Excavator Control Valve Composite Action Operation Techniques That Separate Pros From Amateurs

Running one function at a time is easy. Any operator can dig a hole with just the boom or just the arm. But real excavation work demands composite actions — swing and boom together, arm and bucket at the same time, boom and stick while swinging. That is when the control valve earns its keep, and that is also when most operators destroy it without even knowing.

Composite action puts the valve under a completely different kind of stress. The spools have to split flow between multiple circuits simultaneously, the pressure compensator has to juggle competing demands, and the pump has to deliver enough oil to feed everything at once. Get it right and the machine feels like an extension of your body. Get it wrong and the valve overheats, the controls get sluggish, and the whole system fights you.

This is how to run composite actions the way experienced operators do — smooth, controlled, and without killing the valve in the process.

What Actually Happens Inside the Valve During Composite Action

Before you can master composite operation, you need to understand what the valve is doing when you pull two levers at the same time.

The control valve has a pressure compensator that monitors system pressure and adjusts flow accordingly. When you run a single function, the compensator sees one demand and adjusts flow to match. Simple.

But when you pull two levers, the compensator sees two demands at once. It has to split the available pump flow between both circuits. If the combined flow demand exceeds what the pump can deliver, the compensator reduces flow to both spools proportionally. Both functions slow down. The machine feels lazy.

At the same time, each spool is shifting to a different position. The spool for function A might be at 60 percent stroke while the spool for function B is at 40 percent. The valve internals have to handle both shifts at the same time, which creates more heat and more wear than running either function alone.

The relief valve also works harder during composite action. When one circuit hits a load — say, the bucket meets rock — pressure spikes. The relief valve opens to dump excess flow. But while it is dumping, the other circuit is still trying to run. That means the pump is working at maximum output, the relief valve is dumping hot oil, and the valve body is absorbing all that heat. This is why composite action generates more heat than any other operating mode.

Mastering the Two-Lever Combination

The most common composite action on any excavator is boom and arm together — digging while the boom is raising or lowering. This combination puts the two highest-flow spools under simultaneous demand, and it is where most operators make mistakes.

Sequencing Your Inputs Instead of Slamming Both Levers

The biggest mistake operators make with composite action is pulling both levers to full stroke at the same time. That sends a massive flow demand to the valve instantly. The pump cannot respond fast enough, pressure drops, and both functions stall.

Instead, start with one lever — usually the boom. Pull it to about 70 percent stroke and hold it there for a half second. Then add the arm lever, also to about 70 percent. This staggered input gives the pump time to build flow and the compensator time to adjust. Both functions engage smoothly instead of fighting each other.

Once both functions are running, you can increase either lever gradually. But never take both to 100 percent at the same time unless the machine absolutely needs it. Keeping each input around 70 to 80 percent leaves enough flow margin for the valve to breathe.

Using Boom-Arm Composite for Efficient Digging

When you dig with boom and arm together, the goal is to keep the bucket tip moving in a smooth arc. If you move the boom too fast while the arm is slow, the bucket tip jumps. If you move the arm too fast while the boom is slow, the bucket digs too deep.

The trick is to keep the ratio between boom and arm inputs roughly constant. For most digging tasks, that ratio is about 60 percent boom to 40 percent arm. The boom does the heavy lifting — it raises the whole assembly. The arm does the fine positioning — it controls where the bucket goes.

Practice this ratio until it becomes second nature. Your hands should move both levers in a coordinated pattern, not independently. Think of it like driving a car — you do not steer with one hand and accelerate with the other at random. You coordinate both inputs for a smooth result.

Swing Combined With Any Other Function

Swing combined with boom, arm, or bucket is the most stressful composite action on the valve. The swing motor demands high flow at relatively low pressure, while the work function demands high pressure at moderate flow. The valve has to satisfy both at the same time, and the pressure compensator often cannot keep up.

Timing the Swing Input to Avoid Pressure Spikes

When you swing while digging, the swing motor creates a sudden flow demand that steals oil from the work function. The result is a momentary slowdown in the digging action — the bucket stalls for a split second while the swing catches up.

To avoid this, initiate the swing slightly before you start the digging stroke. Start the swing at about 30 percent input, let the machine begin to rotate, and then add the boom or arm input. By the time the work function reaches full demand, the swing is already at speed and the flow demand stabilizes.

Do not start the swing and the work function at exactly the same instant. That simultaneous demand spike is what causes the pressure drop and the sluggish feel. Offset them by half a second and the valve handles both smoothly.

Reducing Swing Speed During Heavy Digging