Application Tips: Pumps

Chances are, you aren’t a pump expert. And when you run into water at a jobsite, most of the time you aren’t expecting it. The good news is you don’t need to become a pump specialist when this happens. Many pump suppliers offer services that can include everything from installing the pump system to sticking around to monitor it.

This allows you to remain focused on the job you need to get done while the pump supplier takes care of its forte, says Marie Holmdal, marketing director for Godwin Pumps.

But be aware that not all companies that sell pumps can offer this kind of expertise, warns Majid Tavakoli, vice president of applied products, Thompson Pump. Do your homework and pick a manufacturer or supplier with professional, knowledgeable employees. “Our life is pumps,” Tavakoli says. “When we get up in the morning we are thinking about pumps. When we go on vacation with our families, we go see pump jobs. Don’t deal with a suitcase salesman.”

Details matter
Neglecting to fully discuss application details with your pump supplier could cause you to purchase an incorrectly sized pump, which can lead to problems such as poor hose life or the pump running hot, says Olivia Kardos, product manager, Watson-Marlowe Pumps.

For a checklist of topics to discuss with your pump supplier to help ensure the pump you purchase is suited to your applications, see the box on page 88.

A classic mistake is buying the cheapest pump available as part of a knee-jerk reaction, says Jim Widwick, manager of construction equipment sales, Gorman-Rupp. The purchasing process should entail looking for the overall best value, he says. You might need special features such as stainless steel components if you’re pumping salt water or a unit made of abrasion-resistant material if you’re pumping sand and gravel. These features may cost more initially, but will save you money and grief in the long run, Widwick says.

Radu Murgescu, construction and mining market manager, ITT Flygt, cautions against using the solids handling spec, which can give you a good idea of engine-driven pump performance, to evaluate an electric submersible pump. The impeller design of electric submersibles creates either high head with low volume or vice versa. Choosing a pump based only on the pump discharge size can result in the pump being too small or too big for the application.

Murgescu says it’s better to look at the pump performance curve, which can be found in most manufacturers’ brochures and tells you the elevating capabilities at different volumes.

At the jobsite
The following are some common errors contractors or their employees make when operating pumps and ways you can avoid them.

  • Running the pump at the highest speed setting unnecessarily – Contractors commonly run diesel-driven pumps in the full-speed throttle position, sometimes using twice as much fuel as they would if the pump ran at the minimum speed required to do the job. But running the pump beyond half throttle doesn’t always significantly increase flow rate when pumping through a low-pressure system, says Ron Askin, Western regional manager, Godwin Pumps. To solve this problem, don’t run the pump faster than the minimum speed required to get the appropriate flow.
  • Constricting discharge lines – This can happen when a vehicle runs over a line or when rocks or other materials fall over the discharge pipe. It will cause the pump to overheat.
  • Not placing the pump as close as possible to the fluid you are pumping
  • Operating the pump without the suction hose strainer
  • Letting the suction strainer get caked with mud, grass or debris – This starves the pump of water and causes it to overheat. To keep it from happening, clean the suction strainer every day. If you are having a difficult time priming the pump, you should also check the suction hose and suction hose connections, says Steven Spence, pump product manager for Multiquip.
  • Forgetting to drain the pump of water at the end of the day or when the job is finished – If the water freezes, it could crack the pump housing.
  • Not flushing the pump with clear water after it’s been used to move salt water – Running clear water through the pump will improve its performance the next time it’s used, Spence says.

Safety Tips
Most safety transgressions involving pumps happen when people accidentally do things they know they aren’t supposed to do. “Many times people rush to finish a job and make stupid mistakes,” says Radu Murgescu of ITT Flygt. Here are some things to keep in mind when using electric submersible pumps:

  • Don’t touch exposed wires. At a construction site, everything is temporary; pumps have to be moved and wires may come loose.
  • Keep the control box door closed.
  • Be sure the ground wire has a solid connection.
  • Don’t pull a pump by its cable. This happens often, especially with small pumps. You could pull the cable out of the housing, causing water to leak into the pump and creating the potential for electrocution.
  • Don’t grab the pump in the water or submerse it with the power on.

Advice for wellpointing and moving standing water
The most common mistake contractors make when wellpointing is not doing a proper soil investigation beforehand, says Majid Tavakoli with Thompson Pump.

Among other things, soil boring will give you water calculations and the approximate time it will take to draw the water table down. You have to have this information today because municipalities want to know how much water you’re going to pump into their systems and often limit the amount of water you can discharge.

Tavakoli advises hiring a good geotechnical company to do soil boring at your jobsite. You’ll get a report on the soil’s gradation, how much of the soil is silt or limestone, whether granite is present, etc.

Your pump supplier will most likely set up the wellpointing system and adjust it during the first 24 hours. After the pump starts pulling water out of the ground, it begins taking in air. In order to get the proper vacuum, you have to tune the system daily after the first 24 hours to make sure no air is leaking.

To size the pump or pumps for standing water dewatering, you need to know how large the body of water is, average rainfall amounts at the site and the amount of ground water infiltration.

The key to this kind of dewatering is suction lift, Tavakoli says. Surface-mounted pumps will only lift water vertically 25 to 28 feet. If you need to lift the water higher, you’ll have to use a submersible pump.

You also need to use the right size piping so you don’t burn too much fuel. The larger the piping, the less friction loss you will have. If you want to pump more than 5,000 gallons per minute, you should use a pipe 12 inches in diameter or larger, Tavakoli says.

Using a pump that will automatically shut down when it’s not pumping water and automatically start up when water gets to it again can help you conserve fuel and reduce wear on the machine. While electric units have had this capability for a long time, some diesel pumps now have it as well.

Before-you-buy checklist
Discuss these points with your pump supplier:

  1. Your application – what you need to do with the pump
  2. What liquid you will be pumping (If it’s water, describe the condition of the water and if it’s something other than water, be specific about the liquid and its properties.)
  3. The type of solids (if any) that will be in the water you’re pumping
  4. The distance you’ll be pumping the fluid
  5. The jobsite environment (Will there be any vertical rise in the discharge hose? If so, what is the vertical distance from the pump to where the water is discharging or the highest point along the discharge hose?)
  6. How quickly you need to move the material you’re pumping
  7. Whether sound is an issue at your jobsites
  8. The type of discharge hose/pipe you will be using (Include details such as length, fittings, diameter and connections.)