Think about how many of your tools and applications are pneumatically powered, from air wrenches and hoists to blowoffs and cooling. But do you know how much it costs to power this equipment?
“It can be very efficient, but when you compress air, it can be fairly expensive,” says Rick Hand, Product Sales Manager for Parker Hannifin’s Pneumatic Division North America.
Parker Hannifin calculates the cost to produce 1 HP of pneumatic is six times greater than electricity.
“We figure that on a national average it costs, depending upon where you’re at, about 30 cents a thousand cubic feet to generate it,” Hand says. “That number varies between 15 cents and probably 50 cents depending upon where you live and what your electricity costs you. If you’re close to a hydroelectric plant it’s probably pretty economical, if you’re on the east coast it’s a little more money.”
Wherever your plant is, you certainly don’t want to waste money. But it’s likely that you are when it comes to compressed air. It could be slipping away in nearly every pneumatic application you have.
We want this new year to be one where you cut waste and maximize profits, so here are five simple ways to improve your air flow:
1. Change Dirty Elements
You can lose 5 to 10 psi from a dirty filter element. Think about how much harder it is to walk up the stairs after two weeks of eating nothing but Christmas cookies and comfort food. Your legs have to work that much harder. It’s the same with a compressor, which has to create more pressure to move air past dirt filter. And that energy adds up.
Assuming that 9¢/KW HR = .03¢/ft3 @ 100 PSIG, a 5 psi increase would cost you more than $9 a shift, or almost $29 a day. So if your plant runs five days a week, you would lose $7,569/yr.
What we are not advising you to do is grab that element and run it under the faucet.
“The solution is just to clean the elements out of there and replace them with new ones,” says Hand, who adds the average element filters is about $10 to $15. “I have a lot of customers who try to take the element out and wash it, clean it, to put it back into service, and that’s not a good idea either because with the depth element a lot of the contaminants are on the inside, you just can’t get to it.”
For coalescing filters, a pressure differential indicator, which pops up with a red marker similar to a meat thermometer’s, is an available add–on to tell you the filter is done.
Image: Parker Hannifin
2. Size components correctly and avoid pressure drops
If you size an application for 90 psi, but the compressor is 400 ft away and it travels through a turn or coupling that causes a pressure drop, you won’t have the right amount in the end. Hand says oftentimes plants he’s worked with may set the level to a higher level and just reduce the pressure at a regulator.3. Use Quick Disconnects Only When Necessary:
If you’re mechanic and changing out tools, a quick disconnect coupling makes sense, but are all the quick disconnects in your pneumatic system necessary?
“They’re great if you are coupling and uncoupling devices a lot” Hand says, “but they really have a pretty high pressure loss as far as moving a lot of air.”
He says these are not widely used, but has seen some plants use a big coupler on a new line going to a machine, which can have adverse effects on your air flow.
“That can add to starving for air if everything is working at its maximums,” Hand says. “Quick-disconnects are widely used, they are great devices, but they’re not for every application.”
4. Use a Dryer
The air your compressor takes to feed your pneumatic application is the same air you breathe, the same air that has dust and moisture in it.
“So if you were going to compress air at 100 PSI, you would be bringing in 7.8 cubic feet of free air and jamming it down into that little box,” Hand points out. “You also bring in 7.8 times the water and the dirt and everything that’s in the environment around you.”
If you’re in wetter region, such as Seattle, this is more of a problem than in Phoenix, which has less humidity.
Taking this moist air, which is of course a gas, and compressing it causes it to heat, and when it expands downstream in the system, it cools.
“As the air cools off, it’ll rain,” Hand explains. “And it rains in your pipes and that’s where the water comes from. So there are a lot of different mechanisms to reduce the water that goes downstream, but typically what we would start off with would be a dryer.”
This excess moisture can lead to corrosion in the distribution system, as well as damage to production machinery and an application's end products, Hand says. Other negative effects include washing wash away of cylinder and valve pre-lubricants, decreasing their operational life, as well as reducing production efficiency and increasing maintenance costs.
Filters can remove secondary particulates, but should never be their primary source of removing moisture, Hand says.
“People will try to apply filters also to kind of Band-Aid it because it’s a much cheaper approach,” Hand says. “A lot of plants do a very poor job of taking the water out. It’s just a fact of life to them. They have a lot of trouble with it.”
5. Find and Minimize Leaks
“Leaks are insidious,” Hand says. “They are all over a plant, and they’re difficult to find, and because when the plant is in operation, you just typically will not hear them.”
They can be anywhere, from a fitting to a seal.
And how much can they cost you?
The answer, my friend, is not blowing in the wind, because most leaks are nearly undetectable. But you can go to Parker’s very handy leak calculator -- which allows you to plug in values for leak size, electricity price, and operating pressure -- find out. One example is a 1/32 in leak in an 80 psi system. That will cost $200 over a year.
“There are plants that are literally wasting hundreds and hundreds of dollars a day just because they haven’t done an efficient job of fixing the leaks,” Hand says.
Parker says that 25% of compressor air costs are due to leaks, with a 3/8 in. leak costing nearly $30,000/yr in certain situations.
The solution, he says, is just diligently looking for leaks anyway possible. When the plant is quiet during a down period, you can walk the pipes and listen. There’s also Snoop, from Swagelok, a liquid leak detector, which you can spray on a pipe, and if there’s a leak, it will bubble.