How to reduce machine downtime caused by waiting for spare parts

Reducing downtime through better spare parts procurement starts with one number: what an hour of a stopped line costs. That number decides how much speed is worth paying for. Most plants know their output per hour; few have turned it into a rupee figure that purchase can use.

A workable estimate adds four costs for each bottleneck machine or line:

• Lost contribution: the output you can't make, multiplied by the contribution margin per unit (selling price less variable cost). Use contribution, not revenue.
• Idle labour: operators and supervisors paid while the line is stopped, plus the overtime needed later to catch up.
• Recovery costs: restart scrap, rework, extra changeovers, and the premium freight paid to get a delayed customer shipment out on time.
• Customer penalties: line-stop charges or late-delivery penalties in your supply contracts, where they apply.

An illustrative example: a line making 150 parts an hour at ₹60 contribution a part loses ₹9,000 an hour. Add ten idle operators at ₹250 an hour and the stop costs about ₹11,500 an hour before any penalty. A two-day wait for a bearing on a two-shift line, 16 working hours, costs around ₹1.84 lakh. Against that, paying ₹800 more for a bearing that arrives the same day is not a hard decision.

A critical-spares list is the short list of parts whose failure stops production and which can't be bought fast enough on the day. Build it from two questions per part: what happens if it fails, and how long does it take to get?

1. List the bottleneck machines first: those with no standby, no alternative routing, or that feed several lines downstream.
2. For each machine, list the parts that fail or wear: bearings, seals, belts, contactors, proximity sensors, solenoid valves, drive cards, encoders and hydraulic hoses.
3. Rate each part on the consequence of failure (stops the line, slows it, or no effect on output) and on supplier lead time (same day, within a week, longer).
4. Pull failure history from maintenance records: how often has the part failed in the last two or three years?
5. Mark a part critical when its failure stops the line and it can't reliably be had the same day. Record the machine, its location and the hourly downtime cost against it.

Many Indian plants already run VED analysis (vital, essential, desirable) on store items. The critical-spares list is the vital class, tied to specific machines. Keep it separate from ABC analysis, which ranks items by annual spend: a ₹400 proximity sensor is a C item by value and can still stop a line.

Make the list the maintenance head's document, reviewed with purchase and stores at least twice a year, and give every line its item code so an indent can be raised in seconds.

Critical parts that can't be bought quickly should be on the shelf before they fail. There are two kinds of stock to hold, and they're managed differently.

Safety stock for wearing spares

Bearings, belts, filters, seals, contactors and sensors are consumed regularly. Give each a reorder level: average daily consumption multiplied by the supplier's lead time in days, plus safety stock to cover a late delivery or a jump in consumption. If a plant uses two 6208-2RS C3 bearings a week and the lead time is ten days, consumption during the lead time is about three; with a safety stock of four, the reorder level is seven.

Set safety stock by risk, not habit: more for a part with an unreliable supplier or a long lead time, little or none for one that several local stockists can deliver the same day.

Insurance spares for rare, expensive failures

A spare gearbox for a main drive, a spindle motor or a PLC CPU may never be used. But if it's needed and isn't there, the line can be down for weeks. These are insurance spares: bought once, held against one machine, and judged by the downtime they prevent rather than by stock turns. Finance will query them at every inventory review, so record the machine and its hourly downtime cost against each one.

Breakdown purchases need an approval route agreed in advance, so nobody improvises at 2 a.m. The usual delay isn't a slow approver but an absent one: the person with authority is in a meeting, travelling or asleep, and the indent waits.

• A breakdown flag on the indent. The engineer sets it when raising the indent, with the machine and a photo of the failed part.
• A named approver on every shift, with a backup, written into your approval matrix.
• A higher spend limit for breakdown indents, so the maintenance head can approve most of them without waiting for the plant head.
• An escalation timer. If nobody acts within an agreed time, say 30 minutes, the indent moves to the next approver.
• Approval at the time, review afterwards. Breakdown buys are approved when they happen and reviewed later. A purchase approved retrospectively is a purchase nobody approved.

Guard against misuse. If the share of indents flagged as breakdowns keeps rising, the flag is being used to skip the queue. Track it monthly by department and ask for reasons. For setting up the matrix itself, see our guide to the purchase approval matrix.

When a machine is down, the fastest way to find the part is to ask every capable vendor at the same time, not one after another. Calling four vendors in turn, each taking an hour to call back, uses half a shift.

An urgent request for quotation should:

• Identify the exact part: make, model or part number, size, and the photo from the indent.
• Ask for stock in hand, the time it can be ready for dispatch and the dispatch mode, as well as price.
• Set a short quote window measured in hours, and say when the order will be placed.
• Go to every stockist and distributor who actually carries the category, not only the vendor who supplied it last time.
• Rank the answers on time to the machine first and price second.

Approve equivalents before you need them

Many breakdown delays come from insisting on a brand nobody nearby stocks, when the part has a standard designation. A 6208-2RS C3 deep-groove ball bearing is defined by its dimensions, seals and internal clearance, not by its maker. A contactor is defined by its rating, coil voltage and auxiliary contacts; an inductive proximity sensor by its thread size, sensing distance, output type (PNP or NPN, NO or NC) and connector.

Let engineering approve equivalents in the item master before the breakdown, so the buyer can accept them during one. Where a machine builder's warranty or a safety certification depends on a specific part, mark it 'no substitute' and keep it in stock instead.

A breakdown order isn't finished when the vendor says it's dispatched; it's finished when the part is fitted.

• Get an ETA and a dispatch mode at order time: your own vehicle, a local courier or the vendor's delivery. For a vendor across town, sending your own vehicle can save a day.
• Check the paperwork travels with the goods. The consignment needs a tax invoice, and an e-way bill when its value exceeds ₹50,000, or it can be detained in transit.
• Tell security and stores it's coming. A breakdown part shouldn't wait at the gate in a queue of routine deliveries.
• Receive and issue in one step. Check the part, record the GRN and issue it to the machine straight away, rather than letting it wait for the day's receipts to be booked.

A short review after each breakdown is how a plant stops having the same one twice. Maintenance looks at why the part failed; procurement should look at why it took so long to arrive.

Log the time of each step and see where the hours went:

Then change one thing: add the part to the critical list, raise its safety stock, approve an equivalent, add a backup approver, or drop a vendor who quoted stock they didn't have. Keep the log. After a year it shows which machines, parts and vendors cause most of your waiting.

GODOWN is one procurement partner for every MRO category, on a platform customised to your plant's workflow. Urgent breakdown requirements are prioritised: you get competitive quotes and one PO, and delivery is tracked to your gate with a GST tax invoice. See how sourcing works for your plant.