Push-to-Connect Pneumatic Fittings (Parker Prestolok)

Overview

All tube fittings must perform two functions. First, they must seal the gas or liquid contained in the line; and second, they must mechanically hold the tubing in place against system pressure or mechanical pull. Most fittings try to achieve both goals by causing the tube to be squeezed between a ferrule and the fitting body by the advancing action of a tube nut. In plastic tubing applications, the squeezing action can be jeopardized after initial makeup by material creep and cold flow caused by pressure and temperature variations.

Prestolok two stage design uses an o-ring to achieve the sealing function and a spring collet to achieve the mechanical tube holding function. The o-ring seal is self compensating for pressure and temperature. The spring collet grips tighter as pressure increases, yet the tubing can easily be disconnected and reconnected almost without limit.

Because Prestolok push-in fittings self adjust in both sealing and holding functions, they automatically compensate for creep and cold flow.

Swivel Action Elbows and Tees

Cartridge construction allows fittings to swivel around the port axis.

Pressure Rating

Zero to 200° F at up to 300 psi (150° F and 150 psi for glass filled nylon) depending on the tubing being used. All applications should be carefully tested through the range of conditions which may be encountered in use.

Installation

Cut tubing with a PTC-001 cutter so that the end is as square as possible. Soft metal tubing should be cut squarely and deburred carefully so no sharp edges cut the o-ring. Push tube into fitting until it bottoms against the tube stop. Note that as the front of the tube presses against the "spring finger washer", the fingers flex forward allowing the tube to pass through. The tube then continues forward, passing through the light squeeze fit of the o-ring until it bottoms against the tube stop. Force, caused by system pressure (approximately 13 lbs. on a 1/4" dia. tube at 250 psi., Force = Pressure X Area) or external pull on the tubing pushes the tube back against the grip of the spring fingers causing them to grip the tube tighter. Sealing is achieved by the system pressure acting upon the lightly squeezed o-ring. Pressure pushes the o-ring back against the backup washer causing a pressure loaded seal between the o-ring and the tubing as well as between the o-ring and the fitting body.

Removal

To remove the tubing, press the plastic "release pusher" forward into the fitting until resistance is felt. Then pull out the tube. Pull-out is allowed because the conical angle at the front of the pusher forces the spring fingers to flex forward and lift away from the tube. The fingers are protected against excessive flex because they bottom against the conical seat of the o-ring Backup & Spring Finger Travel Limiter. Because the fingers are no longer in contact with the tube, it can be simply pulled out of the fitting.

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