Excavator Control Valve Boom and Arm Operation Guide: How to Move the Big Functions Without Killing the Valve
The boom and arm circuits do more work than any other function on an excavator. Every dig, every lift, every curl — it all goes through the main control valve spools for boom and arm. These two circuits share the highest flow demand, the highest pressure, and the most heat generation of any function on the machine. How you operate them determines whether your control valve lasts thousands of hours or dies in a few hundred.
Most operators treat boom and arm like separate functions. They are not. They share pump flow, they share valve real estate, and they share the same relief valve. One bad move on the boom affects the arm, and vice versa. This guide breaks down exactly how to operate both functions together without destroying the valve that controls them.
What Makes Boom and Arm So Hard on the Control Valve
Shared Flow Means Shared Stress
The boom and arm circuits are fed from the same pump through adjacent spools in the main control valve. When you lift the boom and curl the arm at the same time — which is every dig — the pump has to split its flow between two high-demand circuits. The valve spools for boom and arm are both shifted simultaneously, which means the relief valve is working at or near full capacity.
This is different from swing or travel, where only one circuit is active at a time. Boom and arm together put the control valve under its heaviest continuous load. The spools are fully shifted, the pressure is at peak, and the oil is moving at maximum velocity through tight clearances. Every second of combined operation generates heat and wear that no other function can match.