Apr. 29, 2024
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No matter what new developments occur in the world of diaphragm pumps, there are certain questions that never change. Here, we’ll resolve ten of the most frequently asked questions about air operated diaphragm pumps.
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While this seems like a loaded question, there are only five things you need to know when selecting the right pump for your particular application.
Fluid: The type and composition of the fluid you plan to pump is the most important factor when choosing a pump. In order to avoid wear and tear or corrosion, determine the fluid’s chemical makeup and consistency. Is it a clean fluid or slurry (semiliquid mixture)?
Viscosity: Fluid viscosity is an important factor in to the pump selection process. Robust pumping equipment is needed to move highly viscous fluids. To provide some perspective, at All-Flo, nine out of ten customers are pumping fluid less viscous than motor oil.
Flow rate: In order to select the appropriate pump, it’s important to determine the flow rate, measured in gallons per minute (GPM)—or in simpler terms, the existing pump size (diameter). Usually if you desire a higher flow rate, you’ll need both a larger pump and larger pipe size.
Pressure: Determining the potential pressure conditions on the inlet and outlet of the pump will help establish the right equipment needed.
Temperature: The temperature of the fluid dictates the pump material best suited to a particular application.
Diaphragm pumps will move nearly any kind of fluid. Some common examples of fluids pumped using a diaphragm pump are water, oil and acid.
Diaphragm pumps are capable of pumping high viscosity fluids from adhesives and gear oils to hand lotions, surfactants and resins. The rule of thumb: If it pours, it pumps. Use large suction lines when pumping viscous fluids, in some cases up to three times the size of the pump ports. The pump should also be positioned close to, or even below, the fluid level. Higher viscosity fluids cause the pump to stroke more slowly; adjusting the air control valve on the pump to slow the air flow will keep the pump from stroking too fast.
Plastic diaphragm pumps are best suited for applications involving chemicals like acids, caustics, and bleach. Some chemicals are not suitable for plastic pumps such as styrene and certain resins like isocyanate and polyol.
A common follow up to this question is, “Do plastic pumps always leak?” The answer is no; however, they should be regularly inspected and retightened more frequently than a metal or stainless pump. Frequency of tightening depends on the application; pressure, hours in service and fluid temperature will all affect the flow of plastic. Remember, plastic materials flow when compressed. Tightening the fasteners on your plastic diaphragm pump should be a part of any preventative maintenance program, based on the pump’s service duty.
In order to avoid expensive repairs and delays, and keep your production running smoothly, you should implement a regular pump maintenance schedule. The good news: air operated diaphragm pumps are very easy to clean and maintain, compared to other types of pumps with a lot of electrical components and parts. Even better, in most cases, you’ll only need a wrench and a screwdriver to keep your pump in top working condition.
There are four main tasks to keep in mind when performing regular pump maintenance:
Air quality: Since air operated diaphragm pumps depend on air to operate, air quality and air moisture are critical to maintaining your pump’s health. Regularly check the air filter, which can become dirty and clogged with poor air quality. Moisture in the air should also be monitored to ensure proper pump flow.
Elastic components: Examine the pump’s elastic components every two months to safeguard against uneven wear.
Inlets/Outlets: Consistently inspect your pump’s inlet/outlet, also known as suction side/discharge side. It is common for rocks or other debris material to build up and clog pump flow.
Torque settings: Particularly with plastic diaphragm pumps, you should regularly check the torque of the pump’s bolts. Plastic components can compress over time.
Facilities of all sizes, and in a broad spectrum of industries, use air operated diaphragm pumps. These include petrochemical, metal fabrication, mining, water, construction, cleaning, food and beverage, and printing and ink.
There are three ways to regulate the flow of a diaphragm pump.
There is only one firm warning when regulating flow: Never restrict your pump’s fluid suction lines. Restricting fluid lines causes your diaphragm to fail and begin running in a state of cavitation, causing parts to wear rapidly and creating vacuum-void bubbles in the fluid being pumped.
Sometimes. The key factor when considering a different brand of diaphragm pump is your existing footprint. Several major manufacturers, including All-Flo, produce nearly every diaphragm pump specifically to drop-in ready specifications. This means that most of our pumps can be used in any existing footprint. If you are looking to make a switch, carefully consider your existing set up and ask your distributor to help identify a suitable alternative.
Features like suction lift tend to vary widely from manufacturer to manufacturer, and depend on factors like the size of the pump, fluid viscosity, and whether you’re looking for wet or dry lift. A safe, average range would be between 8 to 15 feet (2.44 to 4.57 meters) depending on the pump’s elastomers.
Yes, a diaphragm pump can be submerged if the fluid is compatible with the pump housing and fasteners, and if the exhaust is piped above the fluid level.
As with all things related to diaphragm pumps, the cost to run it depends on several factors including pump size and hours in service. Another key factor is the brand of pump you choose and that product’s efficiency rating. To give you an idea, 2-inch (51-millimeter) diaphragm pumps range in price from $1400 to $6000 and can cost anywhere from $3000 to $11,000 per year to operate.
The cost to run a diaphragm pump can often significantly surpass the cost of the pump itself. Because of this, a great deal of time and research is spent on maximizing pump efficiency, and significant strides are being made to reduce the cost of operation.
Across a range of industries, pump users demand equipment that works as reliably as it does efficiently. And when your equipment performs with the versatility and durability that your application demands, you can keep things running smoothly. Air operated diaphragm pumps are rugged, lube-free, non-stall/freeze pumps that provide the high quality, trouble-free, continuous output—even under the toughest conditions.
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Steve Weirich is the application engineer at All-Flo Pump Co. A thirty-year veteran of the pump and process equipment industry, Steve regularly runs educational webinars and pump training courses. For more information about All-Flo, visit www.all-flo.com.
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MODERN PUMPING TODAY, June 2013
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When buying an air pump, you want one that is quiet, low in power usage, while continuously delivering enough air to your pond.
To get the reliability, the pump must be able to do the work demanded of it.
When exerting the pump beyond that specified point, it will heat up, shortening its working life from a few years to a few months. It is therefore well worth the effort considering some aspects of using these pumps and air stones for aeration.
Air pumps - What you need to know
To help you choose the right pump for your application, some aspects using the specifications of a Waterfall LP-100 as an example are presented:
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Meaning of “Max Pressure: 0.042 MPa”
Pressure is usually quoted in MPa (note 1)
A pressure of 0.042 MPa equals 0.42 bar or 420 mbar equals 6 psi. It also happens to be equal to 4.2 meters of water pressure (mH2O) at standard conditions i.e. the pressure exerted by a column of water 4.2 meters high or exerted on any bubble from an air stone placed at a depth of 4.2 meters in the pond.
That means, if at a depth of 4.2-meters, ZERO air escapes from the air stone, you will have NO aeration. In that condition the air pump will work hardest yet deliver no air. This will cause the pump to heat up while significantly shortening the life of the rubber diaphragm. Once the diaphragms are torn, the pump becomes ineffective. Mechanical damage can very quickly occur thereafter with unpredictable consequences.
Every pump comes with a work curve specification from which you can deduce the pressure and air output relationship. (See the graph below)
For example: At a depth of 1.5 meters (0.015 MPa) the LP-100 should deliver 120 litres per minute. 7200 litres or 7.2 m3 air per hour.
Rule of thumb is not to operate the pump above 80% of the stated maximum pressure. For continues work operating at a pressure of 20%-60% of maximum pressure is advised. That is theoretically the most economical point of operation. For a more accurate figure you should consult the relationship between work done (air pressure) and electrical power (Watt) used for that specific pump, information normally only available for larger pumps.
Meaning of Max Air Output: 8400L/hr
8400 litre per hour is 140 litre per minute.
This specification is at the other end of the scale. No pressure. No point in running a pump for no reason is there?
You will notice an ‘open’ pump has a different sound. You should not run the pump in this condition for an extended time. It will not last.
Use the curve to determine the flow you will get for your set-up.
How warm is too warm?
The easy answer is when it is too hot to handle. If you cannot pick a pump up with both hands and hold it for 10 seconds, it is too hot.
It is standard for us to employ an adjustable valve to bleed the excess air if the pump is getting hot. It can also be a matter of an under-specified air pump; in which case you must invest in a bigger model.
Since conditions can change, it becomes good practice to also check the temperature of your air pumps whenever you do your weekly or monthly filter maintenance.
Why would conditions change?
Air stones tend to clog up. This is due to environmental dust that passes through the air filter and (blown) into the air stone. Fine pore air stones are more likely to clog, and the low-cost grey or blue mineral sand types are particularly vulnerable. It is recommended that these types of air stones are replaced every 8 to 12 months.
They cannot be cleaned and failing to replace them can lead to damage to air pumps.
Glass bonded air stones are more expensive, have medium sized pores that take longer to clog. The upside is that they can be cleaned and used for many years.
Air stones also clog due to bacterial build-up and must be subjected to the same cleaning treatment from time to time.
For more information on cleaning air stones, please contact us.
Conclusion.
These pumps use efficient electromagnetic linear diaphragm technology. Used widely for aeration of aquaculture and garden ponds, natural swimming pools, bubble baths, wastewater treatment, deep water septic tanks and commercial and industrial water treatment.
Understanding how to get the best pump for your application will be well worth it.
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Servaas de Kock
September 2019
Notes:
MPa, megapascals with a capital while mPa is millipascals which is a unit minute unit 109 times (1 with 9 zero’s) smaller
A work curve of an air pump shows the relationship between the work done (air flow output) for a given load (pressure).
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