Customized AS-C395 Single Cartridge Mechanical Seal

This is customized single mechanical seal in cartridge form.
 

About Asinoseal：

Asinoseal is one of the most professional mechanical seal manufacturers in China. We are always making efforts to providing universal service in different applications field like petrochemical, paper mill, oil refineries, mining and others. With wide ranged products from high-end compressor mechanical seal, agitator mechanical seal, cartridge seal, metal bellow seal to popular component mechanical seals and mechanical seal materials, you are expected to get most types of mechanical seals here.

Background Information：

Case Analysis of Mechanical Seal Failure of Screw Compressor

The mechanical seal of the screw compressor is one of the most important components in the compressor unit. The failure of the mechanical seal will lead to the failure of the entire unit, which will seriously affect the safety of production.In comparison, the radial space size of the screw compressor is small, and the mechanical seal is often limited by the radial size when transforming the mechanical seal.

In the case quoted by this paper, the service life of the original mechanical seal was extended, the normal operation of the unit was ensured, and certain economic benefits were created through the transformation of the mechanical seal of the four-top gas compressor (LG60/1.0) of the atmospheric and vacuum device.

1.Cause analysis of mechanical seal failure
The mechanical seal leaked in less than half a year, and the liquid level of the lubricating oil tank rose. When it was removed, it was found that the stationary seat’s anti-rotation pin of the mechanical seal was cut off, and the auxiliary sealing ring of the compensation seat was worn, which was cut off by the stationary seat anti-rotation pin，thus causing the mechanical seal to fail.

After analysis, it was found that the pre-nitrogen gas of the original mechanical seal caused the mechanical seal to fail due to unstable pressure (after the pressure increased), which caused the liquid level of the lubricating oil tank to rise. The main reasons are the following two aspects: 1. The original mechanical seal stationary seat anti-rotation pin is cut off due to the uneven composition during machining and the large shear force when the compressor is started; 2. The amount of O ring interference of stationary seat of the original mechanical seal is large.

The structure of the mechanical seal is like this: it adopts static structure, the compensation ring is graphite ring, the non-compensation ring uses metal parts spraying ceramics, and the compensation ring uses O-ring.

The following are the main parameters of the mechanical seal： Load coefficient K:The sealing fluid pressure acts on the compensating ring，and the compensating ring under this pressure to act on the non-compensating ring to tend to close，K is thus the ratio of the effective action area Ae to the sealing ring band area A.The formula is given for K = Ae / A.

The numerical size of the load coefficient is related to the extent of the medium pressure acting on the sealing end surface. End face pressure Pc: received force per unit area. The end face pressure of the double mechanical sealing is Pc = Ps + Pf (K- λ) ± Pt. Where Ps is the spring pressure; Pf is the sealing pressure; Pt is the increase or decrease of end surface pressure due to friction.

2.The compensation ring structure of the original end surface of the mechanical seal: The structure uses graphite ring as the compensation ring material. The graphite ring has the characteristics of good self-lubrication, and the sealing surface size is narrow, which is conducive to reducing the heat caused by friction. The graphite ring adds a metal part, which can improve the mechanical strength of the compensation ring.

3.Transformation results: the leakage requirements of the unit (medium side) should not be more than 1000ml / h, and the leakage (atmospheric side) should not be more than 200ml / h. Static pressure test: pressure 0.5MPa for 15 minutes without leakage. Turning test: pressure 0.5MPa, continuous operation for 1 hour, no leakage, meet the requirements of the unit. After the transformation, the mechanical seal has been running continuously for seven months, ensuring the long-term operation of the unit.

4.Modified stationary seat structure: The structure retains the structural characteristics of the original compensation ring, and makes some adjustments to the sealing surface: adjust the internal and outer diameter of the sealing surface of the mechanical seal, reduce the load coefficient to a value in the reasonable range; adjust the interval between the anti-pin hole and anti-pin; change the compensation ring O-ring to all-inclusive fluorine rubber, reduce the friction coefficient between the compensation ring and the sealing ring, and increase the floating of the compensation ring.