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Quotes - Engineering - SalesRequest a Stainless Heat Exchanger Quote
A quotation for a stainless heat exchanger is a thermal calculation, a mechanical design and a material decision, and the form below asks for exactly what those three need. Fill in what you know. One flow with all four temperatures, or both flows with three, fixes the duty; the chloride level and maximum temperature fix the grade; the design pressures and connections fix the shell, frame or plate pack. Missing fields come back as questions, not as assumptions buried in the price.
What the quote form asks for
Every field below maps to a line in the calculation. The ones that most often arrive blank, and most often change the answer, are the chloride level, the allowable pressure drop and the design pressure as opposed to the operating pressure.
- Hot and cold fluid, with concentration for brines, glycol, caustic or acid, and which side needs stainless contact.
- Both flow rates with three of the four temperatures, or one flow rate with all four.
- Operating and design pressure and temperature on each side, and the pressure drop each side can afford.
- Chloride level, pH, fouling tendency, viscosity and any solids or fibers in either stream.
- Grade required or grade suspected: 304L, 316L, 2205 duplex, higher alloy or titanium.
- Construction preference, or none, and the connection type and size at each nozzle.
- Codes and stamps: ASME, TEMA class, PED, CRN, 3-A, BPE, MTRs, as the project requires.
- Sanitary needs: Ra finish, drainability, tri-clamp, double tubesheet, CIP and SIP temperatures.
- Installation: orientation, space for bundle pull or plate pack opening, outdoor or washdown exposure.
How the sizing works
The duty is the heat moved, and for water it is close to 500 Btu/h for every gpm raised 1°F; the utility side has to give up the same amount, which is where a steam pressure or a glycol flow gets set. The log mean temperature difference is the average driving force between the two streams along the exchanger, and it is why a plate pack with 2–5°F approach needs a counterflow layout and a shell and tube with crossing temperatures needs shells in series or a true counterflow pass.
Surface area is the duty divided by the overall coefficient and the LMTD, and the coefficient is where stainless costs you: at about 9.4 Btu/h-ft-F for 304 and 316 against roughly 230 for copper, a stainless unit of the same duty carries more surface. We then check that the water runs 3–8 ft/s in the tubes, that a fouling factor of 0.001–0.002 h·ft²·°F/Btu on tubular water duty, or a 10–25% surface margin on plates, is in the area, and that the pressure drop lands inside what your pump can give.
Replacing an exchanger you already have
Most replacement requests begin with a photograph of a nameplate, and that is the right place to begin. The nameplate gives the design pressures, the test pressure, sometimes the surface area and the year; the connections, overall length and mounting tell us whether an equivalent has to match the footprint or only the duty. Add a drawing if one exists, the fluids as the plant runs them today rather than as the original order read, and a note on how the old unit failed, because a bundle that pitted on the tube side is asking for a grade change, not a copy.
The unit on the floor may be a gasketed plate pack, a sanitary shell and tube or a steam-to-water heater; whoever built it, the nameplate and the drawing tell us what it was designed to do. We size a stainless equivalent from its published specifications and your operating data, and where a figure is not published we say so rather than estimate it. Suitability is checked on thermal duty, pressure drop, design pressure, connection dimensions, material grade and any code or sanitary requirement the installation carries.
An upgrade is often the better buy than a copy. A copper-brazed plate that failed on deionized water becomes a nickel-brazed one; a 304 bundle that pitted in cooling tower water comes back in 316L or, if the water runs above 140°F, in 2205 duplex; a fixed-tubesheet shell that cracked at the tube joints on a steam duty comes back as a U-tube. Tell us the failure and the replacement will be sized not to repeat it.
After you send it
What happens to your request
1.
An engineer reads it
Not a parser. The request goes to an application engineer who checks the fluids against the grade you asked for and flags anything that will not hold: 304L on chloride water, copper braze on ammonia, EPDM on an oil.
2.
Questions come back
Usually one e-mail or call to close the gaps: the fourth temperature, the design pressure, whether the 150 ppm tower water is the makeup or the cycled figure. A quote with assumptions in it is worth less than one with questions.
3.
The selection is run
Thermal sizing, pressure drop, mechanical rating and material are worked together, and if two constructions both fit, you get both priced with the trade-off stated in a sentence, not left for you to find.
4.
You get a drawing and a price
The quotation carries the construction, grade, connections, ratings, codes included, surface finish where it applies, and a general arrangement drawing where the selection calls for one. What is not on it is not included; ask and it is added.
