A set of acceptance criteria is the paragraph in a cleaning contract or a purchase order that says what counts as finished. For machining-fluid residue it is harder to write than for dust, because the deposits on a machining floor are not one substance. Cutting and grinding fluid leaves a spread film, way oil leaves a thicker one, hydraulic bleed creeps into seams, drifted mist dries into a skin, and coolant left where splashes were allowed to dry becomes a paste. Those layers behave differently on painted sheet, bare cast iron, anodised aluminium, plastic guards and glass, so criteria written for one surface routinely fail on another. Before any cleaning method is discussed, decide how the result will be judged, by whom, and against what reference.
Write the criteria as conditions that can be observed on the machine, not as adjectives. "Clean" cannot be signed off; a surface that shows no continuous film when wiped with a white cloth, with no residue transferred to the cloth over a stated length of travel, can be. Each line of the list needs four parts: the surface it applies to, the observation method, the pass or fail boundary, and what happens when the boundary is not met. A list of adjectives gives a supplier permission to argue; a list of observations ends the argument on the spot.
Separate the surface classes before writing a single line
Machine enclosures, machined ways and bare metal, painted panels, transparent guards, and non-metal parts such as cable carriers, handles and labels each need their own criterion. A result that is acceptable on a painted door may be unacceptable on a ground slideway, because any residue left on a sliding surface picks up abrasive fines and carries them into the guide. Equally, a method that clears a bare casting may leave a haze on a polycarbonate window or lift a printed label. Group the surfaces in the drawing order of the machine, then write one row per group, so the inspector is never asked to apply one rule to two materials.
For each group, describe the deposit you expect to find and where it hides: corners, fastener heads, drain trays, the seam between a cover and its frame, the underside of a table, chip conveyors and the splash guards behind them. Naming the hiding places is part of the criterion, because a cleaning that leaves the visible faces bright while the troughs still hold sludge has not removed the source of the film that returns a week later.
State what must not be disturbed
Acceptance is not only about what has been removed; it is also about what has stayed in place. Write a boundary list and treat every item on it as a fail if it has moved. On machine-tool exteriors the usual boundary is at bearing seals and wipers, ways and their lubrication points, electrical enclosures and terminal boxes, encoder and scale covers, pneumatic fittings, labels and data plates, bonded or re-coated paint, decals and any adhesive mounting. A cleaning that drives water or softened grease past a seal is a failure even when the panels look perfect, and the cost of that failure only appears in the maintenance log weeks later.
Give each excluded item a named alternative rather than leaving it blank. A criterion that says "seals excluded" with nothing further guarantees an argument at handover, because the crew has to improvise. Say what will be done instead, and who decides: hand wipe, a protected cover fitted before work starts, or a part removed and reinstalled by the site's own fitter.
Make the observations checkable on the shop floor
Three practical tests cover most machining-fluid work. The white-cloth wipe is the fastest: a defined length of travel, one pass, no visible transfer. The oblique-light check looks for a film that a dry cloth leaves behind, which ordinary workshop lighting hides. The re-soil check is the one buyers skip: after cleaning, the machine runs for an agreed period, and the same surfaces are inspected again. A film that returns quickly says the source was never reached, and that belongs in the criterion as a separate line, because a first-day pass with a second-week failure is a different commercial question from a day-one failure.
Fix the inspection conditions as well as the test. State the light level or the lamp being used, the state of the cloth, whether the surface must be dry, and who is allowed to judge. Keeping the inspector separate from the crew doing the work removes most disputes, and photographs of the same area before and after, taken from one marked position, settle what words cannot.
Set the baseline with a bounded trial, not with a claim
No buyer knows in advance which deposit will resist. Before the criteria are frozen, agree a trial on a small number of representative areas, with the areas chosen by the buyer and not by the supplier, and mark them with tape so the same patch is judged every time. Change one condition at a time between patches; a trial that alters the method, the dwell and the access route at once cannot tell you which of them caused the result. Photograph each patch, record the surface class, the deposit type, the setting used and the outcome, and keep that sheet as the evidence the criteria are written against.
Write a stop condition into the trial before it starts: a seal weeping, a label lifting, a coating blistering, haze on a window, or an area that shows no improvement. A stop condition agreed in advance is a plan; one agreed after something has gone wrong is a negotiation.
Cover the duties a clean result depends on but that no panel shows
Run-off, drying and hand-back are where a technically acceptable clean still causes trouble. Say where the used water and displaced oil must go, and who arranges the route, because oily run-off entering a rain drain turns a cleaning job into an environmental incident. Say what "dry" means at hand-back: no standing water in troughs or on electrical covers, no wet insulation, and a floor that can be walked without a wet-floor sign. Then state the hand-back conditions in operational terms: guards closed, covers refitted, lubrication points checked after work rather than before, and any fault found written down instead of mentioned verbally and forgotten.
Ask what limits the work around the machine: where the supply can be connected, how far the crew can reach without dismantling, whether the area must be isolated and how, and what has to be moved before they start. Those items decide whether a criterion can be met at all, and they are the most common reason a quoted price changes after the crew arrives.
Put the criteria into the enquiry so suppliers answer the same question
Send the draft criterion table to every supplier with the enquiry, and ask each of them to answer the same rows: which surfaces on the list they expect to clear, which they expect to struggle with, which deposits they would refuse, and what conditions their own answer assumes. Identical wording to every vendor is what makes the replies comparable; loose wording invites the cheapest answer rather than the honest one. An answer that leaves rows blank is information, not silence to be filled in later.
Ask for the specification in writing for the exact unit being quoted, and read it as belonging to that unit: published product pages describe the machines, they do not certify your machines, your deposits or your shift pattern. Where a supplier offers purpose-built machines rather than a catalogue unit, the questions belong to the duty, the surfaces and the site, not to a brochure line.
Decide what acceptance does not settle
A signed acceptance sheet says the agreed surfaces met the agreed observations on the agreed day. It does not prove that the same result is repeatable on the rest of the fleet, that the deposit will not return at the same rate, or that the method is safe for a machine the buyer did not include in the trial. Keep those three questions separate and answer them with a per-family standard: one page per machine family, listing the surface groups, the deposit expected on each, the boundary items, the observation to be used and who signs. Name the owner and put a review date on it, so the document is updated when a machine changes rather than when something breaks.
If you want the criteria reviewed before they are issued, the entry point on the site for a duty described in these terms is customized steam cleaning equipment; the product range itself sits under industrial steam cleaning equipment, and machine-side questions are the same ones a supplier should answer for machine tool steam cleaning. Attach your criterion table to that enquiry rather than asking the supplier to propose one.
