What be the best mitigation process if a tank in service with an external floating roof and has a leak on the double deck pontoon?

Now serving as an engineer in training (EIT). I'm using API 650, AISC Steel Const Manual, ASCE 7

My vendor is offering the Body Gas test as per API 6A PSL 3G in which the method to detect the leak is by sniffing probes over the areas of leakage suspected.

When a gate valve is newly manufactured I can understand why it needs a full pressure test to ensure the integrity of the casting or forging and to proove the pressure containment ability.

Building a system which involves an increase in internal pressure via an air tank in order to extend a series of telescoping tubes, and a subsequent full release of pressure back to atmosphere.

Pressure request for installation of double block and bleed valves? It is neccessary to install those valves on the low pressure lines or you can get away with just a block valve and a drain?

Between Globe,Ball,and Gate, which type of valve is capable of maintaning Differential Pressure better

For larger diameter buried waterlines that we need to remove from service (16" diameter and larger), we specify that a flowable fill should be used to fill the pipe.