There are many different cooling unit solutions in the marketplace: units with one pump and units with two pumps. There are also specific classes for pump units: single and redundant, for example.

So, what is the reasoning for this and when should these different variants be used?

One pump cooling unit

In a one pump cooling unit there is only one pump, and this pump circulates the cooling liquid in the system.

In a two-pump cooling unit there are two pumps. One of the pumps circulates the cooling liquid in the system, the other one is in stand-by mode and not running. The role of the pumps is changed after a while so that both pumps will accumulate about the same number of operating hours.

In certain, quite seldom cases, both pumps in a two-pump cooling unit are used simultaneously. In these cases, the purpose is to increase the system flow and pressure higher than would be possible using one pump only. Thus, these units are in practice like one pump versions.

One pump cooling unit is “single”, or “non-redundant” unit and it is used in generic non-critical applications. In these applications the cooling unit failure to operate is not mission critical for the industrial process or marine use, for example.


Two pump cooling unit

Two pump cooling units are “redundant”, and they are used in mission critical applications. In these applications a failure of a system component shall not stop the application. Thus, if one pump fails, there is another pump that will take over the operation. A ships electrical propulsion system is a good example of this.
A two-pump cooling unit isn’t 100% redundant but very close to this. A cooling unit consists of hundreds of components. Some of these components may experience a failure during the operation. However, the only potential risk component is the pump with moving parts, seals, and bearings. Therefore, two pumps are used to ensure the cooling availability. Other components will not fail or when failing will not impact the cooling in the same magnitude.

Some customers require the highest reliability and take into consideration even the most impossible risks in their designs. For them the “redundant” cooling solution is made with two one-pump cooling units or even with two two-pump cooling units.

Selecting the right cooling unit configuration is based on the cooling application. In the end the choice is based on a balance between reliability, risk, and value.


WORDS: Heikki Mustonen, Managing Director, Adwatec Oy
+358 50 477 8685