Ethylene propylene feed pump (bits No. E-GA301A / B) to provide raw materials for the downstream polypropylene plant, the pump for the entire polypropylene plant has an extremely important role in the reaction liquid propylene used all by it to supply, so once The pump problems, it will cause the entire ethylene and polypropylene plant parking, the pump since April 2001 been put into use, two pumps have been frequent oil, sealing liquid and propylene leak fault. Despite repeated repair, replacement of the mechanical seal parts, but the effect is minimal. The frequent pump failures, not only the loss of a large number of propylene, increased maintenance costs, and returned to stable production throughout the polypropylene plant is a big risk. We analyze the causes of the leakage, and carry out a comprehensive reform, it has been a good effect.

First, the basic situation:

E-GA301 pump model GSB vertical speed pumps, 11th Institute of Aerospace Corporation manufacturing. By the motor, gearbox, pump, forced lubrication systems, sealing liquid circulation system and other components.

Growth is geared to two, namely the input shaft speed motor speed 2950R / M, the output shaft speed is 10275R / M, two seal with a different form. The seal (ie, input shaft seal) is a lip seal (rubber lip seal skeleton), under seal (output shaft seal) of the mechanical seal, code-named: 60C, growth is built with oil, the circulating forced lubrication system, to the lower part of the mechanical seal lubricated and cooled.

Pump shaft seal part of the two series of mechanical seals, mechanical seal the upper codenamed 60B, the lower part of the mechanical seal codenamed 60A. Sealed chamber filled with two mechanical seals between the sealing oil, in a sealed fluid replenishment cycle system (including a sealed tank) cycle, mechanical seals lubricated and cooled.

It consists of the following three sets of mechanical seal components: ring, quiet ring, thrust ring, spring, spring seat, secondary seal, card ring. Vertebral ring, spring, spring seat and a snap ring, secondary seal has "O" shaped rubber ring and PTFE wedge ring, stationary ring were made of graphite (M106K). Its ring material is different, 60A and 60C of the ring is made of cemented carbide YG6, and 60B of the ring, the matrix material for OCRL8N112M02TI, in its sealed end surface surfacing layer of thickness 1.5MM carbide.

Second, the mechanical seal leakage analysis:

There is a cavity between the pump speed gearbox with the pump, and seal leakage of lubricating oil have accumulated here, lead to the pump through the drain hole in vitro oil cup. The pump is put into use since then, there is oil leaking oil flow cup, you need to fill the tank to the pump gearbox lubricated every 3-5 days. In 1-2 months after the operation, the mechanical seal sealing performance begins to deteriorate, seal oil leaking out, color inside the cup and seal oil tank oil turns black, and began to flee propylene sealed chamber into the seal tank and oil cup, pump vibration increase, and finally propylene large spills, resulting in high pressure seal tank alarm and parking. High-speed pump disintegration of inspection, found that the mechanical seal stationary ring seal face 60B has been damaged, ring around the end face of sticky black graphite, 60A wear more serious, 60C only slight wear marks.

Third, the transformation plan:

1.60A transformation and secondary seal of the static ring

Static friction ring 60A of resin-impregnated graphite, in the medium of light hydrocarbons, at high speeds, better performance resin-impregnated graphite material. However, resin-impregnated graphite ring in the course of work, wear powder if gathered at the secondary seal, in particular blade-shaped Teflon seal, will seal the edge indentation, or even hinder compensation compensationring . In the transformation, the selection of a high strength, good frictional properties and temperature resistance of immersion silver graphite rings. Maintain the stability of the system operation.

To ensure the sealing performance, the secondary seal should have good flexibility. Based on the above analysis of the secondary seal failure, the secondary seal made of Teflon wedge ring instead Viton O-ring, PTFE gasket installed a rectangular cross-section, the inner diameter of the gasket and seal tightly contact area fit, prevent solid particles from entering the ring sealing surface. In addition, due to higher media pressure, which can also serve to prevent the rubber gasket ring being squeezed out of action. In addition, O-seal with axial float mounting structure, since the spring force to push through a rectangular ring acts directly on the compensation ring, when the compensation loop compensation move, move point O-rings on the two. This can ensure the compensation of the compensation ring, but also to ensure that the auxiliary seal 0-rings, thereby improving the reliability of sealing. Due to the high friction rubber seal, also can increase the buffer loop compensation in the non-normal operation to protect the end surface friction.

2.60B ring transformation

Speeder end face mechanical seal 60B than the pressure value, although small, but its seal face pressure on both sides of zero, pump speed and high, so using a large face pressure values ??it will exacerbate the wear. So take a face pressure does not change, only change the ring material, the structure, the original ring redesign.

After transformation via a seal, since November 2001 has been put into operation in operation, running in good condition, total uptime of more than two years, has not leaking, the sealing effect is very good. Accessories and installation only economic aspects is very significant.

IV Summary

The reason for the high speed pump mechanical seal leakage, through three sets of sealed with comprehensive transformation, extending the high-speed pump maintenance cycle, the complete elimination of this can be very dangerous, a good solution to the problem. This method of solving similar condition equipment leaks, there is a certain reference value.