Air Compressor For Cleaning

1. Reduce impact and operate reliably

2. Constant voltage power saving

3. The voltage adaptability of the AC power supply is strong

4. Low noise

The Principle of Dry Gas Seal System of Centrifugal Compressor and Analysis of Leakage Causes

The sealing system is a tandem double-end dry gas seal, which consists of two groups of single-end dry gas seals placed continuously. The filtered pure synthesis gas enters the primary sealed chamber as the main seal gas, and its pressure is 0.2-0.3MPa higher than the process gas pressure, which acts as a barrier. A small amount of seal gas will enter the cylinder, but it is pure synthesis gas. Therefore, no pollution occurs.

The other part of the gas passes through the comb-tooth seal between the two-stage dry gas seal and is divided into two paths. One part is discharged directly to the flare system as a primary leak (also called a primary leak), and the other part enters the secondary seal cavity to act as a secondary seal gas. Then through the comb-tooth seal, the secondary leakage pipeline is discharged together with the isolation gas and led to the flare system. The isolation gas (nitrogen) plays the role of the last sealing, and its pressure is slightly higher than that of the secondary sealing gas to ensure that the secondary sealing gas will not leak to the atmosphere. air compressor for cleaning

Through the case of centrifugal compressor syngas leakage, analyze the gas leakage of the centrifugal compressor equipped with the dry gas seal system, such as the first-stage leakage gas of the dry gas seal and the main seal gas leaking to the bearing box through the center split surface.

1 Introduction

With the rapid development of the petroleum and chemical industries, the development direction of low energy consumption, high efficiency, zero pollution and long-term cycle has become the development trend of the petrochemical industry. Large-scale compressor units are key equipment in the petrochemical industry, and their sealing performance determines whether the unit can operate smoothly and safely. Dry gas seals stand out for their low leakage, good economy and practicality, long seal life and reliable operation. Dry gas seal is a new type of non-contact seal for rotating shafts. It is based on gas-lubricated bearings and improved from contact liquid film mechanical seals. In the late 1960s, John Crane developed the first set of dry gas seals and applied them to centrifugal compressors. With the rapid development of the sealing industry and fluid dynamics, various types of dry gas seals have been derived. At present, dry gas seals have been widely used in petroleum, chemical, metallurgical, aviation and other industries. Therefore, in this article, it is mainly to conduct a comprehensive analysis and research on the principle of the dry gas seal system of the centrifugal compressor and the cause of leakage, and on this basis, some of the following content is proposed, hoping to be able to work in the same industry The personnel provide a reference of a certain value. air compressor for cleaning

2. Working principle of dry gas seal

Dry gas seal is a new type of non-contact seal, which uses the principle of fluid dynamics to achieve non-contact operation of the seal end surface through a dynamic pressure groove opened on the seal end surface. It is composed of a spiral spring, a rotating ring, a static ring, a sealing ring, a spring seat and a shaft sleeve. The sealing surface of the rotating ring is ground and polished, and a special fluid dynamic pressure groove is machined on it. When the dry gas seal rotating ring rotates, the seal gas is sucked into the dynamic pressure groove and flows along the seal weir. Under the throttling action of the sealing weir, the gas is compressed and the pressure rises, pushing the sealing surface away, forming a very thin gas film between the two sealing surfaces. The gas dynamics research shows that when the thickness of the gas film on both ends of the dry gas seal is 2-3 microns, the gas flow layer is the most stable. Therefore, the design value of the gas film thickness of the dry gas seal is selected at 2-3 microns. When the closing force formed by the gas static pressure and the spring force is equal to the gas film reaction force, the gas film thickness remains constant, and the dry gas seal operates stably turn.

When there is external interference, the thickness of the air film decreases, and the reverse force of the air film increases. At this time, the opening force is greater than the closing force. Under the action of the opening force, the sealing surface gap increases. As the sealing gap increases, the opening force corresponds to Decrease until the opening force is equal to the closing force, at which time the sealing gap returns to the normal value. If the thickness of the sealing air film increases due to external interference, the reverse force of the air film decreases, and the closing force is greater than the opening force. Under the action of the closing force, the sealing gap decreases. As the sealing gap decreases, the closing force also decreases. Correspondingly decrease, until the closing force is equal to the opening force, the sealing surface returns to the normal value. Therefore, as long as it is ensured that the sealing gap is within the design range during installation, the sealing system will return to stability when the external interference disappears. air compressor for cleaning

3. Reasons for seal failure

The first is the failure of the dry gas seal. The operating data of the dry gas seal (coupling side) at the front of the compressor for nearly half a year is obtained. From the data, it can be seen that, for example, the first stage leakage pressure of the dry gas seal at the front of a compressor has been since December 2011. The increase from the original 0.15 MPa to 0.2 MPa, fluctuated abnormally for up to 3 months, indicating a problem with the dry gas seal.

The second is the failure of the rubber sealing ring. The sealing gas of the dry gas seal is synthesis gas, and the process medium is circulating gas (including synthesis gas, propylene and aldehyde gas). The process medium corrodes the rubber seal ring of the dry gas seal system, which may cause the seal ring leakage.

The third is the failure of the facet seal in the housing. If the facet sealant in the compressor housing ages or fails, the process medium will enter the bearing box through the center facet. Since the interface of the first-level leakage pipeline of the dry gas seal is near the mid-face, it is also possible that syngas enters the first-level leakage pipeline through the mid-face, resulting in an increase in the first-level leakage pressure of the dry gas seal. Therefore, it must be sufficiently caused Attention. air compressor for cleaning

4. Leakage analysis

One is that the first-level leakage gas of the dry gas seal enters the bearing box through the connection of the center split surface. The phenomenon is that there is synthesis gas in the bearing box. The scene situation is that there is synthesis gas in the bearing box, so this situation is possible.

The second is that the main sealing gas (synthetic gas) leaks to the bearing box through the middle facet, indicating that the middle facet sealant has failed. Actual inspection and repair found that the sealant on the middle facet of the contact part fell off, and when the leakage occurred, there was a seal inside the bearing box. Syngas, so this situation is possible.

The third is the way of leakage. After the primary seal gas (synthetic gas) passes through the primary seal of the dry gas seal, it enters the primary leakage seal cavity, and a part is discharged to the flare, and the other part of the primary leakage gas passes through the compressor housing connected to the primary leakage seal cavity. Leakage to the bearing box at the split face in the cover. Another way of leakage is that the main seal gas leaks directly to the bearing box through the first-stage seal cavity and the split face seal of the large cover of the compressor housing.

The fourth reason is the failure. The parting surface of the shell is a rigid sealing surface, and a layer of 704 sealant is applied during maintenance. There are no defects such as pits and scratches on the parting surface during disassembly inspection, which can be judged as sealant failure.

Reasons for failure: First, the sealant is of unqualified quality or improperly stored, or continues to be used after the expiration date, while mixing sealants from multiple manufacturers. Secondly, the quality of inspection and maintenance is not strict, the sealant is applied unevenly, the curing time of the sealant is not enough (12~24h is required), and the pre-tightening force of the large cap bolts is uneven. Finally, the operation process is unstable. Frequent production switching, adjustment of process parameters, changes in production load or improper operation of positions. air compressor for cleaning

Hot Tags: air compressor for cleaning, China, manufacturers, suppliers, factory, customized, wholesale, in stock, VFD Three phase Motor Compressor, Variable Frequency Screw Air Compressor 8bar, Energy Saving VSD Air Compressor, 10hp 7 5kw Rotary Air Compressor, Hande screw compressor, 10bar Vsd Screw Air Compressor