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BY HANDYMAN
Page 73
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HAVE covered the emergency valve and how it works in conjunction with the tiler relay valve to apply the trailer brakes the event of line failure, and as this same ie failure could cause tractor air loss, it II be as well to see how the tractor is pro:ted in such an emergency. Claytonmandre provide a valve for this duty and gall it towards the rear of the tractor 'ere the lines feeding the trailer can conniently pass through it. These lines are, of urse, the service line which is connected the brake valve and the emergency line upled to the tractor reservoir.
In the event of air loss at the tractor/ tiler couplings, air will escape from the ictor side until at a predetermined pressure e protection valve will come into operain, sealing both lines on the tractor and rening a "safe" stopping air pressure.
The protection valve is easily recognizle: it is a one-piece casting, topped by two lindrical caps secured by four-stud flanges, d at the base there is again a four-stud nge and a screwed plug.
There are two patterns of this valve, both ke in body shape. although they differ in method of adjustment at the top. One adjustable and has visible threads with :lc nuts; the other has cap nuts and has ims for adjustment. The body houses two .s of valves, side by side, and there is an ernal drilling connecting the two sections. The section coupled to the tractor reserir and the trailer emergency line houses
diverter valve, and the section coupled the tractor brake valve and the trailer -vice line houses the supply valve. Each the valves has air bellows to lift a conical bber-faced valve against a preloaded ring. These springs are normally adjusted take 65 lb.
Air is fed from the tractor reservoir .ough the tractor emergency port, passing
diverter valve stem, and reaches the vity containing the diverter valve bellows L a drilling in the retaining nut. Air also ws through the cross drilling in the main dy to the service valve bellows in the base the valve body, the valves themselves being d in the closed position by the springs Dye.
Each bellows has a vent to atmosphere