Installation Of Thermocouples And Pyrometer{7466} Caterpillar

This instruction gives the procedures to install thermocouples and a pyrometer to measure:

1) Exhaust elbow temperatures only.

2) Exhaust manifold port temperatures only.

3) Exhaust stack and exhaust manifold port temperatures.

The 3N4567, 3N4569, 3N4576 and 3N3478 Instrument Panel Groups are standard equipment on marine engines and are available as attachments on other engines; these panel groups already have thermocouples and a pyrometer to measure the exhaust stack temperatures, so that installation of thermocouples in the exhaust stack is not necessary. The chart on page 2 shows the parts needed for installation.

NOTE: Do not make the thermocouple leads (wires) shorter, since that would cause the pyrometer to show an incorrect temperature. The leads can be made longer by the addition of 18 gauge copper wire, if the temperature at both ends of the copper wire is approximately the same. The pyrometer must be shock mounted (installed so that shock does not get to the gauge) and vibration of frequency more than 60 Hz (cycles per second) must not get to the gauge.

Installation Of Thermocouples In Exhaust Stack

(1) Remove the plugs from exhaust elbow (1). Install 3N5991 Thermocouples (2) and 3N8278 Adapters (3) in the elbow.

Installation Of Thermocouples In Exhaust Manifolds

(1) Remove plugs (1) from the exhaust manifold ports. The plugs can be on either the inner side or bottom side of the exhaust manifold. Install 3N5991 Thermocouples and 3N8273 Adapters.

Installation Of Pyrometer

(1) Make a hole 3.19"-3.25"Ø (81.0-82.6Ø) where the pyrometer is to be installed. The pyrometer is approximately 2.5" (64) thick. Install pyrometer (1) or (2).

Installation Of Selector Switch

(1) Make hole (A) 3.13"-3.19"Ø (79.5-81.0Ø) where the switch is to be installed. The switch is approximately 1.88" (47.8) thick. Make holes (B) .170"Ø (4.32Ø) as shown. Install switch (1).

Wire Connections

(1) For engines which have thermocouples installed in the exhaust elbow only, connect the yellow thermocouple lead from the right side of the engine to pyrometer gauge terminal (1) and connect the red lead to terminal (2). Connect the yellow lead from the left side of the engine to terminal (3) and the red lead to terminal (4).

(2) For engines equipped with thermocouples in the exhaust manifolds, use 18 gauge copper wire (5) to connect switch (6) to pyrometer (7) as shown.

(3) Connect the yellow lead from the No. 1 cylinder position to the outer (8) terminal on the switch. Connect the red lead from the No. 1 cylinder position to the inner (9) terminal on the switch. Use this procedure for all thermocouples leads in order. If thermocouples have been installed in the exhaust elbow, connect the yellow lead from the thermocouple on the right side to the next outer terminal not already used and connect the red lead to the inner terminal.