The finder
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What a service kit is, kit by kit
Makers package service parts in tiers, and although the names differ from one make to another, the logic is the same across the industry. The table below is the structure the finder uses.
| Tier | Usual name | What is in it | What it is for |
|---|---|---|---|
| Minor | A kit, 2,000-hour kit, filter kit | Air intake filter element, oil filter, compressor oil; on portable diesel machines the engine’s oil, oil filter, fuel filters and air filter | Keeps dust out of the airend and clean oil in it; the most frequent service and the cheapest |
| Standard | B kit, 4,000-hour kit, separator kit | The minor kit plus the air–oil separator element with its gaskets, the scavenge line O-ring, minimum-pressure valve seals | Separator elements load up with oil-borne dirt and their differential pressure rises; a tired separator passes oil into the air and costs energy |
| Major | C kit, 8,000-hour kit, overhaul kit | The standard kit plus the inlet (unloader) valve repair kit, minimum-pressure valve repair kit, thermostatic valve element, belts or coupling element, shaft seal where accessible, drain valve kits, sensors as found | Restores the valves and controls that decide loading, pressure and oil temperature; usually a planned day’s stop |
| Airend or bearing review | Not a kit | Vibration and oil analysis, bearing clearance checks, then a bearing kit, an airend exchange or a rebuild | At 16,000–24,000 hours on a screw compressor, sooner on a piston machine, the question is the airend, and fitting kits to a failing airend is money spent twice |
Oil-free screw compressors have no separator, so their standard kit is the minor kit and their major kit centres on the inlet, blow-off and check valves and the cooler drains. Piston compressors replace the separator logic with valve plates and, at longer intervals, rings and wrist-pin bushes. Vane compressors add the vane set at the major interval. Portable diesel compressors have two machines in one canopy, and the engine’s 250 to 300 hour service is the pacing interval; the compressor side follows its own bands.
How the intervals are decided, and why India moves them
A maker’s schedule is written for a reference condition: clean air, moderate temperature, a defined duty. Almost no compressor in Telangana or Andhra Pradesh works in that condition. Three factors move the intervals, and the finder applies them.
| Factor | What it does | Typical effect on the interval |
|---|---|---|
| Dust (workshop, mill, textile, cement area) | Loads the intake filter early; dust that reaches the airend wears it and contaminates the oil | Air filter interval cut to roughly 60 percent; oil interval cut slightly |
| Heavy dust (quarry, mine, rig, crusher) | Fills intake filters in weeks, coats coolers and raises oil temperature | Air filter interval cut to 40 percent; oil and separator intervals cut to about 75 percent |
| Humidity and coastal air | Water condenses in the oil, emulsifies it, corrodes separators and receivers | Oil and separator intervals cut to about 80 percent; drains must work |
| Heat (room above 40 °C in summer) | Oil oxidises faster, varnish forms, coolers that were marginal trip | Oil interval cut to about 75 percent; thermostatic element and cooler cleaning move into the routine |
| Duty (hours per year) | Decides how many kits the year will need and whether the major kit falls inside it | 1,200 hours for intermittent use up to 8,000 for continuous running |
A compressor in a rice mill at Nizamabad, a granite yard at Chimakurthy or a coal-belt workshop at Kothagudem is therefore on a different calendar from the same model in an air-conditioned laboratory, and the finder’s bands reflect that. The final numbers are still set from inspection: the air filter is checked at every service and changed on condition, and the first service after installation sets the real intervals from what the filters and oil look like.
Reading the finder’s result
The finder gives a kit tier for now, based on the hours since the last service against the adjusted bands; where the hours are unknown it assumes the full major kit, because a machine with no service history is treated as overdue. It lists what the kit should contain for the type, adds the parts that usually cure a stated symptom, estimates the oil volume from the power, and lays out a twelve-month plan from the duty so that the year’s kits can be bought once. It also compares the total hours with the typical airend review point for the type and says plainly when the next step is an inspection rather than a kit.
The symptom logic is worth explaining. High temperature points to the thermostatic element and the coolers, not to the oil alone. Oil in the air line points to the separator and the scavenge line. Low pressure or slow pump-up points to the inlet valve, the minimum-pressure valve and the intake filter, and the pump-up test measures how far capacity has fallen. Water in the air points to the dryer and the drains, which have their own service kits. New noise or vibration points to bearings, and the finder refuses to prescribe a kit for it: a kit fitted to a failing airend is wasted.
What a wrong or poor-quality kit does
The parts in a kit touch the airend directly, and the damage from a wrong part is slow and expensive.
- An air filter of the wrong grade or a poor seal lets fine dust through; the airend’s rotors and bearings wear, the oil turns grey, and the separator loads early.
- A separator with the wrong micron rating or a poor gasket passes oil into the air line, fouls dryers and tools, and raises the pressure drop so that the motor works harder for the same air.
- An oil of the wrong type, or a mineral oil where a synthetic was specified, oxidises in a hot room, forms varnish on the thermostatic element and the oil cooler, and shortens the separator’s life.
- A thermostatic element with the wrong opening temperature runs the oil too cold (water condenses in it) or too hot (it oxidises); both end in a failed airend.
- Valve kits with the wrong seals leak, and the machine hunts between load and unload.
- Kits sold by the name on the canopy rather than by the component maker’s number: the same model can carry two or three makers’ filters and separators over its production life, and only the numbers on the fitted parts, or the serial number, settle which.
What to photograph for an exact match
The finder’s last line lists the photographs, and they are the fastest route to the right kit for any make. The nameplate gives model, serial number, year and pressure; the serial number settles which component makers the machine left the factory with. The motor or engine plate gives the power and, for diesel machines, the engine model that sets the engine kit. The fitted filters and separator carry numbers that identify the current parts, and where a previous owner fitted substitutes, those numbers show it. The hour meter and controller display give the hours and any fault code. The oil can or drum shows what is in the sump now, because mixing oils is itself a fault. The spare parts page explains how we identify parts from these photographs, and the find-my-part page sets out the steps.
A worked example: A two-shift workshop screw compressor
A fabrication workshop at Patancheru runs a 37 kW oil-injected screw compressor on two shifts in a dusty shed. The hour meter reads 9,200 hours and the last service was 2,300 hours ago; there is no symptom. The finder scales the typical bands for dust: the minor interval falls from 2,000 to about 1,200 hours, the separator interval from 4,000 to about 3,600, the major from 8,000 to about 7,200. At 2,300 hours since service the minor band has been passed and the separator band has not, so the kit due now is the minor kit: air filter, oil filter and oil, with the separator’s differential pressure checked and the separator changed at the next service if it has risen. The oil volume is estimated at 9 to 13 litres per fill, to be confirmed from the nameplate. At about 4,200 running hours a year the plan is four minor kits, two separators and the major kit falling inside the year, which the workshop buys together with the year’s oil. At 9,200 hours the airend is well short of its typical review point, so no inspection is needed beyond the service engineer’s check at the major kit. Had the workshop reported high-temperature trips, the finder would have added the thermostatic element and a cooler clean to the kit; had it reported oil in the air line, the separator would have moved into this service.
A second example: A rig compressor in the drilling season
A drilling contractor’s 25 m³/min portable diesel compressor has 6,400 hours on the meter and 320 hours since the engine was last serviced, working on a quarry bench at Chimakurthy with no symptom. The finder treats the engine’s 300-hour service as the minor band and, for heavy dust, cuts the compressor air filter interval to 40 percent of its reference; the kit due now is the engine kit (engine oil and filter, fuel filters, engine air filter) with the compressor air filter, and the compressor oil and separator fall due at the next band. At roughly 2,200 hours a season the contractor needs about seven engine kits, two compressor oil and separator changes and, inside the season, the major kit with its valve kits, thermostatic element and belts, which is why the drilling season checklist tells contractors to put the season’s kits on the truck in October.
Kits, maintenance contracts and planned stops
A kit bought and fitted on time is cheaper than the same kit fitted after a trip, and a maintenance contract is the arrangement that makes the timing automatic: the service engineer carries the kit for the exact model, the air filter is changed on condition, the separator’s differential pressure is logged, and the major kit is a planned stop on a date rather than a breakdown on a Saturday. The AMC page sets out the structure; the service kits page explains how kits are matched to a model and serial; and the screw compressor service page explains what a service visit covers.
How Reddy Compressors helps
We supply service kits for every major make of compressor, matched to the model and serial number rather than the canopy name, and we fit them across Telangana and Andhra Pradesh with more than 20 service engineers and technicians working from Tarnaka in Secunderabad. We are an independent, multi-brand business with supply tie-ups across all major makes, and we say plainly when the right next step is an inspection rather than a kit. Send the photographs the finder lists and a service engineer will confirm the kit, the oil and the interval for your machine and its conditions.
What to send us
- The photographs the finder lists: nameplate, motor or engine plate, fitted filters and separator, hour meter and controller, the oil in use.
- The hours since the last service and what was changed then, if known.
- The site conditions and the duty: dust, heat, humidity, shifts.
- Any symptom: trips, oil in the air, low pressure, noise, water.
- Where the machine is, so that fitting is planned with the kit.
Frequently asked questions
Does the finder give exact part numbers?
No. It gives the kit tier, its contents, the oil volume estimate and the plan for your type and conditions. The part numbers depend on the model, the serial number and the component makers fitted, which the photographs settle; send them and we match the exact kit.
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Short explainers on this topic
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Can I use kits for a make you did not supply?
Yes. We supply service kits for every major make of screw, piston, oil-free, portable diesel and vane compressor, matched from the nameplate and the fitted parts.
Why does the finder shorten the intervals for my site?
Because dust, heat and humidity shorten the life of filters, oil and separators, and a maker’s schedule is written for a cleaner, cooler reference condition. The bands shown are typical for Indian sites; the first service sets the real ones from inspection.
I do not know the hours since the last service. What does the finder assume?
That the full major kit is due. A machine with no service history is treated as overdue, and the service engineer inspects it as such.
My compressor is noisy. Which kit fixes it?
None. Noise and vibration point to bearings or the airend; the finder refuses to prescribe a kit for them and recommends an inspection with vibration and oil analysis first.
How much oil does my compressor take?
The finder estimates from the power, but the nameplate or the manual gives the exact sump volume, and the photograph of the oil in use tells us whether the type is right. Mixing oils is itself a fault.
Is a cheaper kit from a general supplier acceptable?
Only if its filters, separator and oil match the fitted parts’ specifications: grade, micron rating, seals, oil type. The section above lists what a wrong part does to the airend over the months after it is fitted.
Can the kit be fitted by my own fitter?
For the minor kit, often yes, with the oil and filters supplied and the procedure explained. The standard and major kits involve the separator, the valves and the thermostatic element, and most customers have a service engineer fit them, under a maintenance contract where the machine is critical.
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.