9 inputs determine the right service part.

A distributor-facing pre-quote checklist. If the customer answers most of these at the first call, the second call is the quote.

1. 01
   What's the compressor make, model, and HP — and do you have a serial number?

   This is the cross-reference input. Photo the nameplate is the fastest capture. Make + model + HP resolves 95% of cross-references cleanly; the serial number resolves the remaining 5% (model-year variations on filters, valves, and oil specs). Without these four data points, no aftermarket catalog can return an equivalent.
2. 02
   What's the operating-hours interval since the last service — and what's the cycle duty?

   Rotary-screw on synthetic = 8,000-hour cycle; on mineral = 2,000-4,000; on food-grade H1 = 6,000. Continuous-duty 24/7 vs. shift-only changes both the interval and the recommended product line. The maintenance log tells you where the customer is in the cycle and whether this call is a scheduled change, an early failure, or a missed service catching up.
3. 03
   Is the current oil synthetic, food-grade, or mineral — and what ISO grade?

   Determines product fit and conversion scope. Mineral → synthetic conversion needs a flush charge for any compressor with accumulated varnish (1-4 hours under light load before refill). PAO / ester / mineral are intermixable; polyglycol is NOT — full flush required. ISO grade is OEM-spec and not negotiable; substitute viscosity = oil-film thickness change = accelerated wear.
4. 04
   Does the plant have an audit requirement driving food-grade H1?

   HACCP, SQF, BRC, FSSC 22000, or direct customer audits — any of these makes H1 a compliance line, not a value engineer. If the customer isn't sure, route to their quality team — don't guess on their behalf. Once H1 is named, the conversation moves from price to compliance, and compliance customers don't switch suppliers casually.
5. 05
   What's the operating environment around the compressor intake?

   Clean indoor assembly = 12-month intake element; light industrial = 6 months; foundry / cement / grain / woodshop = 3 months or less. Environment determines whether the customer needs the aftermarket element on annual or quarterly cadence — and whether the OEM housing is the limit (route to Solberg housing upgrade) or just the element (aftermarket cross).
6. 06
   For valve failures — what's the symptom?

   Symptom-to-part in one question. Hard-start / motor strain → unloader stuck closed. Won't cycle off → inlet control valve stuck open (rotary screw) or unloader stuck open (recip). Pressure drops overnight → discharge check valve leaking backward. Safety valve weeping at operating pressure → safety relief aged or wrong-rated (should be ~25 PSI above max operating). Diagnose before asking for a part number.
7. 07
   Does the customer want a stocking program — spares on the shelf for the next failure?

   Compressor downtime runs $500-2,000 per hour; a $300-500 spare-valve kit + $200-400 service-parts bundle on the shelf is cheaper than one hour of unplanned downtime. Quote the stocking program AFTER closing the emergency replacement — the customer just lived through the downtime and is receptive. Stocking-program customers become multi-year MRO accounts.
8. 08
   Is this a single compressor, or a multi-unit fleet across mixed OEM brands?

   Mixed-fleet plants (Atlas Copco + Sullair + Quincy + IR in one building) consolidate to single-vendor aftermarket cross-reference for procurement simplicity. One PO to KELTEC + Conrader + AMSOIL covers filters, valves, and oil across 10+ OEM brands. The consolidation conversation is where multi-unit accounts get locked.
9. 09
   When's the next scheduled service window — and is it in the customer's MRO calendar?

   Service Parts is the recurring-revenue layer; the MRO calendar IS the recurring contract. Set the next-change reminder at the time of the current order — 30 days out for lead time. Customers who don't have a calendar reminder rediscover the maintenance from a different vendor; customers who do default to the same supplier on every change.