Distillation Columns External Inspection Prior to Entry
1. Support and Foundations
Distillation columns are usually supported by a cylindrical skirt which usually s fireproofed inside and outside with concrete, brick, or other insulating material.
Inspect the fireproofing material carefully for evidence of cracking, spalling, or defective seal at the top edge. Water which penetrates the insulation can cause severe corrosion of the support. Remove small sections of the insulation, if necessary, to permit inspection.
Check the anchor bolts and nuts for corrosion or evidence of failure, and observe the condition of the concrete around the bolts. Cracking of the concrete around the bolts usually indicates corrosion is taking place.
Inspect all foundation support rings, brackets, or lugs for corrosion or indication of distortion or settling. If settling is noted, the equipment should be checked for plumb.
2. Ladders, Platforms, Handrails and Davits
External structures attached to the column for the purpose of servicing the column and providing entry should be inspected with the column. Check ladder supports and clips. Look for missing bolts, broken or weakened handrails, loose toe-boards or defective floor plates. Davits used for lifting materials should be sturdy and not deformed from misuse or overloading. Davits must be load tested. Angle supports where welded to columns are frequently found corroded under the insulation where water collects. Remove the necessary insulation to permit inspection for this condition.
Note the general condition and effectiveness of the insulation on the shell and heads. Openings around manways, nozzles, and brackets should be sealed to prevent the entry of water. All insulation ties or retainer strips should be intact and tight. Evidence of weathering or cracking of the weathercoat should be noted, and repairs made if necessary.
4. External Corrosion
Inspect the external surfaces of the column where exposed or where corrosion is indicated. Note particularly welds, brackets, nozzles, breaks in the insulation, or where water has been allowed to run on the shell, support legs, or skirt. Check the weep holes in the reinforcing pads for evidence of leakage. Gage the areas where corrosion is found and establish the severity, extent, and rate of corrosion.
5. Lines, Instrument Leads and Conduit
Visually inspect and hammer-test all small piping, including instrument piping, level gage connections, vent and drain fittings, and sample connections. Note the condition of all conduit attached to the column or platforms for lighting, instrument, and thermocouple leads. Look for exposed wires, missing cover plates, broken fittings, and improper support.
Inspect the gasket faces on all flanges that might be opened, including the manway nozzles and covers. An adequate inspection cannot be made if the gasket is still in place. Remove it or have it removed. Hammer-test all small nozzles. Inspect the manway cover hinge pins for binding. A frozen pin can prevent tight closure of the cover.
Categories: In-Service Inspection | Tags: Insulation, Nozzles | Leave a comment