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Centrifugal Pump Temperature Rise Effect

By Joe Honeywell

 

Introduction

A condition that sometimes occurs in centrifugal pumps at various flow conditions is a temperature increase of the fluid. This condition is difficult to detect at normal operating conditions. However, as the flow rate conditions change the temperature rise can become more pronounced. For example, at pump shutoff conditions where the flow rate is zero, the fluid temperature increase is very noticeable.

Another interesting fact about the temperature rise effect is that it can vary with different fluids. A good example is a comparison of water and propane. Under the same pumping conditions the temperature rise of water is approximately half the rise of propane. Combine the temperature rise effect in the pump with other fluid physical properties such as the vapor pressure or viscosity, and the consequences can be far reaching. It is important to emphasize that under most normal operating conditions the temperature rise effect has minimal influence on the fluid. What is more important is to know at what condition the fluid temperature rise begins to have an influence on the performance of the pump or process system.

The temperature rise effect is an important factor to consider in the design of pumping systems. Under certain operating conditions the fluid temperature will rise very rapidly and cause serious damage to the pump. It can even cause the fluid to boil inside the pump casing. However, the fluid temperature rise can be slow and have minimal effect if the system is designed properly and the operating conditions are properly adjusted. A pumping system can be designed to minimize or eliminate the effect of rising fluid temperature by understanding what parameters cause the fluid temperature to rise.

This article will examine the cause of the temperature rise effect and how it influences the operation of the pump and process system. Possible harmful effects to the pump will be reviewed along with piping design tips for prevention of damage to the pump and process system. Examples are given that show how the temperature effect varies with fluids, operating conditions and pump size.

 

 

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