Read the residue before choosing the method
Three different things get called oil residue on a machined part, and they respond to steam differently. A fresh flood or mist film of cutting oil is still mobile; it lifts with comparatively little dwell, and the main risk is simply spreading it into a blind hole instead of off the part. A dried coolant film, the kind left when a part moves to a staging rack and the water evaporates, has left its additives and binders behind as a matte or chalky coating; it needs contact time before the film softens, and rushing it leaves a streaked surface that looks clean under shop light and fails under inspection light. A hardened mixture of oil, fine swarf and coolant that has packed into a counterbore or a thread is a third case again: heat alone will not move it, and the operator has to combine heat with a mechanical action and accept a second pass.
Before anything is written down, the operator should state which of these is on the parts in front of them, because that single sentence decides the mode, the number of passes, and whether the residue is being removed or merely relocated. Where the residue type is genuinely unknown, for example a returned part or a part from a process the cleaning crew did not run, the answer is a trial on scrap or on a part already committed to rework, not a decision made from the appearance of the surface.
Dry steam or wet steam, and why the choice is not cosmetic
Units in the PowerDe cleaning equipment range are described with different mode sets: some switch between dry and wet steam, and several mobile models are listed with dry steam, wet steam and hot water modes. On a workpiece with oil residue the practical difference is how much free moisture reaches the part. Dry steam carries more heat per unit of water and leaves less liquid behind, which matters on a part that has to go straight back to a measuring room or into a coating operation, and on a part with blind holes where trapped water is a later corrosion problem. Wet steam and hot-water modes deliver more mechanical force against a packed deposit, which matters on the third residue type, and cost more drying effort afterwards.
A fixed unit such as the Fixed Steam Cleaning Machine PowerDe HW02 publishes rows for heating power, steam temperature, vapour pressure, tank volume, working voltage and a dry/wet steam mode on its product page, together with a tap-water inlet whose fitting type and thread size are printed on the page. Take those rows as an example of the fields a page should answer, not as an allowance for the part on your bench: published figures belong to the quoted machine and do not transfer to other models, and the printed wording on a page should be verified against the machine actually installed. The more useful operator rule is that temperature and pressure are upper bounds of a generator, not the condition delivered at the nozzle after the lance, the hose and the standoff distance are accounted for.
What a workpiece tolerates that a machine exterior does not
A machine exterior is robust sheet metal with tolerances of millimetres. A finished or semi-finished machined part is a dimensional object. The features that decide whether it survives the pass are the ones the next operation depends on: a datum face, a bore that will be gauged, a fine thread, a sealed bearing, a pressed-in bush, an anodised or painted surface, a deburred edge, a lapped or polished finish, a bonded assembly, a nameplate or a marking. Heat can lift an adhesive that was never specified for a cleaning temperature. Pressure can force a swarf-and-oil paste into a gap that was clean before the pass. Trapped moisture under a flange can show up as rust staining a shift later, on a part that left the wash bay looking perfect.
So the operator's exclusion list is written per part family, not per machine: which parts are excluded entirely, which features must not be pointed at, which parts are cleaned without their pressed or bonded components, and which must be dried and oiled immediately after the pass. Where the drawing, the process sheet or the customer specification already forbids a cleaning step or a temperature, that document overrules the cleaning plan, and nobody at the wash station has the authority to waive it.
Handling, fixturing and the run-off path
A workpiece being washed is usually held, not free-standing, and the holding arrangement is part of the process. A part clamped or seated so that a pocket faces upward is a part that will fill with a mixture of steam condensate and removed oil, then carry that mixture into the next station when it is lifted. Parts are presented so that cavities face down or to the side, so that a hole drains rather than holds. Between passes, parts are moved with clean gloves or clean fixtures, because the fastest way to undo a good cleaning result is to put a cleaned part back into the same oily tray it came from.
The run-off also needs a stated destination. Removing oil from parts produces oily water in a small but continuous volume, and that has to be collected, contained and disposed of under the site's own environmental rules; washing parts on an open floor drain is a decision the operator should not be making alone. Where the shop is not set up to collect run-off from a cleaning position, that gap is an equipment and layout question to raise before the trial, not something to improvise around once the first batch is on the bench.
Settle the trial and the acceptance standard first
A cleaning trial on machined parts should be bounded on purpose: one part family, a handful of parts, the residue type as found, and one defined cleaning sequence that is written down as it was run, including mode, standoff, movement speed, dwell, any brushing, the drying step and the storage position afterwards. Then the parts are judged against the standard the next operation actually uses. A wipe test that shows no streak on a white cloth is one criterion. A film-break check, where water sheets evenly and no oily bloom reappears, is another. Gauging the critical features after the pass catches thermal and moisture damage that visual inspection will not. If the parts must be clean for a bonding, coating, welding or inspection step, ask for the cleanliness requirement in writing, because a subjective "looks clean" cannot be audited and will not settle an argument later.
What to ask the supplier before the first pass
The same short list goes to any supplier, whoever the equipment comes from. For the exact machine being quoted: mode availability and how the mode is switched; the published heating power, steam temperature and vapour pressure rows and how they were measured; the accessory set available for small parts, such as narrower nozzle tips, extension lances, brushes and shields; whether the machine is intended for continuous production duty or for intermittent maintenance cleaning; and what the published protection items cover and exclude. Different listings publish different protection lists, so ask what is fitted on the machine being quoted rather than assuming a standard set. Ask, too, whether the machine's water inlet can be fed from the shop supply as delivered and what water quality the unit expects, since tank and heater life follow the feed water.
Where the parts and the residues are consistent, the volume is steady, and the shop needs the cleaning position built around the wash bay rather than a machine placed beside it, that is a request for customized steam cleaning equipment and should be sent as a written brief: part family, residue as found, the exclusions, the acceptance standard, the run-off situation and the throughput the position has to hold.
The four points to have settled before the lance moves
Before an operator starts on machined workpieces with oil residue, four things should already be answered, in writing, for the specific parts on the bench: what the residue actually is and therefore which mode and how many passes; which features, finishes, bearings, bonds and markings are excluded and who wrote that list; how the part is held, drained, dried and stored so the cleaned result survives handling; and what the acceptance test is, with the parts gauged as well as inspected. Everything else, machine choice included, follows from those four answers rather than the other way round.
