Analysis on centrifugal pump leakage

What should we do if our centrifugal pump leaks

1. Leakage during installation and static test 

If the leak is not serious, it is most probably caused by seal ring problems of dynamic ring or static ring, while serious leaks indicate problems between the friction pairs of the two rings. After primary observation on the amount of leakage and judgment on the point of leakage, you can turn the pump with hand and observe the change of leakage amount. If the leakage doesn’t change obviously, then the problem must be in static and dynamic ring, friction pairs and the seal ring of the dynamic ring. Maybe the seal ring of static ring has become ineffective. Besides, it is also possible for the existence of leakage channels.

2. Leakage during test run

After static test on the mechanical seal of a centrifugal pump, the centrifugal force generated when the pump runs at high speed will hinder the leakage of fluid. Therefore, despite of ineffective seal in shaft and end cap, most leakage are caused by the damages to the friction pairs of dynamic ring and static ring. In most cases, you need to dismantle the friction pairs, change for a new one and reassemble it. 

3. Sudden leakage in normal operation 

If a centrifugal pump leaks suddenly during operation, it is most probably caused by tremendous change of working conditions or inappropriate operation or maintenance.  If the pump is exhausted, or holds pressure for rather a long time, or suffers from cavitation, the seal will be broken. If the practical output of the pump decreases, it will leave a large amount of fluids circulating inside the pump with heat accumulated simultaneously. That will vaporize the fluids and lead the seal to lose efficiency. If the pump has been idle for a long time, and you didn’t turn it with hand before starting it, the friction pair will be adhesive and tear the the surface of seal. If the medium begins to contain more corrosive, polymerism and gummy materials, or the environmental temperature changes sharply, the seal will also break. 

Faced with all the above kinds of leakage, we should find out a solution respectively, either change the seal or repair it. We should not mend it casually so as to make the centrifugal pump barely work for a longer time, and overhaul it until a more serious problem occurs.

Leak again?

Still leaking?

Come on,

Change for a shield pump, a magnetic pump for good.

What is Centrifugal Pump?

To understand what is centrifugal pump, first we have to know what is pump. Pump is a machine that transfers mechanical energy from prime mover(motor or internal combustion engine, etc.) to hydrodynamic energy to make fluids move.

What is centrifuge? In fact, centrifuge is caused by the inertia of objects. For example, when you spin an umbrella slowly, the rain drops on it will spin along. That’s because the force of friction between rain drops and umbrella works as centripetal force. But if you spin the umbrella fast, the friction force will not be enough to keep the rain drops spinning along and they will run away from the umbrella and move outward. Just like you tie a stone with a rope, hold the rope and spin the stone in a circle. If you spin it very fast, the rope will break up and the stone will fly away in the radial direction. That is so-called centrifuge.

Centrifugal pump is designed by that principle. The high speed spinning impellers move water and throw it out for delivery. The centrifugal pump converts the mechanical energy from the prime mover to energy in a moving fluid through the rotating impellers. When the centrifugal pump starts working, its impellers filled with fluids will start to rotate. Under the centrifugal force, the fluid is whirled radially outward along flow channels between impellers. The fluid gains both velocity and pressure while passing through the impeller. Then it goes through the delivery chamber, where the flow is decelerated and the pressure is further increased. Finally, the fluids is sent out along discharge piping line. As the fluid is being discharged, the center of impeller will have low pressure or become vacuum. The fluids in suction tank will continuously flow through the suction tube into the center of the impeller under atmosphere pressure. In this way, the rotating impellers keep drawing in and draining out fluids.