TANK ISOLATION – VERIFY AND DOCUMENT!
Posted on Tue, Mar 23, 2010 @ 06:50 AM
By Craig Childres, Director of Business Developmen - Petroleum & Energy
During the performance of the tank cleaning activities, everyone (owner & contractors) must comply with all safety requirements of Federal, state and local laws, rules, regulations along with accepted industry safety practices. Prior to entry into the confined space (tank's interior), one critical aspect is to document (PLAN) and verify that the tank has been properly "Isolated" and that all procedures have been followed before executing and issuing the "permit" for entry.
The PLAN should address:
- Tank isolation requirements
- Tank suction and discharge lines
- Other tank lines, appurtenances and connections
- Electrical, mechanical and pressure sources
- Cathodic protection systems
- Vapor recovery systems
- Fire protection systems
- Tank gauging and overfill protection alarm system
- Interior devices such as mixers, etc.
- Verification of isolation prior to issuing permits
Isolation is the process by which a permit space is removed from service and completely protected against the release of energy and material into the space by such means as: blanking or blinding; misaligning or removing sections of lines, pipes, or valves; a double block and bleed system; lockout or tag out of all sources of energy; or blocking or disconnecting all mechanical linkages.
Blanking or blinding is the absolute closure of a pipe or line by the fastening of a solid plate (spectacle blind, skillet blind, pancake) that completely covers the pipe or line diameter and that is capable of withstanding the maximum pressure of the pipe or line with no leakage beyond the plate.
Double block and bleed means the closure of a line or pipe by closing and locking or tagging two in-line valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves.
It is mandatory that the tank isolation PLAN is reviewed, verified and documented everyday that work is occurring. This includes not only the review of the plan but also physically inspecting the tank to ensure that nothing has changed since the previous day's work.