Respiratory Mimute Volume, RMV, what is it for? In the post on
\nSurface Consumption Rate, SCR you learned how much gas you
\nwould use and\/or need to support a dive to a specific depth for a
\nspecific time. With RMV, you can now identify the volume of gas
\nyou would need to support a dive and perhaps the cylinder you
\ncould use to support the planned dive.<\/p>\n
Take the rate pressure of your scuba cylinder, again for this
\ndemonstration we will use an aluminum 80. An aluminum 80,
\nor 80AL when filled to it’s working pressure, 3000 psi will hold
\n80 cf of gas. The working pressure of the scuba cylinder is stamped
\naround the neck of the cylinder. Take the cubic feet of the cylinder
\nand divide it by the working pressure of the tank. For an 80AL filled
\nto 3000 psi, the formula would be ( 80 \/ 3000 ) = .0267 cf\u00a0 in every
\npsi of gas. That’s .0267 cubic feet of gas for ever pound per square inch.<\/p>\n
Take the value just calculated, .0267 and multiply it your SCR,
\n(See the article on SCR for how to calculate your SCR) which we will
\nuse the value of 30 from the SCR article (30 * .0267) to determine your
\nRVM which is, for this example .8 cf of gas per minute on the surface.<\/p>\n
Using the RMV, let’s calculate any given cylinders ability, when filled
\nto working capacity to support a dive to a given depth for a given time.
\nAgain, using the figures from the SCR article, the dive is planned to 80
\nfeet for 29 minutes.<\/p>\n
We know 80 feet is 3.4242 ATA. We know our RMV is .8cf a minute.
\nMultiplying the ATA and the RMV will\u00a0 tell you how much gas, in cf\/min
\nat 80 feet you will consume. That’s ( 3.4242 * .8 ) or 2.7393 cf\/min at 80
\nfeet. An 80AL filled to 3000 psi has 80cf of gas. Divide 2.7393 into 80,
\n( 80 \/ 2.7393 ) to get the number of minutes the 80cf tank will last at
\n80 feet. ( 80 \/ 2.7393 ) = 29.21 minutes. That is not enough gas to
\nsupport the dive.<\/p>\n
Let’s try this with another cylinder,\u00a0 one that hold more volume.
\nTry the calculations for a 95cf cylinder. ( 95 \/ 2.7393 ) = 34.68 minutes.
\nIs that enough? That equates to only 5 minutes more than an 80AL.
\nI don’t think it is enough gas.<\/p>\n
You can also use the fomula other ways, for example if you know your
\nRMV and the amount of time you would like to spend at depth, you could
\ncalculate the size cylinder to use. For example ( 2.7393 * 30 ) = 82.179cf.
\nWe see here that an 80AL will fall short. Selecting a cylinder that will
\nsupport 30+ minutes will be required. A good practice is to dive on the
\nrules of 3rds, planning to returning to your origin (ie. boat\/shore\/surface)
\nwith 1\/3 as reserve.<\/p>\n
Using the article on SCR and this article on RMV you can now use the
\nfomulas to assist you in planning dives, to get an idea of how much gas
\nyou will spend and will need, as well as the cyclinder you should carry
\nto support the dive.<\/p>\n
Larry Davis<\/p>\n","protected":false},"excerpt":{"rendered":"
Respiratory Mimute Volume, RMV, what is it for? In the post on
\nSurface Consumption Rate, SCR you learned how much gas you
\nwould use and\/or need to support a dive to a specific depth for a
\nspecific time. With RMV, you can now identify the volume of gas
\nyou would need to support a dive and perhaps the cylinder you
\ncould use to support the planned dive.
\nTake the rate pressure of your scuba cylinder, again for this
\ndemonstration we will use an aluminum 80. An aluminum 80,
\nor 80AL when filled to it’s working pressure, 3000 psi will hold
\n80 cf of gas. The working pressure of the scuba cylinder is stamped
\naround the neck of the cylinder. Take the cubic feet of the cylinder
\nand divide it by the working pressure of the tank. For an 80AL filled
\nto 3000 psi, the formula would be ( 80 \/ 3000 ) = .0267 cf\u00a0 in every
\npsi of gas. That’s .0267 cubic …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-385","post","type-post","status-publish","format-standard","hentry","category-training"],"yoast_head":"\n