inner labyrinth seal, which separates the process gas from the gas seal. This interactive tutorial provides an overview, fundamental principles, and control and operating principles for a centrifugal compressor with lube and seal oil system using voice, video, animation and graphics. Using clean buffer gas in oil seals ensures plant safety. Routing centrifugal compressor seal oil degassing emissions to. Atlas copco superior rotor coating for high efficiency and durability. Bp has wet seal gas recovery systems on 100 centrifugal compressors at its north slope facilities. Outboard of the dry gas seal is a barrier seal, which separates the gas seal from the compressor shaft bearings fig.
Use clean, sweet buffer gas whenever process gas is sour andor can contain debris to optimize oil seal mtbf in excess of 120 months. The separation gas should be filtered to 5 microns solid particles and should be 99. The original patent was for kaydons tapered ramp lift geometry, a constant diameter. The oil that flows across the outboard ring mixes with the bearing lube oil and returns to a lube oil tank.
Seal oil uncontaminated seal oil contaminated with gas spinning shaft compressor side inboard process gas leaks through inboard labyrinth seal y s an alternative to the traditional wet oil seal system is the mechanical dry seal system. A compressor seal upgrade by elliott group increases seal reliability and reduces process gas leakage to improve overall efficiency. Sour seal oil vapor recovery system 4 options flare purge 27 psi 65 psi 275 psi boiler. This seal system does not use any circulating seal oil. Optimal seal performance depends upon proper selection for the process application, operating conditions, process gas composition, and design specifications. Centrifugal compressor, mechanical seal, seal face. Is it seal gas require for both centrifugal and reciprocating compressor. In fact, compressor oil seals are not gas seals at all, but rather liquid seals designed to minimize the amount of seal oil that passes into the compressor. A differential pressure is supplied at 35 to 50 psi above the compressor suction pressure. This system is designed to keep the seal oil pressure above the sealed gas pressure. The programmable logic controller plc starts the auxiliary ac powerdriven lubricating oil pump. The oil then passes from the suction port through the compressor and out the discharge port into your air line. Compressor pressurization prior to operating seal oil system. Bloch, claire soares, in turboexpanders and process applications, 2001.
The seal oil system can be considered as having three major levels of operation. Continue running the oil pump while the compressor shaft is being turned to help lubricate the surfaces of the shaft seal. If the compressor unit is installed, wired and charged with oil, open all oil line valves and run the oil pump for 10 seconds prior to rotating the compressor shaft. Gas compressor seal oil system instrumentation tools. A rise in the drainer levels ensures both cone seals are flowing oil and that they are no longer in metal to metal contact between the inner seal ring with the mating cone seal sleeve on the rotating. Pdf analysis of mechanical seals for highspeed centrifugal gas. Oil and natural gas sector compressors ourenergypolicy. Seal oil systems are to be kept running even after a compressor is shutdown. Noncontacting, aka dry, compressor seals are an alternative to traditional wet oil seal systems. The entrance of sour gas andor gas with debris into the oil seal system will expose the seal oil system to the following issues that can reduce seal mtbf, cause unscheduled shutdowns and pose a safety hazard gas release to the plant environment.
As the name indicates, the mechanical contact seal serves as a mechanical standstill seal when the compressor plant is shut down. The original purpose of this galley is to act as a return line for oil thats sucked into the seal cavity through the bearing from the crankcase. The singlestage reciprocating compressor is illustrated in figure 1. Field applications of dry gas seal designs were completed in 1952. The system can be supplied either in the single casing or the twin casing tandem hofim version. Specifying engineers sometimes do not give enough attention to the scope, definition and selection of the most appropriate gas seal type, its control system and auxiliaries for a given service application. To ensure proper functionality, they are always configured with a process side labyrinth seal, a gas seal cartridge, a separation seal cartridge, and a buffer gas. A number of different seal types are feasible see figs. For a more complete description of dry gas seal principles of operation, see shah 1988. Condensate build up is particularly pronounced in hot and humid coastal areas during compressor. Please clarify my doubts i had searched in net but i am not able to get clear idea.
Compression process of gas in centrifugal compressor describes with fig. Typical cutaway drawing of oil free screw compressor. A lube oil system will be required unless, of course, the turboexpander is supplied with active magnetic bearings. Skf installation instructions of hrs and hss seals from skf for wind turbine main shafts duration. For the mechanical contact seal system, a regulating valve maintains the reference gas and the seal oil at a constant differential pressure.
The conventional lube oil system consists of a reservoir, electric cartridge or steam coil heater, lube oil pumps, one and preferably two switchable lube oil coolers. In multi compressor parallel systems, oil levels must be maintained in each compressor regardless of the. Compressor oil seals are designed around the principle of forcing oil into the compressor seals at a higher pressure than the process gas to prevent the gas from escaping from the pressure casing. The support systems for each type of oil seal are described, along with ways to specify the best system for different applications. A clean and dry separation gas is continuously injected into the barrier seal to protect the migration of lube oil from the outboard bearing housing. This is not only to avoid any process gas from escaping to the ambient but also to prevent any particulate or liquid debris from being pressurepushed into the space between the seals or the seal sleeve when a loss of oil pressure occurs. The seal oil is split into two streams in the compressor seals. If the system has an oil cooling arrangement, a compressor with an oil cooler must be selected.
Rotary screw compressor units models 12 101 form 070. The gas properties, pressure differentials, compressor speed, and type of service are all used to determine the proper combination of ring style and material that will provide the optimum pressure seal and oil wiping. The seal oil system may be a completely separate oil system, however in most cases it is apart of the compressor main lube oil system. Also you are not supposed to design any components for your dry gas seal system without taking concurrence from your compressor vendor and or seal vendor. The purpose of the seal oil system is to keep the compressed gas from entering the bearing assembly and escaping from the compressor to the atmosphere. Compressor turbine fuel seal oil circulation pump new fuel pressure seal oil degassing drum and demister sour seal oil trap less gas vented to atmosphere atmospheric seal oil degassing drum note.
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