Cooling tower level probes have stillwell with 1/2 inch holes every 6 inches and 90 degrees apart, from top to bottom of the 18 foot pit. A strange dynamic has occurred causing the level in the stillwell to change by as much as a foot.
It looks like the flow across one of these stillwells is causing the water to draw down within the stillwell, giving a false level reading. At first I thought maybe the holes were plugged but they are not. There can be changes in the flow across the stillwell due to plugging of inlet screens so there may be an increase in velocity at various regions of the 18 foot probe. This is normal and the probe needs to be able to work with that. One question I had was what would be an appropriate quantity and size and location of the holes? I original wanted many holes to prevent such a dynamic. Hydrostatic level measurement has historically been good for this application and I do not want to change that. Maybe I need larger holes or more holes, but someone else has suggested fewer holes. Any comment or suggestion would be appreciated.
It looks like the flow across one of these stillwells is causing the water to draw down within the stillwell, giving a false level reading. At first I thought maybe the holes were plugged but they are not. There can be changes in the flow across the stillwell due to plugging of inlet screens so there may be an increase in velocity at various regions of the 18 foot probe. This is normal and the probe needs to be able to work with that. One question I had was what would be an appropriate quantity and size and location of the holes? I original wanted many holes to prevent such a dynamic. Hydrostatic level measurement has historically been good for this application and I do not want to change that. Maybe I need larger holes or more holes, but someone else has suggested fewer holes. Any comment or suggestion would be appreciated.