How many fills from a cylinder
Posted: Fri Jun 03, 2016 1:44 pm
As an RFD and a dive store owner I am often asked how many fills can I get out of my cylinder
Having a few hours of spare time I decided to calculate the amount of fills available from a range of commonly available cylinders
I have based the calculations on the following, these are approximate figures but are fairly near to the mark
400cc Buddy Bottle filled to a nominal 180 bar, this gives 72 litres of air in the cylinder
Once the pressure in the main cylinder drops below 180 bar I have used the pressure remaining to calculate buddy cylinder volume
I have stopped the list once the main cylinder pressure reached 130 bar as this is about the point most people have their cylinders refilled
A few other variables
I have rounded calculations up or down to the nearest Bar
No allowance has been made for temperature/pressure changes
Remember that many 300 bar cylinders are not fully filled to begin with. Many dive shop compressors struggle to reach 300 bar, cylinders loose a lot of pressure due to cooling. To get a true 300 bar quite often I will need to top the cylinder up about 3 times
No allowance has been made for ambient temperature changes when filling the buddy cylinder
I have also listed air fill prices, and estimated prices for new and used in test cylinders.
Always remember that it will cost about £35 for a cylinder test plus what ever else is required to test cylinder, so a cheap cylinder may not be cheap if it fails the test
AS I have said these figures are approximate, but there are so many variables I have tried to be as accurate as possible
If however someone was requiring a cylinder, the most cost effective route is a 232 bar 15lt or a 232 bar 12lt unit
Cylinder pressure remaining after each fill
No of fills 232 X 15lt 300 X 12lt 232 X 12lt 300 X 10lt 232 X 10lt 300 X 7lt 300 X 3lt 232 X 3lt
1 227 294 226 292 224 279 252 184
2 222 288 220 285 217 268 228 160
3 217 282 214 278 210 257 204 138
4 212 276 208 271 203 247 180 120
5 208 270 202 264 196 237 156 104
6 203 264 196 256 188 226 135
7 198 258 184 249 181 216 117
8 193 252 178 242 174 206 101
9 188 246 172 235 167 196
10 184 240 166 228 160 185
11 180 234 158 220 154 175
12 174 228 152 213 148 165
13 169 222 148 206 142 156
14 165 216 143 199 136 147
15 160 210 138 192 131 138
16 156 204 133 184 131
17 152 198 129 177 123
18 148 192 170
19 144 186 163
20 140 180 157
21 137 174 151
22 133 168 145
23 162 139
24 157 133
25 152 128
26 147
27 142
28 137
29 132
30 129
Fill Price £5.00 £6.50 £5.00 £6.50 £5.00 £6.50 £6.50 £5.00
New
Cyl Price £247.00 £290.00 £218.00 £279.00 £200 £262.00 £175.00 £128.00
Used
Cyl Price £125-140 £220 £120 £200 £75-£140 £180 £130 £60-£80
Hope this helps
Having a few hours of spare time I decided to calculate the amount of fills available from a range of commonly available cylinders
I have based the calculations on the following, these are approximate figures but are fairly near to the mark
400cc Buddy Bottle filled to a nominal 180 bar, this gives 72 litres of air in the cylinder
Once the pressure in the main cylinder drops below 180 bar I have used the pressure remaining to calculate buddy cylinder volume
I have stopped the list once the main cylinder pressure reached 130 bar as this is about the point most people have their cylinders refilled
A few other variables
I have rounded calculations up or down to the nearest Bar
No allowance has been made for temperature/pressure changes
Remember that many 300 bar cylinders are not fully filled to begin with. Many dive shop compressors struggle to reach 300 bar, cylinders loose a lot of pressure due to cooling. To get a true 300 bar quite often I will need to top the cylinder up about 3 times
No allowance has been made for ambient temperature changes when filling the buddy cylinder
I have also listed air fill prices, and estimated prices for new and used in test cylinders.
Always remember that it will cost about £35 for a cylinder test plus what ever else is required to test cylinder, so a cheap cylinder may not be cheap if it fails the test
AS I have said these figures are approximate, but there are so many variables I have tried to be as accurate as possible
If however someone was requiring a cylinder, the most cost effective route is a 232 bar 15lt or a 232 bar 12lt unit
Cylinder pressure remaining after each fill
No of fills 232 X 15lt 300 X 12lt 232 X 12lt 300 X 10lt 232 X 10lt 300 X 7lt 300 X 3lt 232 X 3lt
1 227 294 226 292 224 279 252 184
2 222 288 220 285 217 268 228 160
3 217 282 214 278 210 257 204 138
4 212 276 208 271 203 247 180 120
5 208 270 202 264 196 237 156 104
6 203 264 196 256 188 226 135
7 198 258 184 249 181 216 117
8 193 252 178 242 174 206 101
9 188 246 172 235 167 196
10 184 240 166 228 160 185
11 180 234 158 220 154 175
12 174 228 152 213 148 165
13 169 222 148 206 142 156
14 165 216 143 199 136 147
15 160 210 138 192 131 138
16 156 204 133 184 131
17 152 198 129 177 123
18 148 192 170
19 144 186 163
20 140 180 157
21 137 174 151
22 133 168 145
23 162 139
24 157 133
25 152 128
26 147
27 142
28 137
29 132
30 129
Fill Price £5.00 £6.50 £5.00 £6.50 £5.00 £6.50 £6.50 £5.00
New
Cyl Price £247.00 £290.00 £218.00 £279.00 £200 £262.00 £175.00 £128.00
Used
Cyl Price £125-140 £220 £120 £200 £75-£140 £180 £130 £60-£80
Hope this helps