Portable Pump Primer
When it comes to portable pumps, there’s no such thing as a dumb question. Recently, I received a list of questions about portable pumps that are typical of the kind of information end-users are looking for when buying or renting a pump. Take a look at the questions below and see if you’ve asked the same ones yourself at one time or another. I bet you have.
1. What are the most common types and sizes of pumps?
Before discussing pump sizes and types, defining the applications involved in portable pumping is critical. For contractors, applications pretty much fall into two categories: 1) light-duty, short-term pumping and 2) heavy-duty, higher-volume and potentially continuous pumping. The pump sizes and categories vary based on which application category you address. Let’s look at each one briefly.
Light-duty portable pumping is usually defined as short-term (several hours or less) and lower volumes (up to 200 gal per minute). The pumps typically have 2- or 3-in. suction and discharge hoses and are powered by a gasoline engine. The vast majority of these pumps are wet self-priming pumps, meaning that water must be poured into the body of the pump to get it to prime.
Common applications include landscaping, jobsite dewatering and utility junction box dewatering. Godwin Wet-Prime pumps are an example of this type of gasoline engine-powered, light-duty pump.
Heavy-duty portable pumping is defined as larger volume and potentially continuous pumping that requires either a diesel engine or an electric motor as a drive unit. The most popular sizes in the heavy-duty pumping range are 4- and 6-in. solids handling, or trash, pumps that can produce flows in excess of 1,500 gallons per minute (gpm). The priming system on these pumps differs by manufacturer. Applications include stream diversions, larger jobsite dewatering projects and sewer bypasses, just to name a few.
In both light-duty and heavy-duty pumping, the pumps described are designed primarily for horizontal pumping or transfer of product. Pumping vertically against gravity resistance or into a pipeline under pressure requires a much stronger and more expensive type of pump.
2. How much do pumps typically cost to buy? How about rental? Is it by day, week or month?
When buying or renting a pump, size matters. Light-duty, gasoline-powered pumps can be purchased for around $1,500 for a 3-in. trash pump. Meanwhile, a 6-in., diesel-powered, trailer-mounted pump may list for close to $30,000, which is why rental is an attractive option for heavy-duty pumping applications.
Another thing to remember when talking about pump rentals or sales is that the end-user is not acquiring just a pump. He or she is acquiring a pumping system, complete with accessories such as suction hoses and screens, and discharge hose, pipe and fittings. The amount of accessories on an application will determine the final pricing. The pump rental or purchase is only a portion of the total cost. As for rental costs, pump rentals follow the same pricing structure that general rental equipment uses for daily, weekly and monthly rentals.
3. Should I buy or rent a pump?
Referring back to the difference between light-duty and heavy-duty portable pumping, the industry standard is that, for the most part, light-duty pumps are purchased and heavy-duty portable pumps are rented, but that is not always the case. End-users may find continuous applications for the basic 6-in. trash pump and will, therefore, find it economically feasible to purchase rather than rent.
The big fallacy is that once a customer has rented a heavy-duty, diesel-powered portable pump for several months, he or she has practically paid for it. This is not the case at all. The capital costs of purchasing and then maintaining a pump have to be weighed carefully against the potential rental costs in any situation.
4. Do pumps come standard or are there options? Are the pumps pretty basic machines or can I spec them out to my exact application?
Light-duty, gasoline-powered pumps have virtually no options. With diesel-powered, heavy-duty pumps, many options are available, based on the type of application. Two of the most common accessories are 1) sound attenuation and 2) automatic float controls.
The Godwin Critically Silenced Dri-Prime pump encloses the entire pump and diesel engine to reduce noise levels to 69 decibels at 30 ft. When pumping in a residential area, this is a very popular option. Automatic float controls allow the pumps to be started and stopped based on the level of product in the sump. In sewer bypass applications, where flows vary based on the time of day, this is a very useful and economic option. The float control system is also used on a back-up pump in a sewer bypass application to provide mechanical redundancy in the event of the failure of the primary portable pump.
When specing out a pump, the most important information is to clearly define the required flow and head for the applications in which the pump will be used. This ensures that the pump will operate successfully and reliably in the application.
5. How do I know if I’m operating the pump efficiently?
The biggest mistake when using a portable pump is incorrect operating speed. More speed from the engine does not always translate into more flow from the pump. When you want to go faster in a car, you step on the gas. Portable pumps don’t work the same way. A portable pump application with a throttle control on the diesel engine will only produce a certain amount of flow based on the physical conditions of the application.
Example: Consider a small stream diversion application drawing water from a 4-ft deep sump with a horizontal discharge 250-ft downstream. A 6-in. pump with 6-in. hoses attached on suction and discharge will deliver a maximum of 1,000 to 1,100 gpm (approximately), which translates to a velocity in the hose and pipe of about 12 ft per second. In the stream diversion just mentioned, running the diesel engine at approximately 1,400 rpm will achieve that flow rate. However, most end-users will crank it up and run the pump as fast as it will go, thinking that they will get more flow. It doesn’t work that way. Once a velocity of 12 ft per second is achieved, that’s all you’re going to get. Running the pump faster will not produce more flow. Instead, it achieves the undesired goal of wasting fuel by running at a higher rpm and risking internal damage to the pump.
The best advice is to have a professional pump sales engineer come and look at the application. These pump engineers design a system and recommended an operating speed that is specific for the particular application.
6. How do I know I’m buying or renting a quality piece of pump equipment?
I would suggest two things to help in this regard.
The first is to do a little research on the Internet about the brand name of the pump. Look at the applications the pump is used in. Learn how it achieves prime creates a vacuum to lift product into the pump body. Find out where you can get parts and service. The second is to check out how knowledgeable your local rental house is on portable pumps. If they have little or no knowledge of pump operation or service, you may want to continue looking or better yet, enlist the aid of a professional pump specialist.
7. What else do I need to know?
Pumps are unique. They are not like any other piece of contractor equipment. This is because the physical conditions of the application will dictate a pump’s performance, not the other way around.
End-users think that the 6-in. pump they used the last time will work fine in the next application. Often, that’s not the case. If the physical conditions of the jobsite are different, the pump will perform differently and may even fail. The leading cause of pump failure is misapplication. Remember, one pump size does not fit all.
Getting advice on a portable pump system design from a qualified pump specialist is the best avenue for an end-user who admittedly doesn’t know a lot about pumps. Good advice can save a costly repair bill and ensure reliable running during the application.
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