A clean steam generator produces additive-free steam from purified feedwater, using a heat exchanger so plant steam heats but never mixes with the clean steam – so the output condensate meets Water-for-Injection quality. It is the source of the pure steam that sterilizes product-contact equipment.
How it works
Purified feedwater (RO/DI or better) enters the generator, where plant steam or electric heat evaporates it through a separation stage that removes droplets and pyrogens. The result is dry, additive-free clean steam whose condensate meets WFI standards – suitable for SIP, autoclaves, and humidification that touches product.
What it needs and produces
- Feedwater: purified water (quality drives output quality)
- Heat source: plant steam via heat exchanger, or electric
- Output: pyrogen-free clean steam, WFI-quality condensate
- Distribution: sanitary, sloped, drainable piping to points of use
Related: Clean steam systems · Clean steam vs plant steam · Autoclave sterilization · Request a quote
Frequently asked questions
What is a clean steam generator?
A heat exchanger and separator package that makes steam from treated water without a fired boiler. Plant steam or electric elements supply the heat on one side; Purified Water or better evaporates on the other, so the two never mix and no boiler treatment chemistry can carry across. A separator then removes entrained droplets before the steam leaves the unit. Installed cost typically runs 135,000 to 620,000 dollars depending on capacity, materials and whether pretreatment is included in the scope.
How is a clean steam generator sized?
Sizing is based on peak simultaneous demand, the largest SIP cycle or combined sterilization loads, plus distribution losses and warm-up. Undersizing starves SIP cycles of steam and stalls sterilization; oversizing wastes energy. Paul Industries sizes to your actual demand profile.
What is the difference between a clean steam generator and a plant boiler?
A plant boiler produces utility steam dosed with amines and corrosion inhibitors unsuitable for product contact. A clean steam generator makes additive-free steam from high-purity feedwater for direct process and sterilization use. The distinction is contamination control, not just pressure.
What standard governs clean steam quality?
For the generator specifically, what has to be demonstrated is output quality across its operating range, not just at the nameplate. EN 285 supplies the physical criteria used in testing: non-condensable gases not exceeding 3.5 percent by volume, dryness value at least 0.90 and at least 0.95 for metal loads, and superheat not exceeding 25 degrees C. The condensate is separately held to the Water for Injection requirements for conductivity, total organic carbon and endotoxin. A generator can pass at design load and fail at turndown, which is why range matters.
Why does clean steam condensate need to meet water standards?
When clean steam contacts product surfaces it condenses, so that condensate touches the product path. If it carried boiler additives or contaminants, it would compromise the product. Condensate is therefore held to Purified Water or WFI chemistry, verifying steam purity.
What materials are clean steam generators built from?
316L stainless throughout the wetted path, with the tube bundle, evaporator shell and separator internals all in contact with either feedwater or product steam. Surface finish follows the ASME BPE designation the specification names, and the unit must be fully drainable so it does not hold water between campaigns. Gaskets and seals are typically PTFE or EPDM selected for steam duty. Carbon steel appears only on the heating side where plant steam is the energy source and never touches the clean steam path.
Can a clean steam generator supply SIP directly?
Yes. Clean steam generators are frequently installed specifically to feed SIP, delivering additive-free steam at the temperature and dryness needed to sterilize vessels and piping in place. Paul Industries sizes and integrates the generator with the SIP distribution it serves.
How is a clean steam generator validated?
Installation qualification covers materials and heat numbers, weld records, instrument calibration, drainability and as-built condition against the specification. Operational qualification demonstrates the unit produces steam meeting EN 285 criteria and condensate meeting the Water for Injection requirements across its operating range, including at minimum turndown, which is where carryover usually appears. Performance qualification proves it sustains that under real plant demand, which frequently exceeds the nominal sizing figure because campaign sterilization load is lumpier than the design assumption.
What causes poor clean steam quality?
Carryover is the dominant cause, and it is a hydraulic problem rather than a chemistry one. Too high a water level in the evaporator, rapid load swings, or operating far below design turndown all let droplets escape the separator, and those droplets carry whatever is dissolved in the feedwater straight into the steam. The other causes are feedwater quality drifting, particularly rising conductivity or chlorides, scale accumulating on the heating surface and reducing capacity, and level control instrumentation drifting out of calibration.
Can a clean steam generator run off existing plant steam?
Yes. Many generators use plant steam as the heating medium on one side of the evaporator while producing clean steam on the other, keeping the boiler additives isolated from the pure steam. Electric-heated units are an alternative where plant steam isn’t available.
How does feedwater temperature affect clean steam generation?
It changes effective capacity more than most specifications allow for. Feedwater entering cold consumes a significant share of the heat input simply raising it to saturation, so a generator sized on a warm feed assumption will underproduce when fed cold, sometimes materially. Preheating the feed, often by recovering heat from the condensate return, raises usable capacity and steadies output. It also reduces thermal shock and level swings at the evaporator, which is one of the practical levers against carryover during load changes.
Does a clean steam generator require maintenance?
Yes, and it is mostly predictable rather than reactive. Descaling of the heating surface on a schedule set by feedwater hardness and duty. Level control probe cleaning and calibration, since drifting level control is a direct carryover cause. Safety valve testing and certification. Gasket and seal replacement on a defined interval rather than on failure. Steam trap surveys on the distribution served by the unit, because a failed trap is the usual cause of a SIP cycle missing temperature. Periodic reverification of steam quality against EN 285 closes the loop.
How is a clean steam generator integrated into a facility?
Integration ties the generator to a high-purity feedwater supply, a heating source, clean-steam distribution to points of use, and condensate handling, all in hygienic 316L construction. Paul Industries designs, fabricates, installs, and validates the generator and its connections as one contractor.
How do I specify a clean steam generator for my plant?
Size from real sterilization load rather than a nominal figure, because undersizing is the common and disruptive error. Establish every vessel, filter housing and transfer line to be sterilized, their simultaneous demand during a campaign rather than in isolation, whether autoclaves share the supply, and the peak instantaneous draw at cycle start when a cold system demands the most. Then confirm Purified Water capacity can actually feed it. Specify the required turndown explicitly, since quality at minimum load is where generators most often fail qualification.
How does a clean steam generator work?
Plant steam or electric heating raises treated feedwater to boiling inside an evaporator without the two streams ever mixing. The resulting vapor rises through a separator, typically cyclonic or a demister arrangement, which removes entrained water droplets, since those droplets carry dissolved solids that would otherwise contaminate the steam. Clean steam leaves at controlled pressure while blowdown removes concentrated residue from the evaporator. The separator is what actually determines quality: everything dissolved in the feedwater is still present in any droplet that gets past it.
What feedwater does a clean steam generator need?
Purified Water as a minimum, and Water for Injection in some designs. The coupling is direct: anything dissolved in the feed either concentrates in the evaporator or carries over in droplets, so clean steam quality is capped by feed quality. Chlorides deserve particular attention because they attack stainless at elevated temperature, and conductivity should be trended rather than spot-checked. The practical consequence is that a clean steam generator sits downstream of your Purified Water system and inherits its reliability, so the two are sized and monitored together.
What is clean steam used for?
Sterilization duty above all, and the demand profile differs sharply by application, which is what matters for sizing. Steam-in-place of vessels and transfer lines draws heavily at cycle start when cold metal absorbs energy, then tapers. Autoclaves draw in sharp repeated peaks tied to cycle stages. Humidification of classified space is a low, steady background load. A generator sized on the sum of average demands will struggle when several SIP cycles start together, which is the realistic worst case on a campaign day.
Do you install clean steam generators?
Yes, generation and distribution together with the qualification. On the generator specifically we size from actual sterilization load and required turndown rather than a nameplate figure, confirm Purified Water feed capacity, and qualify output quality across the operating range rather than only at design point. On distribution the details that decide whether cycles pass are continuous fall to trap points, sanitary trap selection and placement, dead leg elimination, and sample points positioned so EN 285 testing can actually be performed.
Scope a clean steam generator
Paul Industries is a single-source supplier, installer, and validator – one accountable partner from design through documented startup. Tell us about your project and we will scope it.
How do you select a clean steam generator?
| Selection factor | What to establish | Common error |
|---|---|---|
| Peak demand | Sized for peak SIP demand with all users running | Sized on average consumption |
| Feedwater | Quality and deaeration, since it becomes the steam | Feedwater treated as a utility detail |
| Steam quality at the point of use | Dryness, superheat and non-condensable gases measured AT the sterilizer | Measured at the generator instead |
| Distribution | Insulated, correctly sized, trapped, with no pockets | Long uninsulated runs producing wet steam |
| Separator and trap | Fitted immediately upstream of the user | Omitted, then blamed on the generator |
| Pressure reduction | Staged, and sited far enough upstream to re-equilibrate | Reduction taken adjacent to the machine, causing superheat |
| Materials | 316L product-contact, sanitary construction | Industrial-grade components in a clean steam duty |
| Validation | Steam quality testing to EN 285 at each point of use | Assumed to pass because the generator is new |