NRV slam on pump stop
NRV slam on pump stop
(OP)
We have swing check valves (NRVs) in the vertical discharge from a pump. When the pump stops the NRVs slam very hard.
Not much room to move the valves.
How can we reduce the slam? Some ideas below, what would be best?
1. Change the valve type. Flapper, ball etc (faster acting)
2. Pump soft stop (opposite to a soft starter)
3. Header tank/accumulator
4. damper on swing check arm
Not much room to move the valves.
How can we reduce the slam? Some ideas below, what would be best?
1. Change the valve type. Flapper, ball etc (faster acting)
2. Pump soft stop (opposite to a soft starter)
3. Header tank/accumulator
4. damper on swing check arm





RE: NRV slam on pump stop
I would tend to go for the first option.
RE: NRV slam on pump stop
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: NRV slam on pump stop
RE: NRV slam on pump stop
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: NRV slam on pump stop
A slamming check valve will fairly quickly be an ex check valve.
Putting a swing check vertically is not helping either - any chance you can relocate to a horizontal system.
You can't get much better than this, but they are not cheap. https://mokveld.com/en/axial-check-valve
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: NRV slam on pump stop
Quick closing check valves (silent checks) will work:
http://www.valmatic.com/silentcheck.html
http://www.valmatic.com/pdfs/DynamicCharacteristic...
The pump soft start will only be successful if you have reliable power. It will not work with power failure situations.
The solution depends on the size of your installation.
RE: NRV slam on pump stop
In my opinion, swing check valves (NRVs) are notorious for their delay in checking up. There's a definate delay as the swing falls into its seat.
During this time your flow begins to accelerate in the reverse direction and when the seat closes you get the slam. You need a prompt (faster) closing check valve that doesn't need to wait for the swing check to fall onto the seat
I'd suggest a spring loaded nozzle check valve that has an internal spring to quickly close the valve before substantial back-flow velocity develops.
Jeff
Pipe Stress Analysis Engineer
www.xceed-eng.com
RE: NRV slam on pump stop
RE: NRV slam on pump stop
RE: NRV slam on pump stop
Ta
LI
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.