How|Compressor|Gas|Seal|System|Works?


in turbo compressor industries more than 80% of all processed gas machines are equipped with gas sealing systems consisting of gas lubricated mechanical seals and supply systems in order to guarantee reliable operation of the system the mechanical seal is flushed and pressurized with dry and filtered product gas and buffered with a clean inert gas at the backup seal the leakage is measured and vented and is the basis to evaluate the function of the mechanical seal the tandem arrangement of two gas lubricated mechanical seals with intermediate labyrinth plus atmospheric labyrinth or segmented carbon bearings reliably prevents any leakage of product gas towards the atmosphere the secondary gas seal serves as a backup seal in case of a breakdown of the primary mechanical seal the pressure to be sealed of a single shaft compressor equals nearly the suction pressure of the compressor the axial gap hate of the gas seal is only a few micrometers to prevent contamination of the sealing phases and to ensure a proper tracking of the stationery spring-loaded unit gas taken from a higher pressure stage of the compressor this gas is filtered and injected through connection a as clean flashing gas onto the product side gas seal a labyrinth limits the volume of the flushing gas towards the impeller the leakage of the primary gas seal is vented to the flare where it will be disposed connection see the space between the atmospheric gas seal and the intermediate labyrinth is buffered with nitrogen which serves as a barrier gas connection B this prevents leakage of the product gas towards the atmosphere the barrier leakage across the intermediate labyrinth is vented together with a clean gas leakage of the primary ceil there is a minimal leakage of nitrogen of less than one norm liter per minute towards the atmosphere this leakage is conducted through the secondary gas seal respectively through the backup seal in order to avoid any bearing oil contamination of the gas seal the space limited by labyrinth or segmented copper rings between the tendon gas seal and the bearing is buffered with nitrogen or air in front we have the thick suction pipe of the compressor in the background the smaller discharge pressure pipe at this point of the discharge pressure pipe product gas is taken and inserted into the gas supply system [Music] the product gas flows towards the seal supply system and is inserted as a flushing gas onto the gas seal with a slightly higher pressure than the suction pressure the flushing gas is filtered by means of a switchable dual filter system with a mesh size of maximum 5 micrometers absolute in case of wet gas is a maximum liquid fraction of 50 ppm can be accepted using a standard coalition filter the size of the filter depends on gas pressure and flow rate and is influencing price and size of the control system considerably the function of the filter is controlled by measuring the pressure drop with the differential pressure gauge there will be an alarm of the pressure gauge if the filter is polluted the standby filter has to be activated and the filter cartridge can be exchanged experience shows that the filter cartridge should be changed at least once a year should the liquid fraction of the gas exceed 50 ppm or does the gas have a tendency to condense we strongly recommend a gas heating system in order to avoid damage of the pressure measuring devices and to fulfill job safety regulations the temperature of the flashing gas must not exceed 150 degrees Celsius the flashing gas flow is limited by orifices the flow is computed to achieve an excell velocity of 10 meters per second over the labyrinth to the impeller we want to highlight that this corresponds to a pressure difference of only a few millibar to guarantee a proper operation this alternative should only be chosen in case of constant product gas pressure [Music] the product gas is inserted into the gas supply system and is flowing through the collector filter and heating system onto the primary gas seal the mass flow is controlled by orifices [Music] the flow of the flushing gas through the sealing system the product gas leakage of the primary seal is vented to the flare the leakage rate small taneous Li serves as a criterion for the wealth function of the seal should the leakage exceed the guaranteed value the increased impact pressure in front of the orifice triggers the high alarm at the pressure gage in case of a failure of the gas seal this orifice also limits the gas lost towards the flare in the event that the secondary seal is failing both the function as a throttle of the gas seal and the leakage towards the flare pipe is decreasing and eventually the lower arm of the flow indicator is activated to allow maintenance of the control devices during operation we have the possibility to switch over to a bypass pipe equipped with a pressure indicator non-return valves ensure that no third respective gas from the flare can penetrate the gas seal this shows the high contact pressure gauge in front of the orifice which serves as a leakage control of the primary gas seal a flow indicator with a low flow alert controls the function of the backup seal the leakage flow of the product gas towards the flare to pressurize the seal with gas nitrogen is taken from the nitrogen network of the plant if the nitrogen supply is not stable we recommend a backup by means of a nitrogen tank should the nitrogen be neither clean or dry we recommend that you’ll fill the system with Cola elements as installed in the gas supply of the primary seal the gas volume is regulated by a needle valve and is computed to achieve a flow velocity across the labyrinth of five meters per second in case of a failure of the nitrogen supply low alarm will be given by the flow indicator the nitrogen injected is conveyed through the filters the differential pressure gauge indicates the degree of contamination of the filters the flow of the Flushing gas is shown here at the flow indicator and is regulated by a needle valve this is an example of a nitrogen supply done by a customer showing their respective controlled system should the main nitrogen supply fail the system automatically switches over to standby set respectively to a nitrogen tank [Music] the barrier gas flow through the ceiling system [Music] to supply with buffer gas nitrogen is taken from the barrier gas module downstream the pressure control valve this pressure is adjusted by a pressure control valve and is 1.5 to 2 bar above the high alarm of the flare pipe depending on the allowable buffer gas consumption a labyrinth or segmented carbon steel is used as in this case sufficient nitrogen is available a labyrinth seal has been chosen when a labyrinth seal is selected a buffer gas flow rates across the labyrinth of at least 10 meters per second is obligate to use an orifice is the easiest way to achieve this due to the leakage control in the flare pipe a monitoring of the leakage in the vent pipe s is not necessary both the leakage of the backup seal and a part of the barrier seals leakage are cleared through the vent pipe a dual filter system is cleaning the nitrogen coming out of the nitrogen supply here we split the nitrogen flow into the barrier gas supply for the intermediate labyrinth and into the buffer gas supply for the barrier seal between the gas seal and the bearings a pressure control valve connected to a pressure gauge monitors the buffer pressure supply for the barrier seal the flow of the buffer gas through the sealing system our tandem seal with intermediate labyrinth this shows the source of higher pressure for the Flushing gas supply at this point gas is taken off passes a heater and a filter not shown here and finally flows through an orifice to the gas seal shown in red here is the leakage of the gas seal flowing across an orifice with pressure gauge and a flow meter currently 83 normally to a per minute here we are with our nitrogen supply at this point nitrogen is arriving the pipe splits piping one towards the intermediate labyrinth a defined quantity is adjusted here

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