Industrial pump mechanical seal failure analysis of external causes

A large shaft axial channeling
Mechanical seal sealing faces have a certain pressure ratio , so as to play seal, mechanical seal which requires to have a certain amount of compression spring , a force to the seal faces , the sealing surface rotating together produce the desired ratio of the sealing pressure . In order to ensure that a specific pressure, mechanical shaft seal requires channeling can not have too much , generally guaranteed within 0.5 mm . However, in practical designs, due to improper design , channeling tends to have a great amount of shaft , the use of mechanical seals are very unfavorable. This phenomenon often occurs in a multi- stage centrifugal pumps , especially during startup of the pump , channeling a greater amount .
When working at the equilibrium balance disc and balance automatically changing the axial gap between the ring b, thereby changing the front and rear sides of the pressure balance disc , generates a force in the opposite direction to the axial force to balance the axial force. The inertia of the rotor runout and transient fluctuations in pump mode , operation will not be resting on a rotor axial equilibrium position . Always in balance disc ran around the state . In normal operation, the balance disc axial channeling is only 0105 ~ 011 mm, to meet the mechanical seal to allow the amount of 015 mm axial channeling requirements, but the balance disc in the pump start, stop , drastic changes in working conditions are likely when the axial channeling greatly exceeds the permissible axial mechanical seal channeling .
Industrial pumps after a long run, the balance disc and balance ring friction and wear , the gap b with increasing the amount of mechanical seal axial channeling increasing . The axial force on the suction side of the sealing surface of the pressing force increases , the sealing surface wear increased , until the sealing surface is damaged , lost seal. The discharge side of the mechanical seal , with the balance of the wear plate , the axial direction of the rotor member is greater than the sealing requirements channeling channeling the axial sealing surface of the pressing force decreases , id cable ties less than sealing requirements , the final side of the pump lost all mechanical seal seal.
2 axial force is too large
In the course of the mechanical seal is not able to withstand the axial force , if there is an axial force of the mechanical seal is serious. Sometimes, because of the axial pump unreasonable force balance mechanism design and manufacture , installation, use and other reasons , resulting axial force is not balanced out . Mechanical seals to withstand an axial force , the operation temperature is high gland , the polypropylene of the medium may be melted at high temperatures , thus the pump starts soon lost sealing effect of the sealing face when the pump is stationary there intermittent spray drain phenomenon .
3 shaft deflection is too large
Mechanical seals known face seal is a rotary seal axially movable contact , which is in a fluid medium and the role of the elastic member , the two lines perpendicular to the axis of the seal faces close contact , relative rotation , so as to achieve sealing effect ,security seal labels thus requiring two sealing force between to evenly. However, the unreasonable design of the pump , pump operation, the mechanical seal installation deflection generated at the larger the discontinuity between the sealing surface , resulting in good sealing effect .
4 no auxiliary flushing system or auxiliary flushing system set unreasonable
Auxiliary mechanical seal flush system is very important, it can effectively protect the sealing surface, for cooling , lubrication, and other debris washed effect. Sometimes designers no rational allocation of auxiliary flushing system , reach the sealing effect ; although sometimes designers designed the support system, but because there are impurities in flushing fluid , fluid flow, pressure is not enough, rinse mouth position unreasonable design and other reasons , also reach the sealing effect.