I would like to ask how to calculate the diameter of an overflow pipe
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There is a small head tank with a volume of 10 m³. I would like to ask how to calculate the diameter of the overflow pipe. The flow rate of the lift pump is 10 m³/h, the diameter of the outlet pipe of the head tank is DN40, and the maximum flow rate at the outlet is 5 m³/h. What should be the diameter of the overflow pipe? Is there any simple way to estimate it?
The general principle behind the design of the overflow pipe is to ensure that the equipment does not get filled under any circumstances. Therefore, many factors must be taken into account during design, such as the inflow volume, outflow volume, medium viscosity, pressure in the high-level tank, diameter of the overflow pipe, pipeline resistance, and the height difference between the overflow port and the discharge port, among others. In the situation described by the poster, if the high-level tank is at atmospheric pressure, the medium is water, and the pipeline resistance is not high, an overflow pipe diameter of DN80 or DN100 can be chosen.
So, can it be assumed that for media like water, the diameter of the overflow pipe is generally chosen to be twice that of the inlet pipe? Is there also a specific calculation formula for this? I would appreciate some guidance
I haven’t really looked at it carefully, but generally, DN50 or DN100 sizes are more common.
When I used to design for overflow, I would simply make the outlet diameter one size larger than the inlet diameter. In making estimates, I mainly considered the following: (1) It takes time for the existing pump to fill the space above the overflow opening of the surge tank； (2) The distance between the overflow port and the overflow sight glass is, in fact, the time it takes before the overflow can be seen ； (3) How long does it take to stop the feed pump after observing overflow? ； (4) Due to pressure issues after stopping the pump, an additional 3–5 seconds are required ； Just estimate the overflow velocity at normal pressure for various pipe diameters.
These days, high-level tanks generally use continuous feeding, with the feeding pump running non-stop
Hehe, I thought it was intermittent operation; when I worked on continuous high-level trough systems in the past, I didn’t include an overflow design – instead, I just added a return pipeline at the outlet of the feeding pump, and controlled the feeding flow by adjusting the opening degree of the return valve.
That’s indeed a good idea; it’s worth trying. Why is an overflow pipe needed in the high-level tank? It’s so that a sight glass can be installed on the overflow pipe, allowing one to monitor the contents of the tank at any time. Since the operators and the feeding pump are located far away, the return sight glass helps to solve this problem. According to what you said, the diameter of the overflow pipe can be chosen to be much larger. Thank you