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This post was last edited by HP0377 on 2017-7-12 at 19:28. Multiple-choice question: On a P&ID diagram, flow arrows indicating the direction of the fluid are placed at appropriate locations along each pipe; these arrows are usually drawn where the pipe changes direction, branches, or enters equipment connections. All pipes that flow under the force of gravity should be marked with flow direction arrows and the word “gravity flow”. A. True B. False. (A) Valves are required to be installed at the outlets of pipes carrying containers filled with flammable, toxic, or corrosive materials. A single valve is generally used for such containers; when there are multiple inlets or outlets that require separate control, valves are installed at those outlets. Valves are installed at the outlets of containers holding flammable, toxic, or corrosive materials; inner containers are generally equipped with a single valve, while storage tanks in the intermediate or entire plant tank areas are fitted with double valves. A drain valve should be installed at the lowest point, and the discharge pipe should be positioned slightly above the drain valve. Except for containers that are small in size (without access holes for maintenance) or can be replaced along with the system, a utility material connection (U.C.) equipped with a shut-off valve must be installed at the bottom of the container, and a vent valve must be installed at the top of the container, at a position far from the utility material connection. Containers and tanks that require inert gas protection should be equipped with self-acting control valves in series with check valves; refer to the industry standard \"Installation of Gas Seals\" (PS305-03). Large pressure-vessel tanks with conical or domed roofs, used for storing volatile materials, should be equipped with breather valves. Tanks located in the entire tank farm should have dual-disc valves and safety valves; these components need to be labeled and numbered