Paul Industries designs precision cleaning and parts washing systems for New Hampshire device and precision manufacturers. Cleaning a medical device is not cleaning a process line, and the difference is the acceptance criterion. A process vessel is clean when no meaningful residue remains. A device is clean when the residue that remains is below a limit derived from what a patient can tolerate, measured in micrograms, on a part that may have geometry a swab cannot reach.
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What is actually on the part
A machined device component arrives at cleaning carrying a specific and predictable set of contaminants, and it is worth listing them because each behaves differently.
Cutting and forming fluid. Oils and emulsions applied deliberately during machining. They are designed to adhere to metal under pressure and heat, which is exactly what makes them difficult to remove afterwards.
Metallic fines. Swarf and particles generated by cutting, which lodge in features, burrs and threads. These are particulate rather than chemical and they need mechanical action, not solvency.
Handling residue. Skin oils, glove residue, and whatever the part rested on between operations.
Previous process chemistry. Passivation or electropolishing solutions, deburring media, marking residue.
The cleaning agent. This is the one that catches people. A detergent that removes everything above becomes, itself, the last thing on the part, and it has to be rinsed to below its own acceptance limit. On many device lines the final rinse is doing more validated work than the wash.
The process, and why the last stage matters most
Aqueous ultrasonic cleaning in stages is the dominant approach, and the arrangement matters more than the equipment.
Ultrasonic action is not uniform. Cavitation intensity varies with position in a tank, with load density, with liquid level and with temperature, and parts nested together shadow one another. A basket loaded to maximize throughput is a basket in which some parts are cleaned considerably less than others. Fixturing that holds parts in defined positions with clear separation is worth more than a larger machine.
Stage the process and move the part, not the chemistry. Wash, then rinse, then final rinse, in separate tanks with the part transferring between them. A single tank that is drained and refilled leaves the part sitting in progressively contaminated liquid.
Counterflow the rinses. Fresh water enters the final rinse, cascades back to the earlier rinse, and is discarded from there. That holds the cleanest water where it matters, at the last contact the part has, and it substantially reduces consumption.
Dry properly and immediately. A part that air-dries slowly leaves whatever was dissolved in the residual water as a spot on the surface, which is why a perfectly cleaned part can fail inspection. Hot air, vacuum drying, or a solvent displacement step depending on geometry, and prompt rather than eventual.
Control the water. Final rinse water must be of a grade that leaves nothing behind. Rinsing a device in water carrying dissolved solids deposits those solids on it as it dries, which means the water system is part of the cleaning process rather than a utility supporting it.
| Continuous load | New Hampshire per year | At the 8.13 cent US average |
|---|---|---|
| 25 kW | $35,500 | $17,805 |
| 50 kW | $71,000 | $35,609 |
| 100 kW | $142,000 | $71,219 |
At 16.21 cents per kilowatt-hour, 1.99 times the national average (EIA, 2024), heated tanks held at temperature through a shift are a meaningful cost. Tank insulation, lids that are actually used, and heating that follows the production schedule rather than running continuously are unglamorous measures that pay noticeably better here than in a low-tariff state.
Validation, which is where device cleaning genuinely differs
Under 21 CFR 820 and ISO 13485 a cleaning process is validated, not merely performed, and the validation has to demonstrate that residues are reduced below limits that were themselves justified.
Three elements do the work.
Establishing the limit. Derived from toxicological consideration of the specific residue and the patient exposure, rather than adopted from a general convention. This is the same logic that governs pharmaceutical cleaning limits, and it produces a number that is specific to the product rather than inherited.
Demonstrating the method can detect it. An acceptance criterion the analytical method cannot see with margin is not an acceptance criterion. Establishing that before committing to the limit avoids a validated process that cannot evidence its own compliance.
Sampling where the residue would actually be. Worst-case locations, justified and documented, which on a device means blind holes, threads, internal lumens, joints and any re-entrant feature. Extraction testing of the whole part rather than swabbing is frequently the only workable answer on complex geometry, because a swab reaches what a swab can reach.
The recurring practical failure is a cleaning process validated on a simple representative part and then applied to a family that includes considerably more difficult geometry. Worst case should mean worst case in the family, not the part that was convenient to test.
We design and install multi-stage cleaning systems, ultrasonic tank arrangements and fixturing, counterflow rinse systems, final rinse water treatment and distribution, drying systems, and the water and effluent handling around them, and we support cleaning validation with the sampling access and instrumentation that make it demonstrable.
Standards referenced: EIA electricity price data · 21 CFR 820 · ISO 13485 · ASTM A967 · ASTM F86 · ASME BPE
Frequently asked questions
Do you build precision cleaning systems in New Hampshire?
Yes, across Manchester, Nashua, Salem, Portsmouth and statewide: multi-stage cleaning systems, ultrasonic tanks and fixturing, counterflow rinses, final rinse water treatment and distribution, drying systems, and the water and effluent handling around them.
How is device cleaning different from process cleaning?
The acceptance criterion. A process vessel is clean when no meaningful residue remains; a device is clean when residue is below a limit derived from patient tolerance, measured in micrograms, frequently on geometry a swab cannot reach.
What is actually on an incoming machined part?
Cutting and forming fluid designed to adhere to metal under pressure and heat, metallic fines lodged in features and threads, handling residue, previous process chemistry, and ultimately the cleaning agent itself, which becomes the last residue to remove.
Why does the final rinse matter most?
Because the cleaning agent that removed everything else is now the contaminant, and it has to come down below its own acceptance limit. On many device lines the final rinse is doing more validated work than the wash stage is.
Is ultrasonic cleaning uniform across a tank?
No. Cavitation intensity varies with position, load density, liquid level and temperature, and nested parts shadow each other. A basket loaded for maximum throughput cleans some parts considerably less than others, so fixturing that holds parts separated in defined positions beats buying a larger machine.
Why counterflow the rinses?
Because it holds the cleanest water at the part’s last contact. Fresh water enters the final rinse, cascades back to the earlier rinse and is discarded from there, which delivers better results and substantially lower consumption than running both on fresh water.
Does rinse water quality matter?
Directly. Water carrying dissolved solids deposits them on the part as it dries, so a perfectly cleaned component fails inspection on spotting. The final rinse water system is part of the cleaning process rather than a utility supporting it.
How should we set the residue limit?
From toxicological consideration of the specific residue and patient exposure, rather than adopting a general convention. Then confirm the analytical method can detect that limit with margin, because an acceptance criterion the method cannot see is not one.
Where should we sample?
At justified worst-case locations, which on devices means blind holes, threads, internal lumens, joints and re-entrant features. Extraction testing of the whole part is often the only workable approach on complex geometry, because a swab only reaches what a swab can reach.
How do I get a quote for a New Hampshire cleaning project?
Use the form on this page or call 201-450-8280. Useful inputs are the part family and its most difficult geometry, incoming contaminants, throughput, the residue limits you work to, current equipment and where it falls short, and your final rinse water source.
What is the difference between ultrasonic and spray washing for device parts?
Ultrasonic cleaning uses cavitation in a bath to reach geometry that spray cannot, and it suits small complex parts. Spray washing delivers mechanical action to accessible surfaces at higher throughput. Many lines use both, with ultrasonics for the difficult stage and spray for bulk removal.
How is cleaning validated for a medical device under ISO 10993?
By establishing a residue limit from the biocompatibility assessment, developing an extraction and analytical method that can measure it on the actual part, and demonstrating that the cleaning process consistently achieves it. The method development is often the longest part.
What analytical methods are used to measure residue on device parts?
Total organic carbon on an extract, gravimetric non-volatile residue, FTIR for identifying residue type, and specific methods where a particular contaminant is the concern. The method has to be shown to recover residue from the part's geometry.
How does an aqueous cleaning line differ from a solvent line?
Aqueous lines use detergent, rinses and drying and produce wastewater; solvent lines use vapour degreasing or immersion and produce solvent waste and emissions. Regulation and environmental permitting have moved most device cleaning to aqueous processes, with solvents reserved for specific soils.
How is drying controlled after aqueous cleaning?
With hot air, vacuum drying or alcohol displacement, to a verified dry condition, because water spots and retained moisture cause corrosion and failed inspections. Drying is a validated step, not an afterthought.
Does the cleaning process itself need to be qualified as equipment?
Yes. Under 21 CFR 820 and ISO 13485 the cleaning process is a manufacturing process and the equipment is qualified, with IQ, OQ and PQ demonstrating that it operates within the validated parameters.
How is bioburden controlled on parts before sterilization?
By cleaning to remove soil that protects organisms, by controlling the cleanliness of rinse water and drying air, and by handling and packaging parts in a controlled environment afterwards. Bioburden testing verifies the outcome and feeds the sterilization validation.
How is a rinse tank prevented from becoming a source of contamination?
By continuous or frequent turnover, conductivity control that dumps and refills when the bath loads up, and materials and fittings that do not shed particles or ions. A rinse tank is a process bath in its own right and needs the same attention as the wash stage.
How do you handle parts with lumens or blind holes?
With flow-through fixtures, ultrasonic energy and rinse sequences that ensure exchange inside the feature, and with validation sampling that extracts from the feature itself. A swab of the outside proves nothing about a lumen.
How does passivation fit into a device cleaning line?
For stainless implants and instruments, passivation follows cleaning as a separate validated step under ASTM A967 or the device-specific requirements of ASTM F86. The cleaning line has to deliver a surface free of oils and particulates for passivation to work.
What about cleaning titanium and nitinol components?
Titanium alloys and nitinol have their own surface chemistry and their own residue concerns, and cleaning chemistry that suits stainless can be inappropriate. The line is designed for the materials the plant actually processes, with separate parameters where needed.
How is a cleaning line kept from recontaminating clean parts?
By separating dirty and clean handling, by controlling the air and surfaces the clean parts meet, and by drying and packaging promptly. Clean parts left in an open shop environment recontaminate quickly.
What documentation supports device cleaning for an FDA inspection?
The cleaning validation, the equipment qualification, the process parameters and their monitoring records, the residue and bioburden results, and change control for any modification. The inspector will want to see the link between the residue limit and the biocompatibility assessment.
Can a machining shop supplying device makers meet these requirements?
Yes, and many New Hampshire shops do. The step from industrial parts washing to validated device cleaning is documentation, water quality and control of the environment, more than a change in equipment.
What is the commonest failure in device cleaning validation?
A residue limit chosen by convention rather than derived from the device's biocompatibility case, and an analytical method that cannot actually measure to that limit on the part. Both are fixed at the start of the project, not at the end.
Where the cleaning chemistry goes afterwards
A precision cleaning line consumes water and chemistry and produces an effluent carrying everything it removed, and that stream is frequently the part of the project nobody scoped.
What leaves the line is specific: emulsified cutting oils, metallic fines including whatever alloys the shop machines, spent detergent, and on lines that follow surface treatment, traces of process chemistry. Several of those attract attention from a municipal treatment works, and metals in particular are commonly limited at concentrations low enough that a device shop can exceed them without producing much volume at all.
Three measures address most of it and they run in the usual order of preference.
Separate at source. The first wash carries nearly all the oil and nearly all the solids; the final rinse carries very little. Combining them makes a small difficult stream into a large difficult stream. Segregated drains from each stage preserve the option to treat only what needs treating, and like all segregation decisions it is a plumbing choice that has to be made at installation.
Remove the oil before anything else. Coalescing separation or skimming on the wash stage takes out the bulk of the organic load cheaply. Emulsified oil is harder and may need splitting, which is worth knowing before selecting a detergent, because a strongly emulsifying cleaner produces a stream that will not separate and shifts the cost downstream.
Recover the rinse water. The final rinse leaves almost clean, and on a counterflow arrangement it is already cascading backwards. Extending that with filtration and, where the water quality justifies it, returning polished water to the front of the line reduces both consumption and discharge. On a site paying New Hampshire utility rates for water in, treatment, heating and discharge, the four costs together make this pay considerably better than any one of them suggests.
Capture the solids as solids. Metallic fines removed by filtration are a manageable solid waste and sometimes a recoverable one, where a shop machines enough of a single valuable alloy. Fines left to reach the drain are a permit problem.
We design the effluent side alongside the cleaning line rather than after it, including segregation, oil separation, filtration, recovery and the sampling provision that makes a discharge position defensible.
Cleaning validation problems in New Hampshire?
Tell us your hardest geometry in the part family and what your final rinse water is. Those two explain most failures we are asked to look at. Call 201-450-8280 or use the form below.