Why the season is won before it starts
Drilling demand follows water. From November the ground is dry enough to move a rig, farmers and institutions want bores before the heat, and contractors run their rigs as hard as the season allows. By March the same rig faces 42 °C afternoons, a water table that has fallen several metres since December, and a compressor that has run eight hundred hours since anyone looked inside it. The faults that stop rigs in March were almost all visible in October: a cooler that was half-blocked, a thermostatic element that opened late, a separator that was already passing oil, hoses that were cracked at the fittings, an engine that smoked on start-up. A pre-season check costs a day; a mid-season failure costs the days it takes to diagnose by telephone, drive a service engineer and the part from Secunderabad, and fit it on a bench 300 km away. The arithmetic is set out in the worked example below.
The season month by month: Heat, water and what it does to the compressor
| Month | Typical afternoon ambient (Deccan uplands) | Water table | What changes for the compressor |
|---|---|---|---|
| November | 30–32 °C | High after the monsoon; holes make water early | Easiest drilling of the year; pump-up and leak tests are most accurate now; the right month for the pre-season check and for baseline readings |
| December–January | 28–31 °C | Falling slowly | Peak drilling months; engine and airend at full output; filters begin loading with dry-season dust |
| February | 33–36 °C | Falling faster | First heat derating; coolers that were marginal start tripping; dust loading rises |
| March | 37–40 °C | Low; deep holes make water only at depth | Engine power and airend capacity both fall; the water column at depth takes more of the pressure; boosters earn their keep |
| April–May | 40–44 °C and above | Lowest of the year | Hardest conditions: derated machine, deepest holes, hottest bench; most seasonal breakdowns happen here |
| June | Rains begin | Rising | Season ends; the right time to overhaul, exchange airends and rebuild engines before the next one |
Two numbers explain the table. A diesel engine loses roughly three to four percent of its power for every 10 °C of ambient above its rating point, and an air-cooled airend loses capacity as its oil runs hotter; between them a machine that delivered its nameplate 25 m³/min in November may be delivering 22 in April. And a water column of 100 feet standing in the annulus adds about 3 bar of back-pressure at the hammer; a hole that stands 400 feet of water in April takes 12 bar before the hammer sees any. The DTH compressor sizing page and the deep-hole air planning page give the method; the point here is that the duty in April is not the duty in November, and the machine must be chosen and prepared for April.
The pre-season inspection: What a service engineer checks
This is the list our service engineers work through on a rig compressor before the season. It is written so that a contractor’s own mechanic can use it; the items marked with a workshop note are the ones that need our Secunderabad workshop.
| Area | Check | Pass condition | If it fails |
|---|---|---|---|
| Engine | Cold start, smoke colour, idle stability, oil pressure at idle and at speed | Starts within a few seconds, clear exhaust after warm-up, pressures within the maker’s range | Injectors, fuel system, compression test; a smoking engine in October is a stopped rig in March |
| Engine | Coolant condition, radiator core, fan belt tension and cracks, water-pump weep hole | Clean coolant at the right mix, core clear of dust when a light is held behind it, belts without cracks | Core cleaned or replaced, belts and pump replaced; a half-blocked radiator is the commonest cause of April overheating |
| Airend | Noise and vibration at load, discharge temperature at load, oil condition and level | No knock or whine change under load, discharge temperature steady within the maker’s band, oil clear | Bearing check and oil analysis; an airend that is noisy in October is an exchange in February (workshop) |
| Oil system | Oil age and hours, separator differential, scavenge line flow, thermostatic element opening temperature | Oil within hours, separator differential within limit, scavenge line warm and flowing, element opens at its marked temperature | Oil and separator changed, scavenge orifice cleared, element replaced; the thermostatic valve page explains the test |
| Cooling | Oil cooler and aftercooler cores, fan, shroud, canopy seals | Cores clear when back-lit, fan undamaged, canopy seals intact so that air goes through the cores not around them | Cores cleaned with the right method for the fin type; a core that cannot be cleaned is replaced |
| Intake and filtration | Intake filter condition and restriction indicator, pre-cleaner, intake ducting seals | Indicator clear with a new element fitted, pre-cleaner clean, ducting sealed | Elements replaced, ducting sealed; dust that bypasses the filter is an airend rebuild |
| Control and safety | Unloader and inlet valve operation, pressure-regulating valve setting, minimum-pressure valve, safety valve test, high-temperature and low-oil-pressure shutdowns | Loads and unloads cleanly at the set pressures, safety valve lifts at its marked pressure, shutdowns trip when tested | Valves serviced or replaced, shutdown sensors replaced; a shutdown that does not trip is an engine or airend destroyed |
| Instruments | Pressure gauges checked against a test gauge, temperature gauge, hour meter, fuel gauge | Gauges within a bar of the test gauge, hour meter running | Gauges replaced; a rig run on a wrong gauge is a rig run blind |
| Delivery system | Hoses, couplings, whip checks, service valves, manifold | No cracking at fittings, couplings undamaged, whip checks on every joint, valves seal | Hoses and couplings replaced; a hose failure at 25 bar is a safety incident, not a breakdown |
| Booster (where fitted) | Inlet and discharge valves, cooling, unloading, lubrication | Valves seal, unloads at the set pressure, no overheating at load | Valve and seal service, booster page explains the duty |
| Undercarriage and chassis | Tyres, hitch, lights, brakes, lifting points, canopy fastenings | Tyres sound, hitch and brakes serviceable, canopy secure | Tyres and hitch repaired; a rig that cannot be towed cannot drill |
| Performance | Pump-up test into a known volume, pump-down leak test, pressure and flow at the hammer under load | Free air delivery within 10 percent of nameplate corrected for the day’s conditions, leakage small, hammer pressure as specified | Diagnosis from the result: the pump-up test calculator gives the figures and the verdict |
Three items deserve emphasis. The pump-up test in November, when conditions are kind, is the baseline against which every later complaint is measured; without it, “the compressor seems weak” in March cannot be separated from “the hole is deeper and the day is hotter”. The shutdown test is the one most often skipped and the one that saves the most money. And the intake filter is the item on which a season’s dust does its work; a rig’s season filter stock is set from what the October element looks like, not from the manual.
Fuel: The largest cost of the season, planned per metre
A 25 m³/min, 25 bar g rig compressor burns diesel at a rate set by its load, and a season of eight hundred drilling hours burns more fuel than the machine is worth in several years. The right way to plan it is per metre drilled rather than per hour, because a slow hole burns the same fuel per hour and earns less. The drilling productivity and cost-per-metre page lets a contractor compare two packages on accepted metres; the own-or-hire calculator shows fuel as the dominant lifecycle cost. For the season plan, three practices keep the fuel figure down: a compressor sized with margin so that it does not run flat out in April; a separate low-pressure machine or a correctly set unloading pressure for the work that does not need 25 bar; and a cooler kept clean so that the engine is not fighting its own heat.
The season spares kit
A rig working 300 km from Secunderabad should start the season with a kit on the truck. The list below is what we recommend for a typical rig compressor; the exact part numbers are identified from the nameplate and a photograph of each component, as the spares page explains.
- Intake filter elements for the season, set from the October element’s condition rather than the manual’s interval
- Engine oil, air and fuel filters for the season’s service intervals, with the oil
- Compressor oil for one change, and the separator element for it
- Fan and drive belts, one set
- A thermostatic element
- Pressure-regulating and minimum-pressure valve repair kits
- High-temperature and low-oil-pressure shutdown sensors
- A pressure gauge of the right range
- Hose couplings, claw clamps, whip checks and a length of hose of each size on the rig
- For a boosted rig, booster inlet and discharge valve kits and seals
Hire planning for the season
A contractor who hires for the season rather than owning, or who hires a second machine to run two rigs, should book before November: the fleet is committed early, and a machine delivered and commissioned in the first week of the season earns the best months. Hire is planned by the month with the hammer and hole sizes, the expected depths and the district’s water conditions stated at the outset so that the machine, and a booster where the depths need one, are matched to the season’s hardest holes rather than its first ones. The borewell compressor hire page sets out what a monthly hire includes and how servicing is handled on hire jobs; the hire-or-buy page and the own-or-hire calculator help with the decision.
District by district: Where the season is hardest
The water table, the rock and the depths differ by district, and so does the compressor the season needs. The notes on our city pages are the starting point: Nalgonda and Kurnool for the deepest holes and the booster question; Mahbubnagar and Nizamabad for the Palamuru and northern uplands; Karimnagar, Khammam and Chimakurthy where rigs and quarries share the same machines; and Warangal for the eastern uplands. A contractor moving between districts in one season should plan the machine for the deepest district on the list.
A worked example: The cost of a March breakdown against an October check
A contractor runs one rig with a 25 m³/min, 25 bar g compressor in Nalgonda district. In October the compressor’s oil cooler is partly blocked and its thermostatic element is opening late; the machine runs, so no one looks. By mid-March the afternoons are 39 °C, the holes are 700 feet and standing 350 feet of water, and the compressor trips on high temperature every afternoon, then stops altogether when the element fails closed and the airend overheats. The diagnosis takes a day of telephone calls and photographs; the service engineer and the parts travel the next day; the cooler is cleaned and the element replaced on site; the airend is checked and found scored, so a loan machine is brought from Secunderabad and the airend goes to the workshop for exchange. The rig loses eight drilling days in the best month of the season, plus the airend exchange. Had the cooler been cleaned and the element replaced in October, a half-day job on a cool bench with parts carried, the airend would not have overheated and the eight days would have been drilled. The contractor’s own figures for metres per day and rate per metre turn those eight days into the season’s largest single loss, several times the cost of the pre-season check and the airend exchange together.
Record-keeping that pays for itself
A rig log that records, for each hole, the depth, the water level met, the pressure and flow at the hammer, the hours on the compressor, the fuel taken and the ambient temperature, does three things. It lets the contractor price the next job from accepted metres and real fuel. It lets a service engineer diagnose by telephone, because “pressure at the hammer has fallen from 19 to 15 bar over three weeks at the same depth” is a diagnosis, while “the compressor seems weak” is a guess. And it shows when the airend or engine is due for exchange before it fails. The borewell production forecasting and variance pages show what the records make possible.
Common mistakes that cost seasons
- Starting the season on a compressor that was “running fine” in June and has not been opened since.
- Sizing the machine for November’s holes and not for April’s heat and water.
- Skipping the shutdown test and losing an engine or airend to a sensor that never tripped.
- Setting the filter interval from the manual in a district where dust fills the element in half that time.
- Running the 25 bar machine throttled down for low-pressure work all day and burning the season’s fuel margin.
- Booking a hire machine in December when the fleet was committed in October.
- Towing a rig on tyres and a hitch that were never inspected.
- Keeping no log, so that every fault is diagnosed from scratch.
How Reddy Compressors helps
We have supplied, hired out, serviced and overhauled borewell rig compressors across Telangana and Andhra Pradesh since 2002, and the pre-season check is the single service that most reduces the calls we receive in March and April. A service engineer works through the checklist above on your yard or site, runs the pump-up and leak tests as a baseline, identifies the season’s spares from the nameplates and components, and reports what should be done now and what can wait. For contractors who hire, we match the machine and any booster to the season’s deepest holes and commission it on site. We are an independent, multi-brand business with supply tie-ups across all major makes; we service every make of rig compressor and booster; and more than 20 service engineers and technicians, a workshop for airend and engine work and our own rental fleet work from Tarnaka in Secunderabad.
What to send us
- Photographs of the compressor nameplate, the engine plate and the hour meter.
- The hammer sizes and the typical and deepest holes you expect this season, with the districts.
- Any faults or trips from last season, and the last service date.
- For a hire: the period, the hammer and hole sizes, the depths, and the districts.
- Where the rig is parked now, so that the pre-season check is planned.
Frequently asked questions
When should the pre-season check be done?
In October or November, when the bench is cool and the pump-up test gives a clean baseline, and before the fleet and the service engineers are committed to the season.
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Can my own mechanic use this checklist?
Yes; it is written for that. The items marked as workshop work, airend and engine internals and exchanges, are the ones that need our Secunderabad workshop. A service engineer can do the full check and the pump-up and leak tests with instruments.
Why does my compressor seem weaker in March than in November?
Because it is: engine and airend both lose output in heat, and the deeper hole with its water column takes more of the pressure before the hammer. The pump-up baseline from November tells you how much is the machine and how much is the hole.
Do I need a booster this season?
If your deepest holes will stand a water column that takes a large share of your compressor’s pressure, yes. Send the hammer size, depth and water level and we will size the pair; the booster page explains the arithmetic.
What spares should I carry for the season?
Filters set from the October element’s condition, oils and separator, belts, a thermostatic element, valve kits, shutdown sensors, a gauge, hose fittings and whip checks, and booster valve kits where fitted. We identify the part numbers from the nameplate and photographs.
Can you hire a compressor for the whole season?
Yes, from our own fleet, by the month, matched to the hammer and the season’s deepest holes, delivered and commissioned on site. Book before the season starts.
Do you service rig compressors of a make you did not supply?
Yes. We service and overhaul every major make of rig compressor and booster and supply parts for them. Send the nameplates.
What does the pump-up test tell me?
The compressor’s real free air delivery against its nameplate, corrected for the day’s conditions, and from the pump-down test the leakage in the delivery system. The calculator page gives the method and a verdict.
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.