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Quotes - Engineering - Sales| SHELL | TUBE | TEMPERATURE | SET BY |
| 150 to 300 PSI | 125 to 400 PSI | 300 to 1000°F | Series and construction |
Pressure and Temperature Ratings
Two Independent Limits
Every catalogued Bell & Gossett unit carries three numbers: a maximum shell pressure, a maximum tube pressure and a maximum temperature. They are established separately, and a duty has to satisfy all three.
Shell and tube ratings differ deliberately. A shell is a large-diameter pressure boundary; tubes and tubesheets are small ones. Raising the shell rating requires substantially heavier construction throughout, so the ranges pair a standard shell rating with whatever tube rating the duty needs.
The compact ranges carry a higher shell rating. The CHX and CHXS are rated 300 PSI on the shell against 150 PSI for the larger SU and WU. That is a consequence of diameter: a 300 PSI rating on a 2 to 8 inch shell is straightforward and on a 30 inch shell it is not.
Temperature ratings span a wide band. 300°F on the WU and the compact ranges, 375°F on the SU, DSU, DWU, HTWU and the tank heaters, and 1000°F on the GC gas cooler. The GC is the outlier and it is the reason that range exists separately.
Check the pressure at the exchanger. In a tall building, static head alone can exceed the standard 150 PSI tube-side rating before any pump head is added. That is what the HTWU's 400 PSI tube rating is for.
Catalogued Rating Summary
Ratings vary by series. The part number on the nameplate establishes which apply to a given unit.
Shell Ratings
- SU, WU, OC, HTWU: 150 PSI
- CHX and CHXS: 300 PSI
- Tank heaters: 150 PSI
- GC: Application specific
Tube Ratings
- 125 or 150 PSI on most ranges
- 150 PSI on CHX and CHXS
- 400 PSI on the HTWU
- Application specific on GC and aftercoolers
- Established per part number
Temperature
- 300°F on WU, CHX, CHXS
- 375°F on SU, DSU, DWU, HTWU
- 375°F on tank heaters
- 300°F on aftercoolers
- 1000°F on the GC
Related
Checking a Duty Against the Ratings
Calculate the Pressure Where the Unit Sits
The relevant number is the pressure at the exchanger, which in a building means static head from the highest point in the system down to the plant room, plus pump head, plus any expansion vessel pressurisation.
It is common for a system to be well within rating at the top of a riser and comfortably outside it in the basement where the exchanger actually is.
Both Limits, Independently
A duty can sit inside the pressure rating and outside the temperature rating, or the reverse. The WU is rated 300°F where the SU is 375°F, so a hot water duty that suits an SU may exceed a WU on temperature alone even at identical pressures.
Check all three numbers against the actual operating envelope, including upset and startup conditions rather than the steady-state design point.
