Hello,
Does anyone have a water level indicator inside the cab? We have one fitted inside 69 but we are not sure how it works. It is measured in feet from 1 to 10.

I don't recall the manufacturer right now , but Milw 261 has a similar gauge which operates off air pressure. You should see an air supply off the air tree , usually on the engineer's side of the cab. This goes to a small regulator which reduces the air pressure down to about 6-8 pounds psi. I usually see a small air filter next in line to keep dirt out of the gauge which then goes to a T under the gauge. The line then goes to the roof of the cab and continues to the tender and ends in a vertical pipe extended down to within an inch of the bottom of the tender and is open ended. It takes .454 pounds of air pressure to push 1 foot of water out of the pipe, so if there is one foot of water in the tender, the air pressure will be .454 pounds at the gauge and the rest of the 6-8 pounds will bubble out of the end of the pipe into the water. If the tender is full at ten feet of water the pressure at the gauge will be 4.54 pounds and read ten feet on the face of the gauge. If five feet, then it's 2.27 pounds, etc. Since the gauge is extremely sensitive, reading under five pounds difference between empty and full, it must be kept very clean. (especially in a coal burning lokey!) I use a electronic spray cleaner to keep it lubed and clean, and have had great success with it. When the needle is accurately set and there are no air leaks, it reads accurately within two inches of water height. If you want more detail on setting the regulator, contact me offline.

Ed Selinsky

Interesting.

Water weights 62.38 per cubic foot. So a one foot high column 1" square weights .433 pounds. A 10' high column of water (of whatever size) produces 4.33 psig of pressure.

The difference between this .433 and your .454 may be friction losses in the system.

The numbers I used were originally from one of my older sources, most probably the ICS correspondence course, and you are corrrect, the difference could well be that yours is a theoretical pressure in calculations and the ICS number could be a working number to include the friction losses on about 30' of pipe the air is pushed through. The point is that once the system is set up and the gauge calibrated to the level of the water in that particular system, it will consistently show the correct amount.

Ed Selinsky

Thank you for the reply Ed I have sent you a picture of the water level indicator in the cab.

Compressed air pressure working against a static head of water (which will of course vary as water is used) in the tank will cause a column of mercury to rise according to the pressure differential.