Dacorum Sub Aqua Club

Filling cylinders using the compressor

This page provides information about using the compressor and the gas blending equipment.

Please read the information shown in the Compressor page.

Reporting problems

If you discover any problem, please contact the Compressor Officer (CO) immediately. The CO's phone number is displayed to the right of the blending panel.

Safety

There are risks involved in running and using a compressor including the dangers of powerful electrical machinery, gases under pressure, the fire risks of oxygen and the need to accurately blend life supporting gas mixtures. The club will service and maintain the equipment correctly but club members must understand that they also share in responsibility for safety. 

Problems which could lead to injury, include:

• diving cylinder failure:
  • the main causes are internal corrosion and DIY pillar valve fitting
  • don't fill a cylinder unless it has passed an IDEST test with the last 2.5 years: it may burst when being filled
  • don't fill a cylinder if its contents have fallen to atmospheric pressure since its last test: moisture may have entered the cylinder causing corrosion which weakens the cylinder
  • don't fill a cylinder if it's in bad condition: rusty, damaged or has particles or water inside it. It may be weakened
  • have your cylinder professionally maintained and tested. There have been cylinder failures caused by a pillar valve with an incompatible thread being fitted to a cylinder
• embolism:
  • caused by high pressure air entering the body through cuts in the skin
  • the air from the compressor is for filling cylinders only: it's not for cleaning equipment
  • never direct high pressure gas near your skin. 
  • keep hands away from pressurised components that could easily fail such as o-rings
• contaminating other cylinders with your gas mix:
  • this is caused by connecting a nitrox or trimix cylinder to the panel while other cylinders are being filled, when the panel pressure is lower than the cylinder pressure resulting in the cylinder's contents flowing into the other cylinders on the panel
  • don't fill cylinders containing gas mixes unless you know what you're doing
• an increased risk of creating hypoxic or hyperoxic gas mixes, when mixing nitrox or trimix, that could lead to unconsciousness or a fit underwater:
  • analyze the oxygen in all mixes after blending and before diving
  • label all mixes after blending
• there is more risk of fire when using pure oxygen to mix nitrox or trimix:
  • there are three components to a fire: heat, oxygen and fuel. Don't allow the three to occur together.
  • don't smoke or allow a naked flame near the shed 
  • if gas blending, make sure your cylinder is in oxygen service. This cleaning and replacement of valve components must be done professionally and only lasts for 12 months
  • keep the cylinder clean - particularly avoid fuels such as oil and grease
  • open all oxygen valves gently to minimise heat caused by fiction
• pillar valve "o" ring failure:
  • the main cause is old or damaged o-rings
  • don't put your ear close to a hissing valve - you may lose your hearing if the o-ring fails
  • check you o-rings, have a stock of spares and replace damaged o-rings before they fail
• cylinder falling over and injuring someone:
  • this can happen easily if the cylinder is left standing upright 
  • lie cylinders down at the edge of the room before and after filling

Club members must educate themselves on these dangers and do everything possible to avoid injuring themselves or other people. 

Procedure for filling cylinders with air

1. Make sure your cylinder is in test

Check the IDEST test date stamped into the metal of all cylinders older than 2.5 years. 

Double click on these small images to expand them.

This cylinder's test stamp reads 2004 V 03 meaning a visual test was done in March 2004, so it's in test until the end of August 2006 when it will need a hydraulic test. 

Check the test stamps of any other cylinders that are being filled while you are filling yours. If any cylinder fails it's likely to kill or maim anyone in or near the compressor shed. Tell the Compressor Officer of anyone filling cylinders that are out of test. 

2. Check the cylinder is in good condition.

There should be:

• No significant rust on the outside
• No damage to the pillar valve or neck of the cylinder
• No sound of moving water or particles inside the cylinder when it's shaken
• Filled with pressurized gas - if the cylinder has been open to the moisture in the atmosphere it will have corroded internally

3. Check the working pressure of the cylinder. 

This will generally be 207, 232 or 300 bar for air cylinders. 

It may be as low as 137 bar for oxygen first aid cylinders. 

The working pressure is stamped on the cylinder's shoulder beside WP. 

4. Replace the cylinder o-ring if it's old, damaged or not properly seated. 

5. Check the compressor humidity indicator. 

The Electronic Filter Sensor has 3 coloured lights, one of which will be lit when you start filling:

If the Red light is on when the Compressor starts up and does not return to Amber and then Green within 2 or 3 minutes:

This means that the filter tower needs a filter change. To continue filling with the Red light showing will put more moisture in the system than is acceptable.

1. stop filling 

2. turn of all valves on panel. The compressor will continue for a few minutes and then stop.

3. contact the compressor officer

6. Make sure you don't contaminate other cylinders

If your cylinder has any gas other than air in it and your cylinder pressure is higher than the current filling pressure, you will contaminate all cylinders that are open to the panel including the air bank. Don't fill your cylinder unless you know what you're doing.

7. Connect the cylinder to the appropriate whip. 

Each 232 bar whip has an A-clamp adapter fitted to a 5 thread 232 bar DIN fitting. Notice the whip bleed valve at the left.

The 5 thread 232 bar DIN fitting can be used by removing the A-clamp adapter. Notice the whip bleed valve at the bottom.

The A-clamp adapter for 232 bar filling only

The 7 thread 300 bar DIN fitting on the 300 bar whip. 

Only ever connect 300 bar cylinders to the 300 bar whip. If you connect a 232 bar cylinder to the 300 bar whip you lose the automatic maximum pressure protection provided by the panel on the 232 bar whips and your cylinder will be filled to 300 bar resulting in much more risk of a failure due to over-pressurisation.

8. Open the pillar valve of the cylinder gently with 3 full turns. 

Open all valves gently. Be prepared for the pillar valve o-ring to fail. Don't put you ear close to the pillar valve. Turn off the pillar valve quickly if the o-ring fails.

9. Close the bleed valve on the end of the whip. 

This is only opened after filling once the pillar valve and the whip outlet valves are closed.

10. Check the pressure of the three air cylinders on the bank. 

To economically use banked gas, you will fill from the bank using the cascade system, filling from the bank cylinder with the lowest pressure that is higher than your cylinder's pressure and then from the next higher pressure bank cylinder until your cylinder is full. For example, if your cylinder has 120bar and the three bank cylinders have 300bar, 100bar and 150bar, you will first use the 150 bar bank cylinder and then the 300 bar bank cylinder to decant gas into your cylinder.

11. Select the bank cylinder from which you will decant into your cylinder

Open the selected bank valve gently with 1 turn.

12. Decant gas slowly into your cylinder

For fills on the 232 bar whips, open the 232 bar outlet isolation valve slowly so that the digital pressure gauge increments by 1 bar each second. 

For fills on the 300 bar whip, open the 300 bar outlet valve slowly so that the digital pressure gauge increments by 1 bar each second. 

Decanting too fast will heat up your cylinder causing the gas in the cylinder to increase in volume and pressure reducing the volume of new gas that can fit in the cylinder. A slow fill results in more gas in your cylinder.

13. Stop decanting 

When the pressure in the air bank and your cylinder equalize, no more gas will flow to your cylinder, so close the inlet valve of the bank cylinder and, if your cylinder is not yet full, select another, higher pressure bank cylinder and decant gas from that cylinder.

The panel automatically stops filling when the pressure in a whip reaches 10 or 15 bar over the limit of the whip. 

14. Disconnect the cylinder

For cylinders on the 232 bar whips, close the 232 bar outlet isolation valve, close the whip outlet valve on the panel, close the pillar valve, open the whip bleed valve and only then disconnect all the filled cylinders. 

If your cylinder has a working pressure less than 232 bar you need to close the whip outlet valve on the panel, close the pillar valve, open the whip bleed valve at the pressure limit for your cylinder and then disconnect the cylinder. 

For cylinders on the 300 bar whip, close the whip outlet valve on the panel, close the pillar valve, open the whip bleed valve and disconnect the filled cylinder. 

Leave the bank valves open so that the compressor fills the bank after you have left the shed.

16. Test your fill

If you are mixed gas blending, or others were blending while you were filling, you should analyze the oxygen in your fill now and label the cylinder to avoid the risk of hyperoxia or hypoxia during a diving with that cylinder.

Connect a regulator to your cylinder and taste the air to check the compressor's filters are working.