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Quotes - Engineering - SalesTwo kinds of rules, one nameplate
A sanitary heat exchanger answers to two separate sets of rules. Pressure-vessel codes, ASME Section VIII in the United States, the CRN system in Canada, the Pressure Equipment Directive in Europe, exist so the shell does not fail under pressure, and they are enforced by law through inspectors and registration numbers. Sanitary standards, 3-A and ASME BPE, exist so the product side can be cleaned, and they are enforced by the plant's inspectors, auditors and QA program. Both end up on the nameplate, and confusing them is the most common error in a sanitary specification.
TEMA sits beside these as a mechanical design standard for shell-and-tube exchangers. It is not a code and carries no stamp, but a TEMA class on the drawing tells the fabricator which set of tolerances, clearances and corrosion allowances to design to, and most industrial buyers expect it.
The pages under this one cover ASME and CRN, PED, and TEMA with the 3-A symbol. This page explains how they fit together on an order.
ASME & National Board
- Section VIII Division 1 governs design, materials, welding and testing
- U-stamp applied by a certificate holder under an authorized inspector
- National Board registration gives the vessel a permanent NB number
- Required by most US states above 15 psig; hydrotest at 1.3 times design
CRN for Canada
- Canadian Registration Number issued per design by each province
- Design reviewed against CSA B51 and ASME; number ends in the province code
- Needed before the unit can be installed, not after
- Fittings on the unit need their own CRNs or category registration
PED for Europe
- Directive 2014/68/EU; category set by pressure, volume and fluid group
- Category I is self-declared; II through IV need a notified body
- CE mark on the nameplate with the notified body number where applicable
- Materials by EN standard or a particular material appraisal
TEMA & 3-A Marks
- TEMA class C for most sanitary units; B or R where the buyer's standard says so
- TEMA covers mechanical design of shell-and-tube only, not plates or cleanability
- 3-A symbol on the nameplate with the fabricator's authorization number
- Sanitary marks never substitute for the pressure stamp
Which codes apply to your unit
Start with where the exchanger will be installed. In the United States, a shell-and-tube unit whose shell or tubes see more than 15 psig falls under the state's boiler and pressure vessel law in nearly every state, and that law adopts ASME Section VIII with a U-stamp and, in most states, National Board registration. In Canada the same unit needs a CRN from the province of installation before it ships. In the European Union it needs a PED conformity assessment at the category its pressure, volume and fluid dictate, and a CE mark. Ship to two countries and it carries two sets of marks.
Plate heat exchangers are pressure equipment too. Small sanitary plate units often fall below the thresholds, but a large frame on steam or a unit above 15 psig on the process side is stamped and registered like any other vessel.
What a sanitary buyer usually needs
For a US food or dairy plant: ASME U-stamp with National Board registration, TEMA class C for the mechanical design, and the 3-A symbol where the plant is inspected. For a US pharmaceutical plant: the same stamp and registration, BPE for the product side, and the documents that go with both. For Canada add the CRN; for Europe substitute or add PED. That covers almost every order, and a specification that lists exactly those items prices in a day.
What the marks do not cover
The U-stamp says the vessel was designed, built and tested to Section VIII for pressure. It says nothing about surface finish, drainability, gaskets or cleanability. The 3-A symbol says the product side conforms to a sanitary standard and was verified. It says nothing about pressure. TEMA sets mechanical tolerances and does not address sanitary features at all. A unit needs each mark for its own reason, and a specification that asks for 3-A and assumes the pressure code is covered, or the reverse, leaves a gap the inspector will find.
Getting the nameplate right
The nameplate is the record of everything above: design pressures and temperatures each side, the code stamp, the National Board or CRN or CE number, the serial number, the year, and the 3-A symbol with its authorization number where it applies. Ask for a nameplate drawing with the order so the marks can be checked before the plate is riveted on. Call and talk it through with an engineer: 1-805-484-2992
Common FAQs
If either side operates above 15 psig and the state or province adopts the code, yes, as a matter of law. Small units below 15 psig or exempt by size can be built to the code without the stamp, but many plants specify the stamp anyway for insurance and consistency.
Yes, and it normally is. The 3-A standard covers the product side and the ASME stamp covers pressure; the two are independent and appear together on the nameplate.
No. It is a design standard, not a code. Specifying a TEMA class tells the fabricator which tolerances and allowances to use and is good practice on any shell-and-tube unit.
It carries the ASME stamp and National Board number for the US and a CRN for the Canadian province. The CRN review is done against the ASME design, so the two are compatible.
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The four details that decide whether the product side cleans, drains and stays uncontaminated.
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The metal in the tubes, the rubber in the joints, and the paper that proves which heat went where.
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