Tests were conducted to document the frost proof capabilities of T.A.P. Co. patented, double screened, insect/frost proof vents.
Test dates: February 28, 2003 through March 03, 2003
Test Location: Tomcat Consultants/T A P Co. fabrication shop and office. 111 South Fourth St., Rosebud, MO 63091
Witness to the test: Ralph Alexander, a consulting engineer for the steel industry.
A mock system was designed to create the most realistic conditions of a water storage tank in operation.
Water was pumped from a 1025 gallon atmospheric pressure plastic tank outside, to a sealed low pressure air charged tank inside. The water moved through a 1 ½” pressure hose through the pump ( which had the check valve removed to allow water to pass both ways ) into the low pressure, air charged tank. That tank was equipped with a low pressure mercury switch. The plastic tank was pumped down to about half full and the pump would shut down. The water flowed, under pressure, back into the plastic tank. The water went in and out gaining temperature inside and losing temperature outside. A complete cycle took about 45 minutes.
The outside plastic tank was equipped with a standard T A P CO. 4” vent ( Model S 4 ), a new 4 1/2” diameter 1% full range accuracy vacuum gauge ( 30” mercury ) and a ¾” steel pipe and ball valve that could be opened allowing the system to cycle and the tank to breath without air movement through the vent or place the system under negative pressure ( vacuum) if the vent is sealed and the ball valve closed.
The 4” vent was stripped of the top cover. This cover shields the vent from rain, snow, blowing dust, etc. The outer screen was removed also. This screen prevents birds or bugs from gaining access to the No. 18 fine mesh fiberglass inner screen, which is the screen we were going to try to freeze up.
With the fiberglass inner screen exposed to ambient temperatures, varying from 16 to 25 degrees F. and the ¾” valve closed, we attempted to freeze the screen closed.
While the tank operated we sprayed water from a bottle, directly onto the screen, in an effort to freeze the screen shut. Ice was ¼” thick in places but it would not seal closed and we could not get a negative pressure reading on the vacuum gauge. We absolutely could not get the vent to seal closed by spraying water onto the fiberglass screen.
In our second attempt we opened the ball valve to allow air movement in and out of the tank and painted the screen closed with a paintbrush. We sprayed water onto the brush and then brushed it onto the screen until we obtained a layer of ice on the screen that would be representative of frost/freeze action under normal operations. The vent screen was actually coated with more than normal frosting and looked like it was frozen solid.
With the vent frozen solid we closed the valve and the plastic tank was sealed. The pump was operating, taking water out. The screen started to draw in and then it gradually started to wrinkle and twist. Even though the screen had a good coat of ice on it and there was no visible opening in the screen it was still able to flex enough to allow air into the tank. The vacuum gauge would not register any pressure.
We then placed a plastic bag over the vent to demonstrate that even though the vent screen is iced over solid to the naked eye, the screen had flexed enough to allow air to pass through the vent without a visible opening. The plastic bag was drawn to the vent and a reading of 3 inches of mercury was registered on the vacuum gauge. The screen was visibly flexing and shedding ice. When we removed the plastic bag the vacuum gauge returned to zero.
We were never able to register a negative pressure reading on this system by deliberately causing ice build up on the vent screen.