Fouling deposits add thermal resistance and pressure drop. Cleaning restores area effectiveness; it does not repair thinned tubes. The method has to match deposit chemistry, metallurgy, and — first — the configuration you bought. A fixed-tubesheet unit cannot offer a bundle pull. A U-tube cannot be rodded through the bend. Specify the cleaning philosophy on the RFQ so the rear head and channel are not fighting operations later.
When cleaning is due
Typical triggers: approach temperatures closing toward the design dirty case; shell- or tube-side ΔP rising well above clean; planned turnaround regardless of instruments. Confirm the process case and instruments before opening the unit — a flow meter error looks like fouling. Isolate, depressurise, drain, and gas-free per site procedure. Cooling-water and process sides may need different blinds and permits.
Mechanical cleaning — tube side, straight tubes
With a removable channel cover (TEMA Type A) and straight tubes, the tubesheet face is accessible. Methods:
- High-pressure water jetting (hydroblast): effective on soft to moderately hard deposits; needs water management and a jetting contractor who will not cut tube ends.
- Rods and brushes: for light deposits and inspection after jetting.
- Drilling / mechanical knock-out: for hard coke or polymer — higher risk of tube damage; thin-wall or exotic tubes need a written procedure.
Chemical cleaning (CIP)
A closed loop circulates a solvent, acid, or alkaline cleaner chosen for the deposit and compatible with tubes, shell, gaskets, and welds. Useful when the bundle cannot be pulled, for U-bends, and for uniform scale. Requires: known deposit, qualified chemistry, corrosion inhibitor where acids are used, vents for gas, and a neutralization / disposal path. Chemical cleaning of the shell side of a fixed-tubesheet unit is often the only practical shell-side method. Do not circulate chloride-bearing water through austenitic stainless and then leave it stagnant.
The cleaner must be qualified against the MOC. Hydrochloric acid on 300-series stainless, or a solvent that attacks spiral-wound gaskets, turns a clean-out into a leak repair.
Bundle pull and shell-side access
Removable bundles (U-tube; in industry also floating-head) can be withdrawn if the plot has pull space, a crane path, and davits or pulling devices as designed. Shell-side deposits are then jetted or chemically washed on the bundle. Fixed-tubesheet exchangers do not permit this without cutting the shell. Ohm manufactures U-tube as the pullable bundle; we do not manufacture floating-head rear ends. If the plant's cleaning standard is 'pull and hydroblast the shell side every turnaround', that must appear on the enquiry so U-tube (or a purchaser-specified floating head from another supply path) is selected instead of a welded fixed tubesheet.
Configuration versus method
| Configuration | Tube-side mechanical | Shell-side mechanical | Chemical both sides |
|---|---|---|---|
| Fixed tubesheet, Type A cover | Yes (straight tubes) | No (bundle stays in shell) | Yes if connections exist |
| Fixed tubesheet + expansion joint | Same as fixed TS | Same as fixed TS | Protect the bellows from the chemistry |
| U-tube | Not through the U; channel-side ends only | Yes after bundle pull | Yes — often the tube-side plan |
| Double-pipe | Inner pipe accessible if closures allow | Annulus depends on design | Yes, simple circuits |
| Kettle | If straight-tube bundle and access specified | Bundle pull if the bundle is removable as designed | Shell chemistry must respect weir and vapour space |
After cleaning
Inspect tube ends, tubesheet face, pass-partition gasket surfaces, and (on pullable bundles) baffle edges for wear. Replace gaskets; do not reuse spiral-wound gaskets as a default. Hydrotest the circuit you opened if the site/code procedure requires it after breaking joints. Record clean ΔP and temperatures — that baseline tells you when the next clean is due.
RFQ: design the unit to be cleaned
Write the intended method (rod, hydroblast, CIP chemistry class, bundle pull interval), whether vents/drains/CIP nozzles are required, and pull-space constraints. Send process fouling character with the duty data to /rfq?product=heat-exchangers. Cleaning access is cheaper on the GA than as a field modification.
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