----------Top quality tandem dry gas seal LP-28 ----------
A tandem dry gas seal is a type of dry gas seal that is used in turbocompressors. Tandem Seal is the most common seal in turbocompressors. The tandem seal is generally used in natural gas applications due to the minimal leakage to atmosphere. The intermediate labyrinth purged with nitrogen (to eliminate fugitive emissions) is nearly always recommended. The primary vent is between the two seals and usually connected to the flare system.
LP-28 tandem dry gas seal is designed to replace john crane type 28AT 28ST 28EXP 28XP series DGS item. this tandem dry gas seal, with a design pedigree stretching back over many years and evolving gradually, installed and proven in thousands of compressors all around the world and remaining the preferred seal choice for many customers.
these Tandem Seals are non-contacting in operation. During dynamic operation, the mating ring/seat and primary ring/face maintain a sealing gap of approximately 0.0002"/5 microns, thereby eliminating wear.
LEPUSEAL is a famous top brand for dry gas seal since 1998, manufacturing many kinds of dry gas seal for China big facotries, such as SINOPETRO, YANGZI REFINERY . and lepuseal also make DGS for many oversea clients like Russia, Iran, Turkey, UAE, and keeping very good reputation in dry gas seal field.
TYPICAL ARRANGEMENT FOR TYPE 28 TANDEM DRY GAS SEAL
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Advanced Technology
Designed to excel in low pressure applications, the 28AT is today's most widely used non-contacting, dry running gas seal.
High pressure LP-28XP
28XP is optimized to provide reliable performance on higher pressure duties. The 28XP's increased chemical resistance and ability to operate over a wider temperature range has established it as an industry benchmark for reliability.
Type 28ST Steam Turbine
The non-contacting, steam lubricated Type 28ST is an effective sealing solution for small to medium-sized general steam turbine applications
Type 28VL Vaporizing Liquidating a gas film that lubricates the seal faces in applications of extremely low temperature
iUses the energy of the rotating equipment to vaporize process fluid at a controlled rate, creating a gas film that lubricates the seal faces in applications of extremely low temperature.
PRODUCT TECHNICAL SPECIFICATION
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- Model Number LP-28
- Shaft size 12.125"/308mm
- Pressure: 1,450 psi(g)/100 bar(g)
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Temperature: -20°C to 200°C
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- Speed: 394fps/120m/s
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Function of Tandem Dry Gas Seals
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1. For seal gas (buffer gas):
The seal gas flows through the primary seal (inboard stage) of a dry gas seal to the primary exhaust port, then through the inboard process labyrinth and back to the process (compressor suction).
The seal gas prevents unfiltered, dirty process gas from entering the dry gas seal. This gas must be cleaned and conditioned to ensure it is completely dry and free of particulate contaminants.
Conditioning is typically achieved through the addition of filters and gas conditioning devices such as separators, boosters, and heaters.
2. For secondary seal gas (applicable only to tandem seals):
(Sometimes called buffer gas, intermediate injection, or intermediate gas)
This gas flows through the secondary seal (outboard stage) of a tandem dry gas seal and out of the secondary vent, as well as through the intermediate labyrinth and out of the primary vent.
It is typically nitrogen and must also be cleaned and filtered to ensure it is dry and free of particulate matter. Not all seals are equipped with an intermediate labyrinth or secondary seal gas, but API 692 requires it as standard. Secondary seal gas offers many advantages, including significantly improved ability to monitor the health of the secondary seal and increased robustness.
3. For Main Vents
The main vent serves as an outlet for leaked gas from the primary seal and, in some cases, for secondary seal gas. It is the primary monitoring point for seal health and is typically equipped with a flow meter and pressure transmitter. Leakage level is a key indicator, and alarms are often set to a threshold, such as 10 times the guaranteed leakage volume, to stabilize readings. Proper instrumentation and backpressure regulation are crucial in vent studies, as they affect the pressure cascade and the accuracy of the dry gas seal system.
![Tandem Dry Gas Seal tandem design 12]()
Dry Gas Seal Control System:
● Dry gas seal and barrier gas control systems are specifically designed to supply gas to the dry gas seal at the correct pressure and flow rate.
● These systems are panel-mounted and installed near the compressor slide.
● Reliable DGS operation requires clean gas. Seal gas filters are installed to filter out impurities.
● Foreign matter entering the seal's operating clearance can lead to degraded seal performance (increased gas leakage) and ultimately seal failure.
Key Design Advantages:
● Dry operation: No wave contamination, extending service life.
● Modular support system: Easy maintenance and standardized interfaces.
● Non-contact operation: Minimizes wear and friction.
● Continuously monitors ventilation flow, pressure differential, and temperature.
![Tandem Dry Gas Seal tandem design 13]()
Recommended Applications:
● Cracking Gas Compressor
● Propylene Compressor
● Ethylene Compressor
● Natural Gas Compressor
● Recycle Hydrogen Compressor
● Recycle Gas Compressor
● Ammonia Compressor
