B-1.1, r. 3 - Safety Code

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277. If a bulk plant is not under the supervision of the owner during normal operating hours, all loading and unloading valves, water drain valves, fill pipes, pump controls and gates must be locked, except electric remote-control valves.
Outside normal operating hours, shut-off valves in the proximity of aboveground tanks must also be closed and locked.
O.C. 221-2007, s. 1.