While drilling, it is common to encounter natural gas, which can present serious health, environmental and safety hazards if it escapes freely. Oil rigs use drilling mud to weigh down the gas and prevent it from escaping during the drilling process. All-Flo’s array of heavy-duty air-operated double diaphragm pumps are tailored specifically for the oil and gas marketplace, designed to handle the constant rigors of processing highly viscous drilling mud.

Look for more information about this story in an upcoming issue of World Pumps Magazine!

Jump over to our website to learn more all about the All-PũR line!

How Freezing Occurs

Compressed air expands as it runs through the AOD pump and becomes very cold very quickly, sometimes dropping down to -10°F. These low temperatures typically are a result of using the pump at high-discharge pressures. Cold air can’t hold as much water vapor as warm air, so this creates a condition known as “super-saturated air,” when the air contains more moisture than it can hold in a stable condition.

Ice forms when that super-saturated air impacts a cold surface, such as a bend in an exhaust pipe or some place that acts as a seed surface for vapor to condense on. Points of impact build up ice for two reasons:

1. They provide a place for tiny ice particles in the air to stick. Any points of impact—anything that sticks out into the air flow—becomes a place where ice build-up can occur.
2. The surfaces are colder, so they accumulate ice through deposition faster. Deposition is where vapor in the air turns directly into solid ice on a surface. Ice buildup is highly dependent on the surface temperature. In the same way that wind-chill is the worst when you are facing directly into the wind, surfaces that are impacted by cold air will be colder.

One step you can take to reduce the freezing problem is to install a dryer on your compressor and only run clean, dry air through your pumps. Removing the muffler—including the muffler plate and rubber seal—is one solution that usually eliminates icing completely, as ice typically only forms on those components. However, the increased exhaust noise usually makes this option impractical for most users. Adding a dryer should be the first step to minimizing the freezing issue.

Fluids Being Pumped Can Contribute to Freezing
Fluids with a higher viscosity will cause the pump to work harder and could contribute to more ice build-up.

For example, consider a 2” All-Flo pump running at 60 psi inlet air pressure. If this pump is running at 10psi discharge pressure, the temperature at the exhaust will be around 42°F. However, if this same pump is running at 55 psi discharge pressure (closer to its maximum capacity) the temperature at the exhaust will be about 2°F.

As the pump approaches its maximum capacity, the temperature at the exhaust significantly decreases, which can result in freezing.

Normal Single Muffler

Preventing the Problem Through Research

We are constantly examining and testing our pump designs to minimize the risk of freezing. So, even if you don’t have a dryer installed on your air compressor, All-Flo pumps have built-in mechanisms to keep the risk of ice build-up at bay. Some of these design features include:

Muffler Plate with Heat Sink. All-Flo research showed that ice buildup could be dramatically reduced by adding a large heat sink to the muffler plate

• Straight exhaust path. The fewer turns the air has to take, the feweropportunities there are for ice to form and accumulate. But when surfacesobstruct or redirect air flow, ice can form (see Figure 1).
• Single exhaust. At All-Flo, we have engineered all our pumps to have a common, single exit port for the main exhaust, allowing cold air to exit directly into the muffler with minimal contact with impinging surfaces.
• Thermally engineered muffler plate

In an effort to continue offering the finest engineered diaphragm pumps available, we are continually researching and testing new pump designs and configurations using real-world tests along with the latest mechanical and thermal Finite Element Analysis software. One of the newest pump designs All-Flo will soon release features an exhaust system designed to function as a heat-sink, drawing heat to the inside surfaces from the surrounding environment and the rest of the pump, effectively preventing those surfaces from becoming cold enough for excessive ice buildup.

Have more questions about causes of freezing in diaphragm pumps and ways to avoid it?

Leave a comment on this post or contact All-Flo.

• AOD pumps are air operated and don’t run the risk of spark and explosion like electric pumps do.
• AOD pumps can run dry without damage. (The pumps can run constantly even if all the water has been pump from the flooded area)
• AOD pumps are lightweight and portable, which makes transporting the pump deep into the mine easier.
• AOD pumps can handle solids. (All-Flo’s 2″ pump can handle up to ¼ ” solids.)
• Many AOD pumps are self priming and non-stall

Many mine companies have recently adopted a trend toward air-operated diaphragm pumps as a better, safer mine dewatering alternative. When Independence Coal Revolution Mine, a customer of Logan Corp., discovered quickly growing water pools in one of its locations, the company became concerned when its existing pump systems could not keep up with the increasing water depths. The West-Virginia-based longwall coal mining company asked a pump distributor for a solution, and its personnel responded immediately by providing All-Flo pumps to solve the problem. Read the whole story>>

Why is this significant?

The All-Flo Max-Pass System is unique because of its ability to handle solids better. Often, when pumping fluids, stray larger solids can block the pump flow. In the above example of the 2” diaphragm ball pump, if a rock or other solid larger than .5” gets sucked up into the pump, it will get stuck and clog the pump, causing the operator to cease pumping and waste valuable time cleaning out the pump. However, with the Max-Pass system, even when using a 1” diaphragm pump, a ¾” solid chunk can still pass safely through the pump without clogging the pump. And a little extra room can make all the difference!

At All-Flo, we really only offer thermoplastic manufactured elastomers.  This process allows you to hold very tight tolerances, minimizes any voids, and it allows you to keep a better diaphragm profile.  In addition, our Santoprene and Geolast elastomers each have a high shore hardness.  Those diaphragms are stiff, which helps them maintain their design profile and gives them a longer cycle life.  Geolast and Santoprene also do very well on abrasive services.

A PTFE diaphragm is excellent because it is inert to almost every liquid, but it has several disadvantages:  it’s more expensive, has cold temperature limitations (good to only 40 degrees), and only does “fair” on abrasive services.

When deciding on a diaphragm, it makes a difference how much PSI you are pumping:  your cycle life at 20PSI will be very different than your cycle life at 120PSI.

Other factors that affect your diaphragm cycle life are:  Liquid media used, Liquid discharge pressure, and Suction conditions.

For more information, check out our Technical Resources page (http://all-flo.com/technical-resources.html) to learn more about diaphragm options and materials used and to view performance curves.

Some of the most common high-viscosity pump applications include those involving gear oils, polymers in wastewater treatments plants, glues, and slurries (such as mud or sand and water mixtures).

All pumps in the industry are rated for water, so it’s important to know the viscosity of your pump in order to determine the optimal flow rate. For example, a 225GPM pump may only be capable of pumping a high viscosity fluid at 30 GPM.

One of the most common problems customers encounter when pumping these high viscosity fluids is causing damage to a pump by keeping the flow rate too high. Listen to your pump as it runs. If it sounds like rocks or marbles are rolling around inside of the pump, this is a good indication that the flow rate is too high.  When we advise our customers and help them through the pump purchase process, we help them de-rate a pump for high viscosity fluids in order to determine the best and most efficient flow rate

Check out our helpful viscosity curve chart to learn more about pumping high viscosity fluids.

Preventative Measures When Handling Hazardous Materials

Taking preventative measures is the best way to avoid a bad situation when pumping hazardous materials. Schedule regular maintenance on your pump and periodically tighten the torque on the outer fasteners. (Since the plastic on non-metallic pumps will move away from the fastener over time, you’ll need to re-torque the fastener from time-to-time.) If you’re pumping a flammable fluid, make sure the pump is groundable and that you’re using a groundable hose to guard against static electricity. You should also house your pump away from direct sunlight, which can cause the pump to crack over time. And watch your pumped fluid temperature. It’s important to make sure that your fluid is not exceeding the material temperature limits of your pump. Our technical resources on the All-Flo website include more info on safely maintaining your pump.

What to do When a Rupture Occurs

If a diaphragm rupture does occur and the fluid starts to leak, turn the air supply off to the pump immediately. Slowly let the fluid leak out into a secondary containment area. Make sure you wear protective clothing and safety goggles when doing this, slowly opening the pump and loosening the fastener. Isolate the pump, closing the suction and liquid discharge valves.

Sometimes a diaphragm rupture can spray hazardous material in the air, so a precautionary exhaust system for your pump should always be available. If it’s a flooded suction condition – meaning that the liquid level is above the pump – install a hose at higher elevation than the liquid level in the suction tank so that you can pipe the exhaust to a safe area.

Air quality – Since AOD (air operated diaphragm) pumps depend on air to operate, air quality is vital to your pump’s health. Check the needle valve regularly. It can become clogged and dirty if the air quality isn’t good. You should also check the air moisture regularly. Lots of moisture in the air can cause problems with pump flow.

Torque settings – Check the torque on the bolts of your pump. Over time, the plastic components can shift and expand. You should re-torque as often as necessary.

Inlets/Outlets – Routinely examine the inlet/outlet (suction side/discharge side) of your pump. Sometimes rocks or other material can build up and clog pump flow.

Elastic components – We recommend that you check the elastic components of your pump every two months to ensure that these parts are wearing properly.

The most important thing to remember is that you don’t have to be a specialist to maintain your AOD pump – you just need to be consistent. Even better news: often all the equipment you’ll need to keep your pump in top shape is a wrench or a screwdriver. For more pump maintenance information and answers to your pump questions, visit our FAQ page on the All-Flo website. We can help you keep your pump running 35 million cycles and beyond!