Website: https://solempipelinesafetyconsulting.com/
One of the most common and easily preventable findings I encountered while a PHMSA inspector was plugged tank telltales. Telltales are holes in reinforcement pads (repads) installed on the tank shell to support fittings. Telltales are designed to indicate a leak in the annular space between the shell and the repad. If there is a leak, operators install a pipe plug in the threaded telltale hole until the tank can be taken out of service and repairs made. Many operators are unaware that the incorporated by reference (IBR) API 650 11TH edition states that telltales must be open to the atmosphere. Operators tend to plug them with pipe plugs to prevent dirt and moisture from entering the annular space. An acceptable practice is to fill the telltale hole with grease that will be forced out in the event of a leak yet if no leak prevent the entrance of dirt and moisture. Another acceptable practice is to install a street ell and a pipe nipple downward so dirt and moisture can’t enter but fluid from leaks can still flow freely.
Here is the IBR code from API 650:
5.7.2.10 Reinforcing plates for shell openings, or each segment of the plates if they are not made in one piece, shall be provided with a 6 mm (1/4 in.) diameter telltale hole. Such hoes shall be located on the horizontal centerline and shall be open to the atmosphere.
I recommend that all hazardous liquids operators with breakout tanks on the next monthly tank inspection ensure that the only plugged telltales are leaking ones and that the telltale holes are filled with grease or a streel ell and downward turned pipe nipple.