TM 5-3805-258-24-1H Y D R A U L I C S Y S T E MS Y S T E M S O P E R A T I O NSEQUENCE VALVEThe sequence valve is part of the attachment orthird hydraulic circuit. It is in the implement pilotsystem between the attachment pilot valve and theshuttle valve. The sequence valve permits the tiltand lift circuits to operate when the attachmentcontrol lever is in CLOSE or LOWER position.SEQUENCE VALVE1. Tank passage. 2. Spool. 3. Chamber. 4. Spring. 5.Reliefvalve. 6. Jamnut.7. Adjustment screw. 6. Inletpassage fromattachment pilot valve (closeor lowerpres-sure).9. Outlet passage to shuttle valve and attachmentcontrol. 10. Passage fromattachment control valve (headend pressure).When the attachment control lever is moved toCLOSE or LOWER position, pilot oil from theclose or lower stem of the attachment pilot valvecomes into inlet passage (8). Implement pressureoil from the head end of the attachment cylinderscomes into passage (10). This pressure oil [in pas-sage (10)], against spool (2), works against spring(4) and relief valve (5). When the pressure of theoil to the head end of the attachment cylinders getsto approximately 15500 kPa (2250 psi), relief valve(5) opens and releases the pressure of the oil inchamber (3). Spool (2) now moves up and lets pilotoil from inlet passage (8) go through outlet pas-sage (9) to the shuttle valve and on to the attach-ment valve spool. There is now pilot pressure atboth ends of the attachment valve spool. Thesprings on the attachment valve spool cause it tomove back to HOLD position. Implement pressureoil to the attachment cylinders is now stopped.When the pressure of the oil in passage (10) getsbelow approximately 12400 kPa (1800 psi), reliefvalve (5) closes, the pressure in chamber (3) in-creases and spring (4) moves spool (2) down. Thisstops the flow of pilot oil from inlet passage (8)to outlet passage (9). There is now pilot pressureoil to one end of the attachment valve spool andthe spool moves back to CLOSE or LOWER posi-tion. Implement pressure oil again goes to the at-tachment cylinders.To change the setting of relief valve (5), loosenjam nut (6) and turn adjustment screw (7) clock-wise for an increase in pressure and counterclock-wise for a decrease in pressure.3-101
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