Is that hissing noise the sound of money going up in smoke?

One thing that never fails to amaze Greg Gillespie is the amount of times he walks into a manufacturing or processing plant and hears hissing. It immediately tells him that they are running an air compressor or a bank of air compressors. It also tells him that the company is throwing money down the drain. That hissing sound is either one, or a series of leaks, coming from the compressed air system.

Gillespie, who is the national sales manager for air compressor manufacturer ELGi, said that in some cases companies are literally throwing thousands of dollars down the drain every year. Not only that, but when he hears that tell-tale sign of hissing, he knows that doesn’t include the ones he can’t hear.

“I’ve walked into a lot of different places – and to be fair my ear is tuned for it – and I immediately hear all the air leaks,” he said. “And I’ll say to the person on site, ‘you’ve got a few air leaks’. They generally reply, ‘no we don’t’. They don’t hear them because it is background noise to them.”

What he encourages people to do is stay back for five minutes after the work day when everything is quiet. He’s confident that they will then hear the noise.

“And the thing is, if you can hear an air leak, it’s a large one. There will be quite a few air leaks you’ll never hear without ultrasonic equipment, especially if they are inside a piece of equipment,” he said.

Gillespie said the culprits in these leaks are usually the same range of suspects – hose clamp connections, seals failing, and worn fittings. And he’s not saying that maintenance managers have to fix them all at once. He knows that, especially in the some of the bigger food and beverage manufacturing and process plants, it can be a big job. A maintenance plan is needed and such a plan is not something whereby a leak is fixed once and then forgotten about. It will depend on the size of the factory and plant and how many compressors are working. He acknowledges it would be a big task to do it all in one go, so maintenance managers would set about a plan to go and rectify the leaks starting with the biggest one first. Then they would just do a constant, weekly check. But what is the cost?

“If someone has an air audit done then they start to realise that ‘holy heck, we’re leaking thousands of dollar per annum’,” he said. “The more plant and machinery you have in place, the more the leaks are going to cost your bottom line.

“If you have a small place with a 2.2kW compressor, then that cost isn’t going to be that high. But if it is a larger factory with 100kW of installed compressor power, then it will cost a lot.

“I know of a place that has three 55kW machines. One of those 55kW machines pretty much services air leaks. If they fixed their air leaks they can turn one of their compressors off. Do the maths of 55kW of power running all day. They operate 24/7 – not at full capacity – but they are aware of it. I’m sure if you put all the numbers down in front of the people running the place, suddenly it wouldn’t be too hard to fix.”

Education is also a key ingredient. A lot of places he visits think the air is free. Quite often Gillespie will see people “sweeping” the floor with an air gun. It’s convenient, it’s quick, but it does come at a cost.

“Some think it is quicker doing it that way because it reduces the labour cost involved,” he said. “I routinely see people cleaning down their areas using air. It’s not a safe practice to do it.”

But what causes the leaks in the first place? The leak itself is being caused by faulty equipment, but what caused that equipment to become faulty in the first place? Gillespie believes that not only does the factory need the right air compressor for the right job, but it is also the type of air distribution network that is being used that can be a problem. This includes not only the size of the pipe that is distributing the air, but what it is made out of, too.

“I talk to people about becoming efficient, which starts with the right compressor and the right distribution network,” he said. “That is where things like the pipe size, pipe type (poly, aluminium, copper) and how you articulate it comes into play.”

A good distribution system will be one that will be less likely to leak over time – what sort of pipe and the distance over which it is set up are important considerations to limit pressure losses.

“The type of pipe is important because with some piping temperature changes can cause it to expand and contract, and start to bend and twist, so I much prefer people investing in rigid pipe,” said Gillespie. “Depending on the type of rigid pipe system you go for – if you go for something like a braised copper, or stainless steel or even aluminium/copper pipe with fittings – these are going to be less leaks than some other methods.”

If it is the wrong size pipe it will put unnecessary load on the compressor under pressure, which can induce something called artificial demand. This can be magnified if there are multiple compressors in the system, which can be very costly, he said. Gillespie also pointed out that there are also lots of government grants that can help companies become more energy efficient. They change on a regular basis. At the moment there is grant that finished recently that was available for companies that were replacing existing equipment with more efficient equipment with variable speed drives.

“I helped a customer do that and they got nearly 50 per cent of the price of the compressor rebated,” he said. “There is another grant available at the moment which is up to $5,000 rebate for people to put permanent monitoring equipment in to their plant so they can monitor the efficiencies of their compressed air system. Compressed air systems account for about 30 per cent of all industrial power.”

As part of the government’s push to increase energy savings and reduce emissions, they are encouraging industry to work in a more economical way and an area to do that is air compressors, said Gillespie. A lot of people think these things revolve around lighting and solar power. However, quite often there are grants going around to make more efficient compressed air systems.

For the bigger companies that are setting up a new system or refurbishing an older system, Gillespie said putting some budget aside for a monitoring system is also a good idea.
“I have a company I’m dealing with at the moment and they are going to need about 300kW of power. It’s going to be a couple of hundred thousand dollars’ worth of equipment and I’m putting monitoring equipment in my quote – $6,000 worth. To me, it would be absolutely crazy not to do it. The advantages are a no brainer on a system that size.”

Gillespie also cautions against overthinking too much about what to do. An air audit is a simple thing to do and that will give a clearer indication of what a company’s needs are and how they can be remedied.

“I would try not to oversell it because sometimes you can take somebody down that rabbit hole and they can become overwhelmed because they have been inundated with the information and data,” he said.

“You have to find that balance. There are instances where you might spend $10,000 to modify pipework and save yourself $1,000. There’s no payback.”

There are lots of things going on with flow and thermodynamics, you could easily make someone’s head spin.

“At the end of the day, a well-designed and maintained compressed air system is going to be more efficient. And that will save money every day of operation.”