1-805-484-2992
Quotes - Engineering - SalesThe pressure side of the specification
Sanitary or not, a shell-and-tube exchanger is a pressure vessel, and in the United States that means ASME Boiler and Pressure Vessel Code Section VIII, Division 1. The code sets how the shell, heads, tubesheets and nozzles are designed, what materials may be used and at what allowable stress, how they are welded and by whom, what is inspected, and how the finished vessel is tested. A shop that holds an ASME certificate of authorization may apply the U-stamp to a vessel built under those rules, witnessed by an authorized inspector from an insurer or jurisdiction.
National Board registration adds a second step: the completed data report is filed with the National Board of Boiler and Pressure Vessel Inspectors, which assigns a permanent number stamped beside the U. Most states require it, and it is what an inspector looks up when the unit is installed or later sold. Canada runs its own system: a Canadian Registration Number issued per design by the provincial authority, required before the vessel is installed in that province.
ASME U-Stamp
- Section VIII Div. 1 for vessels above 15 psig
- Hydrotest at 1.3 times MAWP, inspector witnessed
- U symbol stamped, Form U-1 signed by inspector
CRN
- CSA B51 with ASME design, per province
- Drawings and calculations reviewed, several weeks
- Registration number issued before shipment
ASME and CRN essentials
ASME Section VIII Div. 1
- Applies: Vessels above 15 psig; most states adopt it by law
- Design: Allowable stresses, minimum thickness, nozzle reinforcement, tubesheet rules (UHX)
- Welding: Qualified procedures (Section IX) and welders; inspected joints
- Test: Hydrostatic at 1.3 times MAWP, or pneumatic at 1.1 by agreement
- Stamp: U symbol applied by the certificate holder under the authorized inspector
- Data report: Form U-1 (or U-1A) signed by fabricator and inspector
National Board and CRN
- NB registration: Data report filed; NB number stamped on the nameplate
- Who requires NB: Most US states and many Canadian provinces alongside CRN
- CRN: Design registration per province; number format 0xxxx.5 for the province code
- CRN basis: CSA B51 with ASME design; drawings and calculations reviewed
- Fittings: Clamp fittings and valves need their own CRN or category registration
- Timing: CRN obtained before shipment; allow several weeks for review
The stamp proves pressure; nothing else does
How a sanitary exchanger gets its stamp and numbers
ASME Section VIII design and fabrication
Design begins with the maximum allowable working pressure and temperature on each side, which on a sanitary unit are set by the steam or utility pressure, the CIP pump head and the SIP steam temperature, not the product. From those the code fixes the shell wall, head thickness, nozzle reinforcement and tubesheet thickness, the last by the UHX rules that account for the tubes stiffening the sheet. Stainless allowable stresses are lower than carbon steel, so sanitary shells run slightly thicker for the same pressure. Welds are made to procedures qualified under Section IX by welders qualified to those procedures, and the authorized inspector checks material certificates, weld records and fit-up at hold points during the build.
- Give the utility pressure and the SIP steam condition; they set the MAWP, not the product
- Sanitary clamp fittings are rated separately from the vessel and can limit the MAWP on the product side
Hydrotest, the U-stamp and the data report
When fabrication is complete the vessel is hydrotested, each side in turn, at 1.3 times its MAWP corrected for temperature, held while the inspector examines every joint for leaks. On a sanitary unit the test water is clean and the unit is drained and dried afterward so no residue is left on the product side. With the test passed, the fabricator stamps the nameplate with the U symbol, the MAWP and temperature each side, the serial number and the year, and completes the Form U-1 data report, which the inspector signs. That report is the legal record of the vessel and a copy goes to the buyer.
National Board registration
The fabricator files the signed data report with the National Board, which assigns a sequential number to the vessel and stamps it on the nameplate beside the U. The National Board keeps the report on file permanently. When a state inspector visits the plant, the NB number is what is entered in the state's vessel register and what is checked at each periodic inspection. Specify it; the cost is small and a missing number complicates every future inspection.
CRN for Canada
Canada requires a Canadian Registration Number for any pressure vessel before it is installed. The number is issued for a design, not a serial number: the fabricator submits drawings and calculations, done to ASME and CSA B51, to the provincial safety authority, which reviews and registers the design and issues a number whose decimal suffix identifies the province. A design registered in one province can be extended to others by a further filing. Fittings on the unit, including sanitary clamp connections and any valves shipped attached, must also be registered, either individually or under a category registration held by their maker.
CRN review takes weeks, and the unit cannot legally be installed until the number is issued, so the CRN is applied for when the order is placed, not when the unit is ready to ship.
Specifying pressure certification
State the MAWP and temperature each side, ASME Section VIII Division 1 with U-stamp, National Board registration, and the CRN province if the unit goes to Canada. Ask for the data report and the nameplate drawing as deliverables. Call and talk it through with an engineer: 1-805-484-2992
Common FAQs
Built to ASME means the design and fabrication followed the code without third-party inspection or the stamp. Stamped means an authorized inspector witnessed the build and test and the U symbol is on the plate. Only the stamped vessel satisfies a state law that requires the code.
The stamp covers the vessel as a whole, with MAWP stated for each side. If the product side operates below 15 psig it may be marked as such, but the CIP pump and SIP steam usually put it above that, and it is rated accordingly.
Only if the design documentation exists to submit. It is far easier to register at the time of manufacture. A unit built without a CRN and later moved to Canada faces a difficult review.
No, provided clean water is used and the unit is drained and dried. The test is done before final passivation on most pharmaceutical units so any water spotting is removed.
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