Month: May 2015

Pneumatic Capacitance

Published on by Lee EvansLeave a comment

Brian Farno and I attended a compressed air training seminar years ago that highlighted best practices, pitfalls, calculations, efficiency, and a variety of other things facing the compressed air industry.  At the same seminar we also discussed pneumatic capacitance.

As it was laid out, pneumatic capacitance is the stored air within a compressed air system – OK, simple enough.  And, in order for there to be any stored energy, there has to be a pressure differential across the storage device – THIS was an AHA moment for me.

I guess I had never really thought about the need for a pressure differential across the storage device in order for there to really be any air stored.  I’m sure if you go back through the tests and exams I took in college there’s some question about it, and I may have known it somewhere in my studies – but the concept really clicked for me in that seminar and at that moment.

I thought about this when visiting a customer’s facility and hearing them complain of dropping line pressure during compressed air operations.  We went to their compressor room and I saw the compressors and tanks in the photos below.

IMG_1439
(3) 75HP Atlas Copco compressors putting out 300 SCFM each. Two of these provide air to the storage tanks below. The third is for operations unrelated to this blog.
IMG_1440
(3) 2200 gallon receiver tanks

Wow!  All this horsepower and air storage and the line pressure is still dropping?  That seems odd.

So, we checked the input and output pressure of the tanks – less than 2 PSI ΔP, effectively limiting the real ability of the tanks.  At this ΔP the tanks were little more than just an addition to the compressed air plumbing of the facility.

We checked output from the compressor and found they had been deliberately decreased to between 80 and 85 PSI.  So, I recommended to leave the output pressure of the compressors (which feed into the tanks) up to 120 PSIG, and to leave the output pressure of the tanks untouched at 80 PSIG.

This change would allow 3 minutes of steady line pressure for the existing compressed air demand (with compressors still loaded) – per tank!  (Calculations at the bottom of this blog.)

This change, while significant, was only part of the solution for this end user.  The bulk of their solution was the installation of EXAIR Super Air Knives at the point of use, which reduce cooling time, improve throughput, and lower compressed air use.

If you think your application may benefit from an EXAIR solution, contact an EXAIR Application Engineer.

 

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Air calculations:

Receiver tank capacity formula

V = ( T(C-Cap)(Pa)/(P1-P2) )

 

Where,

V = Volume of receiver tank in cubic feet

T = Time interval in minutes during which compressed air demand will occur

C = Air requirement of demand in cubic feet per minute

Cap = Compressor capacity in cubic feet per minute

Pa = Absolute atmospheric pressure, given in PSIA

P1 = Initial tank pressure (Compressor discharge pressure)

P2 = minimum tank pressure (Pressure required at output of tank to operate compressed air devices)

 

In this application, the values are as follows:

V = 294 cubic feet (per tank)

T = ?

C = 857 CFM (The application required just under 3,000 cubic feet over a duration of 3.5 minutes.  3000 CF/3.5 min = 857 CFM)

Cap = 600 SCFM

Pa = 14.7 PSI

P1 = 120 PSIG

P2 = 80 PSIG

 

So if we manipulate the volume equation just a bit, considering that we know all the values except T, we come up with the following:

T = ( (V(P1-P2))/((C-Cap)(Pa)) )

Therefore,

T = ( (294(120-80)/((857-600)(14.7)) )  —  (units omitted for sanity)

T = 11760 / 3778

T = 3.11 minutes

Memorial Day

Published on by Russ BowmanLeave a comment

It all started the year after I bought my house. My next door neighbor – a Vietnam-era veteran, Honor Flight Guardian, and the best neighbor ever – bought a bunch of American flags & poles, and asked if it would be OK to put them out along the sidewalk in front of our houses to observe the upcoming Independence Day holiday…he had enough to go all the way to the corner of our street. We all thought it was a fantastic idea. And it was just the start.

The following year, just before Memorial Day, as Monty raised the flags down our street, another row popped up around the corner. And, come Fourth of July, there were more. Now, every sidewalk in our neighborhood is decorated every Memorial Day and Independence Day, at 10- to 12-foot intervals (to be fair, nobody published a standard, so it is what it is) with the Stars and Stripes.

I DO love this neighborhood.
I DO love this neighborhood.

Memorial Day, is, of course, the day that we honor the sacrifice of those who gave their lives for the great country that my awesome little neighborhood is part & parcel of. And honor it we will. There will be parades with marching bands and floats. Veteran’s groups will perform ceremonies and vigils. Military aircraft will perform fly-overs at ballgames & special events. Monty will set the flags down our sidewalk. And most of us will enjoy a long weekend.

I’ve seen a lot of posts on social media, reminding us of the meaning of Memorial Day, “in case you thought it was national grill-out day, just another 3-day weekend, etc.” It’s a good reminder; that much is true. But we can honor their sacrifice in celebration too. This weekend, dear reader, I encourage you to light up the grill. Go see some fireworks. Bicycle around the neighborhood (or further) with your kids.  Go camping. Sleep in. Stay up late. Spend time with friends and family. These things are the way of life that our heroes fought and died for, right?

But in the midst of whatever you do, remember them: From the Minutemen who fell at Lexington & Concord, to those who didn’t make it home from the recent campaigns in Iraq and Afghanistan.  May God bless them all, and those they left behind.

In closing, as a former submariner, I am also reminded of the ninety-nine members of the crew of USS Scorpion (SSN-589,) which was lost 47 years ago today (presumed, based on last communications.)

Sailors, rest your oars.
Sailors, rest your oars.

Please enjoy your Memorial Day weekend.  It’s been paid for dearly.

Russ Bowman
Application Engineer
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Memorial Day 2013 image courtesy of Tony Alter.  Creative Commons License

Video Blog: Meet EXAIR’s Application Engineer, Justin Nicholl

Published on by exaircorpLeave a comment

Please let me know how I can provide assistance with your compressed air application or technical questions.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

EXAIR & Tough Mudder Ohio 2015

Published on by Brian FarnoLeave a comment

Several months ago, maybe even last year, a group of EXAIR employees started joking and talking about trying to get a team together to do the Tough Mudder in 2015.  After several months of joking, things got serious and 4 of us signed up to do the event at Mid Ohio Sports Car Course.   You may have seen a few of my blogs that involve Mid Ohio but they normally also involve a motorcycle.    The event was held on Saturday, May 9th, and was my first official “race” at Mid Ohio.   Prior to a few months ago, if you asked if I would ever “run” (I use the term run very loosely here.) a 10 mile race, I would have laughed in your face and said no way.   Let alone a 10 mile race with a whole slew of obstacles. Never underestimate the power of co-worker’s friendly chastising aimed at one’s toughness…

This was after the first wall during the pre race pump up speech / comedy show.
This was after the first wall during the pre race pump up speech / comedy show.

For the team, an Application Engineer (me), our CFO, and two from Shipping & Receiving.  As soon as we hit the first obstacle, which was a 6′ wall you had to clear in order to get to the starting line, our EXAIR mind-set kicked in.   There was no discussions on who would go first, who is going to take what position, or who is going to be the weak link.   It was simply teamwork.   We each helped where we knew our strengths were, anytime we needed a solid ballast, or good step off point, I was the man.   If we needed upper body strength, it was obvious that the handling of heavy freight found in shipping and receiving provided the necessary muscle – most definitely not me.

Needless to say, we made it through the entire course in less than three and a half hours which was absolutely shocking.   Not as shocking as the last obstacle, where we got shocked with 10kV before the finish line (see below).

Electroshock Therapy 2.0 - 10kV wires that will make any man scream.
Electroshock Therapy 2.0 – 10kV wires that will make anyone scream.

The fact of the matter is, we went there as a team, we conquered each obstacle and didn’t only worry about ourselves, but helped many others clear the same obstacles, and each one of us faced and conquered a personal fear.   For me, it was being able to complete a 10 mile run, and a slight fear of heights.  (You can see here that we had to jump out and grab onto a pendulum then swing and hit a bell, after which you would fall 12-15 feet into a pool of 15′ deep water. )

Didn't even come close to that bell, but I did remember to let go of the swing at least.
Didn’t even come close to that bell, but I did remember to let go of the swing at least.

The fact that people from three different departments in EXAIR worked so well together on something only one person on the team had ever done before speaks volumes to the environment and the way we conduct our day-to-day business here.

From the front offices, to the shipping dock, EXAIR is here to help you tackle any obstacle and face any fear you might have (involving your compressed air system that is).

Brian Farno
Application Engineer Manager
TOUGH MUDDER FINISHER
BrianFarno@EXAIR.com
@EXAIR_BF