Process plants use more than one heat-exchanger family. The useful split for a buyer talking to Ohm Engineers is: types this shop manufactures, versus types that exist in the industry and may appear on a comparison study or an EPC spec. Mixing those lists is how RFQs ask for a floating-head plate exchanger that nobody should quote.
Types Ohm manufactures
All four are tubular. They are selected from process data, cleaning access, and expansion — not from a stock model number. Manufacture is at Vadodara under ISO 9001:2015.
| Ohm type | Construction | Choose when |
|---|---|---|
| Fixed-tubesheet shell-and-tube | Tubesheets welded to shell; optional bellows in the shell | Shell side clean or chemically cleanable; high integrity; ΔT modest or relieved by expansion joint |
| U-tube shell-and-tube | Single tubesheet, U-bends, removable bundle | Large differential expansion or shell-side bundle pull; tube side not mechanically rodded |
| Double-pipe / hairpin | Inner pipe and annulus, often hairpin banks | Small area, high pressure, or modular series/parallel add-on |
| Kettle reboiler | Enlarged K-shell, weir, vapour disengagement | Vaporising duty with liquid hold-up; column reboil when thermosiphon is not the specified layout |
Inside the shell-and-tube family (TEMA letters)
A TEMA three-letter code (front, shell, rear) describes heads and shell flow — BEM, AEL, BEU, AKT, and so on. Front heads (A, B, N, …) set channel access. Shell letters (E, F, J, K, X, …) set flow path. Rear letters include fixed tubesheets (L/M/N), U (U-tube), and floating heads (S/T/W). Ohm builds fixed-tubesheet and U-tube rear ends, and K-shells for kettles. Specifying AES on an enquiry is a purchaser TEMA selection; it is not an announcement that this shop's standard product is a floating head.
Industry landscape — plate exchangers (not an Ohm SKU)
Gasketed and brazed plate exchangers pack a large area into a small frame and achieve close temperature approach on clean, moderate-pressure, moderate-temperature liquids. Narrow channels foul quickly; gaskets limit pressure and temperature; phase-change and hazardous-fluid duties are constrained. They are the right machine for many utility and hygienic liquid-liquid duties. Ohm does not manufacture plate packs. If your study has already selected plates, that RFQ belongs with a plate OEM — not on a tubular fabrication enquiry.
Industry landscape — air-cooled (not an Ohm SKU)
Air-cooled heat exchangers (ACHE, fin-fans) reject heat to ambient air when cooling water is scarce or when the process wants an aerial condenser. They are a different commodity: bundles, plenums, fans, and plot-area rules (often API 661 in refining). Ohm does not manufacture air-cooled bays. A process condenser against cooling water can still be a shell-and-tube unit from this shop; an aerial condenser is a different purchase.
Industry landscape — floating-head rear ends (TEMA option, not Ohm manufacture)
A floating head lets the rear tubesheet move with the tubes and allows the bundle to be withdrawn for shell-side cleaning. TEMA S (split backing ring), T (pull-through), and W (packed gland) are the usual letters. Buyers specify them on refinery and dirty-shell duties with large ΔT. Ohm does not manufacture floating-head exchangers. The manufactured alternatives for expansion and/or bundle removal are: fixed tubesheet with a shell expansion joint, or a U-tube removable bundle. If the purchaser specification mandates S or T rear heads, say so on the RFQ so scope can be declined or clarified — do not assume the shop will silently substitute.
A TEMA code on a datasheet is a design instruction, not a catalogue. If the rear letter is S or T, you are specifying a floating head. Ohm's manufactured removable-bundle type is U-tube.
A short selection path among Ohm types
- Vaporising with disengagement and level control → kettle (K-shell), if that is the process layout.
- Area too small to justify a multi-tube shell, or pressure that punishes a large tubesheet → double-pipe.
- Large tube-to-shell metal ΔT or shell-side bundle pull, tube side clean enough → U-tube.
- Otherwise → fixed-tubesheet shell-and-tube; add a shell expansion joint when differential growth requires it and the shell side will not be pulled as a bundle.
RFQ: name the type or describe the constraints
You do not have to pick the TEMA letters yourself. Send fluids, duty, pressures, fouling, cleaning method, and whether the bundle must come out. If an EPC spec already freezes the type, attach it. Use /rfq?product=heat-exchangers. Configuration pages: /products/heat-exchangers, /products/heat-exchangers, /products/heat-exchangers, /products/heat-exchangers.
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