Presence of pyrophoric material and vessel internal inspection

[ben]

Operations must be having a controlled procedure to handover pressure vessels for internal inspection carrying potential of pyrophoric material.
What sort of controls are exercised before the vessel is handed over to Inspection and maintenance?

[ww2i]

API RP 2016 discusses the spontaneous-ignition hazard of pyrophoric iron sulfide and controls such as wetting, inerting and appropriate treatment. Although it is a tank-cleaning recommended practice rather than a pressure-vessel handover standard, it provides useful technical guidance for developing site-specific procedures.

[chem51]

For pyrophoric materials, a controlled procedure stays in place covering the following:

Remove hydrocarbons and other process inventories using sequence mentioned.
Determine whether water washing, steam-out, chemical cleaning or another method is suitable for the specific service and deposits.
Where pyrophoric FeS is suspected, establish a specific control for keeping the deposits wet or otherwise preventing ignition during exposure to air (the most important one).
Maintain wetting during opening, deposit removal, transportation and waste handling wherever required by the approved method.
If inerting is used, control oxygen ingress and maintain the specified atmosphere until a formally approved transition to air is permitted.
Assess wash-water compatibility, wastewater disposal, chemical reactions, sludge handling and the possibility of H₂S release during cleaning.