Tips and tricks on keeping AODD pumps in top condition

Insights from the Graco AODD-specialists on how to take care of your equipment.

Air-operated double diaphragm pumps (AODD) are preferred in transfer applications because their simple design makes them easy to operate and cost-effective to repair. To achieve top performance, it is important to install and operate these pumps correctly. Paying attention to a few details will help you spend less time correcting problems and more time pumping. Let’s have a closer look.
 

Apply the correct torque

When receiving a new AODD pump, it needs to be commissioned, which involves applying the correct torque to all the pump’s bolts and screws. This operation is necessary because during the pump’s transportation from manufacturer to distributor to end user, it will probably have experienced a lot of vibrations and shocks.

It’s not necessary to lubricate a Graco Husky AODD pump when putting it into operation for the first time, because the air valves and all the moving parts are already lubricated during assembly. They are not lubricated for life, but the initial lubrication is perfectly adequate until its first service; normally one year later.

For a Graco Husky 1050 AODD, all of the bolts on the fluid covers and manifold need 10.2 N⋅m of torque. If the center section of the pump is made out of plastic, apply 6.2 N⋅m of torque. If it’s metal, apply 9 N⋅m of torque.
 

Locate the exhaust correctly

Take care that the exhaust (muffler) is correctly located. It should be positioned inside or over a bucket or similar container. This is to collect any spillage of fluid from the exhaust in a bucket instead of it spilling onto the floor, in the rare case of a diaphragm leaking and fluid entering the air side of the pump. 

Add a purge valve

Adding a purge valve to the pumping installation is recommended to accelerate maintenance. For example, if you want to clean the pump after pumping paint, you can close the purge valve and put the suction hose into a solvent tank. The solvent will then circulate through the purge valve and back to the solvent tank. In effect you have created a small circulation system to clean the pump. This method maximizes the efficiency of the pump and also minimizes solvent usage at the same time. An inlet check valve can also be useful if you need to supply the fluid at a very high suction height, because closing it will prevent the drain of the suction hose.
 

Set up remote operation

It is a little known fact that a 1-inch air-operated double diaphragm pump can be controlled by a PLC. This is possible by using a kit called the CycleFlo (note: it is currently not yet CE marked). The CycleFlo is a pneumatic pump controller that allows precise control over the amount of product that is delivered by the pump, as well as the pump speed. It achieves this by operating the pump for a preset number of cycles and then halting the pumping cycle. Up to 32 different batch sizes may be programmed into the memory of the CycleFlo for easy delivery of different product volumes. The CycleFlo also features an adjustable pumping rate. This allows the CycleFlo to be used with different pump types and also to tailor the pump cycle to deliver fluids with a variety of flow characteristics. Only a Husky pump with remote air valve can be used with a CycleFlo.
 

Prevent icing from happening

When compressed air expands, it decreases in temperature. When this occurs in high humidity environments, a small build-up of ice can appear on the pump. This may affect the pump’s performance. In the worst case the pump could stop running. 

One way of preventing icing is to slow down the cycle rate of the pump. However this isn’t particularly smart, because it will mean that the pump isn’t doing the job it’s intended to do. 

A better solution is to install a remote exhaust. Normally the exhaust is mounted directly on the pump. But if you add a long exhaust hose of 2-3 meters, this means that the air will be expanding and decreasing in temperature 2-3 meters away from the pump. In other words, ice will build up on the exhaust instead of the pump!

An equally good alternative is to add a pneumatic tool airline antifreeze and lubricant such as Killfrost. This will atomize through the lines and prevent icing.

Consider a fluid pressure relief kit

This kit protects pump components against fluid pressures over 63 bar caused by thermal expansion of fluid in the outlet line, which can cause over-pressurization. Thermal expansion can occur when using long fluid lines exposed to sunlight or ambient heat, or when pumping from a cool to a warm area (for example, from an underground tank). Over-pressurization also can occur if the AODD pump is used to feed fluid to a piston pump, and the intake valve of the piston pump does not close, causing fluid to back up in the outlet line. Installation of a pressure relief valve at the pump outlet prevents over-pressurization and avoids rupturing of the pump or hose. 
 

Choose the optimal cycle rate 

Commercial and technical literature can give a lot of recommendations on cycle rates. This can often lead to confusion, so the best approach is often just to use your logic and common sense:

• If the pump is running continuously and the pump contains very stiff membranes of a material like PTFE (Teflon®), then run the pump at a low cycle rate.
• If the pump is running 24/7, set your pump to a maximum of 20-25 cycles per minute.
• If you need to do intermediate pumping, such as refilling a bucket or evacuating a container, go at full speed but only for short runs. This could be at 90-140 cycles per minute, but only for 2-10 minutes, and then the pump needs to stop.
   

Further information

These tips and tricks will enable you to get the most out of your Husky AODD pump. If you require further support for your AODD pump, or would like to see a demonstration of a Graco Husky AODD pump, then please fill in the contact form below.