WHY CENTRIFUGAL PUMP HAS LOW FLOW …?

In the Industrial Industry, Centrifugal pump is most useful pump of the most of industry line. After using so much time of centrifugal pump, their media flow has been low in some reason,

So there are the most 8 reasons to solve this problem.

1

   .   Reversed Impeller Rotation: This may seem like a no-brainier, but it really is a common problem. When wiring the pump’s motor to power, it’s important to test which way the motor is turning first. “Bump Starting” the motor is a common practice where the motor is started without the pump hooked up to ensure proper rotation of the shaft. If the motor turns the wrong way, the impeller could potentially back off the shaft, causing serious damage to the internals.

  .     Clogged Suction: Make sure the suction pipe is free and clear of debris. Less flow into the pump will obviously yield less flow out of the pump.

3.    Worn impeller, wear ring, wear plate: If the vanes on the impeller are worn, the hydraulic capacity of the pump is reduced. Same with the wear ring and wear plate. When clearances open up due to wear, more re-circulation occurs inside the pump, reducing the pump’s flow.

4.    Excessive Clearances: If clearances are too wide for the type of fluid pumped, excessive slip will occur. Fluid will continue to recirculate inside the pump, yielding lower flow out of the pump.

5.    Debris in the impeller: If the eye of the impeller is plugged with debris, it removes the hydraulic capacity of the impeller to create an area of low pressure.

6.    Closed Discharge or Suction Valve: Again, this one seems really simple, but something that can be easily overlooked.

7.    Open Bypass Valve: Check to make sure the flow isn’t being diverted somewhere else through a bypass valve.

8.    Vortexing: This is more common with pumps in suction lift conditions, like a self-priming pump, or a vertical turbine. Make sure you’re meeting minimum submergence requirements to prevent vortex.

MECHANICAL SEALS FOR WATER AND WASTEWATER PUMPS

Because mechanical shaft seal failures are the number one cause of pump downtime, the writer decided to dedicate this column to mechanical seal basics.

Years ago, most pump shafts were sealed using rings of soft packing, compressed by a packing gland, but this type of shaft seal required a fair amount of leakage just to lubricate the packing and keep it cool. Then came the development of the “mechanical seal,” which accomplishes the job of restraining product leakage around the pump shaft with two very flat surfaces (one stationary and one rotating).

Main elements of a Mechanical seals

Here is mentioned below, there are two seal face :

• A set of (very flat) machined and lapped primary sealing faces: The very close (near) contact between these two flat mating surfaces, which are perpendicular to the shaft, minimizes leakage. Dissimilar materials are usually used for the faces, one hard and one softer, in order to prevent adhesion of the two faces. One of the faces is usually a non-galling material such as carbon-graphite. The other surface is usually a relatively hard material like silicon-carbide, or ceramic. However, when handling abrasive, two hard surfaces are normally used:
• One face is held stationary in a housing
• The other face is fixed to, and rotates with the shaft.
• A set of secondary static seals, typically O-rings, wedges and/or V-rings.
• One static seal, seals stationary component(s) to the housing
• The other seal, seals the rotating component(s) to the shaft (it normally moves axially on the shaft or shaft sleeve)
• A spring member to maintain face contact, such as a single spring, multiple springs or metal bellows.
• Other mechanical seal hardware, which includes shaft sleeves, gland rings, collars, compression rings, and/or pins.

Mechanical seals require clean water, or other compatible liquid, for the lubrication of the seal faces. The faces in a typical mechanical seal are lubricated with a boundary layer of gas or liquid between the faces. Lubrication can be provided from the pumped liquid itself or from an external source, depending on system requirements.