TABLE OF CONTENTS The main consideration in the selection of a compressor plant is the production of an adequate supply of compressed air at the lowest cost consistent with reliable service. The installation of a compressed air system, as with all forms of power transmission, calls for capital investment with consequent operating and maintenance costs. The information on which the selection of plant is based should be as accurate as possible. Important factors to be considered are the following.
Most compressed air equipment operates at about 6 bar (gauge) and it is usual for the compressor to deliver air into the mains at 7 bar (gauge) in order to allow for transmission losses (see Tables 26.1-26.4). If some of the air is to be used at a lower pressure (for example, for instrument control) the pressure is reduced by means of a pressure regulator to the required line pressure.
| Nominal bore(mm) | Actual bore(mm) | Rate of free air flow at 7 bar (l/s) |
|---|---|---|
| 6 | 6 | 1 |
| 8 | 9 | 3 |
| 10 | 12 | 5 |
| 15 | 16 | 10 |
| 20 | 22 | 17 |
| 25 | 27 | 25 |
| 32 | 36 | 50 |
| 40 | 42 | 65 |
| 50 | 53 | 100 |
| 65 | 69 | 180 |
| 80 | 81 | 240 |
| 100 | 100 | 410 |
| 125 | 130 | 610 |
| 150 | 155 | 900 |
| Velocity of air flow must be restricted to less than 6 m/s as shown if carry over of moisture past drain legs is to be avoided. | ||
| [a]Medium-weight steel tube... |
