Top 10 Questions About Air Operated Diaphragm Pumps

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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1. HOW DO I KNOW WHAT TYPE OF AIR OPERATED DIAPHRAGM PUMP TO BUY?

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.

2. WHAT KIND OF FLUID DOES A DIAPHRAGM PUMP TRANSFER?

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.

3. ARE THERE SPECIFIC CONSIDERATIONS FOR PLASTIC DIAPHRAGM PUMPS?

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.

4. WHAT ARE THE KEY FACTORS FOR DIAPHRAGM PUMP MAINTENANCE?

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.

5. WHAT KINDS OF FACILITIES USE DIAPHRAGM PUMPS?

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.

6. HOW DO YOU REGULATE THE FLOW OF A DIAPHRAGM PUMP?

There are three ways to regulate the flow of a diaphragm pump.

1. Increase or reduce air pressure, ensuring you are within the pump&#;s operating limits.
2. Increase or decrease the amount of air volume using a valve on the air line.
3. Open or close a valve on the fluid discharge.

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.

7. CAN I REPLACE ONE BRAND OF DIAPHRAGM PUMP WITH ANOTHER?

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.

8. WHAT SUCTION LIFT CAN I EXPECT FROM A DIAPHRAGM PUMP?

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.

9. CAN A DIAPHRAGM PUMP BE SUBMERGED?

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.

10. HOW MUCH DOES IT COST TO RUN A DIAPHRAGM PUMP?

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 $ to $ and can cost anywhere from $ 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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ABOUT THE AUTHOR

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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Goto Huakai Anti-Corrosion Equipment to know more.

MODERN PUMPING TODAY, June
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To ensure safe operation and the life of your pump and to form part of a planned preventative maintenance schedule, routine and complete inspection of the pump is recommended. Routine Inspection can be done by frequent observation of the pump operation is required to detect problems.

There can be many first signs of diaphragm pump troubleshooting such as If the sound of your pump operating changes, this could indicate worn parts, leakages or a change in performance. The intervals for a complete inspection depend upon the operating conditions of the pump. The characteristics of the liquid, temperature, materials used in the pump and running time decide how often a complete inspection is necessary.

Nevertheless, Tapflo recommends that customers should inspect their pump at least once a year.

As part of this inspection, Air and Liquid Kits should be changed and Valve Kits should be changed once every 2 years. Tapflo recommends stocking at least a Liquid Air Kit to ensure that expensive downtime is avoided.

Diaphragm pump troubleshooting : Common problems

Your pump won&#;t run

Air pressure too low: The air supply pressure needs to be higher than 1.2 bar and greater than the system pressure that the pump is working against. Adjust the air supply pressure with the Air Filter Regulator. Ensure that the mains air supply pressure is adequate for your requirements.

Blocked air connection or contaminated air valve: Check your air supply, is it clean, free of any obstructions or kinks? Additionally, check your air valve hasn&#;t been contaminated inside the pump.

Blocked muffler or exhaust: This means the pump cannot expel air efficiently which has a direct effect on a Diaphragm Pumps ability to operate. Check whether there are any obstructions at the pump&#;s exhaust and check that the pump&#;s muffler is in good condition.

Solids in the pump chamber: Solids that have settled in the pump chamber or body can block the diaphragms from moving, preventing your pump from operating. Solid particulates can also settle around the ball valve seats which can prevent the ball valves from re-seating properly which can lead to poor performance or even prevent your pump from working. Clean your pump and install a suitably sized filter on the suction of your pump to prevent the pump from becoming blocked inside.

Damage diaphragms or ball valves: Damaged, broken or misshapen diaphragms and ball valves will reduce the efficiency of your Diaphragm Pump. This can be solved with regular checks to the condition of your diaphragms and ball valves, it&#;s important to carry out these checks regularly to increase your pump&#;s operating life.

Blocked suction or discharge pipework: This will prevent your pump from functioning properly and could cause it to stall. Check the position of manual valves on the suction and discharge of the pump regularly, do this before turning the pump on to ensure that it isn&#;t put under stress. Cleaning of pipework if operating on particularly stick or solids laden fluids is also recommended as these types of process media can quickly reduce the internal bore of your pipework and change the system pressure requirements to the detriment of the pump performance.

Further Diaphragm Pump Troubleshooting Causes

The liquid is leaking from your pump

This certainly isn&#;t right, here are a few things that could be causing this and ways to check and rectify it:

Loose side housings: The pump is sandwiched between approximately 6 tie rods, if these aren&#;t tightened to the recommended torque setting, liquid could leak from the side housing.

Damaged O-Rings: If the O-Rings on your pump&#;s inlet or outlet manifolds have perished or are damaged, this could suggest that the mounting hasn&#;t been reassembled correctly after maintenance, it could also be caused by forcing the manifold positioning without loosening the side housings first which can deform the O-Rings.

Diaphragm rupture: Causes of a failed or ruptured diaphragm include overuse, abrasion, chemical attack or overpressure to name a few. A rupture means fluid will leak into the air valve and leak through the pump&#;s muffler. Diaphragms will need to be replaced and should be checked regularly for wear during maintenance checks to prevent this from happening.

Pipework problems: If your pump has not been matched for rigid pipework, for example, inadequate pulsation dampener or over the permitted loads for manifolds, pumps can become loose and cause leaks. Ensure the pump has been matched to your installation and adjust accordingly to eliminate stresses to pipework and the pump. This can be achieved by flexible expansion bellows a hose on the suction and discharge of the pump and/or installing a Pulsation Dampener.

Worn or blocked valve balls/seats: This will lead to fluid circulating inside of the pump and syphoning back through it causing a drop in both flow and pressure.

Damaged diaphragms: Damaged or bent diaphragms can have a direct impact on the flow and pressure generated by the pump.

Air leak or changes to the supply: As compressed air is the driving force of the AODD, any changes in the quality, flow & pressure of the air supply can have a direct impact on the performance of the pump. Therefore, routine checks are required to ensure that there are no air leaks, changes in pressure or flow to ensure good operating performance & reliability. It is also recommended to check the status of the air filter and moisture separators on the air supply line to ensure the air quality to the pump is adequate.

Suction or discharge pressure changes: If the pipework becomes encrusted or has a leak it will impact the performance of your Diaphragm Pump. Routine checks on the integrity of connections for possible leaks or air ingress & cleanliness/condition of the lines are recommended, as well as valve positioning and suction & discharge pressure gauges to ensure that the system pressure remains within the working parameters of the pump.

Blocked or worn air valve or muffler: Damage, corrosion or dirt on the air valve will affect the function of your Diaphragm Pump. Additionally, if the muffler is blocked, the pump cannot expel air effectively meaning the pump won&#;t operate efficiently. Monitor the performance of your pump, apply preventative maintenance measures and monitor the condition of the pump&#;s muffler to ensure the pump is performing reliably.

Diaphragm pump troubleshooting & Solutions finder

Problem Possible Fault Possible Solution The pump does not run The air pressure is to low Increase air pressure via a filter-regulator The air connection is blocked Check/clean air supply connection Muffler is blocked Check/clean/replace the muffler The air valve is defective Clean/replace complete air valve Dirt in the pump chamber Remove debris from the chambers Diaphragm breakdown Replace diaphragm The suction is bad The suction connection is not tight Tighten the suction line The suction connection is blocked Clean suction line Muffler is blocked Check/clean/replace the muffler Valve balls are blocked or damaged Check the dimensions and shape of valve balls Valve seats are worn. The pump starts with high-pressure air in suction/discharge line dry suction against a discharge pressure Check the dimensions and shape of valve seats. Start the pump slowly (see chapter 2.2 of manual) Vent suction/discharge line, wet the pump/start without discharge pressure The Pump runs irregularly Valve balls are blocked Check the dimensions and shape of valve balls Sealing in centre block, air valve is defective Replace sealing. Clean/repair air valve Diaphragm breakdown valve seats are worn icing on the muffler Replace diaphragm. Check dimensions and shape of valve seats. Improve air quality (see chapters 1.7.1 and 2.2.2 of manual) Bad flow/pressure





Pressure fall in air supply. Pressure losses on suction side air supply/air valve leaking Increase air pressure via a filter-regulator. Check/change installation on suction side. Check/repair/replace air supply/air valve. Suction or air connection blocked Check/clean air supply/suction connection Muffler is blocked Check/clean/replace muffler Valve ball worn or broken. Valve seats are worn Check dimensions and shape of valve balls. Check dimensions and shape of valve seats. Air in liquid Seal suction line; check/refill container Diaphragm Breakdown. Icing on the muffler Check/replace diaphragms. Improve air quality (see chapters 1.7.1 and 2.2.2 of manual) Liquid leaks from the pump Screws on the housing not properly tightened O-ring on manifolds damaged. Damaged diaphragm tension/stress form the installation Check tightening torques of the screws. Replace O-rings. Check/replace diaphragms. Adjust installation, eliminate stress, when using a dampener provide separate support for it (see dampener IOM manual) Liquid comes out of the muffler Diaphragm breakdown Replace diaphragm Diaphragm breakdown Wrong selection of material. Too high pressure in the installation. Long periods of dry running. Too high pressure on suction side. Contact us for information on material selection. Use air treatment system for protection. When dry, run pump slowly (see chapter 2.2 of manual). Make sure there is pressure balance between the air and liquid side of the diaphragm.

 

For more information about diaphragm pump troubleshooting, refer to our manuals or contact the team to arrange a site visit.