I was speaking with a friend that is a project manager, and he was telling me about a new project to install a new air compressor / dryer / receiver system for an existing facility. The new air system would provide air for recently completed and planned organic growth. And I was amazed at the problems he was having – until I thought about it.
He was being asked to install a system that no one takes seriously into a facility, but if his system does not work, the entire facility does not work.
And … for something as basic and well established as compressed air, why are we still finding ways to get it wrong? The most basic issues are frequently re-visited for many new projects, and existing facilities are still creating “lessons learned” stories. Why? Why have we not learned to learn? We have been using compressed air since 1800s when it was used for mine locomotives. Since then it has been used in pneumatic tools and controls in numerous facilities around the world. Why are there still problems?
Let’s look at some of the issues with compressed air that we seem to never learn.
Compressed air is dangerous. A simple search of websites such as youtube will show examples of how an organisation tried to use pneumatic-testing instead of hydro-testing to save a few dollars … and the result was an explosion. A small leak will dissipate a significant amount of stored energy … when the fluid is a liquid. But when the fluid is a vapour, the dissipation is trivial. Tony Sofronas states in an article in Hydrocarbon Processing magazine (September 2006, page 119) that (using an example from the article) a 10 kilogram end cap will drop about 1 metre away from the system when pressurised with water (to the circumstances in the article). In the same circumstances, when pressurised with air, the end cap will travel at about 200 kilometres per hour over a distance of about 20 metres. In addition, I have lost track about how many times I have been in a HAZOP while reviewing a compressed air system and the team tends to “mentally shut down”. After all … it is only air.
Material selection. After over 100 years, we still do not have comprehensive guidelines on what to use for compressed air piping. People are constantly looking for a lower cost material, but our efforts have often been unsuccessful. Reduced CAPEX often creates increased OPEX. Some regions have difficult environments, and material selection is based on external corrosion issues. My project manager friend told me about the corrosion of coastal Southern Peru / Northern Chile. The combination of coastal and desert environments is brutal on metals … with many systems requiring painted stainless steel. Most places do not have this problem, and material selection is usually based on internal corrosion and fluid management. While I have not seen everything, I have learned stainless steel often has only one problem and that is high CAPEX. Other materials (carbon steel, galvanised steel, PVC, polyethylene, etc) all tend to have higher OPEX than stainless steel for a variety of reasons.
Inventory. This is one we seem to get correct most of the time, but occasionally we get it wrong. From my experience, the biggest problem with insufficient inventory is that the response of the compression system is not fast enough to keep pace with variable demand. One of the good things about this problem is that it is relatively easy to rectify … just adding volume (usually in the form of another receiver) is often all we require to fix the problem.
Dryness. Companies in colder climates will almost always use desiccant dryers which dry air to about -40degC – and they tend to have very reliable compressed air systems. Companies in warmer climates often use refrigerated dryers, which dry air to about +4degC, and realise significant CAPEX savings. Anecdotally, the companies with refrigerated dryers tend to have more problems with their air systems. This may be because they have air with higher moisture content, or because they tend to look for ways to reduce CAPEX (which often involves an increase in OPEX).
Air Quality. This issue was potentially a major issue for my friend, because (due to organic growth of the facility) my friend had to deal with vehicle emissions as a potential contaminant in the air inlet. Unburned diesel and compressed air do not sound like a good combination.
Source Compressor and Driver. This is one area where we have made very good cost reduction decisions in the design of air compressors. Compared to 30 years ago when fixed speed motor driven reciprocating compressors were the norm, the progress is very impressive.
We would like to hear about your compressed air systems, or (better yet) your horror stories about compressed air systems. Please contact us to tell us about them