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Quotes - Engineering - Sales| DUTY | TYPICAL SERIES | CONSTRUCTION | MEDIUM |
| Process Water | SU / DSU | Single or double wall | Steam or hot water |
Process Water Heating
The Utility That Touches Everything
Process water goes into product, washes equipment, makes up solutions and rinses lines. Heating it is a continuous duty with a load profile that follows the production schedule, and the water quality requirement follows whatever it eventually contacts.
Double-wall where it contacts product. If the process water will touch food or become part of it, a steam or boiler circuit heating it across a single tube wall is the cross-contamination case double-wall construction exists to prevent.
Scaling depends on surface temperature. Hard water scales on the hottest surface. Using high-pressure steam produces a tube wall temperature far above the water outlet target and accelerates scaling considerably. Lower-pressure steam with more surface runs cleaner.
The load follows production. A plant running one shift has a very different profile from one running continuously, and a heater sized on the peak will spend most of its life at part load. Turndown behaviour is worth designing for.
Removable bundles matter here. Process water scales and the bundle needs cleaning. Put the water on the shell side where it can be reached and specify clearance to withdraw the bundle.
Process Water Selection
Flow, temperature rise, the medium available and whether the water contacts product.
Duty Inputs
- Water flow: GPM peak and normal
- Temperatures: Inlet and required outlet
- Medium: Steam pressure or hot water temperature
- Contact: Does it touch product
Series
- SU on steam, non-contact duty
- DSU on steam, product contact
- WU or DWU on a hot water circuit
- TCS or TCW for tank heating
- 2, 4 and 6 pass available
Watch For
- Scaling on hard water
- Medium temperature and wall temperature
- Part load behaviour
- Bundle pull clearance
- Double-wall requirement
Related
Lower Medium Temperature, More Surface
Scaling Is a Wall Temperature Problem
Scale forms on the hottest surface in the system, which is the tube wall. Using 100 PSI steam to make 140 degree water produces a wall temperature far above the target, and hard water responds by depositing on it.
Reducing the steam pressure and adding surface lowers the wall temperature and slows scaling markedly. It costs exchanger and saves descaling labour and downtime, and on genuinely hard water that trade is strongly favourable.
Design for the Shift Pattern
A plant running a single shift puts its heater through a daily cycle of full load and no load. One running continuously does not. The first is a thermal cycling duty and benefits from the free expansion a U-tube bundle provides.
Both need the control arrangement checked at the load the plant actually runs at most of the time, which is frequently well below the design peak.
