01Identify the existing assembly
Photograph the complete heater, nameplate, terminal enclosure and mating connection before removal. Record the manufacturer’s part number and any approved drawing revision. Where possible, use the original documentation as the starting point rather than reconstructing every dimension from a worn part.
Isolate the electrical and process equipment and follow the site’s removal procedure. An old heater may retain liquid or contamination. Dimensions taken from a damaged bundle should be marked as uncertain rather than treated as manufacturing data.
02Measure from a stated datum
| Check | Information to provide |
|---|---|
| Flange | Standard, nominal size, pressure class, facing, outside diameter and bolt pattern |
| Bundle | Insertion length from mounting face, maximum diameter and support positions |
| Vessel | Nozzle bore, nozzle length, internal obstructions and minimum liquid level |
| Enclosure | Orientation, cable entries, access space and environmental requirements |
| Removal | Clear withdrawal route and any lifting or handling constraints |
03Why insertion length alone is insufficient
A bundle with the right length may still foul a nozzle, baffle, coil or internal support. Mark obstructions on a section sketch. Include the distance from the flange face to the inside of the vessel, so the supplier can locate the active section beyond the nozzle where the design requires it.
Allow for withdrawal as well as installation. A bundle that fits into a vessel during construction may be difficult to remove after nearby pipework or platforms have been added. Check the route at the site before ordering.
04Confirm electrical and fluid duty
Record supply voltage, phase, rated power, circuit grouping, terminal links and the available control arrangement. Do not copy the old terminal links without checking the new wiring diagram. Where the design changes, have a qualified person review the complete circuit and protection.
Provide the fluid identity, operating temperature and pressure, minimum level, contamination and cleaning conditions. The replacement sheath material and surface loading need to suit those conditions. An existing flange connection does not establish that an alternative bundle is suitable.
05Approve the replacement as an assembly
Ask for a dimensioned general arrangement, electrical diagram, materials list and stated design conditions. For hazardous-area equipment, review the applicable marking and documentation for the supplied assembly. Do not transfer an approval from the old unit simply because the replacement looks similar.
↗Technical references
Manufacturer references provide background. Use the approved drawing and instructions for the actual heater; the examples above are not purchase specifications.