Can You Add a Desiccant Dryer to Just One Production Line?
A new process arrives with a −40°C pressure dew point requirement, while the main compressed air ring serves the rest of the factory adequately. A point-of-use desiccant air dryer on that one branch avoids treating every cubic metre of site air to a specification only one line needs.
So yes, you can add a desiccant dryer to just one production line, provided the branch is a small share of total demand and the dryer is selected for its real operating conditions. Anglian Compressors, a Branch of Atlas Copco Compressors, checks the points below before recommending one.
When a Point-of-Use Desiccant Air Dryer Makes Sense
The HSE compressed air safety guidance states that where exceptionally dry air represents only a small percentage of total compressed air use, the dryer may be placed immediately upstream of the plant that needs it. HSE gives no numerical cut-off, so the decision rests on measured branch flow, operating hours, purge volume and pressure loss.
The case weakens where low-dew-point demand is a large or growing part of site consumption, or where the process needs duty and standby drying. A short batch demand with a high instantaneous flow is also a different selection from a small, continuous instrument supply. For background on the technologies, see our guide to compressed air dryers.
Confirm the PDP the Machine Needs
Take the pressure dew point (PDP) from the process specification at the machine, without adding an arbitrary margin. HSE relates the dew point to the actual plant requirement, and a lower target raises regeneration demand, equipment cost and maintenance with no process gain. Our practical guide to pressure dew point explains why PDP and atmospheric dew point are not interchangeable.
The three most stringent water classes in ISO 8573-1 (excluding Class 0), Classes 1, 2 and 3, correspond to maximum PDPs of −70°C, −40°C and −20°C, as set out in our Atlas Copco guide to ISO 8573-1 air quality classes. Confirm the stated class refers to water, because ISO 8573-1 classifies particles, water and oil separately.
Measure Branch Flow and the Operating Envelope
A dryer’s rated flow applies only at its stated inlet pressure, inlet temperature and ambient conditions. Size it from the maximum simultaneous flow through the branch under those conditions. Several valves, actuators or nozzles operating together can create a short peak well above the shift average.
Record:
- Required outlet PDP or ISO 8573-1 water class
- Maximum simultaneous branch flow and the demand pattern
- Normal and minimum inlet pressure at the dryer
- Maximum inlet and ambient temperatures
- Daily operating hours
- Any duty and standby requirement
Where the profile is uncertain, temporary flow monitoring gives a sounder basis than estimated tool consumption, and one unresolved batch peak can move the selection up a dryer size. Check that shortlisted figures were tested to ISO 7183:2007, which covers PDP, flow rate, pressure drop and compressed-air loss.
Check Upstream Filtration and Ring Moisture
Oil, liquid condensate and particles reaching the desiccant impair performance and shorten its life, so fit the manufacturer’s specified filtration ahead of the dryer. If the ring already carries water, fix the drains, separators or central dryer first rather than expecting a local unit to absorb the fault. Our guide to water in your compressed air lines covers the usual causes.
Allow for Pressure Drop at the Machine
Check the pressure available at the machine after the dryer, filters, valves and branch pipework. Raising compressor discharge pressure to cover a local restriction makes the whole system use more energy. Any bypass needs a controlled procedure, because opening it sends untreated air straight to a moisture-sensitive process.
Account for Purge Load on the Compressors
A heatless dryer regenerates by expanding part of its own dried air through the off-line vessel. Our Atlas Copco technical data puts heatless purge consumption at approximately 15–20% of the dryer’s nominal capacity at 7 bar(e) working pressure. Treat that as a manufacturer figure and confirm it against the tested data for the model you shortlist.
The compressor room has to supply branch flow plus purge, using air it has already generated, cooled and filtered. Heated regeneration cuts the purge air but adds heaters, electrical load and maintenance, so a higher or steadier demand may justify evaluating it.
Review the Written Scheme of Examination
Desiccant dryer vessels contain compressed air, so adding them can change the scope of the site’s pressure system. Adding vessels may require the Written Scheme of Examination (WSE) to be reviewed by a Competent Person so the dryer vessels, protective devices and relevant pipework are covered, as described in the HSE PSSR ACOP L122. The duty stays with the user even where a supplier arranges the examination.
Give Us the Data Needed for a Quote
For a useful quotation, send the process PDP or ISO water class, available inlet pressure, expected inlet temperature, branch flow data, operating hours, duty pattern, current filtration and any redundancy requirement. A layout drawing and details of the existing WSE help set the installation and examination scope.
Our team can flow-monitor the branch, select and install the dryer and filtration, calculate the resulting pressure drop and review the WSE requirements. Once the PDP and operating envelope are defined, you can compare suitable industrial air dryers, and we will return a point-of-use selection based on the line’s operating conditions.
Book a free energy audit and we will data-log your system for 7–10 days, including the branch that needs drier air, then show where air is being lost, what it costs per year and the payback on any recommended changes.