Stop and leakage reasons analysis
Centrifugal pump stop is mainly composed of mechanical seal failure causes. Failure of performance is mostly leak, leakage reasons have the following kinds:
① Dynamic and static ring sealing surface leakage, reasons mainly have: end flatness, roughness can not reach requirment, or surface has scratch; between end has particulate matter, causing two ends can not operate samely; installation can not in place, wrong way.
② Compensation ring sealing ring leakage, reason mainly has: gland deformation, uneven pre-compression, installation uncorrectly; sealing ring quality does not accord with standard; sealing ring selection is wrong.
The practical use results show that, most sealed component failure part is dynamic, static ring end, centrifugal pump mechanical sealing move, static ring end appears crack is common failure phenomenon, main reasons are:
① when installation sealing face clearance is large, flushing liquor can not take away friction produced heat generation, it leaks from sealing face gap, caused damage due to end overheating.
② liquid medium vaporization expand, make two ends separated by vaporizing expansion force, when two sealing force joint, damaging lubricant film to cause end surface overheating.
③ liquid medium lubricity is poorer, coupled with the operating pressure overload, two seal face tracking rotation is not synchronization. For example, high speed pump rotating speed is 20445r/min, seal face center diameter is 7cm, after operation the pump linear speed up to 75 m/s, when there is one seal face lag cannot track rotation, instantaneous high temperature will cause sealing surface damage.
④ seal rinses orifice plate or mesh jams, cause water is insufficient, make the mechanical seal failure.
In addition, sealing surface smooth channel, when the ends joint, it will appear gap to result in the sealing failure, main reasons are:
① the liquid medium is not clean, have tiny particles, with high speed to slide in sealing surface, scratching the surface and failure.
② pump drive piece coaxial tolerance is poor, after pump starts each one circle, end is shaked one friction, dynamic ring working track is decentraction, causing end vaporization, overheating and wear.
③ liquid medium hydraulic characteristics frequent occurrence causes pump vibration, causing sealing face malposition and failure.
Liquid medium corrosion to seal components, stress concentration, soft hard materials matching, erosion, assisting sealing O-rings, v-shaped ring, concave rings and liquid medium are incompatible, deformation, etc, will cause mechanical seal surface damage failure, so to the damage form needs to comprehensive analysis, find out primary cause, ensure mechanical seal long time running.
