Add campaign end dates and the last known drain-down to the vessel history. They show how long older material may have remained in low connections before the current product arrived.
Campaign material in separate streams
Current product, earlier campaign material and any unidentified layer remain separate recovery decisions. Dosing lines and sample points belong in the same product-route check.
Do not combine uncertain chemical residues
The site first traces the known contents and keeps any newly exposed layer separate.
Check the recent contents history
Current contents, lining information and connected process routes come from the site. Unknown layers stay separate until their handling has been decided.
When an exposed layer differs from the record, the site reviews the new information before the cleaning method continues.
Match the method to the oldest relevant layer
Show Infused Media the vessel drawing, contents records and the reason it is coming out of service. The contractor can then define chemical tank cleaning without hiding critical assumptions. The tank contents information sheet helps gather the initial facts.
Stop if the exposed material differs from the record
A product name does not reveal concentration, mixtures, ageing or material left from an earlier campaign. Current safety information, tank history and any available sample results help identify compatibility questions before a cleaning agent or recovery method is selected. A sample point can contain material from a different date or concentration, so its contents should remain identifiable until the site has resolved the appropriate route.
Pipework, vents, dosing lines and recirculation routes can retain material or reintroduce it. The site should confirm each isolation and the equipment that remains live. HSE guidance on dangerous substances and explosive atmospheres is relevant where cleaning can introduce or disturb hazardous material.
Unexpected material is kept separate and linked to the vessel until the site confirms the revised handling route. The contractor notes where the observed condition differs from the supplied history.
State whether inspection, repair or reuse follows
Inspection, repair, product change and decommissioning require different surfaces and records. Name the next task and the parts it needs to reach. Cleaning does not declare the tank gas free, safe for entry or ready for chemical use; those decisions remain with the responsible specialists and site procedures.
Any recent reaction, off-specification batch or unplanned addition belongs beside the routine contents history because it can alter both cleaning compatibility and the recovered-material route. If operators observed heat, pressure or colour change, that observation should travel with the affected layer rather than being reduced to the normal product name.
Connected transfer lines may contain a different chemical and therefore need their own isolation and recovery arrangements.
Campaign vessels may contain a thin current layer above older hardened material. Keeping the sequence visible helps the site decide whether the layers can share containment or require separate handling before further washing.
Connected dosing lines and sample points can hold a different concentration from the main shell. Their inclusion is stated explicitly, along with the person who can answer substance questions if the material exposed during cleaning differs from the supplied history. That contact remains available while the vessel is open.