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    Pipework energy savings – it’s more than just fixing leaks

    You can hear an air leak. You know some of your valuable compressed air is being wasted. But it’s one leak – no big deal.

    Although, it is a big deal as more than likely it is not your only leak, and air leaks may not be the only thing wasting energy on your compressed air pipework system.

    In this article we look at:

    • Finding and fixing pipework leaks
    • Zoning pipework
    • What size pipework is best?
    • Designing your compressed air pipework system
    • What is the best type of pipework for factory use?

     

    Finding and fixing pipework leaks

    Air leaks can have various causes, from corrosion holes to damaged seals and poor pipe connections. Whatever the source, they will be costing you money.

    The most common method of finding air leaks in a factory is to employ a hand-held ultrasonic acoustic detector. Easy to operate and highly effective at locating air leaks, this will pinpoint the location of each leak and measure the air loss in litres per minute.

    As well as reaching hard-to-access pipework, a leak detector also has the benefit that it can be used without disrupting production.

    Leaks can then be tagged and logged by your compressed air engineer, in preparation for replacing pipework and seals as necessary.

    PPS customer example

    A plastic recycling firm spent £809.35 to detect and repair 16 air leaks, in order to save £15,356.97 per year on their compressed air energy bill (based on a price of £0.12/kWh). Their application uses a lot of electricity to melt plastic and compressed air is critical to the manufacturing process.

    This site had an estimated leakage rate of 74CFM, the compressor they were running was capable of 150CFM – by fixing the leaks they saved money, reduced their carbon footprint and increased capacity.

     

    Zoning pipework

    A compressed air system comprises a number of different elements, not all of which operate at the same time or to the same pressure. One way to save energy, therefore, is to zone your system.

    This is carried out by analysing when and how each element is used and splitting the system into zones. These can then be pressurised as required, rather than pressurising the whole system at the same time and in the same way.

    Any redundant pipework can be removed or isolated. As there will always be some air leaks that go undetected, this will reduce the cost of air loss from pipework that isn’t being used.

    Isolation valves are also useful when it comes to maintenance, as you can shut off selected sections without affecting the rest of the system.

    Things to think about

    What if you needed a hire machine adding to your system to temporarily increase production? What if you needed to replace a dryer? Can you zone off sections without stopping production?

    PPS Customer Example

    A kitchen manufacturing customer’s full production ran on an Atlas Copco GA90 FF and two Atlas Copco GA55+ FF air compressors. While production was 7 days a week, only one process ran at the weekend. The installation of remotely controlled zoning valves meant they could run their weekend work on just one Atlas Copco GA55+ FF. This made the system much more efficient – they are only producing the compressed air they need.

    Zoning valves are easy to install, especially on smooth bore aluminium pipework, and can drastically improve compressed air efficiency. On the control side you do have options – they can connect to a BMS system, be done through a manual switch or can be operated by a key switch. In the example above they choose to control it via a key switch to help to protect their system.

     

    What size pipework is best?

    When it comes to pipework, one size does not fit all. You may save on the initial outlay by installing smaller pipework, but this is often a false economy as it will cause a greater drop in pressure across your compressed air system.

    The result will be increased energy use and higher energy bills, outweighing the cost savings of the purchase price of the pipework.

    A good rule of thumb is to calculate the diameter of pipe required in the main supply line based on a maximum air velocity of 6m/s. If you have branch lines shorter than 15m, then velocities up to 15m/s can be used.

    PPS Customer Example

    A site team were struggling to get the 6bar pressure they needed to run one of their processes. To achieve the downstream pressure of 6bar, their compressor setpoint was up at 13bar. A visit from a PPS Engineer identified that the issue was caused by mismatched pipe size on their system. The pipe they were using was too small. As pressure and flow are inversely related, they had too much flow trying to go through a small pipe. They increased the diameter on the pipework to that line and were able to turn their compressor set point down – keeping their system working effectively and efficiently.

     

    Designing your compressed air pipework system

    There are several considerations to take into account when designing pipework for a compressed air system.

    These include:

    • Creating a system that minimises pressure drop
    • Using large radius bends rather than elbows
    • Fixing pipework firmly in place to reduce movement and sagging; this minimises leakage and fluid build-up
    • Future proofing the system by designing it to accommodate potential expansion

    Single main and ring main are the most common ways of distribution in a compressed air system. Ring main systems are the best option when designing a large system with several take-off points.

    PPS Customer Example

    No one likes a dead leg. A customer was experiencing pressure drop that would disrupt production in one area when another department were using large amounts of air. Introducing link lines to create ring mains throughout the system combatted this effectively making their system much more efficient.

     

    What is the best type of pipework for factory use?

    From an energy saving perspective it has to be smooth bore aluminium pipe. Why?

    1. Leakage free install – so a full flow of air and the lowest pressure drop from generation to point of use.
    2. No corrosion – it doesn’t corrode overtime like galvanised pipe, so no inner rough surfaces and a flow rate maintained over the life of the system.
    3. Low friction coefficient – the smooth bore and low surface roughness of an aluminium pipe system increases the flow rate, meaning a lower diameter of pipe can be used in comparison to a galvanised system.

    If you’re upgrading or expanding your factory, a qualified compressed air engineer will be able to give you expert advice on the best kind of pipework to use, as each has different properties and suitability, depending on environment and use.

    PPS Customer Example

    For some customers smooth bore aluminium pipe doesn’t work for their specific application. A food and beverage customer were having compressed air issues in an area where heavy clean down was in operation. On investigation we found that the low-level galvanised steel pipework was in contact with this process, this had led to high levels of corrosion on this area of pipework. Our solution swapped the galvanised steel for stainless steel pipework. This has a much higher resistance to corrosion and will make that area more efficient for the customer.