JohnWeal
Mechanical
- Dec 16, 2012
- 124
Good evening,
Hopefully what I describe here can be visualised....
We have 9 pumps installed in a dry well, 7 will operate with 2 standby. The pumps are split case with vertical shaft with motor on floor above.
The discharge from each pump is 700mm Ida and the first item in the direction of flow is a non-return valve followed by a butterfly valve which may be used for pump startup / shut down sequence. Beyond the butterfly valve the pipe passes through a reinforced concrete wall then after a few metres joins a common header pipe which receives the pipes from.
The other pumps. The header is 1400mm diameter and in this installation is not within a building or a chamber but in the ground with the recommended backfill procedure.
From the header there two parallel pipelines each 1400mm diameter delivering flows to an elevated reservoir with a static head of 140m. So with that head and the 1400mm pipe, I calculate a pressure force in the pipeline against the closed butterfly valve of approx 540kN.
Now the question is this, when the pump stops, the column of water will initially slam the non return valve closed. But also if the butterfly valve closes, then the water column comes to rest on the butterfly valve.
So, with the resulting pressure force, how much of the force is transferred to the reinforced building wall in which the 700mm pipes pass which contain a puddle flange encase into the wall?
How should the thrust be absorbed? I am concerned that the load will axially present itself to the pump and create misalighment problems over time.
Does the wall need to prevent the puddle flange having excessive force within the wall?
We do have a surge vessel installed in the pipeline but it is the static head force and where it is acting that I cannot quite visualise.
Regards
John
Hopefully what I describe here can be visualised....
We have 9 pumps installed in a dry well, 7 will operate with 2 standby. The pumps are split case with vertical shaft with motor on floor above.
The discharge from each pump is 700mm Ida and the first item in the direction of flow is a non-return valve followed by a butterfly valve which may be used for pump startup / shut down sequence. Beyond the butterfly valve the pipe passes through a reinforced concrete wall then after a few metres joins a common header pipe which receives the pipes from.
The other pumps. The header is 1400mm diameter and in this installation is not within a building or a chamber but in the ground with the recommended backfill procedure.
From the header there two parallel pipelines each 1400mm diameter delivering flows to an elevated reservoir with a static head of 140m. So with that head and the 1400mm pipe, I calculate a pressure force in the pipeline against the closed butterfly valve of approx 540kN.
Now the question is this, when the pump stops, the column of water will initially slam the non return valve closed. But also if the butterfly valve closes, then the water column comes to rest on the butterfly valve.
So, with the resulting pressure force, how much of the force is transferred to the reinforced building wall in which the 700mm pipes pass which contain a puddle flange encase into the wall?
How should the thrust be absorbed? I am concerned that the load will axially present itself to the pump and create misalighment problems over time.
Does the wall need to prevent the puddle flange having excessive force within the wall?
We do have a surge vessel installed in the pipeline but it is the static head force and where it is acting that I cannot quite visualise.
Regards
John
