AS-C5600DPR Double Cartridge Mechnaical Seal To Replace Johncrane 5620PR Seal

AS-C5600DPR double mechnaical seal in cartridge form is to replace Johncrane 5620PR seal which is one of the 5620 range.We have AS-C5600S & AS-C5600SQ & AS-C5600SL seals to replace JOhncrane 5610& 5610Q $ 5610L single mechnaical seals in cartridge form respectively. We have AS-C5620 $ AS-C5620P & AS-C5625 & AS-C5625P seals to replace Johncrane 5620 $ 5620P & 5625 & 5625P double mechanical seals in cartridge form respectively. These seals can be customized for specific installations. 

Operating Limits:

Temperature:  -30 °C  to  205 °C

Pressure: Up to 75 mm: 21  bar g/ 300 psig

75 mm and beyong：13 bar g/ 200 psig max

Speed：up to 25  m/s / 5000 fpm

Features：

Double seal arrangement includes an rubber O ring as a seconary dynamic sealing element.

Reverse balance designs which permit OD & ID pressurization，allowing for  it to work as a dual or  tandem

Outside the item nonclogging wave spring

Optimized design of rotary face

Outboard drive without setscrews

 OD pressurization protects secondary components from tensile stresses & realizes better cooling condition

About Us：

Background Knowledge：

What are the characteristics of mechanical seals for methane pumps
The working temperature of the methane pump is around -95~-100°C. At such low temperatures, the properties of the material change and become generally brittle, making common plastics and rubber unusable and limiting the use of other materials. Another feature of the methane pump is the high working pressure. The inlet pressure of the methane pump is about 3MPa. The deformation of the parts should be considered when designing the sealing rings and other parts of the mechanical seals. In addition, the low-temperature medium has a small specific gravity, poor lubricity, and is easy to vaporize. Once it leaks out, frost will emerge, which will aggravate the wear of the sealing end faces of the mechanical seals. In view of these characteristics, most of the mechanical seals of methane pump adopt double seals, and an isolation chamber is set between the medium and the atmosphere, and a sealing liquid is passed through it to alleviate the influence of low temperature and achieve sealing.

Now Let’s take the methane pump of a factory as an example to briefly introduce its mechanical seal structure. The critical temperature of the pump is -82.6°C, and the critical pressure is 4.64MPa (45.44 atmospheres). Obviously, the temperature delivered as a liquid is lower than the critical temperature, and the working pressure is higher. One recommended mechanical seal structure for the pump is a rotary, multi-spring internal flow, double balanced seal. The two moving rings share a set of springs, so that the spring forces on the two moving rings are equal. The material of the friction pair is cemented carbide and graphite, and the combined moving ring is heat-fitted. Due to the high working pressure, in order to reduce the force deformation of the graphite ring, it is reinforced with a jacket. The auxiliary sealing ring of the mechanical seal is made of synthetic rubber. And it is equipped with a sealing liquid and control system for double mechanical seals.

The outlet of the pump is connected to the mixing tank. The mixing tank is filled with a mixture of water and ethylene glycol, the ratio is 1:1, which is called antifreeze, and its pressure is equal to the outlet pressure of the pump which is 3.43MPa (33.6kgf/cm²). The bottom of the mixing tank is connected to the bottom of the pressure equalizer, the pressure equalizer is separated by a piston, and the upper part is the sealing liquid. The sealing fluid is automatically injected into the sealing cavity under pressure. When the sealing liquid in the pressure equalizer is exhausted, the piston in the pressure equalizer will withstand the liquid level alarm switch, and the operator will be notified to start the hand pump to replenish the sealing liquid to the pressure equalizer, and the piston of the pressure equalizer will move down to the original position to form a sealing liquid supply system. Obviously, the system is driven by the outlet pressure of the methane pump, and the pressure equalizer is pressurized through the mixing tank.

The sealing fluid of this system is refrigerating machine oil, so the temperature in the sealing chamber of the mechanical seal should not be too low, otherwise it will be unfavorable to the sealing operation. The temperature of the sealing liquid should be between 0 and 5°C. For this reason, a heating system is equipped in the sealing chamber of the seal. The upper junction of the temperature indicator is 5°C, and the lower junction is 0°C. When the temperature of the sealed cavity is lower than zero, the temperature indicator sends a signal to the regulator to open the solenoid valve, and the air enters the steam heater through the solenoid valve. After the air is heated, it enters the heater in the sealed chamber of the mechanical seal to heat the refrigerating machine oil to keep it in the range of 0~5°C to ensure the normal operation of the seal.

It can be seen from the above introduction that although the working temperature of the methane pump is very low, the use of double mechanical seals and a sealing liquid control system improves the working conditions of the cryopump and enables the seal to operate normally. Therefore, the key to the sealing of the cryopump lies in how to solve the problem of its sealing system.