A Boom Hunting Condition May Occur During Modulation of the Boom Up Function

Usage:

A Boom Hunting Condition May Occur During Modulation of the Boom Up Function

CONFIDENTIAL

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TECHNICAL INFORMATION BULLETIN	JUNE 20, 2001
EXCAVATORS	365B L (9PZ, 9TZ, AGD) EXCAVATORS
	Component Code(s) 5067, 5079

SUBJECT: A BOOM HUNTING CONDITION MAY OCCUR DURING MODULATION OF
THE BOOM UP FUNCTION

PROBLEM:

A hunting condition may be exhibited during BOOM UP operation. The hunting condition usually occurs when the BOOM UP function is modulated. The condition is especially prevalent during fine grading or bank forming operations. Boom hunting may occur in either single function or multi-function operation.

SOLUTION:

The installation of two 131-0753 Shuttle Valve Groups will prevent the BOOM UP instability. The illustrations show the location for the shuttle valve installation.

The 131-0753 Shuttle Valve Group contains a 131-0752 Shuttle Valve. The orifice size of the pin in the shuttle valve controls the restricted flow of hydraulic fluid in one direction. Various pins can be assembled in the 131-0753 Shuttle Valve Group. The range of pin orifice sizes will provide options for the elimination of the boom hunting condition. The table lists the pin orifice sizes.

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Throttle Pin Orifice Diameter
Part Number	Description	Orifice Size
131-0752	Shuttle Valve	0.30 mm (0.012 in)
201-1521	Pin	0.45 mm (0.018 in)
124-9957	Pin	0.55 mm (0.022 in)

JUNE 20, 2001 Component Code(s) 5067, 5079

FOR 365B L (9TZ, AGD) EXCAVATORS

Illustration 1. Location Of The Components On The Main Control Valve For 365B L (9TZ, AGD) Excavators

Illustration 2. Detail A From Illustration 1 Of The Components Prior To The Installation Of The 131-0753 Shuttle Valve Groups

JUNE 20, 2001 Component Code(s) 5067, 5079

Illustration 3. Components For Shuttle Valve Group Installation In 365B L (9TZ, AGD) Excavators

(B) Connection to Main Control Valve
(C) 8J-6875 Shuttle Valve Assembly
(D) 3J-1907 O-Ring Seal
(E) 8C-8431 Tee
(F) Load Signal Hoses From Pump Regulator
(G) 6V-8397 O-Ring Seal
(H) 131-0753 Shuttle Valve Group
(J) 6V-0484 Adapter (90 degree) NOTE: Orient 6V-0484 Adapter
to provide clearance for reassembly of load signal hose (F).

Illustration 4. 131-0753 Shuttle Valve Group
(K) 131-0752 Shuttle Valve

JUNE 20, 2001
Component Code(s)5067, 5079

Illustration 5. Hydraulic Schematic of Illustration 3

FOR 365B L (9PZ) EXCAVATORS

Illustration 6. Location Of The Components On The Main Control Valve For 365B L (9PZ) Excavators

JUNE 20, 2001
Component Code(s)5067, 5079

Illustration 7. Detail L From Illustration 6 Prior To The Installation Of The 131-0753 Shuttle Valve Group

(F) Load Signal Hoses From Pump Regulator
(M) Original Tee

Disconnect the two load signal hoses (F).
Remove the original tee (M).
Install a new 5I-4376 Tee.
Assemble two 131-0753 Shuttle Valve Groups to the 5I-4376 Tee. NOTE: Make sure that the "Free Flow" direction is from the main control valve to the hydraulic pump as shown in Illustration 4 and Illustration 5.
Reconnect the two load signal hoses (F) to the shuttle valve.