In the metalizing process for a valve, which action is performed last?

• A. Caulk all penetrations
• B. Apply primer
• C. Inspect for leaks
• D. Install insulation

Answer: (A)

Sealing penetrations is done last to finish and protect the assembly after all other work is complete. The surface is primed to ensure the metalizing coating sticks properly, insulation is installed to provide thermal protection, and a leak test is performed to verify there are no openings. Once everything is in place and the system passes inspection, caulking around penetrations creates a tight, moisture- and air-tight seal that protects the insulation and prevents water or dust ingress. If caulking were done earlier, it could be damaged or disturbed during subsequent steps, undermining the seal. So the final step is to caulk all penetrations.