Comment

March 2009

CCST conversion question

Regarding the January InTech CCST question, I used my own conversion and got the exact answer, making me believe your conversion is not as accurate.

Assuming 27.7 inwc= 1 psig

and inches of level (of any liquid) X SG = level equivalent to water, in inwc

20 ft level X 12 in/ft = 240 inches level

with a SG of 1.5 the equivalent pressure is 240 inches X 1.5 = 360 inwc

360 inwc          = 12.9964 psig

27.7 inwc/psig

I have been using 27.7 inwc/psig since the late 1970s when I was training to be a Reactor Operator on Navy submarines. By my calculation, B is not only the best answer for the CCST question in January, it is the exact answer to two decimal places.

Stephen Curran, Reno, Nevada

Response:

Using 27.7 inches of water equaling one psig, we do indeed get the answer you cite.

These days, what with our handheld computers, which have the computing power and accuracy of all the computers in the 1970s combined, we get answers of remarkable accuracy. In fact, answers far more accurate, in most cases, than are necessary. Use your own situation and length of successful service as a primary example of that.

My TI-85 calculator works this problem using the conversion one (1) psig = 27.6799047102 inches of water. And it uses that number unless I manually override it by keying in a different, shorter, or less exact number. That is the difference in my answer, your answer, and the CCST answer.

Thanks for writing in and regards to you.

Nicholas Sheble

In it together

Gregory Hale’s words about teamwork to weather the storms were good (InTech, December 2008 “Talk to me”). I hope I can get our management to think about them (wish me luck). Too much minor fiefdom fighting around here.

Jerry McMurry