What a stainless steel heat exchanger does in your line
It moves heat between two fluids that must never touch each other, in a material that will not rust into the product. In a dairy it is the pasteuriser or the ice-water cooler; in a pharma plant it is the WFI cooler or the reactor jacket; on a ship it is the seawater cooler that keeps the engine alive.
Stainless is not one material. The grade decides whether the unit survives chlorides, caustic cleaning and weld heat — and that single decision is the one buyers most often get wrong, because it is invisible on a quotation.
What we can change for you
Grade and wall: 304L, 316L, 321, 2205 duplex or titanium, in the wall you specify.
Connections: flange, tri-clamp, thread or welded stub, to your standard.
Finish: mill, pickled and passivated, or mechanically polished to your Ra.
Documents: certificates, PMI, weld maps and test records to the level your inspector asks for.
Six problems B2B buyers meet before the unit ships
None of these show up on a quotation. All of them show up in commissioning, in an audit, or in year two of service.
Problem 01
304 was quoted, 316L was needed
Chlorides in cooling water or cleaning chemicals pit 304 in months. The price difference is small; the failure is not.
Problem 02
The weld is where it fails
Heat tint and unpassivated welds become the first corrosion site — usually inside the shell, where nobody looks until it leaks.
Problem 03
A "sanitary" unit that cannot be cleaned
Dead legs, flat bottoms and a rough finish pass a visual check and fail a CIP validation. The drawing never showed the drain slope.
Problem 04
Wall thickness cut to win the price
Thinner tubes raise velocity and erosion at the inlet, and shorten life. The quotation looks equal; the tube wall is not.
Problem 05
No traceability when the inspector arrives
Certificates that do not match the heat numbers on the shell, or no PMI report, turn a delivered unit into a rejected unit.
Problem 06
It fits the drawing, not the skid
Nozzle orientation, lifting points and footprint are settled after fabrication. Rework at that stage costs weeks, not money.
How our process removes each of those risks
One answer per problem, in the same order. Each of them changes what is written on the drawing, not only what is written on the brochure.
01 · Grade fixed to the water chemistry
Chloride level, cleaning chemicals and operating temperature are asked for before a price is given, and the grade goes into the data sheet in writing.
02 · Welds purged, pickled and checked
Wetted welds are purged, pickled and passivated, then dye-penetrant checked on critical joints. Heat tint is removed, not shipped.
03 · Drainable, CIP-ready geometry
Lowest-point drains, no dead legs, full-bore connections and the Ra you specify. Where an audit is coming, the drawing is reviewed against 3-A or EHEDG practice first.
04 · Wall, velocity and erosion calculated together
Tube wall is not a lever for cutting price. If a thinner wall is the only way to reach a budget, you are told what it does to service life.
05 · Heat numbers traced to the certificate
Shell, tube, tube sheet and flange heat numbers are recorded against the serial number, with 3.1 certificates and a PMI report when the RFQ asks for them.
06 · Drawing approved before cutting
Nozzle orientation, lifting points and footprint go onto a GA drawing for your sign-off. Nothing is cut until you return it marked approved.
Which overseas buyers request a quotation
Eight buyer groups send us most of the stainless enquiries. The chip under each one is what a real RFQ from that group looks like.
Food, dairy and beverage processors
Pasteurising, ice water and CIP duty, where a rust stain or a dead leg fails an audit before it costs a repair.
Typical RFQ: 316L, 2-pass, tri-clamp, Ra 0.8 µm, CIP at 80 °C
Pharmaceutical and biotech projects
WFI, purified water and reactor jacket duty, where the documentation package is audited as closely as the unit itself.
Typical RFQ: 316L, double tube sheet, WFI tube side, 3.1 certs + Ra report
Marine, offshore and shipyards
Seawater cooling for engines and auxiliaries, where the alloy and the certificate decide whether the unit is accepted at survey.
Typical RFQ: titanium or CuNi seawater side, class certificate, sea packing
HVAC, district cooling and chiller OEMs
Water-to-water units that have to drop into an existing frame or plant room without a site modification.
Typical RFQ: water-to-water, 1.6 MPa, EN 1092 flange, footprint to drawing
Chemical and fine chemical plants
Aggressive process fluids and cleaning cycles, where grade selection and weld quality carry the whole guarantee.
Typical RFQ: 2205 duplex, chloride 500 ppm, PMI on all wetted parts
Water treatment and desalination
Brackish and seawater duty, where chloride stress cracking rules out anything below duplex or titanium.
Typical RFQ: titanium tubes, seawater 3.5 %, fouling allowance stated
Sanitary equipment builders and skid integrators
The exchanger is one component in your package, so the interface has to be exact and the FAT has to happen before it ships.
Typical RFQ: coil or shell unit inside our skid, nozzle positions fixed, FAT
Replacement and retrofit buyers
An existing unit has failed and the piping cannot move. The new bundle has to match what is already on site.
Typical RFQ: match old nameplate — tube count, pitch, passes, nozzle centres
Which stainless grade for which duty
The cheapest decision on the project and the most expensive one to get wrong. Read the right-hand column before the price.
| Grade | Where it fits — and where it does not |
|---|---|
| 304 / 304L | Clean water, HVAC and general food loops with low chloride. Not for chloride-bearing cooling water or frequent caustic cleaning. |
| 316 / 316L | The default for food, dairy, pharma and most cooling water. Molybdenum buys tolerance to chlorides and to cleaning chemicals. |
| 321 | Hot duty with repeated thermal cycling, where weld zones are the corrosion risk. Not a substitute for 316L in chloride service. |
| Duplex 2205 | Chloride-bearing process water and brackish cooling, with roughly double the yield strength. Needs a controlled welding procedure; not for hot caustic. |
| Titanium Gr2 | Seawater, brine and hypochlorite — the answer when nothing else survives. Highest material cost, and it needs its own welding and pickling procedure. |
Send the water analysis, not the grade. Chloride, pH, hardness and the cleaning chemicals decide the alloy. We will name the grade and show why the next one down fails.
Documents that travel with the unit
Ten items a buyer, an inspector or a customs broker will ask for. They are quoted as line items, so nothing is assumed.
3.1 certificates
Mill certificates for every wetted heat number.
PMI report
Positive material identification on shell and fittings.
Hydro test record
Pressure, hold time and result per unit, both sides.
Dye penetrant
Weld inspection report on the joints you nominate.
Pickling record
Passivation and heat-tint removal, with the bath and date.
Ra report
Measured surface roughness where a hygienic finish is specified.
GA drawing
The approved drawing, stamped with the revision you signed.
Weld map
Joint numbers, welder stamps and NDT results in one sheet.
IOM manual
Installation, start-up, cleaning and torque values.
Packing list
Weights, dimensions and HS description your broker can use.
How the unit is actually built
Six stages, all under one roof in Gongshu District, Hangzhou. Nothing is subcontracted to a workshop you have never seen.
What we need to quote
Fluids and concentrations · flow rates · inlet and outlet temperatures · chloride level and cleaning chemicals · design pressure and temperature · connection standard · the documentation level your inspector expects.
Send the duty data01
Material in, heat numbers booked
Sheet, tube and bar are booked against the order in ERP before anything is cut, so the certificate can be matched later.
02
Tubesheet, bundle and shell
Drilling, tube-to-tubesheet welding with argon purge, baffle spacing to the drawing.
03
Pickling and passivation
Immersion or paste, then rinse and dry. Heat tint is removed before the unit leaves the bay, not after it leaks.
04
Assembly and pressure test
Both sides tested and recorded per serial number, with a leak test where the duty calls for it.
05
Final check and FAT
Dimensions against the approved drawing, nameplate, and a witness test if your project requires one.
06
Packing and documents
Seaworthy case, desiccant, nozzle caps, and the document set in a waterproof sleeve inside the crate.
Factory, trading company or catalogue fabricator
Three quotes for the same duty rarely describe the same object. This is what separates them.
A factory with its own tube shop
Grade, wall and weld procedure are decided where the tubes are welded. Changes are possible after the drawing, and the person who answers the phone can see the unit.
Watch for: too few references in your exact duty.
A trading company with a good catalogue
Fast on price and paperwork, and useful when you need several items on one purchase order. The technical answer comes second-hand, and so does the delivery date.
Watch for: grade substitutions made without telling you.
A catalogue fabricator
Cheapest per square metre, because the design is fixed. Fine for a standard water-to-water unit; expensive the moment your nozzle layout or documentation differs.
Watch for: change orders once the drawing is issued.
From enquiry to delivered unit
Four steps. You approve a drawing before production, and you know the price of the alloy before you approve it.
01
You send the duty
Fluids, flows, temperatures, pressure and the water analysis. A photo of the old nameplate works for a replacement.
02
We answer with a calculation
Design type, grade, area, pressure drop on both sides, price and lead time — in one document, not in three emails.
03
You approve the drawing
Nozzle positions, footprint, lifting points and material list, signed off before the first cut.
04
We build, test and ship
Test records and the document set go with the unit, and the packing list is ready before the container is booked.
Questions buyers ask before the RFQ
Which grade do I need — 304, 316L or duplex?
It follows from the chloride level, the cleaning chemicals and the temperature. 304 for clean low-chloride water, 316L for food, dairy, pharma and most cooling water, duplex where chlorides are higher or strength matters.
Will a sanitary unit pass a CIP validation?
It will if the geometry is right: drains at the lowest point, no dead legs, full-bore connections and the Ra on the drawing. Tell us the validation standard your auditor uses and the drawing is reviewed against it before fabrication.
What is the difference between pickled and polished?
Pickling removes weld oxide and restores the passive layer; polishing changes the surface roughness. A hygienic duty usually needs both, and they are quoted as separate operations.
Can you replace a unit we already run?
Yes, where the piping cannot move. Send the nameplate, the old drawing or measured nozzle centres and we match tube count, pitch, pass arrangement and footprint so it drops in.
What documentation can you supply?
Material certificates, PMI, hydro test records, dye penetrant and weld maps, pickling and Ra records, the approved GA drawing, the IOM manual and a packing list ready for your broker.
Do you build coils as well as shell and tube units?
Yes — stainless coil, shell and coil, and the coaxial coil series for chillers and heat pumps, all from the same works.
Is there a minimum order quantity?
Single units are built routinely, including for OEM qualification. The price break depends on size and repeat quantity, so it is quoted per project rather than published.
How is the unit shipped, and who prepares the export documents?
Seaworthy case with desiccant and capped nozzles, FOB or CIF to your port. The packing list, HS code and certificate set are prepared by us so clearance does not depend on your forwarder chasing us.
Hangzhou Airman Environmental Technology Co., Ltd. is one of the most professional stainless steel heat exchanger manufacturers and suppliers in China, specialized in providing high quality products. We warmly welcome you to buy customized stainless steel heat exchanger made in China here from our factory.