The operation of two compressors and two dryers, operated in parallel, is shown on Fig. 10.4.6.1 and can be regarded as ideal. Line 1 (item 1 - 5) takes on the base load and Line 2 (item 1.1 - 5.1) is for stand-by operation
Figure 10.4.6.1
As desired, duty periods are allocated to the compressors via a base load change-over switch. Should one line fail, the second line takes over the total supply. Also see section 10.4.4. A further development of dryer control is called for if the system is meant to run fully automatically. Both dryers are fitted with a load depending control system and linked to the compressors.
Figure 10.4.6.2
Line 1 operates, the dewpoint at the outlet of the dryer is better than the set point. The valve after the downstream filter (item 5) is opened to the take-off point. If the dewpoint rises and reaches the set point, line 2 becomes automatically activated. Depending on the loading, each line can take on 50% or line 2 takes on the entire load when required. Regeneration of line 1 is timed and automatic. One option for timed regeneration is shown with Fig. 10.4.6.2. External regeneration lines (item 6 and item 6.1) connect the dryers of line 1 and line 2. As required, regeneration air is taken to the dryer to be purged.
