VOLVO EC240C L Excavator Service and Repair Manual

2 stage port relief valve, description Overload operation (for option) When the high pressure setting is used [Pl servo hydraulic signal: OFF] Piston (E) moves to the right due to the action of spring (F). Figure 1 2 stage port relief valve A. B. C. D. E. F. Piston Main poppet Spring Servo hydraulic poppet Piston Spring Pressure oil from the cylinder port goes through orifice (3) in piston (A), and enters chamber (2). Because d1>d2, the main poppet (B) remains securely seated. When the pressure oil exceeds the pressure set by spring (C), servo hydraulic poppet (D) opens, and oil flows through passages (4) and (5) to the tank passage. Figure 2 2 stage port relief valve Due to the oil flow past poppet (D), the pressure drops before and after orifice (3) in piston (A). The piston moves to the left, into its seat at the tip of the servo hydraulic poppet (D). Oil from chamber (1) flows through orifice (3) in piston (A), through side hole (4) and passage (5), to the tank passage. Figure 3 2 stage port relief valve The pressure drops before and after orifice (6) in servo hydraulic poppet (D). When the following condition: Chamber (1) pressure x d2 surface area > chamber (2) pressure x d1 surface area, is achieved, main poppet (B) opens, and pressure oil from the cylinder port flows to the tank passage, protecting the actuator.

Figure 4 2 stage port relief valve When the low pressure setting is used [Pl servo hydraulic signal: ON] Piston (E) moves to the right because Pl servo pressure compresses spring (F), the pressure set by spring (C) decreases, and the low pressure setting condition is achieved. Figure 5 2 stage port relief valve Anti–cavitation operation Because d1>d2, the cylinder port pressure is normally greater than the tank pressure, and the main poppet (B) remains securely seated. When the cylinder port pressure falls below the tank pressure (close to negative pressure), the main poppet (B) comes under pressure corresponding to the difference between the surface areas of d1/d2, and opens. Oil flows from the tank passage to the cylinder port, preventing cavitation. Figure 6 2 stage port relief valve

2 stage port relief valve, disassembly and assembly (For assembly, reverse disassembly procedures) When disassembling, mark each part to make assembling easier. NOTE! It is difficult to adjust the pressure when this component is located on the machine, so do not dismantle the pressure adjustment section. Figure 1 2 stage port relief valve 1. 2. 3. 4. 5. Loosen sleeve (1), and remove cartridge completely.   Tools: Spanner 32 mm Tightening torque: 147 Nm (108 lbf ft) Loosen nuts (3 and 4) with spanner 32 mm. Loosen cap (2), and remove subassembly completely. Remove spring (5) and servo hydraulic poppet (6).   Tools: Spanner 32 mm Tightening torque: 98 Nm (72 lbf ft) Remove servo hydraulic seat (7), and springs (8, 9), piston (10) and main poppet (11). Remove adjusting screw (12), and piston (13).

Adjustable boom (1st boom), description Figure 1 1st boom structure (1)

Figure 2 1st boom structure (2) 1 Pin with bracket 9 Hose assembly to plate ’1’ 2 Pin with bracket 10 Hose assembly to plate ’3’ 3 Pin with two holes 11 Hose assembly to plate ’2’ 4 Pin with bracket 12 Hose assembly to plate ’4’ 5 Pin with bracket 13 From adjust boom valve ’a’ to pedal ’2’ 6 2 mm gap (nut and pin lock part) 14 From adjust boom valve ’b’ to pedal ’1’ 7 Dust seal 15 From adjust boom valve ’c’ to servo valve ’Pi’ 8 Bushing 16 From adjust boom valve ’Pi’ to main control valve ’Pg1’ Gap and shims Gap (mm) Necessary for max. gap Position Min. Max. Shim part No. (1t) Quantity Shim part No. (0.5t) Quantity Gap1 + 0.25 + 0.9 – – 1173 – 03680 1 Gap2 + 1.0 + 2.5 1173 – 01630 2 1173 – 01390 1 Gap3 + 1.0 + 4.0 1173 – 01630 3 – – Gap4 + 0.4 + 0.8 – – – – Gap5 + 0.5 + 2.5 1173 – 03630 2 1173 – 03640 1 Initial lubrication table (unit: cc) Sign Initial grease amount Position GR1 65 × 2 = 130 Boom rear bushing GR2 150 × 2 = 300 Boom cylinder rod GR3 13 2nd boom cylinder tube NOTE! Grease hose / bearing inner space included.

Adjustable boom (2nd boom), description Figure 1 2nd boom structure 1 Pin with bracket

2 Pin with bracket 3 Pin with hole 4 Dust seal 5 Bushing Gap and shims Gap (mm) Necessary for max. gap Position Min. Max. Shim part No. (1t) Quantity Shim part No. (0.5t) Quantity Gap1 + 0.2 + 0.5 – – – – Gap2 + 0.5 + 2.5 1173 – 03460 2 1173 – 03470 1 Gap3 + 0.5 + 2.5 1173 – 03460 2 1173 – 03470 1 Gap4 + 0.15 + 0.5 – – – – Initial lubrication table (unit: cc) Sign Initial grease amount Position GR1 18 Boom rear bushing (right) GR2 13 2nd boom cylinder rod GR3 14 Arm cylinder tube GR3 18 Boom rear bushing (left) NOTE! Grease hose / bearing inner space included.

Adjustable boom selector valve Figure 1 Adjustable boom selector valve Specifications, adjustable boom selector valve Description Unit Specifications Maximum operating pressure MPa (kgf/cm²) (psi) (bar) 3.92 (40) (569) (39.2) Operating flow rate Litre/min (gal/min) 20 (5.3) Cracking pressure MPa (kgf/cm²) (psi) (bar) 0.49 (5) (71.1) (4.9) Internal leakage, at 70 kgf/cm² and 20 cSt cc/min (cu·in/min) 30 (1.8)

VOLVO EC240C L Excavator Service and Repair Manual

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