Q. Show the vessel internals?
Functional design of trays and other removable internals are outside the scope of this document.
Removable internals shall be sized to pass through designated vessel openings. On vessels with internals, where a vessel manway is not located in the top head, internal rigging clips shall be provided to facilitate handling of the internals. An external davit for lifting the removable internal components shall be provided.
Vessel internals such as distributors, dip tubes, baffles and thermowells, should not be located near manways in a manner that would interfere with personnel access or rescue. Special consideration should be given to the area directly below manways, and to head knockers above manways. In some circumstances, the addition of handholds may be necessary.
Welding of vessel internals, attached to a pressure boundary component, shall be continuous on all surfaces to eliminate corrosion pockets. All seams and corner joints shall be sealed.
Internal piping and baffles shall be mounted in a manner that will not unduly restrict thermal expansion. Consideration shall be given to vibration and the possibilities of fatigue failure. Where vibration and fatigue is a governing design requirement, internal non-pressure parts, such as baffles, that may be subject to vibration or cyclic loading, shall be continuously welded.
Internal bolting in vessels, especially where vibration is expected (e.g. where agitators are installed), shall either be double nutted, tack welded to the clip, baffle, or have a lock wire placed in the nut/bolt or other supports.
The nominal chemical composition of internal, non-pressure piping shall be compatible with that of the inside surface of the vessel and the process. Flanges for internal non-pressure piping, must conform to ASME/ANSI B16.5, Class 150. Butt weld fittings are to be used; miter bends and stub-ins are not allowed.
Vessel internals and all portions of each vessel shall be self-draining, to ensure complete elimination of liquid from the vessel when drained.
For integrally clad and/or for weld overlaid vessels, lightly loaded supports such as those for trays, baffles, etc., may be welded directly to the alloy clad or weld overlay. Where supports are carrying an appreciable load (>25% of the allowable stress for fillet welds), such as packing bed support rings, consideration shall be given to welding directly to the base metal.