The limits belong to the machine being cleaned, not to the steam machine
Buyers are used to comparing equipment on output: temperature, pressure, pump power. On a machine-tool exterior that comparison answers almost nothing, because the same setting lifts cutting oil off a painted column and destroys a reader head in the next bay. The machine on the shop floor decides the outcome, so the machine on the shop floor should be the first thing specified.
That means the buyer, not the supplier, owns the first document in this purchase: a surface list per machine envelope, written in the shop's own words, with three columns added by whoever walks the line. The opening column names the deposit on each row: cutting oil, way oil, a film of mist, paste left by dried coolant, hydraulic bleed, crust in which swarf is bound. The next column records the state of the surface itself, since the paint and its age, exposed ways and ball screws, and the condition of wipers and scrapers decide whether a heated pass is possible at all. The third records reachability: fixed access, a platform, or a ladder, and what stands in the way.
Each row of that list becomes an instruction to the supplier or a line in the standard that the site signs. Ask for the exclusion list in return, and with it the replacement method and what that replacement costs in time and in result. A supplier who cannot produce an exclusion list is not refusing to share a secret; they have not looked at your machine.
Enclosure, seals and the boundary of a wet job
The hard boundary on a machine-tool exterior runs through its enclosures and openings. Enclosed guideways and the covers that protect them, the wipers and scrapers that close them, telescopic steel and fabric covers, cable carriers and the cable in them, chip and coolant conveyors and their joints, coolant tank lids and level gauges, drive housings and their joints, motor housings and terminal boxes, electrical cabinets and every cable entry and conduit seal into them, operator panels, and the linear scales, encoders and probes with their connector tails: these are the rows where a wet pass is normally refused.
Seals and wipers are usually aged and torn by the time a cleaning method is discussed, and an exterior clean does not repair them. Ask the machine builder or the site's own maintenance record what the sealing condition is on each envelope before the first wet pass is proposed. A torn wiper turns a controlled pass into liquid inside a guideway.
Where a row is refused, name the fallback in the same column and price it: wipe with a solvent or detergent cloth and a dry finish, a low-volume hand-clean, or deferral until a rebuild. Then have a competent person sign the list. The signed list also states what stays dry when the machine is handed back.
What lubrication inside the machine forbids
Machine tools are full of lubricant that must stay where it is, and heat plus forced liquid is a good way of moving it somewhere else. Ways and the slides they sit on, ball screws and their nuts, gearboxes and geared heads, spindle housings and their seals, bearing housings, the hydraulic side with its bleed points, tanks and return lines, coolant circuits with their pumps and tanks, and slideways under the covers: all of them are limits on a wet method.
Two rules cover most of them. First, isolation happens with the lubricant still inside: nothing is drained, purged or flushed as part of a cleaning job, and the isolation record states what was locked, where and by whom. Second, the cleaning task never opens a circuit. Seals, drain plugs, sight glasses and joints are cleaned around, and only dismantled by the maintenance trade with the machine's own procedure.
Ask, in writing, how deep the supplier intends to work on any of those rows, and what they stop at. "We clean the outside" is a useful answer only when the outside they mean matches the surface list you handed them.
Surface and finish: the heat that works on paint and the heat that ruins it
The finish decides the mode long before the machine specification does. Castings with textured paint, sheet guards and painted panels, decals, machine badges and painted identity, printed and etched nameplates, safety markings and instruction labels, anodised and painted handles and knobs, plastics and cast nylon parts, glass on sight glasses and viewing panels, and rubber hoses and grips with years of oil on them: each is a limit, and each has its own failure.
Heat and dwell lift a film of oil off sound painted steel, and the same heat and dwell lifts paint at a chipped edge, softens the adhesive under a decal, and blisters a re-coated panel. Repaired, re-coated and touched-up areas are a separate category from original finish, and a shop that has repainted a column should say so on the surface list. Printed and etched markings are commonly destroyed by a pass that the surrounding metal survives, so nameplates and safety markings go on the exclusion list with a hand-clean as their replacement.
Uncoated machined faces, exposed ways, ground surfaces and polished parts carry their own risk in the form of flash rust once the oil film that protected them is removed. If a row on the list is bare metal in service, decide in advance how it is dried and what it is re-protected with, and confirm the machine builder's own instruction for that surface.
Metrology, controls and anything that measures
The most expensive limit on a machine-tool exterior is the group of parts that exist to measure. Linear scales and their read heads, encoders and their connector tails, tool setters, probes and their styli, cameras and lights, and the reference surfaces and datum features used for setting and inspection: none of them tolerate liquid or displaced swarf.
For these rows write the exclusion first, then the alternative: a dry pass or a lint-free cloth with the machine's approved cleaner, a hand-clean by the metrology owner, and no cleaning at all on a reference surface unless that surface is inspected afterwards. Precision is not a cleaning result, and it is not restored by cleaning; it is restored by inspection and, if needed, by the machine builder.
Buyers should expect an accuracy consequence on any quotation that covers a machine with a scale system and does not mention one. Ask who checks accuracy after a wet job, with what, and against what record, and expect that answer to name the metrology owner.
Run-off: usually the real limit in a machining shop
Steam is often chosen because it uses less liquid than a hose. Less is not none, and the liquid that leaves a machine has to go somewhere that the site has decided in advance.
Answer these before a trial, not after: which floor area can receive liquid and which cannot; where the nearest drain is and what it discharges to; whether oily swarf and coolant-contaminated liquid may enter that drain at all; how liquid is intercepted under the machine during a pass and how it is collected and removed afterwards; whether the shop has bunding or a containment kerb, and whether the machine stands on a plinth or a sealed floor.
Write the route, show it on the floor plan, and let the site sign it. A cleaning method with no run-off answer has a waste bill waiting inside it, and possibly a permit conversation. Low liquid use is a genuine advantage in a shop with no drainage at the machine; it is not a licence to leave liquid on the floor.
What the shop, not the supplier, has to provide
Most failed trials are site-condition failures. Before any equipment is quoted, confirm five site-owned items. Power: the available supply at the point of work, and the length and protection of cable needed to reach it in a wet area. Water: the supply point, and the inlet arrangement of the machine matched to that point. Access: aisle and doorway clearance, the route the unit travels, thresholds, cable covers, kerbs and drainage channels along that route, and whether the work is on ground level or up. Time: the production window that the clean sits inside, and how long the machine is out of service for the pass, the drying and the re-check.
Then ask for what the machine on the quotation actually delivers for your shop, as a written data list: steam temperature, vapour pressure, how far that temperature has fallen by the time it leaves the nozzle, the heater and supply figures for the exact unit quoted, the water use stated for that machine, the volume and material of the tank, and the footprint including handles and the working radius of the hose. The published figures on a product page belong to the machine on that page and to its test condition, so ask for the test condition that sits behind any figure that decides your choice.
How to read one product page
PowerDe's fixed unit is documented at Fixed Steam Cleaning Machine PowerDe HW02. The page for that unit records 220 V working voltage, 6 kW heating power, a tank of 80 L made from SUS304, overall dimensions of L1200 by W800 by H1200 mm including handles, and a tap-water inlet with a 4-point internal-tooth joint, with switching between dry and wet steam. It also lists protection for that machine against leakage, short circuit, overheating, high voltage and running out of water. Those rows are a record of one unit: they do not travel to another model, and none of them tells you what happens on your machine.
Two standing cautions apply to any machine on the PowerDe cleaning equipment list. A generator temperature is not the temperature at the nozzle once the hose and the wand are accounted for, and the volume of a tank says nothing about how long a machine will run. Both figures decide a job, and both are usually read the wrong way.
Read the site's published scenarios the same careful way. The cleaning pages describe vehicle exterior cleaning at filling stations and parking areas, engine-compartment cleaning, and disinfection work, alongside the wider manufacturing capability described under customized steam cleaning equipment. Machine-tool exteriors are not published as a product claim on those pages, so the cleaning work described here is carried by the site's own surface list and its own trial, not by a scenario printed on a supplier page.
One bounded trial is what turns the limits into a decision
A trial should fail small. Choose one envelope on one machine and mark the test area with tape so that the boundary of the job is physical. Photograph the area as it stands, taken at an angle that reveals texture rather than gloss. Write the stop conditions before the first pass: paint lifting at an edge, a decal or label lifting, liquid at a joint or an opening, moisture at an electrical entry, or any change in how the machine behaves afterwards.
Set the record for one pass in the six blocks that consume the day: isolation and the isolation record, shielding and interception, the cleaning pass itself, drying and re-check, re-protection of bare faces and restoration of guards and covers, and hand-back to production with a named acceptance by a competent person.
Take the figures for your own cycle time from the second run, not the first. Photograph the same area again after a full production shift, since a finish that looks clean in the evening and shows residual oil in the morning has not been cleaned. One row per test area, with the inspector being a different person from the operator, is enough evidence to keep or reject the method.
What steam will not do for you
Buyers should carry a written list of things that will not be solved by the equipment in the quotation. A steam pass does not restore accuracy on a machine that measures. A steam pass does not repair a torn wiper, a split cover or a perished seal; it reveals how bad they are. A polymerised, baked-on layer is not made to disappear by any cleaning method; it is removed mechanically or by a different chemistry, with a different trade and cost. A cleaned exterior does not extend the interval between lubrication service. And a cleaned machine does not become a different machine: nothing about a cleaning job changes what the equipment builder warrants.
Where the limits go when the purchase is made
The output of a good purchase decision is one page per machine family: the surfaces in scope, the deposit on each, the mode chosen for each and why, the excluded rows with their fallback and their cost, the run-off route, the utility conditions at the point of work, who owns each line, and the defect route when a row fails. Train against that page at the machine, not in a classroom. Put a review date on it, and put the reason for the next change next to the date.
Ask your supplier to hand over that page with the machine, together with the exclusion list and the written data answers. A quotation that comes back with those three documents is telling you the limits were understood before the price was set.
