Coolant sump log sheet template with trend columns per machine

What is a coolant sump log sheet for, and who keeps it?

A coolant sump log sheet is a table with one row per reading of one water-mix coolant sump, kept by the machine operator, the shop's fluid owner or the supplier's service engineer, so that a change in concentration, pH, tramp oil or bacteria shows as a trend before it shows as rust, odor or skin complaints.

The US OSHA manual on metalworking fluids says the data on fluid condition, laboratory analyses and additions "should be tabulated so that relationships and trends in the data can be spotted" (OSHA Metalworking Fluids manual). UK guidance asks for test records in a table or graph for the same reason and tells employers to keep records of all tests for at least five years (HSE MW5, 2021). The German rule for coolant work recommends keeping them at least three years and explicitly recommends longer (DGUV Regel 109-003, April 2026).

The template on this page is built for the trend, not for a single audit. Every row carries the sump ID, so one workbook can hold every machine and be filtered by sump. Every value has its unit in the column header and its method in its own column, so readings taken by different people can be compared. The editable Excel log and a CSV with the same columns are at the end of this page. For the routine of collecting the readings at a site, see how to keep a coolant concentration and pH history per site.

Coolant sump log columns: concentration, pH, tramp oil and bacteria

The coolant sump log has fifteen fields: the ten core columns, plus the raw refractometer reading and factor behind the concentration, the concentrate added, the reader and a notes field that explains any gap. In the Excel log, the fifteen fields become 21 columns, because date and time are split and the concentration method, tramp oil method, pump state, bacteria unit and bacteria method each sit in their own column. The table below previews every column, with each method shown beside its value, and decides what a reader can compare between two rows; the example values are illustrative and describe no real machine.

The key row is concentration and method: a refractometer reading is not a concentration until it is multiplied by the product's factor (Blaser Swisslube), so the log keeps the raw value, the factor and the result in separate columns. If the factor changes because the product changes, the raw readings before and after stay comparable only through their own factors.

The sump header, written once per sump on the Sumps sheet of the Excel log or at the top of a paper copy, holds what the rows do not repeat: machine, fluid product, sump capacity in litres, charge date, fresh-fill pH, the refractometer factor, the target concentration and pH ranges from the fluid's data sheet, the source of those targets (data sheet and revision) and the person responsible.

How do you measure and record tramp oil in a coolant sump?

You measure tramp oil in a coolant sump with the method your fluid supplier advises and record it as a value, a unit and the method in the same row, because UK guidance gives a recommended level but no single method: check weekly that tramp oil is "kept to a minimum (recommended below 2%)" and "get advice from your fluid supplier on a suitable measurement method" (HSE MW5, 2021).

Tramp oil is non-emulsified oil carried into the fluid in large droplets, often from hydraulic or way lube leaks, and it separates and floats when agitation stops (OSHA Metalworking Fluids manual). A reading taken with the pumps running and one taken after a weekend shutdown therefore measure different things, so the log notes whether the pumps were on and whether the sump had just been skimmed. A visual class is also a valid record: the example table in UK guidance grades tramp oil as none, light, moderate or heavy (HSE MW5, 2021). The OSHA manual gives a field check for too much tramp oil: the sump surface is fully covered and cannot be swished clear for more than 5 to 8 seconds (OSHA Metalworking Fluids manual).

Tramp oil also changes other columns. The German rule for coolant work notes that a hand refractometer gives wrong values when tramp oil is present, while acid titration does not depend on tramp oil (DGUV Regel 109-003, April 2026). A high tramp oil row is the row to check the concentration method on.

Which coolant sump log columns turn top-ups into a trend?

Top-up volume in litres, top-up mix in percent and the concentrate added in litres are the coolant sump log columns that turn top-ups into a trend, read together with the concentration on the same row and the sump capacity in the header. A top-up written only as "topped up" shows that something was added, not how much or why.

Losses have more than one cause, and the columns tell them apart. The OSHA manual says a low sump level, 30% below the full mark, shows fluid loss or water evaporation; if the concentration is then too strong, water is added, and if the concentration is correct, the fluid was lost by dragout (OSHA Metalworking Fluids manual). UK guidance adds that water-mix fluids evaporate and become more concentrated in use, so it says to "top up only with fluid below recommended concentration" (HSE MW5, 2021). The top-up mix column shows whether that was done.

Read the columns down the sheet. Rising weekly top-up volume with a steady concentration points to dragout, a leak or splash loss; rising concentration with small top-ups points to evaporation; falling concentration with weak top-up mix points to dilution by the top-ups. Dividing the weekly top-up volume by the sump capacity gives a loss rate that can be compared across machines of different size (illustrative calculation, a site's own baseline decides what is normal). For whether a drifting sump should be corrected or replaced, see coolant concentration and pH drift: correct it or dump the sump.

Why should a coolant sump log leave a missed reading blank instead of zero?

A coolant sump log should leave a missed reading blank instead of zero because zero is a measured value: a tramp oil reading of zero says the sump was clean, and a concentration of zero says the sump held plain water. A zero typed for a skipped check enters every average, chart and filter as a real reading.

The arithmetic shows the damage. With weekly concentration readings of 5.8%, a missed week and 5.4%, the average of the two readings is 5.6%; with the missed week entered as zero, the average of three values is 3.7%, which looks like a sump far below any target (illustrative). A chart of the same column would draw a fall to zero and a recovery that never happened. A dipslide column full of zeros looks like a run of clean results, not tests nobody took.

Write the reason for the gap in the notes column, such as "pH strips out of stock" or "machine down". Gaps matter on their own: UK guidance says that to reduce dipslide frequency you need to show that fluid quality management is effective, for example with dipslide, concentration and pH test records (HSE MW5, 2021), and a record full of gaps shows the opposite. In the Excel log, the concentration and concentrate-added cells stay empty when their inputs are empty, so the formulas never turn a gap into a zero. A test the site does not run at all is a column to hide, not a column of zeros.

How to fill in the coolant sump log, with an illustrative example

Fill in the coolant sump log at each check in the same order, so readings from different people stay comparable, and compare each row with the header's target ranges before leaving the machine.

1. Sample from the same point in the sump, wearing the gloves and eye protection named in the fluid's safety data sheet (SDS). Stir the sump before a dipslide test so tramp oil does not coat the slide (HSE MW5, 2021).

2. Record tramp oil with its method and whether the pumps were running.

3. Record the raw refractometer reading, the factor and the concentration, naming titration if it was used instead.

4. Record pH, sump temperature and the bacteria result with its method, entering a dipslide count only after the incubation the slide supplier specifies (HSE MW5, 2021).

5. Record top-up volume and mix since the last row, then the action, even "none", and your name.

The table below is an illustrative four-week log for sump M-07, factor 1.1, target concentration 5 to 7% and fresh-fill pH 9.2.

The key row is 2026-10-19: top-up volume had more than doubled in two weeks while concentration fell below target and the dipslide reached 10,000 CFU/mL, the level UK guidance reads as microbial growth (HSE MW5, 2021). The rising top-ups and the leak report explain the fall (illustrative interpretation).

When does one coolant sump log sheet per machine stop being enough?

One coolant sump log sheet per machine stops being enough when sumps must be compared with each other, when one central system feeds several machines, when laboratory results join the field readings, or when the sump is recharged and a new fluid charge begins.

A paper sheet at each machine is easy to fill but hard to compare; the Excel log on this page holds every sump in one table with the sump ID in each row, so a filter shows one sump and a sort shows all sumps on one date. A central system is one sump for logging, with one ID, even if it feeds many machines; per-machine notes go in the notes column.

Laboratory data need their own columns. The OSHA manual lists factors a fluid manager may track beyond concentration and pH, including foaming tendency, system stability, biocide levels, corrosion resistance and emulsified oils, and says the manager should choose and prioritize them for the facility (OSHA Metalworking Fluids manual). Add those as columns with their units rather than writing them into notes.

A recharge starts a new trend. Record the new charge date and fresh-fill pH in the header, because the German rule for coolant work refers a pH drop of more than 0.5 against the first fill to the maker's measures and a drop of more than 1.0 to a possible fluid exchange and system cleaning (DGUV Regel 109-003, April 2026). Readings from two charges in one unbroken column read as one trend.

Where this coolant sump log template does not fit

The coolant sump log template on this page does not fit neat cutting oils, sumps whose fluid maker runs its own monitoring program with its own forms, or jurisdictions and sites whose rules require columns it does not have.

Straight oils, also called neat oils, are not intended to be diluted with water before use (ASTM E1497-23), so concentration, refractometer factor and top-up mix do not apply to them, and they need a different set of checks. Some fluids need columns this template leaves out: in Germany, employers must check the nitrite content and pH of water-mixed coolants regularly under TRGS 611 and document the results, and the test plan should also hold the nitrate or nitrite content of the make-up water (DGUV Regel 109-003, April 2026). Bacteria results also need care. ASTM E2694-26 reports adenosine triphosphate in pg ATP/mL and notes that ATP data generally covary with culture data but are affected by different factors (ASTM E2694-26), so dipslide counts and ATP values stay in separate columns and are never converted into each other. Target ranges come from the fluid's own data sheet.

Lubinpla's trend analysis keeps missing readings as missing rather than counting them as zero and reads only changes that are reliable given that coverage, and this log can reach it as work logs through bulk import, which takes txt, md, csv, pdf and image files, so upload the CSV version rather than the Excel file.