Five Things To Know About Single Acting Reciprocating Compressors

With the development of highly efficient air compressors, there’s still a place for the most basic design: the single acting reciprocating compressor.  When the piston moves out of the cylinder, it draws air in, at atmospheric pressure.  When it moves in to the cylinder, it reduces the volume that air occupies, increasing its pressure.  These machines are durable, effective, relatively inexpensive, and pretty easy to maintain.  Here are a few interesting things to know about them:

1. Popularity. Because of the simplicity of their design, they’re the most common air compressor in the 10HP and under sizes.  You can get them from a number of sources, and they’re not going to set you back as much as some other types.
2. Oil free air (part 1) While the most basic design uses oil to lubricate the piston rings in the compression cylinder, oil-less reciprocating compressors have cylinders with very smooth (and hard) bore surfaces, like nickel or chrome plating. A series of guide rings around the whole circumference of the piston prevent metal-to-metal contact, eliminating the need for liquid lubrication in the compression cylinder.
3. Oil free air (part 2) If oil in your compressed air is a problem, an oil-free (as opposed to oil-less) compressor is another option. While an oil-less compressor doesn’t use lubricant for the piston movement, an oil-free compressor’s moving parts are oil lubricated, but that oil is kept away from the compression cylinder(s) with connecting rod(s) so that the oil is confined to the lower moving parts…the crankshaft and bottom ends of the connecting rods, and away from the pistons & compression cylinders.
4. Foundation. Reciprocating machinery, as the name implies, has parts that move back and forth. The sudden reversal of direction of heavy metal pistons & rods, dozens of times a minute, means that their operation is inherently unbalanced. This out-of-balance condition, though, can be absorbed by properly securing the compressor to a properly prepared foundation.
5. Higher pressures. If your facility’s compressed air usage primarily entails pneumatic tools, cylinders, and blow off devices like air guns, the system header pressure is likely maintained at around 100psig. While a one-stage reciprocating compressor is usually rated for discharge pressures up to 125psig, a second stage can increase that to 175psig. Multi-stage compressors are used for applications that require up to 3,000psig compressed air. Examples of these are scuba breathing air, pneumatic excavators, and my personal favorite: ballast tank blowing air, used to surface a submarine.

4-stage reciprocating compressors charge 3,000psig air tanks that are used to rapidly push water from a submarine’s ballast tanks to create positive buoyancy.  Because keeping your ‘diving-to-surfacing’ ratio at 1:1 is important.

At EXAIR Corporation, helping you get the most out of your compressed air system is important to us.  If you’ve got questions about how to do just that, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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EXAIR Cabinet Cooler System Used on Cement Barge

I joined the Navy, right after high school, to get out of Ohio, see the world, and never come back. “My recruiter said” (if you are considering military service, those can be famous last words, just so you know) that I would be a good candidate for Nuclear Power School, so I took the test. As a math & science nerd scholar, I qualified for admission easily.  About halfway through Nuke School, I volunteered for submarines.  My decision was based in no small part on the sea stories of our instructors, the strong reputation of better food, and my deep appreciation for the movie “Operation Petticoat.”

Upon graduation, I was assigned to a new construction Trident submarine.  I did not see the world…I saw the Electric Boat shipyard in Groton, Connecticut, and Naval Submarine Base King’s Bay, Georgia.  Hilarity occasionally ensued, but never in the context of that movie I so adored.  I moved back to Ohio (on purpose) soon after my enlistment was up.  The food WAS good…I can unreservedly vouch for that.

In the new construction environment of the shipyard, I became quite familiar, and developed a deep respect for, the high level of attention paid to the materials and workmanship that a seagoing vessel demanded…not to mention, one with a nuclear reactor on board.  Reliability and durability are obviously key factors.

I had the pleasure recently of assisting an electrical contractor who was looking for a cooling solution for a new Variable Frequency Drive enclosure installation on a cement barge.  The ship’s engineer (a Navy veteran himself) had told the contractor that his priorities were reliability, durability, and dust exclusion.  He couldn’t have made a better case for an EXAIR Cabinet Cooling System.

Based on the specified heat load of the VFD, the size of the enclosure, and its location, a Model 4380 Thermostat Controlled NEMA 12 Cabinet Cooler System, rated at 5,600 Btu/hr, was specified.  This equipment is internal to the ship; had it been exposed to the elements, a NEMA 4X system would have been presented.

Up to 2,800 Btu/hr cooling capacity with a single Cabinet Cooler System (left) or as much as 5,600 Btu/hr with a Dual system (right.)

EXAIR Cabinet Cooler Systems have no moving parts to wear, no electric motor to burn out, and no heat transfer surfaces (like a refrigerant-based unit’s fins & tubes) to foul.  Once it’s properly installed on a sealed enclosure, the internal components never see anything but cold, clean air.

If you have a need to protect an electrical enclosure in aggressive environment, give me a call.  With a wide range of Cabinet Cooler Systems to meet a variety of needs, we’ve got the one you’re looking for, in stock and ready to ship.

Russ Bowman
Application Engineer
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Optimizing Compressed Air with EXAIR Innovative Static Eliminators

A dear friend is turning 50 this month, and I have no intention of making a big deal of it, considering the spectacle that her husband (who is younger than both of us) is no doubt going to make of it. I was reminded of her impending birthday when I read that Alvin is also turning 50 this year.

Even at this depth, Alvin doesn't look a day over 49.
Even at this depth, Alvin doesn’t look a day over 49.

Alvin (DSV-2) is a deep-dive submersible, built in 1964. Built to dive to depths of over 8,000 feet, Alvin has had quite a storied career:

  • 1966 – Used to locate a hydrogen bomb that was lost off the coast of Spain when a US Air Force bomber “had an accident.” The bomb was retrieved a few weeks later, without incident.
  • 1967 – On dive #202, Alvin was attacked by a swordfish, at a depth of about 2,000 feet. The swordfish became entangled, forcing an emergency surface. Upon removal, the swordfish was cooked for dinner.
  • 1968 – Alvin’s tender ship accidentally dropped Alvin when some steel cables snapped, in the middle of the ocean. Three crew members onboard at the time were able to escape, but left their lunches behind. Severe weather and the development of the required technology put off Alvin’s recovery for almost a full year. A full rehab of the vessel was slated. The fruit and sandwiches left behind were found to be well preserved, and soggy but edible.
  • 1986 – Alvin was used to find the wreckage of the Titanic. While the mission was making headlines at the time, it was actually a cover story for the highly classified “real” operation: the search for USS Scorpion (SSN-589), lost under unknown circumstances in 1968. In a remarkable stroke of good fortune, both vessels were found.

That’s all neat stuff, but I’m sure there are a few spine tingling stories we’ll never hear about a deep submergence vessel, operated by the US Navy, during the height of the Cold War. Another bit of interesting trivia, though, is who built Alvin: General Mills. That’s right, the breakfast cereal folks. Turns out, they had an electromechanical division back then that pioneered advances in packaging technology, and had previously applied some of their mechanical arms to other submersibles, leading them to successfully bid the project that Alvin was born from.

This, of course, is what engineers do. EXAIR has been making Intelligent Compressed Air Products, aimed at optimizing compressed air use, increasing safety, and lowering noise levels for over 31 years now. Along the way, we’ve added products, and added TO our products to meet other frequent needs of our customers.

Consider the Air Knife: the Air Knife had been a product for years when EXAIR developed the Ionizing Bar  and added it to the Air Knife to turn it into an efficient, quiet, and safe Static Eliminator. The Air Knife then provided good information toward development of the super efficient Super Air Knife which has become the hallmark of efficiency and performance within industry.  After years of successfully solving thousands upon thousands of static dissipation applications with the Super Air Knife, we recently added one-piece designs from 60 – 108” long which used to be a two piece construction.

3to54 siak
EXAIR stock SIXTEEN different lengths, from 3″ to 108″. Custom lengths are available in as little as three days.

A quick look at our complete and comprehensive line of Static Eliminator products shows that, if you’ve got a static problem – big or small – we’ve likely got a solution for it.

Russ Bowman
Application Engineer
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expl1874 image courtesy of NOAA Photo Library.  Creative Commons License

Submarines, Shipwrecks, Air Knives, and Corrosion

Monday was a notable day in naval warfare history. On February 17th, 1864, the H.L. Hunley sank the USS Housatonic, a Union sloop that was blockading the harbor in Charleston, South Carolina, during the American Civil War. In doing so, the Hunley became the first combat submarine to sink a warship in battle. Unfortunately, they never returned.

Treasure hunters and archaeologists searched for the sunken vessel in the years following the war. Despite grand efforts, one even spurred by a $100,000 reward offer from legendary showman P.T. Barnum, the ship and crew were lost to history until 1995. So many people had mistakenly thought they’d found the wreckage that when underwater archaeologist Harry Pecorelli actually did find it, he radioed to his boat, “I don’t know what it is, but it is definitely not the Hunley.” Because of this, the preservation group, Friends Of The Hunley, have affectionately dubbed him “the first person to have never found the Hunley.”

In 2000, the intact ship was raised and placed in a specially built tank, where the conservation team immediately went to work. Because of her iron construction and age, this turned out to be an engineering (mechanical and chemical) feat like no other. Over the next four years, precision excavation efforts allowed the team to exhume the remains of the crew, and they were buried with full military honors in the spring of 2004. They still haven’t proven conclusively why the Hunley sank, but as restoration work continues, she may give up her final secrets yet, as long as they can keep corrosion at bay.

hunley in tank

The prevalent use of aggressive chemicals in certain manufacturing processes today can likewise take their toll on equipment made from materials that aren’t compatible for use in these environments. As advances have been made in the development of these chemicals, metallurgists and materials engineers have kept pace in the field of corrosion resistance. EXAIR has taken full advantage of these innovations by offering our Super Air Knives in a variety of materials that can stand up to just about whatever you can throw at them:

Two grades of Stainless Steel are available: Type 303 is well suited to mildly corrosive environments. Type 316 offers even better corrosion resistance, and is often specified in the food, pharmaceutical, and surgical product industries. Both are also good to 800°F (427°C).

PVDF (Polyvinylidene Fluoride) Super Air Knives are resistant to harsh conditions where UV light, inorganic chemicals, solvents, ozone, weather, fungi, chlorinated hydrocarbons, strong acids, and/or salts are present. They are equipped with PTFE shims, 316SS pipe plugs, and Hastelloy C-276 hardware for superior performance in the most aggressive environments.  These are rated for temperatures up to 275°F (135°C).

Of course, if your application doesn’t concern any of these, our Super Air Knives in aircraft grade aluminum construction are perfect for general purpose applications in standard conditions. Just about wherever you need to install it, though, EXAIR has a Super Air Knife that is up to the task. Try us.

Russ Bowman
RussBowman@EXAIR.com
@EXAIR_RB