API Standard 660, Shell-and-Tube Heat Exchangers, is an American Petroleum Institute specification used heavily in refining and related energy projects. It tells the manufacturer how to interpret a purchaser datasheet, which TEMA requirements to treat as mandatory, and what fabrication, inspection, and documentation extras apply beyond a bare pressure-code vessel. It is not a licence, stamp, or ISO-style certificate that a fabricator 'holds'. Ohm Engineers is not 'API 660 certified'. When a buyer attaches API 660 (and the filled datasheet) to an RFQ, Ohm designs and fabricates to that purchaser specification to the extent the order agrees — for the exchanger types this shop manufactures.
Where API 660 sits relative to TEMA and ASME
TEMA is the mechanical design standard for shell-and-tube geometry (nomenclature, class R/B/C, spans, many fabrication details). ASME VIII-1 or another pressure code (IS 2825 when specified) governs the pressure boundary. API 660 is an industry/purchaser overlay: it typically requires TEMA Class R as a baseline for the services it covers, points to ASME for pressure design, and then adds refinery-oriented rules on data sheets, materials, fabrication, inspection, and preparation for shipment. Conflicting clauses are resolved by the order of precedence written in the purchase documents — usually purchaser spec, then API 660, then TEMA, then the pressure code. Do not assume a website page replaces that hierarchy.
What the standard is trying to standardise
- A common datasheet language so process, mechanical, and inspection data are not scattered across emails.
- Minimum mechanical and fabrication practices appropriate to general refinery service (often aligning with TEMA R).
- Inspection and testing expectations tied to the datasheet, including who witnesses what.
- Documentation and marking so the unit can be received, installed, and later rerate or repaired against a known baseline.
Datasheets — the actual working document
Projects that 'specify API 660' still fail when the datasheet is blank. The API 660-style sheet is where you freeze fluids, duties, design pressures and temperatures, fouling, materials, TEMA type and class, corrosion allowance, NDE, and special requirements (NACE/ISO 15156, PWHT, painting, TPI). Ohm rates and mechanically designs from that sheet plus any attached owner addenda. A cover letter that only says 'API 660' without the sheet is not a specification.
If your company uses a proprietary cover sheet plus TEMA, that is also a purchaser specification. The same rule applies: attach it. The words 'API 660' on a website do not put those clauses on our shop floor.
Scope limits a buyer should watch
API 660 addresses shell-and-tube exchangers for the services it defines. It is not a plate-exchanger standard (API 662 is a different document) and not an air-cooled standard (API 661). Kettle reboilers, U-tubes, and fixed-tubesheet units can all appear on 660-style sheets; floating-head types appear frequently on those sheets as TEMA S/T. Ohm will execute fixed-tubesheet (with or without expansion joint), U-tube, double-pipe, and kettle construction. A 660 datasheet that freezes a floating-head rear end is specifying a type we do not manufacture — raise it at enquiry.
What Ohm does when API 660 is attached
We treat it as the purchaser specification: design mechanical details and inspection to the clauses that apply, in combination with TEMA practice and the named pressure code (ASME VIII-1 or IS 2825 when specified). We do not advertise API 660 as a company certification, membership, or stamp. We do not imply that every unit leaving Vadodara is built to 660 by default. ISO 9001:2015 remains the quality-management certification we actually hold. Code stamping, TPI, and extra NDE remain as written on the order.
RFQ: attach 660, do not just name it
Include the API 660 edition you are buying to, the completed datasheet, owner exceptions, and whether TEMA type is frozen. Send the pack via /rfq?product=heat-exchangers. If you need a tubular exchanger to that specification in a configuration Ohm manufactures, engineering review can start from the sheet. If you need a certificate that says 'API 660 certified manufacturer', that is not something this shop claims — and a reputable fabricator should not.
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