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Quotes - Engineering - Sales| MATERIAL | RANGES | RATING | SUITS |
| Steel or Brass | By series | 150 or 300 PSI | Shell-side fluid |
Shell Materials
Steel Across Most of the Range, Brass on the Compact CHX
The shell is the largest single pressure component in the exchanger and the one in contact with the shell-side fluid over its whole area. Material selection follows that fluid and the pressure rating the duty requires.
Steel is standard. The SU, WU, DSU, DWU, OC, HTWU, CHXS, GC, the aftercoolers and all the tank heater ranges use a steel shell. It is economical, weldable, well understood and entirely suitable for treated water, condensate, steam and general industrial service.
Brass appears on the CHX. The compact CHX uses a brass shell where the CHXS uses steel, covering the same size band and the same 300 PSI rating. The choice between them is made on the shell-side fluid rather than on pressure.
Diameter drives the rating. The compact ranges carry 300 PSI on the shell against 150 PSI for the larger SU and WU. That is a consequence of size: the same rating on a 30 inch shell would require far heavier construction.
Corrosion allowance rather than resistance. A steel shell in water service relies on treatment and on an allowance that is expected to be consumed over the design life. Where the shell-side fluid is genuinely aggressive, that is a conversation about a different construction rather than a thicker shell.
Shell Material by Series
The part number establishes the shell material for a given unit.
Steel Shell
- SU, WU, DSU, DWU: Steel
- OC, HTWU, CHXS: Steel
- GC and aftercoolers: Steel
- Tank heaters: Steel
Brass Shell
- CHX compact range only
- Same 300 PSI rating as CHXS
- Chosen on shell-side fluid
- 2 to 8 inch diameters
- Cast iron bonnets
Consider
- Shell-side fluid chemistry
- Required pressure rating
- Water treatment reliability
- Corrosion allowance
- Whether the shell can be cleaned
Related
The Shell Is the Part You Cannot Easily Change
Bundles Are Replaceable, Shells Are Not
Over a long service life a bundle may be replaced several times while the shell stays in place. That makes the shell material a longer-term decision than the tube material, and one worth getting right at the outset.
Where the shell-side fluid has changed since the unit was installed, it is worth checking that the shell material still suits it before specifying another bundle for a shell that may be nearing the end of its own life.
Inspect the Shell While the Bundle Is Out
A bundle replacement is the one good opportunity to examine the shell interior: baffle contact areas, nozzle entries and gasket faces. A shell that has thinned or eroded will not seal a new bundle any better than it sealed the old one.
Finding that while the bundle is out is inconvenient. Finding it after the new bundle is installed is considerably worse.
