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Application And Maintenance Of Dry Gas Seals In Propylene Refrigeration Compressor
Nov 02, 2017

Refrigeration compressor is the key equipment of ethylene plant, the device was modified when the transformation of the 4H-8S, 11H-6S two compressors, and select the series dry gas seals technology. From the current operating conditions, the unit sealed operation is stable, the adaptability of the work conditions, in line with the long-term operation of the equipment requirements. The following examples of propylene refrigeration compressor as an example.

1 Introduction to dry gas seals

The dry gas seals is a non-contact seal, the movable ring is fixed by the drive pin, and the static ring base is provided with a symmetrical spring. Dynamic ring material is generally hard material, above the uniform open from the deep and shallow (outer edge to the inner edge) of the spiral groove, and in the spiral groove tail set the weir, the direction of the spiral groove is running on the pump shaft direction. So in the course of operation, the gas into the sealed end, the spiral groove and sealing weir under the effect of being compressed into a gas film to make the sealing end of the separation, due to the static ring on the spring force to fit, so in two Force, the sealing gas in the end face to form a stable air film, to establish a sealing effect. When the operating conditions fluctuate, the balance of the membrane build-up is changed until it is established again, and this process does not destroy the sealed end face.

2 This device controls the program

The compressor medium is 99.6% propylene. Due to the chemical properties of propylene, high purity, can not be leaked into the air, the air can not enter the body, so the sealing system to be selected with the middle seal gas tandem seal. In the middle of two sets of single-sided seal to join a level of intake, with a labyrinth seal connection. The seal gas is thus divided into primary seal gas, secondary seal gas and isolated gas. There are three sources of sealing gas, one in the normal operation of the four parts of the compressor from the export of propylene; the second is to stop the car before and after the process of nitrogen; three external propylene. The secondary seal gas and the isolation gas come from the utility's nitrogen. Two-stage sealing gas is required to pass through the plain weave stainless steel filter to filter into the sealed face.

Comparison of dry gas seals and floating ring seal

(1) floating ring seal is to seal the gap fluid resistance to achieve the process of oil gas, and the pressure is higher than the body pressure, it will cause some problems. Such as: oil pressure will cause the sealing section of the wear and tear; regulation is difficult; the body of the media easy to pollute the oil; oil separator on the atmosphere pollution, the operation and maintenance costs have a great impact.

(2) the emergence of dry gas seals, sealing technology is a revolution, gas seal is no longer subject to sealed lubricants. Dry gas seals has the following advantages:

① because there is no sealed oil seal, eliminating the pollution of the body of the media, affecting the cooling effect of the media.

② system process is simple, more floating ring seal to reduce the sealing oil control system, oil and gas separation system.

③ body media leakage is small.

④ low power loss.

⑤ open, parking operation is simple.

4 operation and maintenance experience

The device is cooled and compressed for many years, and there is no unplanned parking accident due to sealing failure. But the sealing system maintenance needs to be more refined, the following from my device operation and in recent years to sum up the experience as follows:

(1) to ensure that the sealing surface of the rigid film formed by the relatively stable, so the gas source should be relatively stable, should not have too much pressure, flow fluctuations.

(2) every day to observe the pressure gauge of the seal to ensure that the filter clean to achieve the purpose of filtration, so as not to have impurities into the sealing section induced diversion tank and seal weir damage.

(3) to switch the sealing gas filter should pay attention to the first open downstream valve, to avoid excessive pressure caused by excessive deformation of the filter.

(4) each time before driving the first access to the isolation gas to prevent the lubrication of the lubricating system into the sealed section lead to damage.

(5) When the compressor is driven, it should first use the nitrogen or external medium gas of the utility project to act as a sealing gas because the outlet pressure of the compressor can not completely open the static and static seal.

(6) The guardians should observe the leakage of the seal, and the change in the amount of leakage indicates that the gas film formed on the sealing end faces changes instantaneously, such as the gradual increase in the amount of leakage, which means that the face is slowly damaged.

(7) every two hours to check the sealing system, and focus on a record of gas pressure and leakage, sealing gas pressure. And timely analysis and processing of the problems that arise.

5 Conclusion

Two compressors, four sets of dry gas sealing system composed of the system is stable, compared to other centrifugal compressor operation is simple, no impact on the media and lubricants to meet the three-year ethylene plant maintenance of the long-term operation of the target. But in the dry gas seal is not factory maintenance and maintenance aspects to be studied.

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