Why service is by the hour meter
A screw compressor’s oil, separator and filters wear by running hours and by the dust and heat they run in, not by the calendar. A machine that runs 20 hours a day reaches a 2,000-hour service in four months; one that runs two shifts in a clean room may take a year. In a Hyderabad summer, with ambient air at 40–45 °C and dust on every surface, the oil also ages faster than the interval suggests. We read the hour meter, look at the oil and the differential pressures, and service to the machine’s condition and the manufacturer’s schedule, whichever comes first.
What each service includes
| Service | Typical interval | What is done |
|---|---|---|
| Routine (A) | Every 2,000 h or as specified | Air filter, oil filter, oil change, condensate drain check, belt tension or coupling check, cooler clean, control and safety-valve check, readings recorded |
| Intermediate (B) | Every 4,000 h or as specified | All of A plus separator element, inlet valve and minimum-pressure valve inspection or kit, thermostatic valve check, electrical terminations, motor greasing |
| Major (C) | Every 8,000 h or as specified | All of B plus airend bearing assessment (vibration, play, oil analysis), coupling or belts, cooler core clean, sensor calibration, VSD/drive checks |
| Airend overhaul | By condition, typically 20,000–40,000 h | Workshop rebuild or exchange airend; see the airend rebuild, exchange and replacement guide |
Intervals vary by make and model; the figures above are typical and we follow the manual for your machine. Oil-free screw machines have their own schedules for the element and gearbox, which we also cover.
Which machines
Oil-injected and oil-free rotary screw compressors from about 7.5 hp to several hundred horsepower, fixed-speed and variable-speed, belt-driven and direct-drive, with their dryers, filters and receivers. All major makes supplied in India are covered; parts for the common ones are stocked, the rest are sourced against the serial number. The brands we support page lists the makes and the service kits page explains how a kit is matched to a model and serial range.
Signs your screw compressor is due, or overdue
- Discharge temperature creeping up, or a high-temperature trip on hot afternoons
- Pressure band wandering, or the machine loading and unloading more often than it used to
- Oil in the downstream filters or at the tool, or oil level dropping
- Differential pressure across the separator rising
- Service lamp or hour-counter warning on the controller
- Oil darkened, smelling burnt, or showing varnish on the sight glass
Any of these on a machine that matters to production is a reason to book a visit, not to wait for the next scheduled service.
AMC, or service on call?
For a single workshop machine, service on call works. For a plant that depends on its compressors, an annual maintenance contract gives planned visits with parts on the day, readings recorded over time, and breakdown support on agreed terms. The compressor AMC page compares comprehensive and non-comprehensive contracts.
Buying, replacing or adding a machine
Because we sell, rent and service, the service engineer can tell you when a machine has reached the point where overhaul costs more than it is worth, and what a replacement – new, used or refurbished – would cost to buy and to run. For long-term projects we supply brand-new machines of the make that suits the duty. The overhaul versus replacement decision tool puts the numbers side by side.
What happens inside a screw compressor between services
Understanding why each part is changed makes the schedule easier to keep. In an oil-injected screw machine the oil does three jobs at once: it seals the gap between the rotors, it carries away most of the heat of compression, and it lubricates the bearings. As it ages it oxidises, its viscosity drifts, and it begins to leave varnish on hot surfaces. Varnish on the thermostatic element makes it open late; varnish in the separator raises the differential pressure; oxidised oil raises the discharge temperature. The oil filter protects the bearings from the debris of this process, and the separator element pulls the oil mist back out of the air before it reaches the plant. Each has a life measured in hours at a given temperature, and each shortens that life for the others when it is left too long. That is why the service kit is a set, not a menu.
Reading the machine’s own signals
A screw compressor reports its condition continuously to anyone who reads the controller and the gauges. The three readings that matter most, and what they mean:
| Reading | Healthy | Watch | Act |
|---|---|---|---|
| Discharge (element outlet) temperature at full load | Within the manufacturer’s band, typically 80–95 °C depending on model and ambient | Rising week on week at the same ambient | Approaching the trip point; or a sudden jump after a hot day |
| Separator differential pressure | Low and steady after a new element | Rising toward the manufacturer’s limit | At the limit, or oil appearing downstream |
| Load/unload cycling | Steady pattern matched to demand | Cycling much faster than it used to with no change in demand | Short cycling that risks the motor and wastes energy; usually a leak, a valve or an undersized receiver |
Recording these at every service, and asking the operator to note them weekly, turns servicing from a calendar event into condition monitoring. It is also how an airend problem is caught at the bearing-noise stage rather than the seizure stage.
Oil: The decision that decides the rest
Most premature separator failures, varnish problems and bearing complaints trace back to oil: the wrong type, a mix of types, or a change interval set for a European ambient and applied in a 45 °C Indian summer. Mineral oils have a short life at high discharge temperatures; synthetic oils last longer and resist varnish, and are usually the economical choice for a machine that runs long hours or hot. Changing from one oil type to another needs a flush, not a top-up. Food, pharmaceutical and some electronics plants need food-grade or specific oils. We specify the oil for your machine and your ambient and record it on the service sheet, so nobody tops up with the wrong drum. The lubricants and lubricant and oil analysis pages cover the choice and the testing.
Oil analysis and airend life
For machines above about 50 hp, or any machine the plant cannot do without, periodic oil analysis is cheap insurance. A sample at each major service, tested for viscosity, oxidation, water and wear metals, shows an airend bearing deteriorating thousands of hours before it fails, and lets the overhaul or exchange be planned for a shutdown rather than forced by a breakdown. The airend rebuild, exchange and replacement guide explains the choice between rebuilding the existing airend, fitting an exchange unit and replacing the machine.
Servicing in Hyderabad’s conditions
The manufacturer’s interval assumes clean, cool intake air. In an industrial estate in summer the compressor room may be at 45 °C, with the cooler drawing in dust and the intake filter loading in weeks. Practical adjustments we make for machines here: cooler cleaning at every visit, not just at the major service; a pre-summer check of the thermostatic valve and oil condition in March; intake filter inspection between services in dusty plants, with a pre-filter where the environment justifies it; ventilation checks, because a compressor room that recirculates its own hot exhaust air adds 10 °C to every reading; and dryer and drain checks before the monsoon so that water does not reach the plant in July. The compressor room ventilation worksheet shows how much air a room needs.
Variable-speed machines
VSD screw compressors need the same mechanical service plus attention to the drive: cooling fans and filters on the drive cabinet, terminal tightness, a check of the motor insulation and bearings, and confirmation that the pressure band and ramp settings still match the plant’s demand. A VSD machine running mostly at the top of its speed range is telling you the plant has outgrown it; one running mostly at the bottom is short-cycling in disguise. We read the drive’s hour and speed histogram at the major service and tell you what it says. The VSD compressors page explains the trade-offs.
Mixed fleets and multi-compressor stations
Plants with two or more machines of different makes gain most from one independent service partner: one schedule, one set of records, one engineer who knows the whole station. At service time we also check the sequencing, so that the machines share the load sensibly and the VSD unit does the trimming rather than fighting a fixed-speed machine for the band. The controls and sequencing guide explains the settings that matter.
A worked example
A plastics moulding unit in Pashamylaram runs a 75 hp fixed-speed screw compressor and a 40 hp VSD machine around the clock, with an older 30 hp piston unit as standby. The 75 hp machine was serviced on the calendar by the previous provider – once a year – and had reached 6,800 hours since its last oil change, with the discharge temperature sitting 8 °C above its band every afternoon. On our first visit: oil, filters and separator changed, cooler core cleaned, thermostatic element replaced, the controller’s service counter reset to 2,000-hour intervals, and oil samples taken from both screw machines. The sequencing was reset so the VSD unit trims and the 75 hp machine carries the base load. The temperature came back into band; the oil analysis on the VSD machine showed early bearing wear, so an airend exchange was scheduled for the Diwali shutdown instead of waiting for a failure. The plant now runs on a 2,000/4,000/8,000-hour schedule under an AMC, with readings recorded at each visit.
What a service visit looks like from your side
You receive a date based on the hour meter; the engineer arrives with the kit matched to the model and serial range; the machine is isolated and depressurised safely; the work is done and the readings recorded before and after; the sheet is signed and a copy left with the machine; and the next service hour is written on it. Parts replaced are shown to you on request. If anything beyond the scheduled work is found, it is quoted before it is done.
How Reddy Compressors helps
Independent multi-brand specialist since 2002; more than 20 service engineers and technicians across Telangana and Andhra Pradesh; service kits and common parts in stock; own workshop for airend and engine work; rental fleet for cover during repairs.
What to send us
- A photo of the nameplate and the hour reading
- When the machine was last serviced and what was done
- Any symptoms you have noticed
- For a mixed fleet, a list of machines with these details; WhatsApp 99590 60718
Frequently asked questions
Do you service all makes of screw compressor?
Yes. We are independent and service every major make supplied in India, with parts matched from the serial number.
Watch
Short explainers on this topic
Slide-by-slide engineering explainers from Reddy Compressors. More in the video library.
Should I use genuine or compatible parts?
Either can be right. For airends, controllers and drives we normally recommend genuine; for filters, separators and oil, good compatible parts are often the sensible choice. We explain the trade-off for each part.
What oil should my screw compressor use?
The grade and type the manual specifies for your machine and ambient. Mixing oils or using the wrong type is a common cause of varnish and separator failure; the lubricants page explains.
How long does a routine service take?
Typically a few hours on site for a routine service; longer for a major service or if the coolers need a full clean.
Do you service compressors outside Hyderabad?
Yes, across Telangana and Andhra Pradesh and districts within about 300 km of Hyderabad; further afield on a project basis.
Can you take over a machine that another company has been servicing?
Yes. We start with a full inspection and readings, bring the schedule onto the hour meter, and keep the records from that day.
Do you service oil-free screw compressors?
Yes, including element, gearbox and cooling checks on the schedule those machines need.
Can you supply and fit the oil only?
Yes, though a filter change with the oil is almost always the right thing to do; we will say if it is not.
How do I know when my machine is due?
The hour meter against the last service date on the sheet, or the controller’s service counter. Send a photo of either and we will tell you.
Related pages
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 4 November 2026. How our engineering content is reviewed.