ORIFICE AS 3706346 - Caterpillar

1. Engine Compartment Shields
All 621B, 623B Tractors should be equipped with the current spray shield arrangement. See Illustration 1. These shields help to prevent hydraulic oil from being sprayed into the engine compartment in the event of a high pressure oil leak.
Illustration 1. Rear view of protective shielding parts.Do not remove the spray shields or permit them to become loose. Reports have been received of serious fires on machines caused by hydraulic oil or fuel being sprayed on hot parts of the engine because spray shields were removed or not installed, or shields were loose.
In some conditions, the hot air directed to the operator's compartment by the spray shields is not desired. The hot air can be directed away from the operator's compartment by use of a 5T3459 Heat Shield Group. Early machines need some miscellaneous parts in addition to the shield group.
2. Hydraulic Lines
If hydraulic oil comes into contact with a hot exhaust manifold or turbocharger, it can vaporize and the vapor can ignite. For this reason it is most important that the operator makes sure that all hydraulic lines and connections are in good condition and not leaking.
Protective shielding is provided in areas where these hoses might be exposed to exhaust heat and rapidly deteriorate. Check to be sure that this shielding is firmly in place and in good condition (Illustration 2).
Illustration 2. Muffler shielding and angles on hood.The suction and return line hoses and clamps should be replaced each year or after 2000 hours of operation (see chart). This can be done during periodic maintenance when the hydraulic system oil is normally drained and replaced.
The replacement hose must be the correct hydraulic hose specified in the parts book. Do not substitute radiator hose for hydraulic hose. The hoses must have at least two inches of overlap onto the tubes. This allows enough space for the two "high-torque" clamps which must be used on both ends and tightened to 11.3 N m (100 lb in) of torque (Illustration 3). These hose clamps should be retightened to this torque after the first 100 hours of operation.
Check to see that the mounting brackets are present and securely fastened.
The support assembly used to support the hydraulic return line manifold should be checked for loose mounting bolts.
Illustration 3. Hose clamps.3. Fuel Line
The high pressure fittings at the injection pump and valve covers should be inspected periodically for leakage (Illustration 4). If a connection is leaking, tighten the connectors to 40 7 N m (30 5 lb ft) with a torque wrench.
Illustration 4. High pressure fuel lines, injectors and connectors.The fuel supply and return tubes and hoses (low pressure lines) should be in good condition and securely fastened so as not to interfere with the vehicle structure or moving parts. Any chafed or damaged hose should be replaced.
Check fuel line clamps which secure the high pressure lines at several positions. The mounting bolts must be tight, and clamps should be installed at all locations.
4. Fuel And Oil Pressure Gauge