Selecting Right Mechanical Seals for Pumps and their Benefits

Centrifugal pumps are used to pump different types of fluids. Some of these fluids could be dangerous to outside environment as well as humans. The mechanical seals made for pumps are one of the most effective ways to store the fluid inside and prevent leakage. The pump has a rotor or rotating part which revolves around the stationary housing and there is gap between the two parts. The mechanical seals are used to close the rotating part of the shaft against the stationary housing.

Types of Mechanical Seals

There are different types of mechanical seals for pumps that are used for some or other applications. We can categorize them as:

• Pusher type: The pusher type seals close the faces of the seal by moving axially along the rotating shaft or on the sleeves. These impart fixed sealing force to seal effacement and compensate for the wobbling or chances for wearing near the face of the seal.  These types of seals are easily available in different ranges and are cost effective.
• Non-pusher type: Such types of seals don’t move axially but use seal bellows for closing the two halves together. The seals can be used in applications that require high pressure and low temperature.
• Balanced type: Such types of mechanical seals for pumps work well for applications with high pressure near the face and ideal for working with fluids that have low lubricating characteristics.
• Unbalanced type: These types of seals can be used in conditions where there is vibration, problem with captivation of fluid and misalignment of shaft. However these can only work in low pressure and with fluids that have limited lubrication.
• Conventional seals: These are simple seals used for retrofits and upgrades of compressors and pumps.
• Cartilage type: Such seals provide static sealing to both rotating shaft and stationary part of the pump housing.

How to Select the Right Seals?

Each centrifugal pump has a specific reason and type of mechanical seals that can stop any fluid leakages. This could cause hazardous situation in some cases or at least loss of time, effort and money that goes in installation of the seals. Some factors to consider before choosing the right mechanical seal are:

• The first and foremost thing to consider in the selection of mechanical seals is what is being pumped from the centrifugal pumps. Any ordinary liquid like water does not cause any problem to environment, so any ordinary gland can be used for the sealing purpose. But for corrosive liquids or for hazardous fluids, materials that can handle them such be used.
• There are certain pumps that handle liquids of either high or low temperature. It is ideal to choose the mechanical seal that has the material and mating surface to handle the temperature of the fluid.
• Pumps increase the pressure of the liquid that enters at a certain pressure. So it is important to understand which mechanical seals for pumps can handle the pressure of the liquid.
• There are liquids that flow normally while others have high viscosity and slow flow and some that are corrosive and so on. Choosing the mechanical seal that can handle the nature of the liquid is important.

Benefits of Mechanical Seals

The mechanical seals for pumps are preferred over other means because of the many benefits they offer. With proper installation, the chances of leakage with mechanical seals are nearly zero. The chance of excessive wear down of the equipment is less with correctly installed seal. As the faces of the seals are lubricated and spacing between the faces results in production of less friction which means less loss of power. The maintenance cost of the mechanical seal is less and it is very durable. So with these seals, one can get long term benefits of safe environment, less wastage and low pump failure rate.