Tuesday, July 29, 2014
Re: [californiadisasters] TV news now covering water main break in Westwood
Kim -
Several reasons combined for taking a while to shut down.
1) as someone said pressure surges can damage other pipes and infrastructure. I once saw a 1/2 inch thick stainless in a manifold in a waterworks tear like toilet paper due to surge from a 48 inch main that was at full flow. water has momentum
2) make sure they are shutting valves in a way to minimize disruption and to plan to open valves to maintain pressure in areas where pressure could drop
3) notify all users of water that have critical needs such as hospitals, laboratories etc are notified. Lack of water could damage process and/or equipment
4) Actualy shutting down a valve takes time. A 48 inch gate valve typically takes 340-380 full turns to shut down. A 36 inch gate valve will take around 250-300 turns. With two men on the valve wheel it probably would take 45-60 minutes to shut each valve off. If they are using a T wrench through a street opening it would take a bit longer.
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Posted by: dboconnor1@earthlink.net
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