Why a site survey comes before mobilisation
The duty specification says what the process needs: flow, pressure, air quality, hours and duration. The site survey says what the site allows and what must change before that duty can be delivered. Both are needed. A correctly sized compressor cannot help if the trailer cannot get through the gate, the electrical feeder is too small, or the only tie-in is a 1-inch valve on a 4-inch main.
Most avoidable delays on rental jobs come from things a short survey would have found: a low overhead pipe bridge, a soft unloading area, a locked valve, a missing flange, a generator cable that does not reach. A survey is cheaper than a lost day with a crane and a crew waiting.
A survey should produce decisions, not just photographs. Its outputs are a proposed layout, confirmed interface details, a route for the hoses or pipe, any measurements taken and a list of actions with the person responsible for each.
Prepare around the operating case
Before visiting, review the duty specification: the required flow and pressure at the delivery point, air quality, operating hours, duration and any need for standby. Find out which permanent equipment stays in service and which will be isolated during the hire.
Ask for drawings, connection details and recent operating data, and note their dates. An old drawing helps orientation, but it does not prove that a valve, route or feeder still exists as drawn. Arrange the people you will need on the day: the plant engineer, an electrician, the safety officer and someone who can open locked areas.
The survey may be a visit by our service engineer, or, for simpler jobs, a structured set of photographs, measurements and answers from your team that we review remotely.
Walk the complete installation path
Start where the delivery vehicle will enter and follow the equipment’s path all the way to its final position. Check:
- Gate width and height, turning space, and any weight or height limits on site roads and bridges.
- Overhead obstacles: pipe racks, cable trays, power lines and canopies.
- Ground conditions along the route and at the unloading point.
- Whether a crane, forklift or towing vehicle is needed, and where it would stand.
- Restricted hours for heavy vehicles, inside the site and on public roads outside.
Then walk the same path in reverse. Equipment has to come out at the end, possibly after other construction has closed the original route. Transport is covered in more detail on transport and mobilisation.
What does a temporary air site survey check?
| Area | What we check | Why it matters |
|---|---|---|
| Footprint | Space for compressors, dryers, receiver, generator and fuel, with service clearances | Machines must be maintainable, not just placeable |
| Ground | Level, firm, drained surface; no trenches or drain covers below | Stability and correct oil and separator levels |
| Cooling and exhaust | Open air paths, no recirculation, exhaust away from people and intakes | Avoids high-temperature trips and complaints |
| Intake quality | Distance from dust, chemical vents and engine exhaust | Protects the machine and the air quality |
| Air connection | Location, size, type and condition of the tie-in; isolation valves | Defines the delivery boundary and pressure drop |
| Route | Hose or pipe length, crossings, supports and protection | Pressure drop and safety |
| Treatment and condensate | Dryer position, drain points, condensate disposal | Air quality and environmental compliance |
| Power | Supply point, capacity, protection and cable route, confirmed by the site electrician | Electric compressors and dryers need adequate supply |
| Fuel and service access | Route for refuelling and service vehicles; fuel storage position | Avoids stoppages and unsafe refuelling |
Cooling air, exhaust and the hot season
Look at where cooling air will come from and where hot air and exhaust will go. Walls, containers and other machines close to the compressor cause hot-air recirculation; in Indian summers, with afternoon temperatures of 40–45 °C, and above 45 °C on open sites, this is a common cause of high discharge-temperature trips. Note the prevailing wind, nearby building air intakes and any occupied areas downwind. On dusty sites, note sources of dust upwind of the intended position.
If equipment must go indoors or under a roof, record the opening sizes and any ventilation, so that heat removal can be checked. Our placement and community considerations page explains how to compare positions.
Confirm the air connection and route
The tie-in is where most surprises are found. At the connection point, record:
- Pipe size, material and the type of connection available (flange, thread, coupling).
- Whether an isolation valve exists, works and can be locked.
- Whether a non-return valve is needed to stop air flowing back into the temporary system or into isolated permanent compressors.
- Operating pressure of the permanent system, so the temporary station can be set correctly.
- Who will make the connection and whether welding or hot work permits are needed.
Then trace the route the hoses or temporary pipe will take. Measure the length, count the bends and couplings, and note road crossings, walkways and places where hoses could be crushed or trip people. Long routes need larger hoses to keep pressure drop acceptable, because raising discharge pressure to compensate costs roughly 7% more power for each extra bar. See hose manifolds and distribution and tie-in and changeover.
Treatment, condensate, power and fuel
Where air quality matters, note where the dryer and filters will stand, how condensate will be drained and where it will go. Oil-injected compressors produce oily condensate that should be separated before disposal, according to site rules.
For electric compressors and dryers, the site’s electrical team must confirm the available supply, the protection and the cable route; do not assume that a nearby board has spare capacity. Record the voltage, the available current and the distance. If no suitable supply exists, a diesel compressor or a generator will be needed; our electrical supply page explains the choices.
For diesel units, check where fuel will be stored, how it will be delivered and whether a bund or drip tray is required. Refuelling and service vehicles need a safe route to the machines throughout the hire.
Measure where observation is not enough
Some questions cannot be answered by looking. If the hire is to support or replace permanent compressors, it helps to measure:
- Pressure at the compressor and at key points of use, over a working shift.
- Flow, where a meter can be fitted or the compressors’ load hours are logged.
- Pressure dew point after the existing dryer.
- Ambient and compressor room temperatures at the hottest time of day.
These measurements confirm or correct the duty specification and often show whether part of the problem is distribution or treatment rather than capacity.
Photographs, sketches and shared dependencies
Take photographs that can be traced to a position on the site sketch: the gate, the route, the proposed position from several sides, the tie-in, the electrical board and any obstacles. Include a tape or object for scale where dimensions matter.
Also look for shared dependencies. If the temporary station and the permanent plant rely on the same electrical feeder, the same dryer or the same main, one failure can affect both. Record these, so that the redundancy plan can deal with them.
Turn findings into actions
The survey report should be short and practical. For each finding, state what must happen, who will do it and by when. Typical actions are:
- “Client to prepare level hardstanding 8 m × 5 m at position A before delivery.”
- “Client’s mechanical contractor to fit a 3-inch flanged branch with isolation valve on the main near the boiler house.”
- “Client’s electrician to confirm feeder capacity at board DB-4; if inadequate, a generator will be supplied.”
- “Hose route to cross the internal road at gate 2 using a protective ramp.”
Mark any uncertainty clearly and explain what it affects, for example “tie-in valve condition unknown; changeover cannot be confirmed until tested”. If the site changes before mobilisation, update the survey rather than relying on the old one.
How Reddy Compressors helps
Reddy Compressors has supplied, rented and serviced compressors since 2002 from Tarnaka, Secunderabad. We are an independent multi-brand specialist for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Doosan and other makes, not an authorised dealer. We have tie-ups with all major and reputed brands. Our rental fleet covers 50–2,000 cfm at 2–30 bar, diesel and electric, and more than 20 service engineers and technicians cover Telangana and Andhra Pradesh, with supply across India.
For site surveys we:
- Visit sites in Telangana and Andhra Pradesh, or review photographs and measurements sent by your team for sites elsewhere.
- Propose a layout for compressors, treatment, receiver, generator and fuel.
- Size hoses or temporary pipe for the route, and specify the tie-in arrangement.
- List what we will provide and what the site must prepare, with clear responsibilities.
- Arrange generators through Reddy Generators, under the same management, where power is needed.
On one power-plant project we delivered a 400 cfm electric compressor and a 160 kVA generator and commissioned them within one to two days of arrival, because the site details had been settled beforehand.
What to send us
- Site address, contact person and the hours when access is possible.
- Required flow, pressure and air quality, and the hire duration.
- Photographs of the gate, route, proposed position, tie-in point and electrical board.
- A sketch or drawing with approximate distances.
- Details of the permanent compressors and dryers, if the hire supports them.
- Any site rules on permits, working hours, noise or vehicles.
Frequently asked questions
Do I need a site survey for compressor rental?
For a single portable compressor on an open construction site, a few photographs and answers may be enough. For any hire that connects to plant pipework, needs a dryer, uses site power or must run continuously, a proper survey is worth it. It finds access, connection and power problems before equipment and crews arrive, when they are cheaper to fix.
What information should I prepare for a compressor site survey?
Prepare the required flow, pressure, air quality, hours and duration; drawings or sketches of the site; details of the tie-in point and permanent compressors; the electrical supply available; and any site rules on permits and working hours. Arrange for an electrician and someone who can open locked areas to be present on the day.
Can a site survey be done using photographs?
Yes, for simpler jobs or distant sites. Send clear photographs of the gate, route, proposed position, tie-in and electrical board, with measurements and a sketch showing distances. We review them and ask follow-up questions. A visit is better where the tie-in, power or access is complicated, or where measurements of pressure or flow are needed.
What is a tie-in point for temporary compressed air?
It is the place where the temporary air supply connects to the plant’s permanent pipework. The survey records its size, connection type, isolation valve and condition, and whether a non-return valve is needed. It usually also marks the delivery boundary, where the supplier’s responsibility for flow and pressure ends and the plant’s begins.
Why does a compressor survey check the electrical supply?
Electric compressors and dryers draw significant current, especially on starting, and a nearby board may not have the spare capacity or protection needed. The site’s electrician should confirm the supply point, rating and cable route. If the supply is inadequate, a diesel compressor or a generator is needed, which changes the layout and fuel arrangements.
How long is a site survey valid?
Only as long as the site stays the same. Construction, new equipment, road changes or changes in the permanent plant can make an earlier survey wrong. If weeks have passed or the site has changed, update the key points, especially access, the tie-in and power, before mobilisation, rather than relying on old photographs.
Related pages
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.