1996/06/12 Caterpillar

Improvements To Check Valve Within Prechamber Group Reduce Maintenance Schedule{1106}

Usage:

G3606 (3XF),
G3608 (4WF),
G3612 (1YG),
G3616 (4CG) Engines

Reference: Operation And Maintenance Manual (SEBU6278, SEBU6496), Systems Operation Testing And Adjusting (SENR4258, SENR5528), Engine News, November 1995, "New Check Valve Used In Prechamber Groups".

Recent improvements to the check valves within the prechamber group of the above G3600 Engines have reduced the required maintenance performed on the check valves. As the result, the following maintenance schedule should be used for the check valves.

Check Valve Maintenance Schedule At The 10,000 Hour Interval

Illustration 1: Location of a check valve within a typical prechamber group.

1. Remove the check valve from the cylinder head.

2. Visually inspect the check valve for combustion deposits on the barrel located directly below the threads. If combustion deposits are evident, replace the valve.

3. Perform the following Leak-Down Check on valves which do not show evidence of combustion deposits on the barrels.

Leak-Down Check:

* Attach the Leak-Down Check tooling to a check valve. Refer to Leak-Down Check Tooling.

* Attach a regulated air supply to the leak-down test tooling.

* Pressurize the check valve to 827 kpa (120 psi) and close the isolation valve.

* For a check valve to pass the Leak-Down Check, the pressure must NOT drop below 689 kpa (100 psi) within a 10 second period.

* Repeat the Leak-Down Check for each check valve.

* The valves that do NOT pass the Leak-Down Check should be replaced with new check valves.

4. Place new O-rings and gaskets on the check valves that pass the Leak-Down Check.

5. Replace the new and refurbished check valves.

Leak-Down Check Tooling

The leak-down check tooling, as shown in Illustration 2, is used to supply regulated air to the check valves. The tooling must include a pressure valve with a maximum reading of 1378 kpa (200 psi) and a ball valve (or other quick action valve).

The overall length between the check valve and the isolation valve must not be more than 305 mm (12.0 in).

NOTE: The pressure gauge must be coupled as close as possible to the air line.

Illustration 2: Leak-Down Check Tooling (This is a reference drawing in order to construct this tooling for the purpose of performing the Leak-Down Check.): (A) 11.2 mm (0.44 in) internal thread, 20 mm (0.8 in) depth, thread diameter is 1/4of an inch, 18 threads per inch. (B) 1.5 ± 0.5 mm (0.060 ± 0.020 in) at 45 degrees. (C) Radius 0.4 ± 0.1 mm (0.016 ± 0.004 in). (D) 5.5 mm (0.2 in) internal thread with 20 mm (0.8 in) depth. (E) 30.0 degrees. (F) Slot 11.11 mm (0.437 in) x 20.64 mm (0.813 in). (G) 61.7 mm (2.43 in). (H) Deburr. (I) Radius 3.50 mm (0.138 in). (J) 35.00 mm (1.378 in). (K) Diameter 19.75 mm (0.778 in), to depth shown, 7/8of an inch, 9 internal threads per inch. (L) 16.50 mm (0.650 in). (M) 22.00 mm (0.866 in). (N) 19.00 mm (0.748 in). (O) Diameter 18.36 mm (0.723 in), to depth shown .