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Category: Air Regulator

Why Do I Need an Air Regulator?

Air regulators are pneumatic devices that receive air at any pressure within its tolerance, and then dispense air of a pressure no greater than their intended output. In other words, air comes in at a higher pressure, and departs at a lower pressure in most circumstances. For the purposes of this article, everything that comes before the air regular is ‘upstream’, and everything after it is ‘downstream.’

Air flows from an air compressor somewhere upstream, and it may or may not interact with other upstream elements. When it reaches the air regulator, a system of springs and an internal diaphragm ‘pushes back’ against the incoming air, offering enough resistance that only a set volume of air (and thus, a set air pressure, since air pressure is calculated by volume within a given area) moves downstream. So long as the upstream pressure is enough to open the diaphragm, and not enough to tear the air regulator off of the device altogether, the downstream pressure will be constant regardless of how the upstream pressure changes.

This is a hugely vital function, because many pneumatic cylinders would be harmed by overly powerful air, or at the very minimum the jobs the cylinders are doing would be done poorly if they were done too quickly. For example, without an air regulator, a pneumatic cylinder attached to a carefully-balanced load might jolt upward too quickly and disturb the load it was lifting.

The air compressors have a ‘cutoff point’ at which they stop compressing air, instead allowing the air already compressed into their reservoir to do the work. Air regulators will cause the upstream system to back up such that the upstream pressure will eventually build up and cause the compressor’s cutoff point to trigger, stopping the compression until that high-pressure air has had a chance to work its way through the regulator enough that the air compressor restarts — but the downstream pressure from the regulator never changes until the entire system is shut down and the diaphragm finally closes.

The answer to the title question, then, is simple: you need an air compressor not only to protect delicate devices or delicate work from variations in the upstream air pressure, but to reduce the amount of air that your compressor has to process.

A Word On Laboratory Air Compressor Systems

medical air compressor system does not necessarily make a good laboratory compressor system.  Medical air compressor systems are designed to deliver clean, 50 psi, breathing air as specified by a CSA Standard.  Laboratories may not be best served by a medical air compressor.  Here are some things to think about when procuring a laboratory compressor system

OIL-LESS VERSUS LUBRICATED

Oil-less air compressors are expensive relative to lubricated compressors.  Today’s tight budgeting has required the installation of lubricated compressors in laboratories where the low risk of compressor lubricant in the compressed air is acceptable.

PRESSURE

The 50 psi pressure supplied by a medical air compressor is often not enough for a laboratory.  Laboratory equipment may require 80 to 120 psi pressure.  Determine from the user what pressure is required.  A compressor running start/stop will need to shut off at a pressure 20 to 40 psi above the required pressure to allow for pressure switch  differential, purification pressure loss, pressure regulation and pipeline pressure drop.

CUBIC FEET FREE AIR PER MINUTE VS. CUBIC FEET COMPRESSED AIR PER MINUTE

Compressors are usually rated in CFM free air.  This should be the quantity of air delivered referenced to the compressor inlet conditions.  Cubic feet compressed air equates to free air as follows

Hence, at 80 PSIG, 35 CFM free air equals 5.4 CFM compressed air.

Years ago Peerless Engineering was requested by a consultant to supply a 10 HP, 35 cubic feet free air per minute compressor to a laboratory facility.  It was determined after installation that 35 cubic feet compressed air per minute was required.  To quote Homer Simpson “Do’h!”

The solution was to install a second 50 HP, 175 cubic feet free air per minute compressor.  However, the building was plumbed with only ½ inch compressed air lines.  To quote Homer Simpson again “Do’h!”.

DELIVERED CUBIC FEET VS. INLET CUBIC FEET

Some compressor manufacturers rate their compressor by inlet cubic feet per minute which equals delivered air divided by the volumetric efficiency.   Given that the volumetric efficiency of a compressor can be 70%, rating a compressor by inlet cubic feet per minute makes that compressor look much better to the naïve.

DEW POINT

Compressed air dried to a pressure dew point of -40°C by a desiccant air dryer costs more to make than compressed air dried to a pressure dew point of +4°C by a refrigerated air dryer.  Many laboratories only require compressed air with an acceptable relative humidity at maximum pipeline pressure and minimum pipeline temperature.  This can often be accomplished by a refrigerated air dryer at a lower cost.

Follow Ron Magnolo on Twitter @ronm_peerlesse.