Borewell compressor spare parts: what fails and how to order

Why borewell compressors use parts faster than plant compressors

A borewell or DTH drilling compressor works in about the hardest duty a compressor sees. Typical rig compressors in India deliver 600–1,500 cfm at 200–400 psig (13.8–27.6 bar), and high-pressure units go up to about 35 bar (507.6 psig). They run on diesel engines at high load for long hours, in open ground, in summer ambient temperatures of 40–45 °C, and above 45 °C on open sites, with rock dust and cuttings blowing around the intake.

That combination shortens the life of anything that filters, seals or carries heat. Air filters load quickly, oil runs hotter, separator elements see more carry-over, and hoses and couplings are dragged, kinked and pressurised hundreds of times a month. A plant compressor in a clean room might go a year on one air-filter element; a rig compressor in Telangana or Andhra Pradesh red-soil country may need cleaning daily and replacement within weeks.

The practical result: a borewell contractor’s parts plan should be built around dust, heat and pressure, not around the service intervals printed for clean industrial use.

Which parts does a borewell compressor actually need?

Think of the machine as two halves sharing one frame: the diesel engine that drives it and the compressor package that makes the air. Both need consumables and wear parts.

For deeper detail on individual parts see our pages on separators, inlet valves and portable engine parts.

Filters for dusty drilling duty

Filtration is where rig owners lose most money, either by stretching elements too long or by fitting elements that fit physically but filter poorly.

• Use the restriction indicator. Most portable compressors have a vacuum or restriction indicator on the air-filter housing. Change the element on indication, not just on hours. On dusty sites that may be far sooner than the book interval.
• Keep the safety element. Two-stage housings have a primary and an inner safety element. The safety element is not meant to be cleaned; if it is dirty, the primary has failed or was fitted badly.
• Do not blow out elements carelessly. Blowing a paper element from the outside with high-pressure air drives dust deeper and can split the media. If cleaning is unavoidable on site, blow gently from the inside out and replace at the next opportunity.
• Check the seal, not just the paper. A good element with a hardened or misaligned gasket lets dust bypass completely. Inspect the housing seat each time.
• Treat the engine and compressor filters separately. They are often similar in shape but have different ratings and flows.
• Protect the fuel. Keep a spare fuel filter and water-separator bowl on the rig; drain the water separator daily when diesel is bought from varied sources.

Our pages on compressor air filters and oil filters explain element types and change criteria in more depth.

Separators, oil and temperature

On an oil-injected screw drilling compressor, the separator element is what keeps lubricating oil in the machine and out of the drill string. When it is clogged, differential pressure across it rises, the engine works harder for the same delivered pressure, and the minimum-pressure valve may struggle. When it is damaged or bypassing, oil consumption rises and oily air reaches the hammer.

Typical symptoms that point to the separator or its scavenge system:

• Oil level dropping faster than usual between top-ups.
• Oil mist visible at the service valve or oil on the cuttings at the collar.
• Higher fuel use or a discharge pressure that will not reach set point at full speed.
• A blocked scavenge-line orifice or strainer, which lets oil collect in the separator core.

Normal oil-injected screw discharge temperature is about 75–95 °C. Running repeatedly at the top of that band, or tripping above it, usually points to a blocked oil cooler, a sticking thermostatic valve, low oil, the wrong oil grade or high ambient air recirculating from the engine side. Replacing parts without finding which of these is the cause wastes money; see oil separator performance for the engineering behind it.

Valves, hoses and couplings

Valve problems often look like engine or airend problems, so identification matters.

1. Inlet (unloader) valve. If the machine will not load, loads slowly or overshoots, the inlet valve piston, seals or spring are the first suspects. Kits are model-specific; send the valve’s casting marks along with the compressor nameplate.
2. Minimum-pressure valve. It keeps enough pressure in the separator tank to circulate oil and stops backflow from the line. A leaking or sticking valve can cause oil starvation at start-up or oil in the air.
3. Blow-down valve. If the tank does not vent on shutdown, the next start is against pressure and loads the engine and starter.
4. Safety valves. These must suit the machine’s maximum pressure – a 24 bar unit needs a valve set for that duty, not one taken off a 10 bar machine. Never plug or gag a safety valve.
5. Delivery hose and fittings. Use hose rated above the machine’s maximum working pressure, with correct crimped ends and whip checks across every joint. Long or undersized hoses cost pressure at the hammer; our air hoses and rig connections page covers sizing.

How we identify the right part from the nameplate

Many rig compressors in India are older units, imported second-hand or rebuilt, so the model on the canopy is not always what is inside. We work from evidence:

1. Photograph the compressor nameplate showing make, model, serial number, rated flow and pressure.
2. Photograph the engine nameplate or engine serial number separately; engine parts follow the engine, not the compressor.
3. Photograph the part in place and once removed, with any part numbers, casting marks or element dimensions visible.
4. Note any changes the machine has had – a replaced engine, a converted pressure setting or a non-standard airend.
5. We match the part to the machine, confirm fit, and then quote stating clearly whether it is genuine, a named aftermarket equivalent or reconditioned.

Where we cannot confirm the fit from photos, we say so and ask for the old part or a measurement rather than guess. Our compatibility verification page explains the method.

Keeping rigs earning: a sensible spares kit

A drilling rig earns only while it is drilling. A stoppage far from town, waiting for a filter or a fan belt, costs much more than the part itself. Contractors who run several rigs usually keep a small kit on each truck and a larger stock at base.

Group your fleet by machine make and model so one service kit fits several rigs. If your rigs are mixed brands, a stock-risk review helps decide what to hold; try our spare parts stock risk worksheet.

Two habits pay back quickly: log every part fitted against the rig’s hour meter, and send failed parts back for inspection rather than throwing them away. A torn separator or a scored inlet valve tells you something about how the machine is being run.

When a part is not the real problem

Replacing parts in sequence until a fault disappears is the most expensive way to repair a compressor. Before ordering, check whether:

• Low pressure is really the compressor, or hose loss, a worn hammer or water ingress at depth.
• High temperature is a cooler blocked with dust and oil film rather than a failed thermostat.
• Oil carry-over is from overfilling or a blocked scavenge line rather than the separator.
• Loss of power is fuel filtration, intake restriction or an engine fault.

If the cause is not clear, combine the parts order with a diagnostic visit. Our performance diagnostics and service and repairs pages describe what we check.

Borewell compressor spares by wear interval

A borewell rig is two machines on one chassis: a diesel engine and a high-pressure screw airend. Each has its own wear clock. The table gives typical replacement or inspection intervals in running hours for drilling duty. They are planning ranges, not a substitute for the schedule in the manufacturer’s manual for the exact model; on dusty, hot sites use the shorter end of each range.

Worked example: a spares kit for one drilling season

The existing kit list above says what to carry and what to keep at base. This example turns it into quantities (illustrative). A rig drills 10 hours a day, 26 days a month, for a six-month season from December to May.

1. Season running hours: 10 × 26 × 6 = 1,560 h.
2. Engine oil and filter at 250 h: 1,560 ÷ 250 = 6.24, so 6 changes. Plan 7 sets, including one spare for an early change after contamination.
3. Fuel filters at 250 h: likewise 6 changes, so 7 sets. Diesel bought on the road is a common cause of early fuel filter blockage, so do not cut this.
4. Compressor oil and filter at 500 h: 1,560 ÷ 500 = 3.12, so 3 changes; plan 4 filters and oil for 4 fills plus top-up.
5. Separator element at about 1,500 h: 1 change in the season; plan 2 elements with their gaskets, because one contaminated oil event can finish an element early.
6. Air filter primaries on restriction at about 250 h on dust: about 6 changes; plan 7 primaries and 2 safety elements for each of the compressor and engine filters.

Use the season plan with the drilling season compressor checklist before the first hole.

Reading the three plates: compressor, engine and airend

A borewell compressor carries up to three identities, and each decides different parts. Ordering from the wrong one is a common reason a part arrives and does not fit.

Record all three, with photos, on the day the machine arrives, not when it fails. Paint, dust and replaced canopies make plates unreadable later.

Genuine or compatible parts at drilling pressure

On a 7 bar plant compressor, a compatible filter that is slightly off specification costs efficiency. On a drilling compressor working at about 14–35 bar(g), the wrong part can burst. The parts below must be checked against pressure rating, not just dimensions.

A good compatible part with matching ratings is a legitimate choice. A part bought on size and price alone is not. Ask for the pressure rating in writing for anything in the pressurised oil and air circuit.

Hose and coupling spares rated for pressure

Hose and coupling failures are the most dangerous failures on a rig because of the force involved. The axial force trying to separate a coupling is pressure × bore area:

Check for 1.5 in at 35 bar: area = π × 0.0381² ÷ 4 = 0.00114 m²; 35 × 100,000 Pa × 0.00114 m² ≈ 3,990 N, the weight of about 400 kg. That is why every joint needs a whip check and why hoses must never be uncoupled under pressure.

Bore matters for drilling performance too. At 1,000 cfm and 24 bar(g), a 30 m hose of 38.1 mm bore loses about 0.59 bar, against about 0.14 bar for a 50.8 mm hose. A smaller spare hose fitted in a hurry can take half a bar off the hammer.

• Buy hose by its rated working pressure, which must be at least the compressor’s maximum pressure and its safety-valve setting (35 bar(g) is 507.6 psig). Never use the burst pressure as a working rating.
• Keep the spare hose the same bore and length as the original, with factory-crimped ends.
• Carry coupling seals of the correct material; a hardened seal leaks and lets the coupling work loose.
• Retire any hose that is kinked, blistered, cut through the cover or exposed to oil swelling. See air hoses and rig connections.

How Reddy Compressors helps

For borewell rig owners we supply all types, all brands and all models of borewell compressors: new sales, used and refurbished machines, rentals, service and spare parts.

Reddy Compressors has served industry from Tarnaka, Secunderabad, since 2002. We are an independent multi-brand specialist and support drilling compressors from Atlas Copco, Ingersoll Rand, ELGi, Chicago Pneumatic, Doosan, Sullair, Kirloskar, Bobcat and many others. We are not an authorised distributor of these brands, and we say clearly on each quotation whether a part is genuine, a named aftermarket equivalent or reconditioned. We have tie-ups with all major and reputed brands.

We identify parts from your machine details and photos, confirm the fit before quoting, and supply spare parts across India. Our service teams cover the whole of Telangana and Andhra Pradesh for diagnosis, repair and overhaul of borewell compressors, and we can arrange a hire compressor while a rig’s own machine is in the workshop. On our own hire fleet we change oil and service every 300 running hours, and we apply the same discipline when advising contractors on their parts plans.

What to send us

• Compressor make, model and serial number, with a nameplate photo.
• Engine make, model and serial number.
• Photos of the part, its markings and its position on the machine.
• Running hours, rated pressure (psig or bar) and any modifications.
• Quantity, delivery location and whether the rig is stopped.
• A short description of the fault if the part is being replaced after a failure.

Frequently asked questions

Which spare parts fail most often on a borewell compressor?

On most DTH rigs the most frequently replaced items are engine and compressor air-filter elements, fuel filters, oil filters, separator elements, fan belts, delivery hoses and couplings. Inlet-valve and minimum-pressure-valve kits follow. These are driven by dust, heat and pressure cycling, so dusty sites in summer use them much faster than the book intervals suggest. Airend bearings and seals are less frequent but costly.

How often should I change the air filter on a drilling compressor?

Change it when the restriction indicator shows, and inspect it daily on dusty sites. On red-soil or rock-dust sites the element can load within days, while on cleaner ground it may last much longer. Do not rely only on running hours. Replace the safety element whenever it looks dirty, because that means dust has already passed the primary element.

Can I use aftermarket parts on my borewell compressor?

Yes, provided the part is correctly identified and meets the original specification. Filters, separators and valve kits from reputable aftermarket makers are widely used. The risk is fitting a part that looks the same but has a different rating, flow or pressure setting. We state on the quotation whether each item is genuine, a named aftermarket equivalent or reconditioned, so you can decide.

Why is my borewell compressor using too much oil?

Common causes are a damaged or saturated separator element, a blocked scavenge-line orifice, overfilling the separator tank, the wrong oil grade, or running too hot. Oil on the cuttings or mist at the service valve confirms carry-over. Check oil level at the correct running condition and clean the scavenge line before replacing the separator, then confirm the temperature stays in the normal band.

How do I find the part number for an old drilling compressor?

Start with the compressor nameplate and the engine nameplate, then photograph the old part with any numbers, casting marks or dimensions. Many older or imported rig compressors have had engines or components changed, so the canopy model alone is not enough. Send us these photos and we will match the part to the machine and confirm fit before quoting.

What pressure safety valve does a DTH compressor need?

The safety valve must suit the maximum working pressure of that particular machine and its separator tank, for example a unit rated around 24 bar (348.1 psig) needs a valve set for that duty. Never fit a valve from a lower-pressure compressor, and never plug or gag one. Valves should be checked periodically and replaced with the correct setting, size and capacity.

Which borewell spare parts should I keep on the rig?

Keep the parts that stop drilling if they fail and that cannot be bought on the roadside: engine oil and fuel filters, fuel water-separator elements, compressor and engine air filter primaries, top-up oils, belts, a spare coupling, seals and whip checks. For a 1,560-hour season, plan about seven sets of engine and fuel filters, four compressor oil filters and two separator elements, with inlet valve and minimum-pressure valve kits held at base.

Are borewell compressor spare parts different from normal compressor parts?

Many look the same, but the pressure ratings are not. Borewell compressors run at about 14–35 bar(g), against 7–13 bar(g) on most plant compressors, so separator cartridges, oil filters, minimum-pressure valve springs, safety valves, hoses and seals must be rated for that pressure. Engine-side parts follow the engine serial number, which can differ from the catalogue build for the compressor model. Always order with the compressor, engine and airend numbers.

How often should borewell compressor spare parts be changed?

Typical drilling-duty intervals are: engine oil and filters 250–500 hours, fuel filters 250–500 hours, compressor oil and filter 500–1,000 hours, separator element 1,000–2,000 hours or on pressure drop, and valve seal kits 2,000–4,000 hours. Air filters are changed on the restriction indicator, which on dusty sites can mean every 100–250 hours. The manufacturer’s manual for the model always takes priority.

Related pages

• Borewell compressor service and repairs
• Borewell compressors parts and lifecycle support
• Find my compressor part
• DTH lubrication and air treatment
• Portable compressor service
• Compressor spare parts