Industrial CIP Heat Exchangers

Yes, whenever the steam pressure inside the tubes falls below the back pressure on the condensate line. At part load the control valve throttles until the steam is only as hot as the duty needs; holding a 150 F loop at low flow may take steam at 180 F, which is a vacuum of about 7.5 psia inside the tubes, and no vacuum pushes condensate through a trap into a return line at 5 psig. Condensate backs up the bundle, the outlet temperature wanders, and the slugs hammer the tube joints. The cure is a pump-trap or a vented receiver with a condensate pump at the heater, sized for the stall load, or a vacuum breaker and gravity drain where the receiver can sit below the heater. On a U-tube with steam in the tubes, specify it at the quote; retrofitting it means repiping.

As a scheduled consumable: a full set on the shelf and the whole pack changed at once. EPDM in 5 percent caustic at 190 F gives two to four years, so a plate in that service is regasketed two to four times in a decade. Mixing new and old gaskets compresses the pack unevenly and the old ones leak first, which is how a plant ends up opening the frame three times in a year. Store spares cool, dark and away from motors, and specify clip-on gaskets so the change is a shift, not a weekend.

Through it, yes; heated in it, not unless the solvent's flash point sits well above the steam temperature on the other side of the tube. With 150 psig steam the tube wall is near 366 F, above the flash point of most process solvents, so the sequence closes and locks out the steam valve before the flush and interlocks it with the solvent pump. Drain the rinse water from the shell first so the flush is not diluted, and specify PTFE-envelope gaskets on the solution side because EPDM swells in most solvents. Name the solvent on the quote; the gasket and the drain arrangement follow from it. Pipe the shell vent to a safe location as well, since solvent vapor collects there.

Run it as cool as the soil allows, rinse fully before any acid, and drain the heater after every cycle. Hypochlorite meeting nitric or phosphoric acid releases chlorine gas, so the intermediate rinse is a safety step. On the exchanger, chloride left in a tube-to-tubesheet crevice overnight at temperature is what pits 316, and chloride stress corrosion cracking of austenitic stainless becomes a concern above about 140 F, so a loop that holds chlorinated cleaner at 180 F is a candidate for 2205 duplex tubes. Welded rather than rolled tube joints take the crevice out; a shell drain at the true low point takes the puddle out. Name the cleaner and its strength on the quote.

Split-range steam valves: a small one for trim and low flow, a large one that opens only after the small one is wide. That duty is about 40,000 lb/h of 150 psig steam at full fire, and a single valve sized for it runs at a few percent of travel when the loop is at a third of design flow, where valve gain is highest and the loop cycles. Feedforward from the loop flow meter lets the controller set the valves ahead of a circuit switch. State the lowest flow the loop will ever run so the small valve is sized for it.

Set it by the chemistry: first pull in the first year on strong chlorinated or acid programs, then by what that pull finds. Look at the tube ends at the tubesheet and at baffle contact lines for pitting, and at the shell low point for a tide line that says it has not been draining. A hydrostatic test at the same shutdown confirms the joints before the next campaign. A loop on plain caustic and phosphoric acid can go three to five years between pulls.