There Must Be A Better Way To Save…

 

I’m writing this blog at almost the top-dead-center midpoint of Spring Break week. My teenage sons have been “enjoying” their time off thus far with the housekeeping duties their mother has been assigning them, and the labor they’ve been providing their uncle, as he installs a new garage door for us…the one my mother-in-law paid for. I definitely married out of my league.

The last half of Spring Break, though, we’re taking a little vacation. We looked at the activities and attractions at our destination, came up with a plan on what to do and when (including an analysis of the 10 day weather forecast…which prompted me to find our rain ponchos) and have even purchased some tickets in advance, because advertising “5% SAVINGS!” on stuff really works on me, even when it’s on a $20 ticket. Before you grab your calculator, yeah…that’s a dollar. But since there are four of us, I’ve multiplied our savings by 400%! Yes; I know…four bucks.  Still, I’ll take it.

We talk to folks almost every day who want, like I do, to save money on goods and services they’re going to purchase anyway. Some have performed comprehensive energy audits, and identified opportunities to lower their compressed air generation and/or consumption rates. Others have just been looking at the bent copper tubes that are blowing off their parts and thinking there has to be a better way.

(Full disclosure: I’ve had these two exact conversations so far this week.)

Today, I want to tell you about the latter: It’s an aluminum casting plant with about a dozen lines where a robot grabs a fresh casting from the machine, dips it in a quench tank, and holds it in front of an array of copper tube blow offs for a few seconds before placing it in a bin, bound for the machine shop. Not only were they blowing at it from both sides with the copper tubes, but they were also blowing continuously…including the majority of the cycle time that did NOT include holding the part in the air flow.  Dear reader, if you’re familiar AT ALL with the EXAIR blog, you’ll know that we simply cannot abide that. Continuous flow when flow is only needed a fraction of the time is wasteful and expensive. Not to mention blowing air out of open tubes is dangerous, loud and requires and unneccessary volume of compressed air.

It's like they WANT to upset us.  What's up with that?
It’s like they WANT to upset us. What’s up with that?

They installed (2) Model 110018 18” Aluminum Super Air Knives, in place of the copper tubing, which cut down on their air consumption…and noise levels…considerably. I gave them some further recommendations on reprogramming the robot to turn the part in front of one Air Knife, and using an EFC Electronic Flow Control to turn the air off when a part was not present.

EXAIR's EFC automatically turns the air off when a part is not present.
EXAIR’s EFC automatically turns the air off when a part is not present.

Is there a better way to use the compressed air in your facility? Whether you’ve got comprehensive data from a detailed audit, or if that open pipe is just too darn loud, all the time – give me a call…we’ll find out.

Russ Bowman
Application Engineer
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What Size Pipe Should I Use?

Yesterday, I had a customer with a tough application for a Standard Air Knife. The customer was quenching individual 11″ x 11″ steel plates in oil after they had been heated to over 1,200° Celsius. Following quenching, the plate is pulled out of the oil with a fair amount of excess oil still attached. This excess oil is relatively hot and could be dangerous, if it drips from the plates as they are conveyed to the next process. The oil removed from the tank is also lost, so the tank needed to be refilled regularly. This oil added up to quite a large expense every year for this company. The customer installed (2) 12″ Standard Air Knives above the oil quenching tank to blow the oil off of the plate back into the oil quenching tank as the plate is raised out of the tank and in between the two air knives.

How the Standard Air Knife Works
How the Standard Air Knife Works

The customer called to express some disappointment about the air knife performance, I asked him a few questions about his application.

Q:What pressure is supplied to the air knife?
A: 100 PSI
Q: Where are you measuring this pressure?
A: That is our shop pressure and the pressure I’m measuring at the regulator.
Q: How are you connecting the regulator to the air knife?
A: We are using 10 feet of 3/8″ ID tubing.

At this point I suspected that the problem was in the compressed air supply line. To confirm this, I asked the customer to install a pressure gauge in the unused air inlet of the air knife. This pressure gauge read only 52 PSIG. The customer had a pressure drop of 48 PSI through the 10 foot of 3/8″ tubing, fittings, and valves that connected the regulator to the air knife.  The 12 inch Standard Air Knife utilizes 41 SCFM of compressed air when fed with 80 PSIG. In order to determine what to expect for a reasonable pressure drop, you could use EXAIR’s Air Data charts. According to EXAIR’s air data chart, for 1/8″ schedule 40 iron pipe, which has around 1/4″ ID (Which is very similar to the Inside Diameter of the 3/8″ tube) at 8 SCFM of flow the line will create a 18.6 PSIG pressure drop. When you try and shove more than 8 SCFM through the 3/8″ OD (1/4″ ID) tubing, you create a higher pressure drop. In this customer’s case it created a 48 PSI drop across the air line. This 48 PSI pressure drop was caused by the supply line as well as the fittings or valves used to connect valve to the regulator. This pressure drop limited the air knife to only 52% of its performance. In an application with a viscous fluid like oil , this drop in pressure led to lower force upon the steel plate and disappointing performance.

After getting the proper plumbing in place, the pressure drop was eliminated and the the Air Knives were operating at peak performance to remove the oil from the plates.

During the course of our troubleshooting, the customer also discovered Russ Bowman’s excellent video Proper Supply Plumbing for Compressed Air Products. In the video, our customer discovered the impact both the cross sectional area and overall length of compressed air piping can have on the performance of an air operated device.

The customer wanted to use a 12″ Air Knife to blow off the oil from the plates, which is a great application for the air knife. By properly plumbing the supply of an Air Knife, the customer contained hot oil, reclaimed quenching oil for future use, and maintained a clean shop floor. This installation was well worth the time and effort of installing the air knife properly. If the customer would like, we also have a Super Air Knife which will only use 35 SCFM and could help to save more compressed air. This savings of 7 SCFM may not seem like much, but it will have a significant impact on the energy cost of running his air compressor.

Dave Woerner
Application Engineer
@EXAIR_DW
DaveWoerner@EXAIR.com