Guards, hoods, enclosures and machine housings are cleaned on almost every shift, yet in most plants nobody can say what they cost in water. The volume disappears down a drain, so it never appears in a report. A few sheets of paper and one walk around the cleaning area are usually enough to turn that invisible usage into a number a plant manager will sign off on. This article walks through the measurement method in the order a shift supervisor would actually apply it.
Start with a per-task standard volume
The first figure you need is not a machine specification. It is the standard volume one person uses for one task, such as rinsing one conveyor guard or one motor housing. Ask three operators to clean the same type of part and let them work at their normal pace. Then measure the water they actually used — with a metered hose reel, a measured bucket, or by weighing a drum before and after. Do not interview people about what they think they use.
Recording the elapsed time for each trial matters just as much as the litres. Water use per part means nothing on its own; litres per hour tells you whether the constraint is the cleaning method, the crew size, or the queue of parts waiting to be cleaned.
Two figures come out of this step:
- Standard litres per part or per guard, with a range between the lightest and the heaviest user.
- Standard minutes per part, which converts the litre figure into an hourly rate you can compare across shifts.
Count frequency, not intention
Guards and housings are cleaned more often than the maintenance schedule claims. Log every wash for one typical week: who cleaned what, when, and why. Most plants find the same panel rinsed twice in one shift — once to clear a spill, once again because the first pass left a film. Repeats like that are invisible in a written procedure, and they are where a large share of the water goes.
Split the log into three causes: scheduled cleaning, spill response, and cleaning done to satisfy an inspection or an audit photo. Only the first two belong in a baseline. The third is a symptom of a cleaning method that leaves residue, and it is the first place to look for a reduction.
Add the water that is not in the procedure
Written cleaning instructions cover the target surface. Real work includes the floor around it, the tray under it, the tools left on it, and the hose left running between steps. Walk the area while a wash is taking place and write down every water use the procedure does not mention. Then take one week of meter readings and compare total consumption against baseline volume multiplied by the number of completed tasks.
The gap between those two numbers is your uncontrolled share. In most plants it is the largest single block of water in the cleaning area, and no capital purchase is needed to reduce it — usually a nozzle shut-off and a stated stop point are enough.
Factor in the surface, the soil, and the access
The same housing behaves differently depending on three variables, and your standard volumes should be stated per combination rather than as one plant-wide number:
- Surface condition. Smooth painted steel rinses quickly. Porous gaskets, welded seams and textured plastic hold soil and need more passes.
- Soil type. Loose dust comes off with a rinse. Cutting fluid, lubricating grease and food residue release only with heat, which changes the method rather than the duration.
- Access. A guard that bolts off and goes to a wash bay carries a different water budget from one that has to be cleaned in place, on a ladder, with a hose.
Keep the three variables in separate columns. If the log shows that in-place cleaning is heavier than bay cleaning, that is an access finding, not a water finding.
Where heat changes the arithmetic
Cold-water rinsing works by volume: the more soil, the more water. Heat works by releasing the soil from the surface, so a small amount of very hot water or steam can lift grease that a large volume of cold water only moves around. Plants comparing a hose against a cleaning equipment series such as a fixed steam cleaning machine should compare litres per completed task, not the machine's rated flow, because rated flow says nothing about how many passes an operator needs.
Two conditions matter before you run that comparison. First, the unit has to be close enough that operators use it without dragging hoses across the shop; equipment parked far away gets used less and the baseline never moves. Second, the comparison has to be run on the same soil and the same parts, on both shifts, by the same crew. One demonstration on a single clean guard proves nothing either way.
What to log so the number holds up
- Water source and meter identity, so a leak upstream is not read as a cleaning increase.
- Site or line, shift and crew, so a one-off event is not treated as a new baseline.
- Task type and part type, using the same short list every time.
- Detergent name and dose, because a detergent change and a water change move together and will otherwise confound each other.
- Waste route — which drain, and whether the rinse water reaches an oil separator or a treatment step that charges by volume.
Store the log in one place with one owner, and leave it open so anyone can read it. A sheet nobody reads stops being filled in within two weeks.
Common errors that invalidate the figures
Three mistakes appear repeatedly. Estimating from nameplate flow multiplied by hose-open time overstates usage, because nobody runs a hose wide open for a whole task. Extrapolating from one shift hides weekly cleaning, which is often heavier than daily cleaning. And ignoring trade effluent charges understates the real cost, since treating or disposing of the rinse water can cost more than the water itself. If your site pays by volume for discharge, put that charge in the same column as the water.
Reading the result
Once litres per task, task frequency and the uncontrolled share sit on one page, the decision stops being a matter of equipment preference. You can see whether the water goes to the cleaning method, to how often people clean, or to the way hoses and access are set up. Fix the access problem and the repeat washes first — they cost nothing. Then evaluate any equipment change against a baseline you can defend.
If you are specifying equipment instead of building a baseline, start from the same task data: state what you clean, how often, and where the water drains, and let the supplier size the unit against those three facts rather than a catalogue page. Shenzhen PowerDe Automation Precision Equipment Co., Ltd publishes its cleaning equipment series and answers specification questions through its contact page.
