Compressed air accessories are not optional extras. The filter, dryer, and drain you select determine your energy bill, your air quality, and whether you’re compliant with UK environmental law. Get the combination wrong and you’re paying 5-8% more in electricity before you notice anything is wrong.

Key Takeaways

• Accessories control pressure drop, condensate, air quality and running cost.
• Filters, dryers, drains and receivers should be specified as one system, not bought as separate extras.
• The cheapest accessory can cost more if it increases pressure loss, breaches condensate rules or shortens service life.

Search Air, Atlas Copco Premier Distributor since 2002, has been specifying and installing compressed air accessories for industrial sites across Yorkshire and the East Midlands since 1952. This guide covers the decisions that affect your running costs, your legal exposure, and your system reliability.

Why Accessories Are a Running Cost Decision

Every 0.14 bar of pressure drop from a restriction in your system adds approximately 1% to your compressor’s energy consumption. Chain three common restrictions together and you’re looking at a 5-8% energy penalty before maintenance is overdue.

The most common accessory restrictions on a typical industrial site are:

• Coalescing filters (new: 0.10-0.15 bar. Overdue replacement: 0.30-0.40 bar)
• Refrigerant or desiccant dryers (undersized: 0.15-0.2 bar additional drop)
• Distribution pipework (poorly designed runs add further resistance)

A saturated filter element adds 0.2-0.3 bar. An undersized dryer adds another 0.15-0.2 bar. Where demand varies significantly between shifts, the Air Compressor Sizing Guide covers how to calculate your actual system requirement before specifying accessories.

For a 100 kW compressor running two shifts, cumulative pressure drop across filters, dryer, and pipework represents thousands of pounds in preventable annual spend, before you factor in accelerated wear on downstream pneumatic tools.

Why Moisture Load Matters

Air that appears dry at atmospheric pressure becomes fully saturated once compressed. A 100 kW compressor operating in typical UK ambient conditions produces approximately 85 litres of liquid water during a single eight-hour shift. The accessories you choose determine whether that water goes into your drain or your pneumatic valves.

Aftercoolers and Initial Moisture Removal

Aftercoolers are fitted immediately downstream of the compression stage and reduce compressed air temperature to a level where 70-80% of water vapour condenses before the air enters your distribution system. That bulk liquid is removed by a centrifugal or cyclonic separator. What leaves the aftercooler is still saturated air at 100% relative humidity, which is why aftercoolers are a starting point, not a complete solution.

• Air-cooled aftercoolers: lower installation cost, suitable for most Yorkshire manufacturing environments
• Water-cooled aftercoolers: more compact, preferred where ambient plant room temperatures are high
• Both types require automatic drains at the separator to expel condensate continuously

The A Guide to Using Air Compressors in Humid UK Environments covers how UK ambient humidity affects moisture load across seasons.

Filters and Pressure Drop

Coalescing filters remove oil aerosols and particulates that aftercoolers and dryers miss. The selection decision turns on two variables: the ISO 8573-1:2010 purity class your application requires, and the pressure drop penalty for the filtration grade.

A UD+ filter combines the coarse and fine coalescing stages into a single unit, halving annual element replacements and reducing wet pressure drop from approximately 0.53 bar (conventional DD+/PD+ train) to approximately 0.25 bar.

Replace filter elements at least every 8,000 running hours or once per year, whichever comes first. Genuine replacement elements are available with next-day delivery to most Yorkshire and East Midlands postcodes via our compressor spare parts service.

Air Dryers: Refrigerant vs Desiccant

The correct dryer type depends on your pressure dew point (PDP) requirement. For general industrial applications where air lines are kept indoors and ambient temperatures remain above freezing, a refrigerant dryer delivering a +3°C PDP is typically sufficient, achieving ISO 8573-1 Water Classes 4 to 6.

Desiccant dryers are required when:

• Air lines run outdoors or through unheated spaces (risk of ice formation below 0°C)
• The application is pharmaceutical, food production, or paint spraying
• ISO 8573-1 Water Class 1, 2, or 3 is specified

Desiccant dryers use a twin-tower design where one tower adsorbs moisture while the other regenerates using a purge of dried air. That purge air consumption is a real system cost and must be factored into your sizing calculation.

The CD+ series desiccant dryers available through Search Air use Dew Point Dependent Switching, which delays tower changes until the desiccant is genuinely saturated rather than switching on a fixed timer. Independent testing shows this saves up to 90% in energy compared to fixed-timer models. Desiccant media should be replaced every 2 to 5 years depending on type.

For system monitoring including dew point tracking via the Elektronikon controller, see A Guide to Air Compressor Monitoring Systems.

Compliant Condensate Disposal

Compressed air condensate is classified as hazardous waste under UK law. Discharging it untreated to drain, surface water, or storm drains is a criminal offence.

The Water Resources Act 1991 (England and Wales) and the Water Environment and Water Services Act (Scotland) 2003 establish the legal framework. Untreated condensate from a lubricated compressor typically contains 100-200 mg/l of mineral oil, well above the threshold that constitutes a polluting discharge. Crown Courts can impose unlimited fines and, in serious cases, company directors face personal liability including custodial sentences.

There are two compliant disposal routes:

• Collection and removal by a licensed hazardous waste carrier
• On-site treatment via an oil/water separator to below 10 ppm residual oil, followed by discharge to foul sewer with a Consent to Discharge permit from your local water authority

Our condensate management solutions cover both routes, including OSC series separators sized for your condensate volume.

Zero-Loss Drains

Timer-based drains open on a schedule regardless of whether condensate is present, bleeding compressed air to atmosphere with every cycle. Electronic zero-loss drains (the Atlas Copco EWD series) use capacitive sensors to open only when the reservoir is full and close before any compressed air escapes. The energy savings from eliminating that unnecessary air loss typically deliver full ROI within the first year.

Distribution Pipework

Horizontal main lines must slope downward at a gradient of at least 1:100 in the direction of airflow, directing residual moisture toward drip legs. Air drops to tools and equipment must exit from the top of the header pipe using a swan neck take-off, not from the side or bottom where pooled condensate collects.

Traditional galvanised steel corrodes from the inside when moisture contacts it. The resulting scale travels downstream as abrasive particulate contamination, accelerating wear on pneumatic valves and tools. AIRnet’s aluminium construction eliminates that failure mode.

Cold Weather Accessories

The ideal operating temperature for an air compressor is between 5°C and 30°C. Below 5°C, oil viscosity increases significantly, reducing lubrication effectiveness and increasing motor load at startup. Many Atlas Copco GA units include a low-ambient temperature switch that prevents startup below 4°C to protect internal components.

Cold weather accessory checklist for Yorkshire and East Midlands sites:

• Plant room heater: maintains temperature above 5°C. A thermostatically controlled heater costs far less than an emergency call-out for a seized air end
• Trace heating and insulation: heat tape prevents ice jams in external distribution lines and control lines
• Low-viscosity oil: specified for sites where plant room temperature regularly falls below 10°C
• Refrigerant dryer monitoring: cold weather can cause condensate to freeze within the heat exchanger. Monitor dryer cycles November to March

For heat recovery opportunities that offset plant room heating costs, see A UK Guide to Air Compressor Heat Recovery.

Safety and Compliance Accessories

PSSR 2000 (Pressure Systems Safety Regulations) governs compressed air systems in the UK. Any system where the pressure-volume product exceeds 250 bar-litres requires a Written Scheme of Examination. Most industrial rotary screw installations fall into this category.

Accessories relevant to PSSR compliance include:

• Calibrated pressure gauges and relief valves at the receiver
• Automatic drain systems that prevent liquid accumulation affecting vessel integrity
• Isolation valves and lockout points for safe maintenance access
• Pressure regulation downstream of the receiver to prevent distribution pressure exceeding WSE limits

FAQs

What Pressure Dew Point Do I Need for a UK Food Processing Site?

Food processing applications typically require ISO 8573-1 Water Class 1 or 2, meaning a pressure dew point of -40°C or lower. A refrigerant dryer delivering +3°C PDP does not meet this requirement. You need a desiccant dryer with Dew Point Dependent Switching and downstream filtration to achieve the class your HACCP assessment or BRCGS audit specifies.

How Often Should Condensate Drains Be Inspected on a Two-shift Site?

Check that automatic drains are actively discharging during operation daily. On a two-shift site running 6,000-7,000 hours per year, zero-loss drain sensors and float mechanisms should be serviced annually as part of scheduled maintenance.

Do I Need a Consent to Discharge Permit If I Already Have an Oil/water Separator?

Yes. An oil/water separator reduces condensate to below 10 ppm residual oil, but it does not replace the need for a Consent to Discharge permit from your local water authority. Operating without that permit, even with a separator in place, still constitutes a breach of the Water Resources Act 1991 (legislation.gov.uk).

If you’d like a frank assessment of your current accessory specification, contact Search Air. We cover Leeds, Sheffield, Nottingham, and the surrounding region, and we offer a free airCHECK audit that covers pressure drop, condensate compliance, and cold weather preparedness in a single site visit. Call us on 0113 263 9081 to arrange yours.