In the pipeline
May 1st 2005

Installing the right compressor is only part of the job in obtaining an energy efficient compressed air system

Best industrial practice demands, in the case of compressed air, that the first step is to install the most costeffective compressor for the job. But that is only a part of the story. If the compressed air system itself is not designed for the purpose, there is a good chance that much of the costs associated with compressed air are going out of the window - quite literally.

This has typically been the case with galvanised pipework, the long-time industry standard. Installation of steel pipe can be a lengthy process, involving cutting and threading, with careful calculations required to ensure that drops are drilled in precisely the right position. The weight of galvanised pipework can often prevent its location in the most ideal positions, such as in roof spaces, and when alterations have to be made, the entire system must often be shut down.

Once installed, pressure drops through galvanised pipework can be extensive, so the compressor must work harder - and at greater cost - to supply the required quantity of air.

Condensation that builds in this type of pipework leads to internal rusting which will quickly contaminate the air supply and, of course, lower the pressure through the system even further. If left unattended, the rust perforates the pipework leading to leakage.

Alternatives Recognising that, although time-honoured, galvanised steel is often far from the best method through which to transmit compressed air, a number of companies have developed alternatives. With most of them, quite rightly, the attention has been on ease of installation to minimise downtime, and of a guaranteed supply of good, clean - though not necessarily economical - air.

These new systems have relied on different materials for pipework, principally to eliminate rust. Nylon or plastic tubing, used in a variety of other applications, is certainly clean, but each glued connection requires time to cure -- which can translate into downtime of anything up to 24 hours.

The development of rapid fit connections has overcome the need to glue lengths of plastic pipework, but for most serious compressed air operations the problems of economic air supply through this type of material have been insurmountable. Particularly in a warm environment, plastic or nylon tends to sag, collecting moisture and reducing the flow of air, while ultra-violet light will ultimately cause it to become brittle, leading to cracks and leaks. Box-shaped aluminium tubing, again produced originally for an entirely different purpose, has proved effective against corrosion, but less so in terms of best air flow. Flow paths are not consistent and are hampered even further by the insertion of connectors that reduce the pipework’s internal bore.

When pneumatic equipment manufacturer Legris looked at the requirements of compressed air pipework and connectors to match the growing sophistication of modern compressors, the need to design a system specifically for the purpose became evident.

Key criteria in developing the Transair compressed air pipework system were corrosion resistant tubing in aluminium and stainless steel that offered the best flow path and therefore the lowest pressure drops, and instant push-fit connectors that did not intrude into the pipework and interrupt the flow. System assembly and modification had to be rapid, for the least possible downtime, and components needed to be interchangeable and reusable.

The Transair range has grown to 100mm, 76mm, 63mm, 40mm, 25mm and 16.5mm pipework sizes. Flow rates are far greater than for galvanised systems of larger diameters, while pressure drop is considerably lower than for box aluminium and plastic systems. All Transair sizes are suitable for ring main use, while the 25mm and 16.5 sizes are ideal for branch networks or for drops direct to machinery, work benches and air tools. Once installed, the system can be modified by the user with no specialist knowledge, making it particularly suitable for the changing needs of industry where new supplies of compressed air must be introduced to different workplaces with the minimum of downtime. Aluminium pipework is supplied in powder coated blue. In effect, Transair can be used straight from the compressor to the workplace, or as an immediate extension to an existing galvanised network.

Push fit aluminium The 3 and 6m lengths of aluminium pipework are much lighter than galvanised steel, making them easier to handle on site and offering greater opportunities to position the network at high levels. Flexible hoses are also available and enable the installation to be adapted further where building layouts demand. The aluminium tubing is fixed into position by a snap-shut pipe clip and the network is then linked by instant push-to-fit connectors. These components are made in polymer and are supplied ready for assembly. There is no need to tighten or untighten nuts as they are delivered screwed and aligned to their location marks for ease of insertion and installation. The connection is sealed and secured with just a simple push of the pipe into the fitting. A location mark on the tube confirms that the connection has been made.

Disconnection - perhaps to adapt the system further - is achieved with just a halfturn of the connector nut and the pipe can be removed. No tools are required for either operation. Branching off the system is achieved almost as quickly, with a “fool proof” pipe cutter and drilling kit (hired from distributor). The drill bit and jig are designed to ensure that the hole is cut quickly and easily, giving a clean, champhered cut. After drilling, the pipe is de-burred and connected with a locating pin ensuring that the bracket is centred into position. Three types of bracket provide Transair with flexibility when changes must be made to the direction of the system. A quick assembly bracket is used to connect a main horizontal or vertical branch line, while more compact threaded mini-bracket allow the installation of a quick acting coupler with single passage - ideal for installing a flexible drop to a work station. A quick assembly reducing bracket is also available to connect, for example, a wall bracket from a 40mm main line via a 25mm diameter drop. Continuing the clean air theme, Legris have integrated a preformed upward “swan’s neck” loop within the bracket to prevent the transfer of condensate from the main airline to the machine feed. There is consequently no need to spend time installing 180-degree bends as in traditional systems.

Rapid fit stainless steel Even at the larger sizes, installation of a Transair system in aluminium or stainless steel is a rapid-fit process. Once cut to size, a pipe can be joined by a cartridge, and clamped into place in less than a minute.

Control of a Transair system is done manually with a quarter-turn of the Transair ball-valve, or remotely by using Legris’ compact self-actuating axial valve. Max working pressure for Transair is 16 bar, with operating temperatures from 20 to +60°C.

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