Turning the valve back 1/4 turn.
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
Surrounding yourself with yes men (and women) is definitely the right move to make in life. Nothing can ever be learned by those that disagree with you. I think that’s a direct quote from either Putin or Kim Jong Un. Maybe notI agree with those who agree with me.
That seems to be how it works around here.
Point taken. I'm really not that black and white. I'll consider the opinions of others but if it makes no sense I'll disregard it, and probably anything else they have to offer, perhaps at my own peril but I'm too old to waste my time arguing and there's not much more I need to learn at this point, and not much that I ever will. At least I'm being realistic.Surrounding yourself with yes men (and women) is definitely the right move to make in life. Nothing can ever be learned by those that disagree with you. I think that’s a direct quote from either Putin or Kim Jong Un. Maybe not
There's a good reason to do that but not the one typically given. If you turn it back the quarter when the boat crew checks your air (and they almost always will even if you tell them you're good and you don't want your gear messed with), they know instantly if it's on when they give it that twist and it turns that little bit more. If it's all the way on, well for all they know, it could be stuck in the off position, it happens often enough and they might just give it an extra hard turn to confirm it's all the way on and that doesn't do the valve any good especially when repeated countless times, and it makes their job just a bit more difficult.Turning the valve back 1/4 turn.
Or simply that it can jam open, especially with changes in temperature as you jump in.There's a good reason to do that but not the one typically given. If you turn it back the quarter when the boat crew checks your air (and they almost always will even if you tell them you're good and you don't want your gear messed with), they know instantly if it's on when they give it that twist and it turns that little bit more. If it's all the way on, well for all they know, it could be stuck in the off position, it happens often enough and they might just give it an extra hard turn to confirm it's all the way on and that doesn't do the valve any good especially when repeated countless times, and it makes their job just a bit more difficult.
At least thats what I read somewhere and it makes sense to me.
It’s still applicable to some valves nowadays. Especially if you need to manipulate valves behind your head.The turning back the valve a little comes from many years ago when valve seals were different. If you turned them fully open with a bit of force the seal leaked. This was still the case with some welding gas cylinders until at least 2012 and they are probably still in use now. This was because part of the fully opened moving part of the valve pushed the gland packing back and broker the seal. As far as I know diving cylinder valves use an O or circular sealing ring system where this does not occur.
Regarding the original posters exam wording questions. I was a university lecturer for several years and came across this "problem" several times on multiple choice questions. What I found was that the questions were very specific to the course text and if you gave the answer that the course text led you to it would be the right choice even though your first thoughts or other teaching may have lead you to believe otherwise.