CO2 Transfer Unit

A carbon dioxide transfer unit (fig. 5-41) is used to transfer CO2 from a 50-pound cylinder to the 15-pound cylinders. The transfer unit consists of an electric motor and pump, a high-pressure hose, a control valve, adapters, and fittings.

Before operating the CO2 transfer unit, be sure that the switch on the side of the motor is in the

Figure 5-41.-CO2 transfer unit.

OFF position. Check the circuit from which the motor is to be energized and make certain that it is the same as that indicated on the nameplate on top of the motor. If 220-volt, 60-cycle, single-phase current is available, the hookup of the motor leads should be rearranged by an Electrician's Mate so the motor will operate on this circuit. A wiring diagram for operation on 220 volts is given on the motor nameplate. Check all CO2 connections on both the inlet hose and the outlet hose (the 6-foot hose is the pump outlet hose). Make certain that all of the connections between the various parts are tight. This is very important because the CO2 is stored under high pressure.

To operate the transfer unit, proceed as follows but always in a well ventilated place:

CAUTION

Do NOT close the valve of the cylinder being recharged or the shutoff valve in the pump outlet hose while the transfer unit is pumping.

1. With the transfer unit, scale, and tilt racks in place, check the supply cylinder. Use only the

50-pound commercial cylinders. The cylinder must be inverted.

2. Connect the pump inlet hose to the supply cylinder outlet. The connection adapter of this hose is fitted with a screen to prevent any foreign matter from getting into the transfer unit or into the cylinder being recharged. Do NOT open the supply cylinder valve.

3. Connect the pump outlet hose to the recharging adapter. The pump outlet hose is fitted with a shutoff valve. Check all connections and make sure they are correct and tight. When making the connections, use a wrench. Use a slow, steady, pulling motion. Do not jerk the wrench and do not hit it with a hammer.

4. Make certain that the shutoff valve in the pump outlet hose is in its tightly closed position. Make certain that the valve of the cylinder to be recharged is in its open position. Then completely open the valve of the supply cylinder.

5. Place the empty cylinder on the scale. If a rack is used, place the cylinder vertically; otherwise, set it horizontally.

6. Balance the scale and note the weight of the cylinder being recharged. On beam-type scales, set the scale to the weight of the cylinder plus its desired charge.

7. Open the shutoff valve in the pump outlet hose and allow the carbon dioxide in the supply cylinder to flow under its own pressure to the cylinder being recharged.

8. When the weight of the cylinder being recharged stops increasing, this is a sign that the carbon dioxide has stopped flowing under its own pressure from the supply cylinder. At this point, start the transfer unit and watch the scale carefully. The transfer pump must be started when all valves are open; otherwise, the CO2 will not pass through the pump properly and may rupture the neoprene seal.

9. When the full capacity of the cylinder being recharged has been reached, perform the following procedures in rapid succession:

a. Stop the transfer unit motor.

b. Tightly close the shutoff valve in the pump outlet hose.

c. Close the valve of the cylinder being recharged.

10. Disconnect the hose from the cylinder being recharged. Do this very slowly to allow the escape of the CO2 that is trapped between the shutoff valve and the cylinder being recharged. Then remove the adapter.

11. Weigh the recharged cylinder carefully.

12. After the recharging is completed, close the supply cylinder valve tightly. Open the shutoff valve in the pump outlet hose very slowly and allow all the carbon dioxide in the unit to be discharged to the atmosphere.

The carbon dioxide transfer unit should be maintained in accordance with the manufacturer's instructions. Some parts require lubrication. The 50-pound commercial CO2 cylinders that are used to recharge the 15-pound portable cylinders must be weighed at the required intervals and replaced when necessary.