21 May 2021
Whatever the project, it always goes faster and easier with the right tools. And that adage applies to any project, no matter how simple or complex. And, while something as simple as repairing a leaky faucet may not take a whole lot of technical knowledge or highly specialized equipment, a project as complex as dewatering a construction site certainly does.
You start by asking yourself some questions. First and foremost, what am I hoping to accomplish? This is always a good place to start. In the case of a dewatering application, it will help you understand where to begin in terms of equipment.
Typical applications include: ground water removal, excavation dewatering, open pit dewatering, stream diversion, face and stage dewatering, open pit dewatering, storm water and flood control.
There are a variety of pumps out there, some designed for a very specific use and others are designed to tackle a variety of applications. No matter which route you decide to take, the most important thing is to have a very good idea on what your specific application requires.
You need to know the weight of the fluid to ensure the pump has enough power to draw the liquid through. In many cases, we find different fluid types at the very same construction site. Sludge, construction materials and other insoluble materials, often ranging in size from particulates to solids of up to 4”, must be pumped along with the fluid.
The pH level is also essential to understand the fluid. It measures how acidic/basic the water is. The range goes from 0 to 14, with 7 being neutral. pH level’s of less than 7 indicate acidity, whereas a pH greater than 7 indicates a base. The further you deviate from the neutral 7, the more chemical impact the fluid will have on the pump internal components. The correct material selection of the pump internals is the key to combat this challenge and keep the pump away from any malfunction.
In short, make sure that the pump you choose is designed to move the type of fluid you are facing. For instance, using a centrifugal trash pump to dewater heavy slurry will end in a damaged pump.
Most pumps are trailer-mounted or skid-mounted. A trailer-mounted pump system is easy to transport but may take up additional space on the jobsite. Also, if there is not a power source nearby, an electric pump will not suit your needs.
If you are pumping up-hill, static discharge head becomes a critical factor, being the height of the source of the fluid you are pumping to the height of its destination. There are formulas that you can use to determine what pump you need based on the elevation, the lift needed, and the distance the fluid must travel.
For every ten feet you pump uphill, you lose 4 PSI (Pounds per Sqaure Inch), which means you must give more consideration to the pump pressure capability when selecting your pump. This is where the pump’s performance curve comes in handy.
Every pump comes with its own performance curve chart, which tells you how much volume over time a pump moves under a given pressure rating. The volume over time is measured in l/s or m3/h or GPMs (gallons per minute) and the chart will tell you what the pump’s flow rate is as a certain pump outlet pressure. This is what we call the pump duty point or operating pump point.
Based on application criteria such as distance of fluid travelling, elevation to overcome and desired flow rate, the pump duty point is going to vary. Why is all this important? Chances are your application is time contingent, meaning you have a certain amount of time to get the fluid from Point A to Point B. If your pump doesn’t supply you with the flow rate needed to move the fluid when and where it needs to in the time you have, then your job doesn’t get done the way it should. Not good.
What’s the best advice we can give, all of the above considered? Seek professional help when choosing a dewatering pump. The professionals at Atlas Copco are experts in dewatering pumps and the myriad number of applications to which they can be assigned. Hopefully, you now have a better idea of what questions to ask yourself. You can get the answers you need from an Atlas Copco pump equipment expert.
About Hunter P
Hunter has been a pump specialist with the three biggest pump brands in the US for over 15 years and is now leading the Pump Application Engineering Team for Atlas Copco.