through the servicing hose. This chemical drier is provided to remove any moisture in the oxygen supply. The oxygen flows into the bottom of the drier, passes up through the drying agent, and out through the servicing hose. SERVICING HOSE AND LINE VALVE. The servicing hose is a high-pressure, nonkinking, metallic flexible hose. The line servicing valve is attached to the servicing hose and is used to control the flow of oxygen to the system being charged. OPERATION The six supply cylinders are connected by means of flexible hoses to their respective control valves (fig. 5-14). The six control valves are attached to the upper manifold. A pressure gauge is screwed into each control valve at a point below the seat. This allows each cylinder pressure to be easily read. The oxygen flows from the upper manifold through either of two pressure regulators via two shutoff valves. The oxygen is collected in the lower manifold where a gauge registers the pressure of the delivery side of the system. The lower manifold is connected by flexible hose to a drier, which filters and dries the oxygen. The servicing hose connects directly to the drier and has a line servicing valve on the terminal end. The line servicing valve is fitted with a standard oxygen cylinder connection. Loading Cylinders The servicing trailer is capable of having its cylinders recharged without removal. However, many operating activities replace the empty cylinders with full cylinders. NOTE: NEVER completely expend the supply of oxygen from a cylinder. Always leave a residual pressure in excess of 50 psi. REMOVAL OF EMPTY CYLINDERS.— When the trailer has been in use and cylinder pressure is low, the cylinders are removed as described below. 1. Close all lever valves on the manifold prior to removing any cylinders. 2. Close the cylinder shutoff valves. 3. Disconnect the flexible hose that connects the cylinder to the manifold. 4. 5. 6. Loosen the clamping arrangement that holds the cylinders to the trailer. Install the cylinder safety caps. Remove the empty cylinders. CAUTION Do not attempt to remove empty cylinders while charging. INSTALLATION OF FULL CYLIN- DERS.— The trailer should be loaded with cylinders while fastened to a towing vehicle. If a towing vehicle is not available, the rear stand should be let down and hand brakes applied so the weight of the cylinders will not cause the trailer to tilt backwards. The retractable swivel wheel should be down if the trailer is not hooked to a towing vehicle. (When the trailer is hooked to the towing vehicle, the swivel wheel should be retracted.) Cylinders should be loaded from the rear and should be handled with safety caps in place. Standing cylinders should be brought to within 4 feet of the rear end of the trailer. If the cylinders are lying down, the safety cap end of the cylinder should be just below the rear of the trailer. The safety cap end of the cylinder should be lifted or lowered and placed in the appropriate channel. The bottom of the cylinder should be raised and the cylinder worked into place. Ensure that the cylinder is in its forward-most position and firmly seated against the forward cylinder stop. Remove the cylinder safety cap. Position the cylinder so that the cylinder valve outlet may be easily connected to the flexible hose without causing undue strain on the hose. Prior to connecting the hose to the cylinder, open the cylinder. valve slightly to blow any foreign matter from the outlet of the valve; then close the valve. Connect the flexible hose nut to the power cylinder valve. As soon as the cylinders are in place and the hoses connected, the clamping arrangement should be tightened. The bottom four cylinders are clamped in pairs by a wheel, and the top cylinders are tightened by a single strap for each one. After tightening the coupling nuts on the hoses, the hoses should be free of twisting strain. This strain can be prevented by gripping the hose with one hand and twisting slightly in a clockwise direction while tightening the coupling nut. When the nut becomes tight, the hose will twist (counterclockwise) slightly as it seats, and will stop approximately at its neutral position. 5-18