Spare parts stock risk worksheet for compressors

What this worksheet decides

A spare part only protects your plant when the correct item can be identified, obtained, stored in good condition, fitted and proved before the process runs out of tolerance. A shelf full of the wrong filters protects nothing. This worksheet helps a maintenance manager decide, part by part, whether to hold stock on site, rely on a supplier arrangement, keep a repairable exchange unit, or hold nothing and accept the risk.

Use it for consumables, repairable assemblies, electronics, valves, seals, bearings, motors and other items whose absence can delay restoration. The output is a stocking decision for each line and an action list. It does not tell you a universal stock quantity, and it does not guarantee that any supplier will have a part when you call.

Start with the function the part restores

Begin with the process, not the parts list. Ask which air supply becomes unavailable when this part fails and how long the process can tolerate that. A small solenoid on a critical instrument-air compressor can matter more than a large component on a machine that has a running standby. Link each line to the criticality record from the criticality and service level worksheet.

Then write the failure and the repair action. Replacing an oil filter during planned service is different from replacing it after oil contamination. A controller fault may need configuration and settings as well as hardware. An inlet valve kit is useful only if the valve body and seats are still serviceable. Stocking decisions should match a real repair, not a generic list.

Record any alternative supply. A working standby compressor reduces urgency, but while the failed machine waits for parts, you are running without reserve. That exposure has a cost too.

Spare parts and service consumables are different decisions

Consumables are best handled by the service plan. Our preventive maintenance page explains how intervals are set. This worksheet is mostly about the last two rows.

The scoring method

Each part line is scored on five factors, usually on a 1–5 scale agreed within your team:

1. Consequence: what happens to production, quality or safety while the air supply is lost or reduced.
2. Restoration time without stock: identification, ordering, transport, customs where relevant, fitting and testing.
3. Tolerable interruption: how long the process can survive on standby, storage or rental air.
4. Demand uncertainty: how predictable the failure is from condition data or history.
5. Compatibility exposure: how likely it is that a part obtained quickly will not fit or will not perform.

The core test is simple: if restoration time without stock is longer than the tolerable interruption, and the consequence is significant, the part is a candidate for on-site stock or a guaranteed supply arrangement. When budget is limited, the worksheet ranks lines by consequence × days of exposure (restoration time beyond the tolerable interruption), but the time comparison should be recorded explicitly, not hidden inside a score.

Worked example

A pharmaceutical plant runs two oil-injected screw compressors with a common dryer. One supplies the base load; the other trims and acts as standby.

Note the dryer drain valve row. It is a small, cheap part, but its consequence is high because wet air reaches a sensitive process, and the standby compressor does not protect against it because the dryer is shared. That is the kind of line a price-based list misses.

Identification and fit: the hidden risk

Many restoration delays are not caused by the part being unavailable, but by the wrong part being supplied. Compressors with the same family name can use different valves, sensors or elements depending on build year, pressure variant and options. Reduce that risk before failure:

• Record make, model, serial number and pressure variant for every machine.
• Photograph each nameplate and keep the photos with the stock record.
• Note part numbers from the old part, the manual and previous orders.
• Confirm fit for every stocked line before buying, not after failure.
• Record whether the part is genuine or a verified aftermarket equivalent.

See compatibility verification for how we confirm fit.

Storage and shelf life

Stock that degrades on the shelf gives false confidence. Rubber seals, hoses and belts age, especially in hot stores. Electronics should be kept dry and protected from static. Sealed oil should be kept closed and away from heat, and filter elements kept in their packaging. Record receipt dates, rotate stock first-in first-out, and check stored items at a fixed interval. In Telangana and Andhra Pradesh, summer store temperatures can be high, so keep elastomer parts out of direct sun and hot roof spaces.

Alternatives to holding stock

• Shared stock between sites or machines of the same model.
• Exchange or repair loop for assemblies such as valves, coolers or motors.
• Supply arrangement with an agreed identification record, so ordering is fast.
• Rental cover for long restoration items such as airends, so the process continues while the repair is done.
• Design change, such as adding a standby dryer or bypass, where one part has too much consequence.

Reviewing the decision

Review the worksheet after every significant failure, after any machine is added or replaced, and at least once a year. Use failure records from the maintenance bad actor analysis tool to see which parts actually fail. Remove stock for retired machines so capital is not tied up in parts that no longer fit anything.

Portable and rental fleets need a different list

Diesel portable compressors working on construction, drilling or blasting sites face different risks from plant compressors. They work far from stores, in dust and heat, often round the clock. The critical lines usually include engine and air filters, fuel filters, fan belts, engine sensors and the safety shutdown switches for high discharge temperature, low engine oil pressure and high coolant temperature. A failed shutdown sensor can stop the machine or, worse, leave it unprotected.

For these fleets, a service kit per machine for the next service, plus a small set of sensors and belts per site, often protects more running hours than central stock. On our own hire jobs, oil change and servicing are done every 300 running hours, so the next kit must be on site before that point. See portable engine parts for the items involved.

How Reddy Compressors helps

We supply spare parts for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Sullair, Doosan, Kirloskar and other makes as an independent multi-brand specialist, not an authorised dealer. We have tie-ups with all major and reputed brands. We identify each part from the machine itself, using make, model, serial number, a nameplate photo and the old part, and we confirm fit before quoting. We can help you build the identification record for your compressor room, review your stocked lines against this method and set up a service plan or AMC that keeps consumables one service ahead. Where a long repair is unavoidable, we can cover the gap with a rental compressor from our own fleet. Our office is at Tarnaka, Secunderabad; service covers all of Telangana and Andhra Pradesh, and parts are supplied across India.

What to send us

• Make, model and serial number of each compressor and dryer
• Nameplate photos and photos of any part you need
• Running hours and service history
• Your current stock list, if you have one
• Which air supplies are critical and whether a standby exists

Frequently asked questions

Which compressor spare parts should I keep in stock?

Keep in stock the parts whose failure would stop a critical air supply for longer than your process can tolerate, where getting the correct part would take longer than that tolerance. Typical candidates are thermostatic valves, sensors, solenoids, drain valves and minimum pressure valves, plus one service set of consumables. Large assemblies such as airends are usually better covered by a rental and overhaul plan.

Should I stock an airend or motor for my compressor?

Usually not, unless a single compressor supplies a critical process with no standby and very long restoration. Airends and main motors are expensive, rarely fail and may not fit a replacement machine later. A planned route for overhaul or exchange, plus rental cover while the work is done, is often a better use of capital. Decide case by case with the worksheet.

How do I make sure I order the right compressor spare part?

Record the make, model, serial number and pressure variant of each machine, and photograph the nameplate. Keep part numbers from the old part, the manual and previous orders. Similar machines can use different parts depending on build year and options, so confirm fit before buying. We identify parts from these details and confirm fit before we quote.

Are aftermarket compressor parts safe to use?

Some are, some are not. A verified aftermarket part that matches the original in dimensions, materials and performance can be suitable, particularly for filters and common wear items. For safety-related and critical parts such as pressure valves, sensors and separator elements, check specifications carefully. Record in your stock list whether each line is genuine or a verified equivalent.

How often should I review my spare parts stock?

Review it after every significant failure, whenever a compressor or dryer is added or replaced, and at least once a year. Check shelf life of rubber parts, remove stock for retired machines and update lead times. A stock list that is never reviewed drifts away from the machines in the compressor room and ties up capital in parts that no longer fit.

Related pages

• Compressor spare parts hub
• Find my part
• Compressor service kits
• Spare parts identification enquiry
• Criticality and service level worksheet
• Compressor AMC