WorldWide Drilling Resource

14.7 PSI by Bill Corey Pentair Water Training Institute Last month we left off with a question. What would the pressure gauge show the astronaut had read when he gave it to us at Cape Kennedy? The average weight of the atmos- phere at sea level is 14.7 psi. Now you may remember from previous articles, 1 psi is equal to 2.31 FoH (feet of head). So if you take 14.7 psi and multiple it by 2.31 FoH, you would get 33.95 FoH - most would just call it 34 FoH. Now let’s take a vacuum pump, a 40-foot glass tube, the material to hold the glass tube in a vertical position, and a lad- der to a freshwater lake at sea level. Here is what we are going to do: set the material to hold the glass tube in the water so we can attach the glass tube about 6 inches under the water. Then place the ladder on it, climb up the ladder, and attach the tube from the vacuum pump to the glass tube. What have we done? We have enclosed the atmosphere in the glass tube. What happens when you turn the vacuum pump on? It starts to remove the atmosphere from the glass tube. What else happens? The water starts to move up the glass tube. How far wi l l it go? Remember you have a 40-foot glass tube...wait for it...some might say 40 feet, but of course we need to remember it is the atmosphere pushing the water up, not the vacuum pump sucking it up; and since the weight of the atmosphere is only equal to 34 feet, it would be the highest it could go - if, now this is a BIG if, we lived in a perfect world. SURPRISE! We don’t. Water, like all other liquids, has a flash point. Flash point simply means the point at which it will convert from a liquid to a vapor. If the temperature of the water were 70°F (21ºC), the flash point would be .4 psi [.4 psi x 2.31 FoH equals about 1 foot]. So what exactly does this mean? At about 34 feet, the water in the glass tube would start to boil. Yes, I said boil. If you were to raise the temperature of the water to 212°F (100ºC), we all know what would happen. So what I’m saying is, you can boil water at any temperature simply by lowering the pressure over the water to the vapor pressure point of the water. Just remember, pump language calls this same point “cavitation”. The definition being “the conversion of a liquid to a vapor in a low-pressure area”. Instead of using heat to raise the temperature of the water, we lower the pressure over the water to the vapor pressure point of the water. So what does this 14.7 psi have to do with how the pump works? More next month! Bill Bill Corey may be contacted via e-mail to michele@ worldwidedrillingresource.com ,2+1 (+ 1 1$0 /,2+# 1$/ 5-, $!/2 /6 1 1'$ .2 /(20 0(+, $0,/1 2&')(+ ,/ ',1$) /$0$/3 1(,+0 " )) +# 20$ ",#$ ,/ *,/$ (+%,/* 1(,+ 3(0(1 20 ,+)(+$ *,2+1 (+01 1$0&/,2+#4 1$/ ",* * () (+%, *,2+1 (+01 1$0&/,2+#4 1$/ ",* '$ ,2+1 (+ 1 1$0 /,2+# 1$/ 5-, (0 ',01$# !6 1'$ 1$/ $)) +# /,2+# 1$/ 00,"( 1(,+0 ,% /(7,+ ,),/ #, $3 # $4 $5(", +# 1 ' 38 JANUARY 2016 WorldWide Drilling Resource ® WWDR ’ s March issue is just around the corner! DEADLINES: Space Reservation: January 25 th Display & Classified Ad Copy: February 1 st