How To Remove Condensation From A Pneumatic System

Pneumatic systems function by taking in ambient air and compressing it at a high pressure in a storage tank. As pressure increases in the tank, so does the temperature, which makes the air carry more moisture. 

When the pressurised air fills the container’s space and begins to cool, the air’s temperature drops, often below the pressure dew point. Lower temperatures mean the air cannot contain water vapour any longer, so the moisture is released as condensation. Moisture collects at the bottom of the tank and if it’s not removed, it can damage pneumatic systems.

Compressed air in pneumatic systems will always generate moisture, but other factors can influence the level of moisture in the system. For instance, the volume of compressed air and humidity levels are direct influences on the amount of moisture that’s produced. Other factors include component failure, moisture in the environment and whether the unit is undersized. 

Removing moisture from pneumatic systems is necessary because it can cause corrosion and damage components. It also causes mould and bacteria to build, bringing contaminates into production. This is hazardous for food production and other sensitive processes. Excessive moisture that leaks out around the system is a health and safety concern, as well as a potential source of contamination.

How To Remove Condensation From Pneumatic Systems

Drain Valves

Installing a drain valve is a common way to release water from the system. Drain valves are usually installed where moisture pools from the air receiver tank, air dryer, or around certain points in the piping system. Different types of drain valves are available: manual drain valves, timer-based drain valves, and zero-loss drain valves. 

Manual drain valves require periodic checking to release excess moisture. It’s recommended to check them daily. Timer-based valves automatically open according to their programming to release fluid, so manual checking isn’t necessary – allowing technicians to focus on other maintenance tasks.

Zero-loss valves are also automatic, but they operate with an automatic release that functions with just enough time to drain water. This is intended to limit the loss of air.

Water Separators 

Mechanical water separators operate by using centrifugal force, or the coalescence concept whereby droplets fuse to form larger drops, which are then filtered out. Centrifugal force is generated through a rotary motion that pushes fluid, oil and air outwards to a drain through a filter. A typical filter is made from polyethylene, with granule-like particles that are housed in the filter to absorb moisture. 

Air Dryers

There are various air drying methods to remove moisture from the system or combine it with another moisture removal method. Refrigerated air dryers cool the air in the system until it condenses, then the water vapour is collected in a water trap and drained. Refrigerated air dryers leave dry air in the system at a dew point around 33F to 40F – suitable for most compressed air requirements.

In some situations, desiccant air dryers are more effective because they produce very dry air and subfreezing temperatures. Desiccant air dryers get their name from the molecular sieve desiccants used to treat the air to remove moisture chemically. Water vapour binds to the chemical compounds in the air dryer. Through the process of treating the air with chemical compounds and compressing air to -40F, down to -100F, desiccant air dryers produce arid air.

Absorption Drying

This method involves using chemicals that bind water vapour to absorption material – either solid or liquid. Chemicals such as sodium chloride and sulphuric acid are often used for this process, although they risk corroding pipes and fittings. Considering the corrosion risk, manufacturers should assess this carefully before using this method. Despite absorption drying being less common, it’s more cost-efficient. 

Piping System Air Drying 

Other options include piping system air drying where drip legs are used to collect and drain water as it condenses. This method relies on drip points installed along the piping. As gravity brings the water down, it is released from the drop points. 

Aftercoolers

An aftercooler is a heat exchanger that cools the air leaving the compressor to prepare it for an air dryer or to be used with air-operated machinery. Aftercoolers add an extra layer of drying to the process to ensure all moisture is removed – a critical factor for certain products. Aftercoolers also minimise the load on equipment downstream, so a smaller dryer unit can be used. This saves space and reduces overheads. Coolers also reduce the risk of fire in the pipes and hoses processing hot compressed air because air is cooled directly after leaving the system.

Air Receiver Tank

Air receiver tanks act as a secondary heat exchanger to support the main one. Compressed air generates more heat and an air receiver tank is designed to reduce temperatures before compressed air moves downstream. When air flows through the air receiver tank, it reduces the temperature of hot compressed air by around 5F to 10F before it reaches other cooling mechanisms. This also reduces moisture and strain on aftercooling systems.

Why Removing Moisture Is Important 

Condensation in pneumatic systems causes rust in the system’s piping and intricate mechanisms. Excess moisture and oil can also contaminate produce and block air lines. All these effects damage pneumatic systems, shorten their lifespan and increase maintenance costs. 

Solutions to remove moisture from the system include manual and automatic drain valves, air separators, air dryers, or a combination of these methods. Efficient moisture removal produces clean, dry air to power pneumatic tools. More significantly, dry, contaminant-free air is needed for quality production. Removing moisture early on also protects equipment downstream by reducing the strain on dryers and other equipment.