What’s “I.D.” stand for?

A visitor asks the question, and I’m embarrassed to being one of those writers that assumes a level of knowledge that isn’t there for the visitor. Sorry.

You will usually find the notation “I.D.” used when referring to a dimension of an object, most often a hose or a pipe.

“I.D.” stands for “inner diameter”. A diameter is the length of a straight line connecting through the center of the opening to two points on the perimeter. For an air hose, the I.D. is the distance across the center of the inner opening.

When you are considering the use of a barbed fitting to be inserted into a hose, the O.D. of the barb will correspond to the I.D. of that hose, in order for the correct sized barbed fitting to be selected.

O.D. stands for “outside diameter” and is the total length of a line connecting two points on it’s surface through the center of the item, for example, the O.D. of a barbed fitting.

Now this is slick – a venturi vacuum to suck up liquid spills

Over the years I’ve sold many compressed air driven venturi vacuum pumps. The way Exair has packaged this one is really slick and one I’ve not seen before.

Check out the story in this ThomasNet press release. It’s a cool product.

Some important information about Pneumatic Safety

I wandered across this article in “Engineer Live” (http://www.engineerlive.com/process-news/20312/pneumatic-products-feature-safety-functions.thtml) and thought I’d pass it on….

Pneumatic products feature safety functions

Festo is launching a number of pneumatics safety products to help automation systems manufacturers comply with Machinery Directive 2006/42/EC. This new directive comes into force on 29th December 2009, and will supersede Machinery Directive 98/37/EC.

Although this is nearly two years away, there will be no transition period – all EU countries are required to incorporate the directive into national law by the end of 2009. Among other things, the directive stipulates various health and safety requirements for the design and construction of machines.

For pneumatically-operated automation, there are four operating states that need to be considered when designing safe systems: commissioning, automatic and manual operation, and emergency functions such as reliable stopping or exhausting. Festo is developing a new range of pneumatics safety products to address each of these areas, to help customers design and build safe automation systems. The first products include clamping units and soft start/quick exhaust valves.

Festo’s new KEC-S clamping unit, and the DNCKE-S cylinder clamping unit, provide a precisely defined braking action, with a choice of 1300, 3200 and 8000N static holding force. The braking action can be initiated by a power failure, pressure failure or drop, or a deliberate output from a safety device. The KEC-S clamping units offer a choice of 16, 20 and 25mm diameter rods.

The braking action is provided by a clamping unit acting on the piston rod under spring force, and can be sustained over long periods. The units are suitable for applications involving varying loads – irrespective of fluctuations in the operating pressure, they have a reproducible and certified actuation time – and they are unaffected by system leaks. Both the KEC-S clamping units and the DNCKE-S cylinders offer a wide choice of mounting options, are approved as holding devices and brakes for use in safety-relevant control systems, and are certified by the BGIA (Occupational Safety and Health Institute). With appropriate additional measures they can also be used for accident prevention in control systems of a higher category.

Festo’s MS6-SV soft-start and exhaust valve will be available in the summer of 2008, and serves as a decentralised/centralised unit for supplying machines and systems with compressed air. It is a self-testing mechatronic system with built-in redundancy; it complies with the requirements of ISO 13849-1. This means that the pneumatic safety measure of reliable exhausting is ensured, even if defects occur within the valve. Furthermore, the safety check of the piston rod position is performed directly by the valve during self-test, which simplifies wiring and installation.

The valve vents the system in critical safety areas in the event of an emergency stop. Exhaust performance amounts to 6000 litres per minute, which is 1.5 times pressurisation performance. The unit can be connected, for example, to a safety door at an assembly station; if an employee opens the cover, the system is exhausted. An additional safety feature, the so-called single-fault safety, is achieved thanks to the unit’s redundant two-channel design – even in the event of a fault, safe exhaust of the system is ensured. Soft-start valves with sensor feedback integrated onto valve terminals are also now available, enabling entire system segments or critical function units to be pressurised slowly and safely.

A visitor asks, “what does SCFM mean?”

When you spend many of your waking hours reading, writing, and handling compressed air equipment, it’s easy to forget that the compressed air world is as full of puzzling acronyms.

Take SCFM. Does everyone know what that means? Apparently not. A reader was looking for information about defining SCFM today.

I’ve written about SCFM many times, but it doesn’t hurt to review. SCFM is the acronym for Standard Cubic Feet of air per Minute.

Since a standard cubic foot of air has a specific temperature, a specific humidity, and is measured at sea level, it’s the normal unit of measure for air that has NOT been compressed.

For example, you might say that a specific compressor has 50 SCFM of air entering it’s intake port.

Some folks and companies use SCFM as a unit of measure for air leaving the compressor; air that’s been compressed.

Air leaving the compressor is in no way “standard”. It’s at a higher temperature, it’s has a much higher humidity (vapor content) level and if the compressor itself is not situated exactly at sea level, well then it misses that SCFM benchmark too.

For purposes of stating the flow of compressed air, that’s air that’s passed through the compressor reaching a higher pressure level than one atmosphere, I use the acronym CFM. CFM is the acronym for Cubic Feet of air per Minute.

Here’s scads more info on using compressed air.

CNC Plasma Cutter (PlasmaCam) Dryer

Wandering around on the net I found this article about a user of a compressed air dryer for a Plasma Cutter.

CNC refers to it being “computer numeric controlled” I believe, which is how the CNC cutter is programmed to make the cuts required.

On this type of equipment it’s almost mandatory to have an air dryer that removes both free water and water vapor from the compressed air stream.

Lot’s of information about treating compressed air can be found here, and this is the link to the article on the Harbor Freight compressed air dryer.

You can’t tell an air hose from it’s cover

There’s lots of information on this blog about air hose, and even more here, but here’s an updated.

I always get a chuckle when people look at an air hose lying on the floor, and declare that it “must be” a 1″ line…and they’re deciding that from looking at the outside diameter of the hose.

Different air hose manufacturers and hoses manufactured to different standards and applications have different wall thicknesses and a variety of cladding. As a result, a 1/2″ air hose might have a 3/4″ O.D., or maybe a 1 1/2″ O.D..

If you want to know what size the air hose is, measure the I.D. (inner diameter). That size, whatever it is, is the actual size of that air hose.

What happens when you cool compressed air?

A reader posed this question…what happens when you cool compressed air?

In most cases, you actually want to cool compressed air. The compressing of air into the compressor’s receiver creates heat. As the heat builds the air in the tank holds more water vapor. It becomes super saturated.

When a downstream application calls for compressed air, the compressed air exits the tank, and flows through the mains, hose and tube to the application.

In so doing, the compressed air cools. As it cools, the water vapor held in it condenses out into free water, and now water and compressed air are reaching your application.

If you cool the compressed air after it’s compressed, where you cool it is where much of the water vapor will condense out, leaving less to travel downstream to your tools, valves, air cylinders, etc.

Here’s lots more information on understanding and using compressed air.