Refurbishing new rolling stock is an important job – managed in a tough environment where engineers constantly handle potentially dangerous tools in noisy surroundings.
As maintenance sheds age, many rail operators face a real problem with compressed air contamination. Compressed air provides power to some of the most- used applications that keep rolling stock operational, but it is generally contaminated with some of the most natural contaminants known – dirt, water and oil. Further contamination in the form of compressor oil and wear particles then mix with the atmospheric dirt and water to produce an abrasive paste, which has no lubricating properties at all.
Unless this contamination is removed from the compressed air system, operators face reduced efficiency, costly repairs and potential system breakdowns. But by being alert to specific technical triggers, maintenance and procurement teams can identify and resolve problems.
Diagnosis one: tool performance
Engineers working on rolling stock refurbishment projects tend to use a lot of compressed air in their tools.
Electricity is required to manufacture compressed air. The more air required in a facility, the more it costs to make. To keep running costs down, it’s critical to keep internal pipework clean and of a consistent diameter; this maintains optimal airflow and means the compressor doesn’t have to work so hard.
For example, The Carbon Trust’s GPG385 states that “for typical industrial systems, compressed air accounts for 10% of the electricity bill”’ and the British Compressed Air Society estimates that reducing pressure at the compressor by 1 bar is equivalent to using seven per cent less energy.
If the air pressure drop in a shed is too high, this usually means that tools are not running efficiently. It’s difficult for site staff to diagnose a problem against the background noise of a busy shed environment, so a typical response might be to turn the pressure up, or add another compressor. However, neither of these options is likely to offer any benefit. Increasing pressure means that it costs more to make the air, whilst adding a compressor generates extra electricity costs without making any difference, as the pipe can’t physically flow any more air.
Diagnosis two: older steel pipework
Older compressed air systems are typically constructed of galvanized steel pipework, as this material has historically been regarded as the most robust option.
But when steel pipework ages it becomes increasingly prone to rust; and rust inside an older steel pipe leads to the internal diameter decreasing. This leads to a reduction in air flowing through the pipe, and subsequently site engineers may find their tools no longer work as effectively.
Another common problem with badly run systems is the presence of water and condensate in the pipework. Where this happens, droplets come down to the tools and will destroy the tools in a much shorter timeframe. That means higher maintenance costs, and potentially unnecessary spend. So whilst technical teams may see tool repair as an inevitable problem, that’s not always the case; and operators may find that checking tool repair spend patterns over time offers clear insights that something is awry.
Permissible contamination
ISO 8573 is the group of international standards relating to the quality of compressed air, and ISO 8573-1 provides guidance on the permissible amount of contamination (oil, dirt and moisture) in an air system.
Once a rail operator has determined the correct air quality for its environment, it usually works in partnership with an original equipment manufacturer (OEM) to agree measurement capabilities of the equipment and the test levels to be provided.
The approach OEMs take to this task varies. Parker’s Transair system was the first high-strength, aluminium compressed air system launched to market. Successfully tested to the highest expectation of ISO 8573 for air quality, the product is totally modular, leak-free and third-party certified.
Past perceptions around the perceived strength of aluminium compared to steel are now changing. Transair’s consistency of airflow, high burst pressures (ensuring reliability and safety) and ease of replacement is key to this shifting landscape. For example, a Transair drop can be installed within minutes, whereas replacing steel pipework is an extremely time-consuming job (and more likely to disrupt busy schedules), so it’s an economical and reliable alternative to traditional steel networks. What’s more, technicians used to steel claw-type fittings will find it easy to use the valve and male thread combination used with this system.
Parker also has a flow calculator which checks existing pipework efficiency. In the event of any problems, the company can advise on options for pipework replacement, ensuring the correct size of pipe is specified and fitted. An energy calculator supplements this advice by working out an estimated payback of changing the system.
