What does the shutdown take out of service?
The work scope decides the temporary air path. Different shutdowns remove different parts of the system:
| Shutdown scope | What stays available | What the rental package must provide |
|---|---|---|
| Compressor overhaul | Dryers, receivers and header | Compressed air into the existing treatment or receiver |
| Dryer replacement or service | Compressors and header | Temporary drying and filtration, sometimes generation too |
| Header or pipework modification | Possibly nothing downstream | Air delivered to a temporary connection beyond the work area |
| Electrical shutdown | Mechanical plant, but no power | Diesel or generator-fed air, independent of the site supply |
| Full plant turnaround | Little or nothing | Maintenance air, essential process air and restart air |
Mark the equipment under maintenance and the users that must stay live on the same drawing. A temporary connection on the wrong side of the isolation boundary either fails to supply the users or pushes pressure back into the maintenance area.
Which users stay live during a shutdown?
A shutdown rarely means zero air demand. Typical users that keep running include:
- instrument air for valves, analysers and safety systems that stay energised;
- packaging, utilities or production lines outside the shutdown scope;
- effluent and water treatment plant;
- maintenance tools – impact wrenches, grinders, needle scalers, blasting and painting;
- cleaning, drying and purging of equipment;
- restart demand, which is often higher than normal as lines are pressurised and equipment comes back.
Each needs its own pressure, flow and quality. Instrument air and pharma or food process air may need dryers and oil-free supply; maintenance tools may run happily on aftercooled air with a separator. Do not size the whole package to the most demanding user if a separate branch can serve it.
Build a phase-by-phase duty
Demand changes through the shutdown. Split it into phases and size for each:
- Before isolation – rental machines running alongside the plant, proving they can carry the load.
- Isolation and drain-down – plant compressors stopped, temporary air carrying essential users.
- Maintenance window – essential users plus maintenance tools, often peaking in day shifts.
- Testing and recommissioning – permanent equipment being run up while temporary air still supports the plant.
- Restart and handback – production returns; temporary air stays as cover until the plant is stable.
The rental package must meet the highest phase, with spare capacity if the air is critical. Where one machine failing would stop essential users, plan for one machine more than needed, so the 300-hour service or a fault does not cause an outage.
Utilities the shutdown may remove
A site survey done during normal operation can mislead. During the shutdown, check whether you will still have:
- electrical supply at the panel the rental machine was going to use;
- cooling water, drains and condensate disposal routes;
- fuel tanker access, if roads or yards are taken up by cranes and scaffolding;
- lighting and communications at the rental machine location for night shifts.
An electric rental compressor connected to the electrical system under maintenance provides no continuity. For electrical shutdowns and substation work, use diesel portables or a generator-fed package. Reddy Generators, under the same management, can supply temporary generators for the shutdown alongside the air.
Planning timeline
| Stage | Key actions |
|---|---|
| Early planning | Define scope, live users and phase demand; agree air quality; choose diesel, electric or mixed |
| Site survey | Agree machine location, tie-in point, hose routes, fuel or power, drainage and access |
| Before mobilisation | Confirm package, standby, operators, refuelling and service plan; prepare tie-in fittings |
| Mobilisation | Deliver, position, connect, start and run in parallel with plant air |
| Changeover | Isolate plant air to the agreed sequence; confirm pressure at the users |
| Return to service | Run permanent plant up, share load, then remove temporary air in stages |
Book early. Shutdown seasons often coincide across industries, and large or oil-free machines are in demand at the same time. Tie-in fittings and valves on the plant header are often easiest to install during an earlier short stop, so the main shutdown is not delayed waiting for them.
Changeover and isolation
The changeover is the moment of most risk. Keep it simple and written down:
- Agree a tie-in point with isolation and a non-return valve, outside the maintenance boundary.
- Run the temporary package in parallel with the plant before stopping plant compressors.
- Follow the site’s isolation and permit-to-work procedure; the plant owns the isolation, not the rental supplier.
- Check that nothing can back-feed pressure into the isolated equipment.
- Name one person responsible for the changeover and one contact on the rental side for each shift.
What if the shutdown overruns?
Shutdowns overrun more often than they finish early: parts are delayed, inspection finds more work, or recommissioning takes longer. Plan for it:
- agree in advance how hire extends, and whether a longer hire changes the package;
- keep enough fuel, filters and oil on the service plan to cover extra days;
- schedule the 300-hour service so it does not fall on the restart day;
- keep the temporary air on site until the permanent plant has run stably under full load.
Air quality during a shutdown
Temporary air feeding the plant header must not contaminate it. Hot, wet or oily air entering pipework that normally carries dried air can cause problems long after the shutdown ends. Match the temporary treatment to the normal plant specification: aftercooler and separator as standard, a refrigerated dryer (typical pressure dew point around +3 °C) or desiccant dryer (typically −20 °C or −40 °C) where the plant uses one, and filtration to the ISO 8573-1 class the process needs. Pharma, food and electronics plants usually need oil-free machines for Class 0 air. We have supplied compressors on breakdown to leading pharmaceutical manufacturers in Hyderabad and Telangana, and the same air-quality discipline applies to planned work.
Running the temporary package through the shutdown
Once changeover is complete, the temporary package becomes the plant’s air supply and should be run like one. Agree a simple daily routine with the shift teams:
- log discharge pressure, header pressure, discharge temperature and running hours at each shift handover;
- check fuel level and refuelling times on diesel units, or electrical connections and cooling airflow on electric units;
- drain separators and check automatic drains, especially in humid or monsoon conditions;
- check dryer dew point indication and filter differential pressure where treatment is fitted;
- walk the hose route for leaks, damage and vehicle crossings, and keep whip checks in place;
- report any safety shutdown – high discharge temperature, low engine oil pressure, high coolant temperature – instead of simply restarting.
Keep the plant’s own maintenance team informed of any change to the temporary arrangement, so that isolation boundaries and permits remain correct as work progresses.
How Reddy Compressors helps
We supply temporary air for planned shutdowns from our own rental fleet: diesel and electric, oil-injected and oil-free, 50 to 2,000 cfm and 2 to 30 bar. As an independent multi-brand business we rent, sell and service ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other machines, and we also overhaul and service permanent compressors – so the same team can often handle both the rental cover and the work that caused the shutdown.
- We help define the phased demand, tie-in point and standby before the shutdown date.
- We supply compressors, dryers, filters, hoses and manifolds, with operators where needed.
- We service hire machines every 300 running hours and keep a contact on each shift.
- Our 20-plus service engineers and technicians cover all of Telangana and Andhra Pradesh, with supply across India and project-based support where feasible.
Reddy Compressors, Srinilayam, 12-13-200, First Floor, Street No. 1, Tarnaka, Secunderabad 500017. Phone +91 99590 60718 or +91 92468 88812; email reddycompressors@gmail.com.
What to send us
- Shutdown dates, duration and what is being taken out of service
- Users that must stay live, with pressure, flow and air quality
- Expected maintenance tool demand and restart demand
- Proposed tie-in point and a sketch or photo of the header
- Power and fuel availability during the shutdown
- Whether operators or a generator are needed
Frequently asked questions
How early should I book rental compressors for a plant shutdown?
As early as the shutdown dates are known. Early booking gives time for a site survey, agreeing the tie-in point, preparing fittings and arranging dryers, oil-free machines or generators if needed. Many plants plan shutdowns in the same seasons, so larger and specialist machines are in demand together. We do not quote fixed lead times; tell us your dates and we will confirm what we can arrange.
How much air do I need during a compressor house shutdown?
Add up the users that stay live, maintenance tools in use at the busiest time, and restart demand, which is often higher than normal. Check existing compressor loading hours or flow meter readings for real figures. Size the rental package for the highest phase, with one spare machine if essential users must never lose air.
Can a rental compressor connect to my plant air line during maintenance?
Yes, through a temporary hose and manifold into a tie-in point with isolation and a non-return valve, located outside the maintenance boundary. Many plants install a permanent tie-in connection during an earlier short stop to make future shutdowns easier. The changeover sequence and isolation must follow your site’s permit-to-work procedure.
Should I use diesel or electric rental air for a shutdown?
If the shutdown includes electrical work, or the rental machine would be fed from the system being maintained, use diesel portables or a generator-fed package. If a separate, reliable feeder stays live and the air is needed inside a building, electric machines may be quieter and simpler. Many shutdowns use a mix of the two.
What happens if my shutdown runs longer than planned?
Agree the extension terms in advance and keep the temporary air on site until the permanent plant runs stably at full load. Plan the service so the 300-hour oil change and filter replacement do not fall on restart day, and make sure fuel or power arrangements cover extra days. A short extension is much easier to handle when it has been discussed beforehand.
Do I need a dryer with temporary shutdown air?
If the temporary air feeds a header that normally carries dried air, yes. Wet air entering dry pipework causes condensate, corrosion and instrument problems after the shutdown. Match the temporary treatment to your normal specification: refrigerated or desiccant drying and filtration to the required ISO 8573-1 class, and oil-free machines where Class 0 air is specified.
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Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.