Earl and the Aboveground Storage Tank Forum for fuel tanks, plastic tanks, fuel oil storage tanksWelcome to the aboveground storage tank forum, a bulletin board dedicated to tanks, fuel tanks, plastic tanks, fuel storage tanks, and above ground storage tanks (AST) API650, API653 & UL142 aboveground storage tanks (AST) and chemical plastic tanks. Remember the forum is made up of volunteers from experts to beginners. Unfortunately, we cannot allow free commercialism that promotes products, services, or sites.
Sponsored by:
Spirax SarcoPE Marketing, LLC
Contact us about advertising

Stephen H on Telltale hole

By: Stephen H 
Date: Thursday, January 26, 2006
Time: 12:00:00 AM

I've seen two different uses. On storage tanks, it is a hole in the repad of a nozzle. If the nozzle welds (or plate) start leaking, it will show up at the tell-tale hole. I guess this avoids trapping product when you try to work on a tank as well. The same hole is typically used to air-pressure-test the repad for leaks. If a nozzle is stress-relieved, it would also serve to vent the area between the repad and shell. In the design of a repad, it is assumed that the shell has pressure against the inside of it. If the area between the repad and shell is allowed to pressurize the same as inside the tank, the tank wall in that area no longer has a net pressure against it. It would theoretically try to flatten into a chord, transferring more force into the repad. At the ASME Section VIII class a while back, they referred to tell-tale holes as small holes drilled almost through the walls of a pressure vessel. The idea being that if uniform internal corrosion exceeds a certain amount, it will start leaking at the holes, and give an indication, rather than progressing on to a possible catastophe. I don't know how commonly these are used.

Published on ast-forum.com

Spirax Sarco

Spirax Sarco: A World Leader in Steam Management

An Energy Engineering Company Specializing in Steam Energy Solutions.  Steam generation from HRSG to Process Heating, Spirax Sarco has your energy solution.


  • Instrumentation and Controls Systems
  • Experts in Steam & Condensate
  • Training Courses
  • Capital Equipment: Condensate Packages and Systems
  • Steam Trap Programs Facility Wide
  • Steam Process Heating Optimization
  • Distributors Worldwide


Invite us to talk to you about your steam consumption today and what we can do for you!


Spirax Sarco

Spirax SarcoPE Marketing, LLC
Want to Advertise on the AST Forum
Confidentiality, Disclaimer & Policy
© 2001 to Aboveground Storage Tank - AST Forum, All Rights Reserved.
Valid XHTML 1.0 Transitional