How to Plan Temporary Compressed Air for a Factory Shutdown

The temporary compressor arrives on time. The shutdown starts. Then production discovers that the air is wet, pressure at the far end of the ring main is too low, or the hired unit cannot follow the changing demand.

Planning temporary compressed air for a factory shutdown means specifying the complete air supply, not just hiring a compressor with a similar motor rating. Flow, pressure, electrical supply, air purity, drying, filtration, pipework and breathing air all need decisions before mobilisation.

Search Air, Atlas Copco Premier Distributor since 2002, plans temporary installations for industrial sites across Yorkshire and the East Midlands. Our starting point is the duty your production equipment must perform during the shutdown.

Start With the Required Air Duty

A permanent compressor’s nameplate is not a temporary-air specification. It tells us what the installed machine can deliver under defined conditions, but not what your site will need while equipment is isolated, cleaned, serviced or restarted.

Record the following before requesting a quotation:

• Required flow in CFM, litres per second or cubic metres per minute
• Minimum pressure at the point of use, not only at the compressor discharge
• Normal, minimum and peak demand during each shutdown phase
• Equipment that will operate at the same time
• Connection size, pipe length and distance to the furthest user
• Available electrical supply and whether it remains live throughout the work
• Required air quality at each point of use
• Ambient conditions and the proposed compressor location
• The consequence of losing the temporary supply

Use measured demand where it is available. A short period of data logging is more reliable than adding together every pneumatic tool’s rated consumption. That calculation assumes every tool runs at full load simultaneously, which can lead to an oversized machine that spends much of the shutdown off-load.

The temporary installation must also cover pressure losses through hoses, filters, dryers and temporary connections. A hired compressor can produce enough volume while the production line still receives insufficient pressure. Our guide to how to spec temporary air for a shutdown or breakdown covers the wider capacity calculation.

Which Temporary Compressor Should You Choose?

An electric VSD compressor may suit changing demand during a shutdown when a suitable electrical supply remains available.

Variable Speed Drive, or VSD, control changes the compressor motor speed to follow air demand. During a shutdown, consumption often rises and falls as maintenance teams isolate machines, use pneumatic tools and bring production areas back online. Matching output to that profile reduces unnecessary unloaded running.

A VSD label does not guarantee an efficient installation. The machine still needs the correct pressure range, flow capacity and connection arrangement. An oversized VSD compressor operating close to its minimum controllable output can be a poor match.

When Fixed-Speed Is the Better Choice

Fixed-speed equipment still has a place. If demand is flat, continuous and close to the machine’s rated output, fixed-speed operation can be commercially sensible. It also provides a straightforward option for a short, predictable duty where the extra control range of VSD will not be used.

This is where the recommendation can flip. A stable production process operating continuously through the shutdown may suit fixed speed better than VSD. The demand profile decides, not the technology name.

When the Compressor Must Be Independent of the Grid

Specify a diesel-driven compressor when the site’s electrical supply will be isolated, cannot support the starting load or forms part of the shutdown risk. Account for exhaust routing, ventilation, noise, fuel storage and access for refuelling.

Grid independence can determine whether production continues. In one food-industry emergency, Atlas Copco mobilised two PTS 800 and three PTS 1600 diesel-driven, Class Zero compressors within 24 hours. The installation restored the site’s compressed-air capacity without relying on its compromised electrical grid, according to the AtlasCopco.com emergency deployment report (atlascopco.com).

If the shutdown includes planned work on the existing compressor house, coordinate the temporary supply with the wider isolation sequence. Our guide on how to plan a compressor shutdown without stopping production explains that process.

Specify Air Purity at the Point of Use

Temporary installations must meet the same air-quality requirement as permanent plant. A production line does not become less sensitive to particles, moisture or oil because its air comes from a hired compressor.

According to the JHFoster.com explanation of ISO 8573-1 (jhfoster.com), ISO 8573-1:2010 (iso.org) classifies compressed-air purity using maximum concentrations for three contaminant groups:

• Solid particles
• Water
• Total oil, including liquid oil, aerosol and vapour

The three class numbers must be stated in that order. Writing “clean air” or “food-grade air” on a hire request is not enough. Procurement should record the required ISO 8573-1 class alongside the flow and pressure duty.

The compressor is only one part of that specification. Ambient conditions, aftercooling, the dryer, filters, drains, receiver and temporary pipework can all change the quality delivered at the point of use. That explanation provides further detail on how the three contaminant classes are structured.

When ISO Class 0 Is Required

Where the process requires 100% oil-free compressed air, specify a compressor certified to ISO 8573-1 Class 0 for total oil. Sterile production, sensitive food contact and some pharmaceutical or electronics processes can fall into this category, subject to the site’s own risk assessment.

Do not treat an oil-injected compressor with downstream filters as equivalent. Filters manage oil contamination after compression. A Class 0 oil-free compressor keeps oil out of the compression process and provides a defined basis for the air-quality specification. AtlasCopco.com rental guidance (atlascopco.com) distinguishes Class Zero equipment from filtered oil-injected rental air.

Class 0 does not mean the air automatically meets every requirement for particles and water. Those two classes must still be specified. A Class 0 compressor may therefore need a desiccant dryer, particulate filtration or sterile filtration before the air reaches the process.

For food and drink production, check the current British Compressed Air Society guidance and the site’s hazard analysis. The required treatment depends on how the air contacts the product, packaging or equipment. Procurement, engineering and quality teams should agree that specification before the rental package is ordered.

Treat Breathing Air as a Separate Supply

If workers will breathe from the temporary compressed-air system, identify it as a breathing-air requirement at the quotation stage.

Process-air quality and breathing-air quality are different decisions. Breathing air needs a separate specification and testing regime.

Tell the rental provider at the quotation stage if the temporary installation will feed airline respirators, blasting hoods or other breathing apparatus. The design must then consider the compressor intake location, exhaust gases, filtration, pressure control and the number of users. A normal plant-air outlet must not be assumed suitable.

Testing should be completed at representative points of use and documented. The assessment covers contaminants including carbon monoxide, carbon dioxide, oil mist and water vapour. The BCASLimited.co.uk breathing-air testing guidance (bcaslimited.co.uk) explains the testing duties and the need to keep records.

Conditions can change after commissioning. Moving a diesel unit, altering the intake position or running vehicles near the compressor can introduce a new contamination source. Agree whether further testing is required when the layout or operating conditions change.

Design the Connections Around the Required Pressure

Temporary hose is often treated as an accessory. In practice, it can determine whether the installation works.

Long hose runs, restrictive couplings, undersized pipe and excessive bends create pressure drop. Raising the compressor discharge pressure to compensate makes the compressor work harder and can expose upstream equipment to pressure it was not selected to handle.

Ask the supplier to size the complete route from the compressor to the connection point. The design should include hose bore, total length, fittings, filters, dryer losses and the peak flow expected through each branch. Where several production areas remain live, a temporary distribution manifold may be better than a single long hose feeding the existing ring main.

Plan condensate handling at the same time. Aftercoolers, receivers, dryers and filters remove water and oil-bearing condensate from the air stream. Drain points need a safe collection route, and oily condensate must not be discharged directly to surface water or the ground.

Position the equipment on firm, level ground with enough ventilation and service access. Protect hoses from vehicles, sharp edges and hot work. If a hose crosses a traffic route, use suitable protection and include the crossing in the site’s permit and inspection arrangements.

Commission the Temporary System Before Isolation

Do not make the first production start the commissioning test. Connect and prove the temporary system while the permanent supply is still available wherever the shutdown plan permits it.

The commissioning sequence should confirm:

• The compressor, dryer and filters match the agreed specification.
• Hoses, restraints, couplings and valves are correctly installed.
• Condensate drains discharge to the agreed collection point.
• Pressure is stable at the furthest and most demanding users.
• Air-quality testing has been completed where the process requires it.
• Alarms, emergency stops and operating responsibilities are understood.
• Fuel, electrical load and service access are covered for the full hire period.
• A response plan exists for a compressor fault or loss of supply.

Record the baseline pressure and air-quality results. That gives the shutdown team something definite to compare against if a tool slows down, a process alarm appears or moisture reaches a production line.

Keep emergency contacts with the permit pack and shift handover. If the existing compressor develops a fault before the planned changeover, the air compressor repairs route may be faster than redesigning the shutdown around an unverified temporary connection.

What We Need to Specify the Rental Package

A useful quotation starts with operational information. Send us the shutdown dates, required flow and pressure, demand profile, available power, connection details, air-quality class and any breathing-air requirement. Include a site plan or photographs of the proposed equipment position and tie-in point.

Our engineers can then survey the site, verify the available utilities and specify the compressor, dryer, filtration, hoses and condensate controls as one package. We can also identify whether standby capacity is justified by the cost of losing the temporary supply.

Search Air provides short and long-term rental and hire from our depots in Leeds, Sheffield and Nottingham. Send us the shutdown programme and current compressor data, and we’ll return a specification that procurement can compare on flow, pressure, purity, power and contingency rather than hire price alone.