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2019-04

Pump bearings and seals are not wear resistant and temperature resistant solutions

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(1) Problems occur: the shaft deviation causes high vibration, shortens the life of the mechanical seal, and generates noise.    

Solution: Use the impeller mouth ring of polyimide carbon fiber composite material to fit the stainless steel pump casing ring; replace the original graphite bushing with the throat bushing of our material.      

The result: reduced vibration amplitude, which extends seal life and bearing life and enhances pump free operation. Many pumps use packing as a filler in their use. The main function of the packing is to prevent leakage, but it also acts as a bearing to stabilize the shaft. At present, many pumps have changed the packing to a mechanical seal. With the change of the mechanical seal, the bearing influence is gone, and the shaft deviation (high vibration and related influence) becomes a problem.

The use of polyimide carbon fiber composite material to improve the pump successfully solved the customer's problems, mainly in the following two points:

1) Polyimide carbon fiber composite material is a metal-free, non-biting material. This allows the running clearance to be reduced (only half of the gap between the metal gaps specified by the API), the bushing with smaller clearances can stabilize the shaft, and the smaller gap ring can further limit leakage and leakage speed.

2) Polyimide carbon fiber composite is a high strength, high performance thermoplastic material. It is easy to injection and absorbs vibrations and shocks, while the metal being replaced can cause vibration and shaft wear.

Parts: with removable sealing bushings and Teflon bearings

(2) There is a problem: the support bearing is severely worn. The factory tried a lot of different materials such as carbon, graphite, and filled Teflon materials, trying to find a suitable solution to the problem of wear and shaft deviation. All materials were scrapped in two to three months. Among them, the product of polytetrafluoroethylene causes wear of the shaft, causing great leakage, resulting in failure of the mechanical seal.

Solution: Replace the previously used filled PTFE bearing with a polyimide carbon fiber composite.

RESULTS: After the polyimide carbon fiber composite support bearing was installed, it has been successfully operated for more than 13 months. At the 8th month after use, the center part of the agitator was removed and temporarily used for other equipment. At that time, the staff tested it. The agitator bearing found that the leakage per inch per inch was less than 0.005, and the average failure interval increased by 300% to 400%.

(3) Problems: This pump is made of stainless steel and stainless steel with a hard outer casing as a ring and bushing. In general, the dry running of the pump is due to the reduction of the suction volume during operation, and the main dry running conditions often lead to premature pump damage and metal parts are also greatly damaged. The average time between failures of these pumps is only six months.

Solution: Replace the stainless steel impeller ring and bushing with a polyimide carbon fiber composite material, reducing the operating clearance by approximately 50%.

The result: Pumps modified with polyimide carbon fiber composites have been in use for more than a year now. Some unfavorable conditions often occur during the previous operation, causing intermittent dry rotation, which makes the pump inoperable, but this phenomenon has been delayed by the renewal of polyimide carbon fiber composites. In addition, the customer also issued a report: by using polyimide carbon fiber composite material to transform it, reducing the operating gap, the pump output flow has increased by 400gpm, and the other two multi-stage pumps have also been updated.

(4) Problems occur: severe vibration, low pump efficiency

Solution: Polyimide carbon fiber composite material is used as the pump casing ring and bushing. The running clearance was reduced from the API standard to 0.0015 inches per inch of turning diameter.

Results: The initial vibration was 0.600 inches/second, the improved vibration was 0.094 inches/second, and the efficiency was increased by 5%.

Vibration: The reason for the vibration reduction is as follows:

1) Recirculation flow and its effect on rotor instability are reduced;

2) the clearance is reduced and the running of the shaft is reduced;

3) Natural thermoplastic materials have easy injection molding properties and absorb shock or impact.

Efficiency: The efficiency gain is due to the reduced clearance between the pump casing and the impeller ring. The gap here in the pump will in turn reduce internal recirculation.

Reliability: This pump has been working continuously for more than four years, and the refinery has already been? Polyimide carbon fiber composites are used on more than ten pumps.

Advantages and applications of polyimide carbon fiber composite anti-abrasive materials:

a. Excellent wear resistance. It is superior to rubber, bronze, carbon graphite and other materials in the case of abrasive particles.

b. Widely used in bushings for sewage pumps, sea water pumps (working environment is sand and other abrasive particles), line pump bearings and bowl wear rings.

c. Recommended only as a fixed part (due to temperature limits of the material).

d. Anti-abrasive composites have better chemical resistance than other non-metallic materials.

e. Polyimide carbon fiber composite materials have a very low coefficient of friction compared to rubber bushings and other metallic materials.

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