The question of the location of a compressor installation is closely linked to being able to call this an ideal installation. The compressed air has to be ducted to individual points of consumption, some of which are located at considerable distances from each other. Practical experience shows that the expansion of a factory is usually linked to an extension of the compressed air installation and to wider compressed air distribution. The traditionally evolved network with a central compressor station becomes an expanded network of higher output. The way in which the network is extended, and the associated question of where to locate further compressors, requires careful evaluation. In principle, there are several potential solutions, three of which are outlined as follows:-
- Central compressor station with economically operating large compressors and air distribution eminating from one point.
- Advantage:
Low investment costs, lower requirement of operating personnel.
Disadvantage:
Unfavourable air distribution, large piping diameters or increased pressure loss. If repairs have to be carried out in the distribution network, compressed air supply cannot always be ensured. - Decentralised compressed air generation at principal points of consumption and thus a small distribution network.
- Advantage: Favourable pressure conditions, low distribution costs
Disadvantage: A larger number of compressor installations, possibly more expensive reserve provisions to ensure continuity of the compressed air supply. - Compressed air generation at two principal points and feeding into a ring main. If the network is very large, a compressor with output regulation can be connected to the point of highest pressure loss in the mains in order to maintain pressure.
- Advantage: The compressors are large enough to be operated within an economical range as basic output providers as well as topping up compressors. By arranging a ring main, compressed air distribution is ensured even if there is a breakdown at one point.
Disadvantage: Increased costs of the ring mains, as larger cross sections have to be selected. Should one station drop out, the station at the opposite point has to satisfy the entire demand.
The operator has to consider the advantages and disadvantages of various piping materials for the compressed air network. Here, too, the decision will be a compromise between optimum procedure and that which is economically and technically acceptable. There is a choice of materials for the distribution network and the following selection provides a survey of the most frequently used materials:
Copper pipes
Advantage : Non rusting, easily worked material
Disadvantage : Expensive, possibility of oxide formation
Utilisation : For smaller outputs
Plastic pipework
Advantage : No corrosion, smooth surfaces
Disadvantage : Temperature sensitive, maximum standard bore 100 mm
Utilisation : Temperatures up to te = 50°C
Operating pressure p = 8 bar
Threaded tubing
Advantage: Quick assembly, can be dismantled
Disadvantage: Maximum bore R 6", possibility of leakage
Utilisation: Low quality requirements
Seamless steel pipes
Advantage: Favourable costs combined with absolutely leak tight connections
Disadvantage: Has to be assembled by welding, liable to corrode
Utilisation: Medium quality requirements
Galvanised steel piping
Advantage: No surface corrosion
Disadvantage: Autogenous (gas) welding required
Utilisation: Higher quality requirements
Stainless steel piping
Advantage: No corrosion, low flow resistance
Disadvantage: Very expensive, welding shielded by protective gas
Utilisation: Highest quality requirements
When sizing the piping, pressure loss should be kept as low as possible. An ideal pressure loss would be a maximum value of 0.1 bar. However, this value is only rarely met in practice. From the planning stage, every effort should be made to achieve the lowest possible pressure loss.
