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Quotes - Engineering - Sales| MATERIAL | STANDARD | ALTERNATIVE | DOUBLE WALL |
| Copper | Across the range | Steel on GC | Copper, vented |
Tube Materials
Copper as Standard, Steel Where Temperature Demands It
Tubes carry the heat and they are the component in contact with both fluids. Across the catalogued Bell & Gossett range the standard tube material is copper, in 3/4 inch outside diameter on most series.
Copper is the default for good reasons. Excellent thermal conductivity, well established in water and steam service, readily formed into the U-bend the ranges are built around, and economical. In treated water, condensate and steam duty it performs predictably for decades.
Steel appears on the GC gas cooler. The GC range offers copper or steel tubes, and at the upper end of its 1000°F rating steel is generally the answer. Steel also resists some gas chemistries that attack copper.
Double-wall copper on the potable ranges. The DSU, DWU, DTCS and DTCW use double-wall copper tubes: two tubes drawn together with a vented path between them so a leak discharges outside the unit rather than crossing between fluids.
Velocity matters on copper. Copper has an erosion velocity limit, and exceeding it thins tubes at the inlet where turbulence is highest. Pass count is how velocity is set, so the arrangement and the tube material are related decisions.
Tube Material by Series
The part number establishes tube material and diameter for a given unit.
Copper
- Most series: Copper
- Diameter: 3/4" O.D. typical
- Double-wall ranges: Copper, vented
- Suits: Water, steam, condensate
Steel
- Available on the GC range
- Preferred at high gas temperature
- Resists some gas chemistries
- Lower conductivity than copper
- Recorded in the part number
Watch For
- Erosion velocity limit on copper
- Inlet end thinning
- Water chemistry attacking copper
- Temperature above copper's range
- Whether double-wall is required
Related
Replacement Is the Moment to Reconsider
If Corrosion Killed the Bundle, Change Something
A bundle that failed by corrosion rather than mechanical damage or plugging is telling you the material was marginal for the service. Replacing like for like repeats the experiment with a known outcome.
Because the shell and nozzle geometry stay the same, a material change on a replacement bundle costs only the material difference. It is the cheapest opportunity you will get to correct the original selection.
Velocity and Erosion
Copper has a practical velocity limit above which the tube wall thins, and the thinning concentrates at the tube inlet where turbulence is highest. A bundle showing inlet-end erosion is running too fast, not just wearing out.
The remedy is usually a pass arrangement that lowers velocity, or in some cases inlet ferrules. Simply fitting another identical bundle will produce the same result in the same time.
