1-805-484-2992
Quotes - Engineering - SalesWhat the generator was doing, and what replaces it
Many CIP systems heat their rinse and sanitize water with a packaged hot-water generator: a steam-to-water heater with its own storage tank or coil, a control valve and a thermostat, bought as one assembly from Armstrong or Cemline years ago and left to run. When the coil leaks, the tank corrodes, or the plant has added a line and the generator can no longer hold 180°F through the sanitize step, the plant looks for the same package and finds the model gone or the price surprising. The duty it performed is a plain one, and a steam-to-water shell-and-tube does it.
What to read off the old generator
The generator's job was to take city or soft water at supply temperature and deliver it at 120–140°F for the final rinse and at 180–190°F for the sanitize hold, in whatever quantity the circuit pulled. A storage tank let a small coil keep up with a short surge. A shell-and-tube steam heater does the same thing once-through, sized for the circuit's gpm and the coldest inlet of the year, with the steam control valve responding to outlet temperature. No storage is needed when the heater is sized for the flow, and nothing stands at 180°F waiting between cycles.
The replacement is therefore not a copy of the package but a heater sized for the water circuit as it runs today. Steam on the tube side of a 316L U-tube bundle, water on the shell side, a solution-side rating of 150 psig at 250°F and tri-clamp or flanged connections to match the rinse line. It is smaller than the tank it replaces, has no tank to inspect, and is sized at the sanitize surge rather than at a stored volume.
Before the inquiry
- Make and model from its plate, and the year; a photograph of the plate is enough
- Rated steam pressure and the pressure actually at the unit now, which are often not the same
- Storage volume in gallons, which tells us how much surge the old coil was leaning on
- Water flow the rinse and sanitize steps draw, in gpm, from the CIP recipe or the pump curve
- Outlet temperature setpoints for rinse and for sanitize, and the inlet water in winter
- Whether the plant wants to keep the storage tank as a buffer or remove it with the generator
the sanitize hold that sizes itRinse at 120–140°F is the easy part; holding 180°F at the return for 5 minutes at full circuit flow and winter inlet is the duty the new heater is sized for.
What changes when the tank goes
A generator with storage and a once-through heater behave differently on the floor, and the plant should know what to expect before the old unit is lifted out.
- The heater is sized for the sanitize gpm, not the stored gallons, so it is often larger in duty than the old coil
- Steam demand rises during the sanitize step and falls to nothing between cycles, instead of trickling to hold a tank
- Outlet temperature follows the control valve within seconds, so the valve and sensor are sized with care
- No stored water at 180°F means no standing loss and no tank to drain, inspect or descale
- If the plant keeps the tank as a buffer, the heater can be sized smaller and the tank becomes a reservoir only
Call and talk it through with an engineer: 1-805-484-2992
Sizing the steam-to-water heater
The governing case is the sanitize step: full circuit flow, winter supply water, and an outlet that must reach 180–190°F so that the return reads at least 180°F at the coldest point for the 5 minutes many plants specify. A 3-inch circuit at about 70 gpm raised from 50°F to 185°F is a 135°F rise and roughly 4.7 MBtu/h; the same circuit on a 120–140°F final rinse is less than half that. The heater is sized at the sanitize figure and the control valve throttles for the rinse.
Steam pressure at the heater decides the approach. Sanitize water at 185°F against 15 psig steam condensing at 250°F leaves 65°F of approach, which is comfortable for a shell-and-tube and is the reason the duty stays on steam rather than moving to a plate exchanger on hot water. At 50 psig the approach is 113°F and the bundle is smaller. We size for the pressure that arrives at the unit during a wash, and we ask for it because generators from Armstrong or Cemline were often installed on a header that has since been turned down.
The water side is ordinary 316L shell-and-tube practice. Water is on the shell, steam inside the U-tubes, the bundle comes out when hardness scale builds on the shell side, and the solution-side head gasket is EPDM because nothing harsher than hot water passes through. Where the rinse loop is treated as sanitary the shell side is drainable, finished to 32 Ra and connected by tri-clamp to 4 inches; where it is utility water, mill finish and flanged connections are right and cost less.
Plants sometimes ask whether to keep the old storage tank. If the tank is sound, leaving it in the line as a buffer lets the heater be sized nearer the average than the peak and smooths the steam draw, at the cost of keeping a vessel at temperature. If the tank is the reason for the replacement, the once-through heater removes it from the system entirely and the plant sizes for the surge. Both are workable; tell us which you prefer and we quote accordingly.
What we need is the gpm and the temperatures for rinse and sanitize, the winter inlet, the steam pressure at the unit, the connection sizes and whether the tank stays. A photograph of the old generator's plate and its connections covers the rest. The steam-to-water heater page describes the construction, and the duty point page covers the arithmetic behind the figures above.
Size for the sanitize surge, not the stored gallons, and the tank becomes optional.
A once-through heater at circuit flow replaces both the coil and the storage it leaned on.
Request a QuoteGenerator swap questions
Not if it is sized for the sanitize flow and the coldest inlet. The tank existed so a small coil could cover a short surge; a heater sized for the surge covers it directly. Keeping the tank as a buffer is an option that lets the heater be smaller and the steam draw smoother, but it also keeps water standing at 180°F. Most plants replacing a generator for tank corrosion are glad to see it go.
On steam, no; the pressure and temperature cycling on the steam side shortens plate gasket life and we do not recommend it. Where the plant has a hot-water or recovery loop that can supply the rinse heat, a gasketed plate exchanger on water-to-water is a sound choice for the 120–140°F final rinse. For the 180°F sanitize hold against plant steam, the steam-to-water shell-and-tube is the right construction.
The replacement is rated for it, with a tube side at 150 psig and 400°F, but it is sized for whatever pressure actually reaches the unit during a wash. Many headers that were set at 100 psig when the generator went in have since been turned down, and a heater sized on the old figure runs short of surface on the new one. Read the gauge at the unit during a sanitize step and send that.
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