Inspection of Spheres
In general, the practices that apply to pressure vessels also apply to spheres although the techniques may vary. The tall legs necessary to support spheres should be carefully inspected to determine the condition of the fireproofing and the rain seals.
Remove cracked or spalled fireproofing and inspect the exposed steel. Earthquake or sway bracing must be tight and in good condition.
Inspect the cooling deluge rings on the upper shell, if any, for deposits of rust and sediment. Severe external corrosion can occur at these rings if the drain openings are not kept clean.
The internal surfaces can be inspected by filling the sphere with water and making the inspection from an inflatable raft. Life jackets must be worn while making this inspection. The sphere is usually filled to a point near the top and then inspected and gaged at various levels as the water is emptied.
Voice communication is difficult in a sphere due to reverberation and echoes. Do not take the portable ultrasonic instruments into the sphere on a raft. A large horseshoe magnet is available for use in the spheres to assist in holding the raft to the shell during gaging operations. All tools and equipment should be tied to the raft to prevent loss. Another method to gage the shell is the use of a magnetic ultrasonic crawler.
Categories: In-Service Inspection | Tags: sphere | Leave a comment