Revision as of 14:12, 29 June 2009 by
***** (***** | *****)Intake
The water intake must be located upstream so it will
always supply the necessary and adequate amount of water to the turbine.
It must include a screen to prevent debris, fish, or rocks from entering the
turbine. A properly designed and constructed screen will be self-cleaning and
require little maintenance. A poorly designed screen will require upkeep
and will rob the system of power.
Forebay tank
Forebay
tank filters debris and prevents it from being drawn into
turbine and penstock pipe. This type of settling tank is not necessary but is
highly advisable. This serves as an area for the water from the intake to
“decelerate” and for any fine materials such as sand and gravel that passed
through the intake screen to settle and not flow into the turbine. As a general
rule, the settling tanks capacity should be about 20 times the turbines water
usage in one minute. So for example if your turbine uses 100 gallons per
minute, the tank should hold at least 2000 gallons of water. The inlet and
outlet from the settling tank should include a sluice gate/ shut-off so the
debris that settles to the bottom can be cleaned out. The outlet should also
include screens as a double check against debris from entering the turbine,
should the inlet for some reason fail to perform it’s intended task.
Pipeline (Penstock)
[[Image:|penstockfrombuilding.JPG]]
Penstock pipeline carries water from forebay tank to the power house. The pipeline delivers water to the turbine from the settling tank and must be sized properly to prevent frictional losses from robbing available power. This will be a cost/benefit trade-off since a long penstock can cost more than the turbine. Penstocks should be buried if possible to protect them and prevent freezing in cold weather climates. The penstock should include a breather pipe, ideally near the settling tank. This will prevent the disastrous event known as an implosion. Depending upon the pipe chosen, and if the intake were to suddenly be shut off – a huge vacuum would develop in the pipe. This is caused by the water’s momentum and can be of a large enough magnitude to cause the pipe to collapse.
A pressure gauge should be installed at the end of the
penstock, right in front of the turbine shut-off valve. It will be a quick way
to monitor how the system and penstock are performing. A quick reading of the
pressure shows if there is a change or a problem. Additionally, by monitoring
this gauge when closing the turbine shut-off valve water hammer problems can be detected. Water
hammer is the opposite of the implosion issue noted above. If the valve is
closed too quickly, the momentum of the water can dramatically increase water
pressure to the point of bursting the penstock. Shutting down systems water
flow should be done carefully.
Shut-off Valve
A shut-off valve is necessary, and should be directly
in front of the turbine in case an immediate shutdown of the system is
required. This valve should be of high quality and very durable. It is
recommended that to close and then open
the valve slightly on a regular basis to insure they don’t become seized in the
open position and then don’t function when most needed.
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