Submersible Pumps vs Surface Mounted Self-Priming Pumps

Posted by  Andy Cruse 13-May-2015 08:30:00

andy-cruse
Andy Cruse is ERIKS' Business Development Director for Pumps.

ERIKS and Hydromarque  have recently worked in collaboration on a pump project at a leading snack food  manufacturer’s site in Teeside. The customer originally used five submersible pumps installed during the 1980’s, which were subsequently replaced by three slightly larger pumps sometime in the 1990’s.

On the basis of this project and best practice tips from ERIKS and Hydromarque pump experts, we have drawn a comparison between submersible and self-priming pumps.

 

hydromarque before submersible pump hydromarque after self priming pump
Before - Submersible Pump After -  Self-Priming Pump

 

Submersible Pumps

Submersible pumps tend to be a “fit and forget” as they are underground in a sump and out of sight. In other words the only time you know there is s problem is when the pump actually stops pumping. 

Submersible pumps are also very difficult to remove once installed. In the particular case, the snack food manufacturer had to install a large lifting gantry above all 5 pumps, which constantly needed testing and calibrating.

Due to the nature of submersible pumps, the main driver, i.e. the electric motor is actually submerged in the liquid being pumped, which is sometimes very nasty effluent waste. Also, the sump becomes prohibitive as it is classed as a confined space and needs specialist training and equipment to enter.

Submersible pumps are a lower capital cost but generally require an overhaul or possibly a major rewind approximately every 5 years.

The customer’s case was worse than this, with the pumps being removed annually due to failures. Repair costs were in the region of £5,000 - £6,000  per pump and had to be sent away for refurbishment. While the pumps were away for refurbishment, the client had to hire in diesel driven pumps to cope with the demand, as you can see from the “before” photo. 

Surface Mounted Self-Priming Pumps

On the other hand, surface mounted, self-priming pumps have the capability to eliminate all these issues.

Once installed the pump and pipework do not need to be removed as any maintenance can be carried out either locally to the pump or in a workshop. The internal workings of the pump can easily be removed without disturbing the motor or any pipework.

These pumps have built-in maintenance features that allow operatives to visually check the condition of the pump whilst still in operation thus preventing any major failures. Self-priming suction lift pumps are mounted “high and dry” above the liquid with only the suction pipe entering the sump. This immediately eliminates the need for sump entry and the requirement of confined space training and escape equipment. This also means that the main drive, an electric motor is nowhere near the media being pumped.

The life expectancy of a self-priming pump with regular maintenance would be in excess of 20 years compared to approximately 5 years on a submersible pump. This greatly reduces the carbon effect as you only buy 1 self-primer to possibly 4 submersible pumps during its life. 

Outcome

After thorough discussions with the customer, a new self-priming pump has been permanently installed as seen in the “after” photo. Early indications show that there may only be the need to run two pumps now to keep up with demand, with the new pump being the main duty pump and an existing submersible as back up until an additional surface mounted pump is installed.

This will greatly reduce the energy and running costs of the plant, ensuring more efficient operation.

To find out more about the Gorman-Rupp Super T Series Self-Priming Pump used in this project, click the image below to download a copy of the brochure.

Gorman-Rupp Super T Series Brochure

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Topics: Best Practice, pumps, Food Industry

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