September 28, 2024

Project and Pump Size: Picking the Right Generator for Your Submersible Pump

Project and Pump Size: Picking the Right Generator for Your Submersible Pump

You’ve got a job, and it’s a big one. There are currently more than 10,200 bridges being built, repaired or modernized according to the U.S. Department of Transportation and with many of those projects comes cofferdam construction. Maybe your crew is putting in a temporary sewer bypass or doing a culvert replacement – another growing need in today’s world.

In each of these jobs the task is to de-water, build, and then restore the flow of water.

That means you’ll be using at least one submersible pump and that pump is going to need the right amount of power to get up and running and keep going. As you know, there’s one basic piece of equipment that generates power on a site, and that’s a generator.

But which generator?

The basic answer is a mobile diesel generator. The detailed answer is the right sized generator (size=the amount of power rated in kVa) for your submersible pump and the type of job.

Two Key Factors that Determine Which Generator is Right for Your Submersible Pump

With thousands of mobile diesel generators to choose from (the global market for these machines was valued at 12.4 billion dollars in 2023 and is projected to reach 24.7 billion by 2030) it’s important to focus on two key factors:

• The size of the project, because you need to size the generator and pump to meet the flow requirements
• The full load amps and the voltage of your pump

Let’s tackle the second point. Electric pumps – all pumps – operate at a specific voltage and have power requirements defined as full load amps. That is, how much power it takes to run at maximum performance.  Pumps and motors, including submersible pumps, also need to account for starting amps which are a higher flow of current to start the motor. Once it’s spinning it takes less power, but you’ve got to get it going in the first place.

In not-layman’s terms, the generator you choose needs the load acceptance capabilities (power output capabilities) to start the motor to meet the running demands of the submersible pumps used in the application. To do that you need to know the horsepower and voltage of the pumps that are going to be run.

Which brings us to the first point – the flow needs of the project. Submersible pump and generator sizing are important to the success of the project because without the correct equipment your water flow is either going to flow too little, too much, or take down your system entirely. This will cost you time and money.

For instance, take a basic cofferdam. Interlocking sheets are driven into soil to create a cell then it’s your job to dewater the area so the team can get down to the rock and install a pier. It’s the total size of this project and volume of water that determine which submersible pump and generator you need to use in this application. A 10×10 foot and a 20×20 foot area with the same water depth on the outside need different size pumps and generators. It’s volume and flow rate, the total amount of water you need to move, and how quickly you’re moving it, are the deciding factors in equipment selection.

What, exactly, happens if you get it wrong? Besides the time-and-money cost?

Wet Stacking and Other Problems with Diesel Generator and Submersible Pump Combinations

Wet stacking – the problem of unburned fuel, carbon particles and moisture building up in the exhaust system – can seriously damage the engine in your diesel generator. Light load operation or long period of no-load operation can lead to wet stacking. Both of these operation issues can happen if your generator is too large.

In the reverse situation, where the generator is too small to start the pump, there’s potential damage to the pump.

For pump applications with highly variable loads, wet stacking prevention might be recommended to prevent potential engine damage to the generator. So, first, make sure you have the correct sized generator and then make sure it’s operating consistently, and with the correct load.

Generators that perform with submersible pumps – for rent or purchase in the Mid-Atlantic
FieldForce rents and sells ten models of diesel generators ranging from the Atlas Copco QAS 25 ID T4F, with 20 kW/25kVa rated prime power, to the QAS 700 JD T4F with 560 kW/700 kVa rated prime power. All are multi-voltage, sound attenuated and mobile generators, and pair with our complete line of submersible pumps.

In addition, FieldForce provides equipment and services for the municipal, construction, manufacturing, and industrial sectors, including temporary pipelines and sewer bypass. Our inventory includes Atlas Copco pumps, compressors, and generators for rent or purchase, and temporary piping and light plants available to rent. We maintain our fleet at yards in the Greater Pittsburgh area and in Central Pennsylvania for convenient availability.

Call us today to learn more. 717-508-0550 or 724-591-8655