Ask a supplier five questions about a cleaning machine and the fourth answer is always about temperature. Nobody volunteers the thing that decides whether the job is legal to do twice: where the dirty water goes. On a machine shop floor that water carries cutting oil, swarf fines, way-lubricant residue and whatever the floor between the machine and the drain picked up for a year. Assessing that before a purchase — not after the first wet Monday — is what separates a buyer who gets a repeatable process from one who gets a stopped job and a call from the site environmental officer.
1. Separate three water streams before costing anything
A lathe exterior clean touches, or risks touching, three different streams. The first is the machine's own coolant and sump system: it is not cleaning wastewater, it is production fluid, and the moment a wash wand gets near an open tank lid or a chip conveyor sump you have commingled two streams with different disposal routes and different costs. The second is the actual wash water — condensate and rinse water that has passed over the guarding, the splash panels, the chuck and the bed wipers, and therefore carries oil and fine swarf. The third is the floor wash: whatever you did not capture on the machine now sits in a shallow sheet somewhere between the machine feet and the nearest building drain.
Write those three on the same page as the machine quotation. If your site treats them separately today — and a compliant shop usually does — a cleaning method that merges them has just created a new waste stream, a new storage container and a new collection contract. That is a purchasing decision, not an operations detail, and it should be priced in the RFQ round.
2. Size the volume from what the machine actually consumes
The arithmetic a buyer needs is: consumption rate of the unit you are considering, multiplied by the continuous working time for one lathe, plus the clean-down water, multiplied by how many machines per shift and how many shifts between emptying. Do not take the rate from a brochure sentence. Take the clean-water tank volume and ask how long a full tank lasts in continuous spraying — those two numbers together give you a rate you can actually test, and the difference between them tells you where the refills land.
Tank size also decides where a water supply has to be. As published examples, the Fixed Steam Cleaning Machine PowerDe HW02 page lists an 80 L stainless tank with a tap-water inlet using a 4-point internal-tooth (1/2 inch) joint, 6 kW heating power, 160 °C steam temperature and 0.8 MPa vapour pressure; the hand-pushed HMW3 page lists a 50 L clean-water tank and 4.5 kW PTC heating. The consumption figures themselves are not published on those pages, so they belong in the RFQ as a numbered question, and the answer has to come back in writing with the quotation.
Here is the trap specific to steam: a low-consumption process makes people assume there is almost nothing to collect. In a machine shop the collected volume is rarely dominated by the wash water. It is dominated by the run-off radius — the floor you wet while moving the lance, the drip trail from the machine to the drain, and the pad or absorbent you threw away afterwards. Size the collection for the floor area, not for the nozzle.
3. Fix the wet and dry boundaries on the lathe first
The volume and the contamination level are both set by one decision made before the wand moves: what may get wet and what may not. Way covers, the chuck and turret interfaces, pneumatic lines, electrical enclosures, encoder and scale housings, distributor and control cabinets, and any open cable entry stay dry — that is not a suggestion, it is how the machine keeps its accuracy and stays insured. Mark those zones on a photograph of your own machine and tape them off on the first trial.
That map is also your wastewater plan, because it tells you where contaminated water will collect: the tray under the splash guarding, the recess around the coolant tank, the drip line along the bed, the seam between the machine base and the plinth. Buyers who skip this step end up with a machine that cleans the outside and quietly pushes oil into the sump or under the plinth, where nobody sees it until a leak investigation.
4. Ask the three questions about content, separation and the permit
Content first: ask your own site team what the run-off from a lathe exterior will be classified as under your existing waste arrangements, and what your current contract says about oil-bearing rinse water. Do not let a cleaning-equipment supplier answer this for you; they sell machines, they do not hold your discharge consent.
Separation second: what sits between the lance and the drain — absorbent matting and a bunded collection tray for a small number of machines, or an oil/water separator, swarf strainer and holding tank for a bay or a line — and who empties it, how often, and against what record. Ask the equipment supplier in writing whether their machine's tank, hose and fittings are compatible with recovering and transferring that run-off, or whether recovery is a separate line item in the quotation.
Permission third, and it is the one that stops the job: identify the authorised receiving point on your site, get the site rules or consent wording for oil-contaminated water in writing, and check whether any treatment step — separation, filtration, scheduled removal by a licensed contractor — is mandatory before that point. A method that is technically excellent and administratively impossible is not a method. If your site discharges to a public sewer or an external treatment works, the applicable discharge conditions govern the design; confirm them with the site's environmental lead or the relevant authority rather than inferring them from a datasheet.
5. Record six measurements on a trial you are allowed to fail
Book one machine, one shift, and the dirtiest realistic lathe. Record: (a) clean-water used per machine, read from tank refills; (b) continuous spraying time before the machine needs a break or a refill; (c) collected volume, measured in the container, not estimated; (d) the wetted floor area, photographed with a machine foot as scale; (e) the exact route the run-off took and where it stalled; (f) how quickly the separated oil and swarf had to be removed. Photograph the machine before and after, and time the job from set-up to a dry, signed-off floor.
A trial with no pass condition is a demonstration. Write the fail conditions first: collected volume that exceeds what your container or separator can hold in one shift, run-off that reaches an unsealed joint, a drain, a doorway or a walkway, or a residue film left on the guarding that will be re-suspended into the cutting zone.
6. Read the result as six signals
Workable: everything you wetted is inside your marked boundary; the collected volume fits the container you already own and can lift; the oil separates and can be removed on a schedule you can staff; the floor is dry enough to walk before the next shift starts; the machine's accuracy checks after cleaning are unchanged; and the records you generated match the ones your environmental file already requires.
Not workable, on this method: run-off reaches the sump, the chip conveyor or under the plinth; the water cannot be contained without a bund you would have to build; the classification of the waste changes and nobody has a contract for it; or the only way to keep the floor dry is to clean fewer machines than the plan assumes. Those are design failures, not operator failures — change the boundary, the recovery setup, the batch size or the machine class, then trial again.
7. Put the wastewater requirements into the RFQ
Send the same five questions to every bidder, and reject any quotation that ignores them. What is the clean-water consumption in continuous operation, and what is the tank capacity behind that figure? Which machine body parts, fittings and accessories are rated for recovering and moving oil-bearing run-off, and which are not? Can the unit run on a shop supply that matches your available voltage and water connection, and what protection does it provide against leakage, short circuit, high temperature, high voltage and water shortage? What is the reach of the hose and wand, so the machine can be cleaned without dragging the unit across a wet floor? And if your bay needs a different tank size, mode set or a fixed installation beside the machine, what does that change to the build — for example as customized steam cleaning equipment rather than a catalogue unit?
Note one honesty point while comparing bids. The cleaning range documented on industrial steam cleaning equipment describes vehicle exterior, engine-compartment and interior work, and the cleaning of hospital beds and medical machinery. It does not document lathe or machine-tool exterior cleaning as a verified application. So use the trial, and ask the manufacturer in writing which of their models they will stand behind for machine-tool exteriors, with what nozzle set and what distance and dwell, before you put a machine-tool figure into your own standard.
Two practical notes for the comparison table: a mobile unit may be offered with or without a battery, which decides whether the bay needs a charging point and a supply run, and it changes nothing about the water. Send the trial measurements — consumption per machine, collected volume, wetted area — to bidders together with your boundary map and your receiving-point rules. Shenzhen PowerDe Automation Precision Equipment also builds process equipment for industries where cleanliness is part of the process, so a written request through the contact page can be answered at engineering level rather than catalogue level. Every figure quoted in this article comes from the published product pages named above; anything those pages do not publish is deliberately left as a question, not filled in.
