WINTERIZING CARBON DIOXIDE CYLINDERS

The PR is not normally tasked with the responsibility of recharging fire extinguishers and engine fire bottles. However, you may be assigned to an AIMD that supports aircraft that require winterizing of CO2 cylinders.

All carbon dioxide portable fire extinguishers installed in aircraft and all aircraft carbon dioxide built-in engine fire extinguishers are serviced to operate throughout the temperature range of ‐65F to 160F. The extinguishers are supercharged with the addition of 200 psi of dry, oil-free nitrogen. This servicing of extinguishers is done in connection with the U.S. Air Force winterization program. Extinguishers charged to meet this winterization requirement are identified by a yellow dot, three-fourths of an inch in diameter or larger, on opposite sides of the cylinder. Extinguishers so marked are winterized

Figure 3-9.\Disassembly of Inflation Valve Safety Disc Assembly.

by the introduction of nitrogen at 200 psi and then the addition of a proper charge of carbon dioxide.

The addition of nitrogen in carbon dioxide cylinders provides additional pressure. This pressure expels the carbon dioxide at extremely cold temperatures (below 0F) at a much higher rate than would the pressure of the carbon dioxide itself. Winterized cylinders have a carbon dioxide charge less than rated capacity. As a result the total pressure is lower at high temperatures than with rated charge, even though nitrogen has been added. Thus winterized cylinders can be subjected to 160F without the safety disc rupturing.

REPLACING SAFETY DISCS AND WASHERS ON INFLATION VALVES

If you are not familiar with the flotation equipment, replacing safety discs and washers on the various CO2 cylinders can be very difficult. You will need some special tools to replace the .

safety disc and washers on inflation valve assemblies A-128/817444, MIL-V-81722 (Flu-6/P), and MIL-V-25492 (figure 3-9). You will require a torque wrench, a five-sixteenth inch socket, and apiece of hex stock 5/16 x 2

inches long. Once you have these tools, changing the safety disc will be a simple process.

WARNING

Before you perform any work on inflation valves, ensure that CO2 inflation assemblies are completely discharged. Do not remove the valve or valve safety disc plug from a charged CO2 assembly. Insert the 5/16- x 2-inch stock into the disc plug and remove the safety disc plug. Then insert the safety disc and washer as shown in figure 3-9. To replace these

items, simply reinstall them into the inflation valve. Remember to install new washers and safety discs. Use a torque wrench to make the following torque valve adjustments.

NOTE: While you are tightening the ^safety disc plug, align the insert with the plug.

CHAPTER 4 _SEWING MACHINE REPAIR

The Aircrew Survival Equipmentman (PR) is called upon to perform an enormous amount of repair work on parachutes and survival equipment in all types of maintenance activities. Although lower rated personnel perform much of this work, the task of maintaining the sewing machines in top running condition falls to the senior PRs. Qualified sewing machine operators may assist in this work under supervision; however, determining the causes of malfunctions, making major adjustments, and replacing parts are the responsibilities of the first class and chief petty officer.

This chapter explains the rotory-hook (111 W 155) sewing machine and the oscillating-shuttle (31-15) sewing machine. We gave you an overview of these two types of sewing machines in chapter 3 of the Aircrew Survival Equipmentman 3 & 2, volume 1; however, as a senior PR, you need more specific information on the basic structure of these two sewing machines. With the information available, you can repair any of these types of machines the Navy uses. We know it is very difficult to find information on sewing machine repair; therefore, you should use this chapter as a reference when working on the alternatingpresser-foot sewing machine and the simple oscillating-shuttle sewing machine.

Your shop may have the Consew Model 225, the Juki LU-562, or the Singer Model 111 W 155 sewing machine. These three sewing machines are essentially identical, and all specifications and instructions are the same for all three sewing machines. For simplicity we will use the Singer 111 W 155 as a model for all three sewing machines.

The oscillating-shuttle, Singer 31-15, sewing machine is representative of the second type of sewing machine used by the Navy. The descriptive term oscillating shuttle refers to the action of the sewing hook (the way it makes a stitch in unison with the needle). The 31-15 is used for sewing lightweight fabrics and is ideally suited for use in the maintenance of aviation survival equipment. Although the physical size of other oscillating-shuttle sewing machines may be quite different from the 31-15, such as the large Class 7 machines, their operation and maintenance are very similar.