A New Line Relief Valve Improves Controllability Of The Stick On Certain Excavators [TIBU4487]

HYDRAULIC SYSTEM

VALVE GP-RELIEF

A New Line Relief Valve Improves Controllability Of The Stick On Certain Excavators

CONFIDENTIAL TIBU4487-00

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TECHNICAL INFORMATION BULLETIN	APRIL 20, 2005
EXCAVATORS	320C (GHA, MAB, AMC, FBC, BEF, BPR, CCD), 320C L (ANB, PAB, BBC, GAC, HBC, BRX), 320C U (MAC, CLM), 320C LU (CLZ), 320C LRR (PAC), 321C LCR (MCF), 322C (DAA, BLP), 322C L (FED, BKJ, HEK, BKM), 322C FMLGP (BYL, SLX), 322C FMST (M2H), 322C FMHW (CAM, C3R, LAR, CBY), 325C (BKW), 325C CR (AMH), 325C L (BTD, BFE, BMM), 325C MH (S2C), 325C FMST (G1L), 325C FMHW (M2K, S3M, Y4P), 330C (MCA, JAB, NAB), 330C L (KDD, SCN, GKX, DKY), 330C MH (D3C), 330C FMST (B3M), 330C FMHW (B1K, B2L, B4N), EXCAVATORS
	Component Code(s) 5117, 5069

SUBJECT: A NEW LINE RELIEF VALVE IMPROVES CONTROLLABILITY OF THE
STICK ON CERTAIN EXCAVATORS

PROBLEM:

The response speed of the line relief valve and the stick drift valve in the main hydraulic control valve may be insufficient during the operation of the stick cylinder. When stick movement is initiated from the full Stick IN position, approximately 40 cm (15.75 inch) of movement may continue after the control lever is quickly returned to the neutral position.

SOLUTION:

If the controllability of the Stick OUT is unsatisfactory, install two new 250-2508 Relief Valve Groups in place of the two former 116-3600 Relief Valves. The relief valves are used for stick cylinder line relief and for stick drift control in the main hydraulic control valve. The location of the relief valves is shown in the illustration.

Illustration 1. Main Hydraulic Control Valve
(1) 250-2508 Relief Valve Group for stick cylinder line relief
(2) 250-2508 Relief Valve Group for stick drift control