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water distribution 1
- Thread starter arj00
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1
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arj00
In my experience, most water utilities limit normal flow to 5 ft/sec with exceptions for fire flow...
limiting factors are:
Friction loss: At speeds greater than 5 ft/sec the friction loss becomes large enough to change the hydraulic gradient such that steady pressures are not maintained or increased cost of pumping play a factor.
Water hammer: for every 1 ft/sec of speed, the pressure wave from a suddenly closed valve changes by about 50 psi. This occurs on both sides of the valve, upstream as a pressure increase, downstream as a pressure decrease. Up stream the pressure rating of the pipe may be exceeded, downstream the pressure can go into vacuum which may include column separation (cavitation), the vacuum conditions may induce backflow from services or leaks. column separation can destroy the lining of the pipe and anything else in the way. Steel and PVC pipe are less vulnerable because they deform to absorb some of the energy, but their pressure ratings are lower.
Lining removal: Destruction of the linings from long term erosion can occur with the water traveling at high speeds, many other factors are involved here, chemistry of the water, imperfections in the lining material ect.
Hydrae
In my experience, most water utilities limit normal flow to 5 ft/sec with exceptions for fire flow...
limiting factors are:
Friction loss: At speeds greater than 5 ft/sec the friction loss becomes large enough to change the hydraulic gradient such that steady pressures are not maintained or increased cost of pumping play a factor.
Water hammer: for every 1 ft/sec of speed, the pressure wave from a suddenly closed valve changes by about 50 psi. This occurs on both sides of the valve, upstream as a pressure increase, downstream as a pressure decrease. Up stream the pressure rating of the pipe may be exceeded, downstream the pressure can go into vacuum which may include column separation (cavitation), the vacuum conditions may induce backflow from services or leaks. column separation can destroy the lining of the pipe and anything else in the way. Steel and PVC pipe are less vulnerable because they deform to absorb some of the energy, but their pressure ratings are lower.
Lining removal: Destruction of the linings from long term erosion can occur with the water traveling at high speeds, many other factors are involved here, chemistry of the water, imperfections in the lining material ect.
Hydrae
Hydrae is right BUT the question was "are there any standards" - none that I am aware of - nothing in BS 8010 but BS 8005 - sewerage systems
umping mains(from memory) mentions economic pumping velocity guide line limit of 2.5 m/s.
As long as you can accomodate the resulting headlosses and surge pressures there is no other reason to limit max. velocity.
umping mains(from memory) mentions economic pumping velocity guide line limit of 2.5 m/s.As long as you can accomodate the resulting headlosses and surge pressures there is no other reason to limit max. velocity.
KRSServices
Civil/Environmental
In standards that I have developed, i prefer a velocity in potable water systems not to excedd 3.0 m/s during a fireflow. The reasons are many, but most importantly related to maintenance costs.
KRS Services
KRS Services
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