HALIDE LEAK DETECTORS

Not too long ago leaks were detected by using soap bubbles and water. If possible, the area of the suspected leak was submerged in soap water. Bubbles pinpointed the leak area. If the unit or suspected area was not easily submerged in water then it was coated with soap solution. In addition, where the leak was covered with soap, bubbles would be produced. These indicated the location of the leak. These methods are still used today in some cases. However, it is now possible to obtain better indications of leaks with electronic equipment with halide leak detectors.

Halide leak detectors are used in the refrigeration and air-conditioning industry. They are designed for locating leaks and noncombustible halide refrigerant gases. See Figs. 1-36 and 1-37.

Fig. 1-36 Halide leak detector for use with a B tank. (Union Carbide)

Fig. 1-37 Halide leak detector for use with an MC tank. (Union Carbide)

The supersensitive detector will detect the presence of as little as 20 parts per million of refrigerant gases. See Fig. 1-38. Another model will detect 100 parts of halide gas per million parts of air.

Setting Up

The leak detector is normally used with a standard torch handle. The torch handle has a shut-off valve. Acetylene can be supplied by a “B” tank (40 ft3) or MC tank (10 ft3). In either case, the tank must be equipped with a pressure-reducing regulator; the torch handle is connected to the regulator by a suitable length of fitted acetylene hose. See Fig. 1-36.

Fig. 1-38 Detectors. (A) Supersensitive detector of refrigerant gases. This detects 20 parts per million. (B) Standard model detector torch. This detects 100 parts per million. (Union Carbide)

An alternate setup uses an adapter to connect the leak detector stem to an MC tank. No regulator is required. The tank must be fitted with a handle. See Fig. 1-37.

In making either setup, be sure all seating sources are clean before assembling. Tighten all connections securely. Use a wrench to tighten hose and regulator connections. If you use the “B” tank setup, be sure to follow the instructions supplied with the torch handle and regulator.

Lighting

Setup with tank, regulator, and torch handle. Refer to Fig. 1-36.

Open the tank valve one-quarter turn, using a P-O-L tank
Be sure the shut-off valve on the torch handle is Then, adjust the regulator to deliver 10 psi. Do this by turning in the pressure-adjusting screw until the “C” marking on the flat surfaces of the screw is opposite the face of the front cap. Test for leaks.
Open the torch handle shut-off valve and light the gas above the reaction Use a match or taper.
Adjust the torch until a steady flame is Setup with MC tank and adaptor. Refer to Fig. 1-37.
With the needle valve on the adaptor closed tightly, just barely open the tank valve, using a P-O-L tank Test for leaks.
Open the adapter needle valve about one-quarter Light the gas above the reaction plate. Use a match or taper.

Leak Testing the Setup

Using a small brush, apply a thick solution of soap and water to test for leaks. Check for leaks at the regulator and any connection point. Check the hose to handle connection, hose to regulator connection, and regulator or adaptor connection. If you find a leak, correct it before you light the gas. A leak at the valve stem of a small acetylene tank can often be corrected by tightening the packing nut with a wrench. If this will not stop a leak, remove the tank. Tag it to indicate valve stem leakage. Place it outdoors in a safe spot until you can return it to the supplier.

Adjusting the Flame

Place the inlet end of the suction hose so that it is unlikely to draw in air to contaminate the refrigerant

vapor. Adjust the needle valve on the adapter or torch handle until the pale blue outer envelope of the flame extends about 1 in. above the reaction plate. The inner cone of the flame, which should also be visible above the reaction plate, should be clear and sharply defined. If the outer envelope of the flame, when of proper length, is yellow, not pale blue, the hose is picking up refrigerant vapors. There may also be some obstruction in the suction hose. Make sure the suction tube is not clogged or bent sharply. If the suction tube is clear, shut off the flame. Close the tank valve. Disconnect the leak detector from the handle or adaptor. Check for dirt in the filter screw or mixer disc. See Fig. 1-39. Use a 1/8 in. socket key (Allen wrench) to remove or replace the filter screw. This screw retains the mixer disc.

Detecting Leaks

To explore the leaks, move the end of the suction hose around all points where there might be leaks. Be careful not to kink the suction hose.

Watch for color changes in the flame as you move the end of the suction hose:

With the model that has a large opening in the flame shield (wings on each side), a small leak will change the color of the outer flame to a yellow or an orange- yellow As the concentration of halide gas in- creases, the yellow will disappear. The lower part of the flame will become a bright, light blue. The top of the flame will become a vivid purplish blue.
With the model that has no wings alongside the flame shield opening, small concentrations of halide gas will change the A bright blue-green outer flame indicates a leak. As the concentration of the halide gas increases, the lower part of the flame will lose its greenish tinge. The upper portion will be- come a vivid purplish blue.
Watch for color intensity The location of small color leaks can be pinpointed rapidly. Color in the flame will disappear almost instantly after the in- take end of the hose has passed the point of leakage. With larger leaks, you will have to judge the point of leakage. Note the color change from yellow to purple- blue or blue-green to blue-purple, depending on the model used.

Maintenance

With intensive usage, an oxide scale may form on the surface of the reaction plate. Thus, sensitivity is reduced. Usually this scale can be easily broken away from the late surface. If you suspect a loss in sensitivity, remove the reaction plate. Scrape its surface with a knife or screwdriver blade, or install a new plate.