Knowing more about the discharge head variations

A water pump has so many things that assure its efficient functioning. Besides other things, let us discuss about the head of the pump. A head is actually a measurement of the water pressure that is expressed in head/feet. Before we go any further, it is imperative that we have holistic knowledge about the discharge head due to the following reasons –

• In order to get assured that the pump has right capacity.
• In order to make a smart choice for the right sized pump for a fresh application.
• So that you have the right knowledge about the issues related to cavitation, if the head is on the lower side.
• To find out whether the pump is functioning at its BEP (best efficiency point).

Are you wondering how you are going to measure the head? Following are the two methods with which you can learn about the head –

• You can analyze both the suction and discharge heads from losses occurred in the piping and other related hardware in the lines.
• The chart recorder (installed on the pump's discharge side) or the discharge pressure gauge should be evaluated (which is installed in the system). The current reading should be subtracted from the reading which is achieved from a gage that is installed on the pump's suction side.   

You can still come across various issues while you determine precise head information with the changes in the discharge system. Let us discuss as how the design, maintenance actions and operation really influence the discharge head –

Functional Issues –

• The system has an all new product.
• A dilatant (its viscosity tends to rise with agitation) is actually being pumped.
• The discharge valve has been shut in order to save amperage. This is a general practice that has been put into use for starting centrifugal pumps having low ‘specific speed' impellers.
• The viscosity of the product has undergone a change.
• The product's temperature has undergone a considerable change.

Maintenance Issues –

• Trimming of the impeller has been done.
• There has been some kind of restriction in the pump's discharge.
• The pipe must have collapsed which is, most of the times, not noticeable.
• A liner must have become loose, which is restricting the passage.
• There must be an installation of a reducer.
• A gasket is sticking out in the piping.

Designing Issues –

• There is a parallel functioning of two or more pumps.
• A smaller sized pump's discharge check valve is closing by a bigger pump.
• A storage tank has been filled from the base and when the tank fills up, there is a variation in the discharge head.
• With the installation of a mechanical seal, the speed of the motor has raised considerably, eventually making changes in the BEP (best efficiency point).  

The above discussion will surely make your aware of the changes, that take place, in the discharge head