The basic principle.

A valve block is a body containing connected passages and valve functions. It can combine check, relief, metering, bypass and lowering functions while reducing the need for separate external pipe connections.

The exterior does not reveal the whole circuit. A drawing shows how passages and elements connect, while the functional description explains how those connections change during operation.

Three states of a conventional lift circuit.

A worked-through example

During ascent, pump flow reaches the actuator through the intended path. At rest, load-holding paths close. During descent, a controlled return path allows fluid back to the tank.

Trace the connected fluid paths.

Follow the same pipes through three different states. This example uses a single-acting cylinder, a fixed-delivery pump and gravity lowering. The drawings show the steady part of each state; a real valve block also manages the transitions.

1. Ascent

Pump running · load rising

1. Ascent in a conventional hydraulic lift circuitFluid travels from tank through pump and open check valve to the cylinder. The bypass and lowering paths are closed in this simplified steady-ascent state.UP123456

Fluid travels from tank through pump and open check valve to the cylinder. The bypass and lowering paths are closed in this simplified steady-ascent state.

2. Hold

Pump stopped · load held

2. Hold in a conventional hydraulic lift circuitNo through-flow. The check valve seats against return flow and the lowering valve is shut. Cylinder pressure supports the load. The pump-side bypass is open but carries no flow.STILLPressureheld123456

No through-flow. The check valve seats against return flow and the lowering valve is shut. Cylinder pressure supports the load. The pump-side bypass is open but carries no flow.

3. Descent

Pump stopped · load lowering

3. Descent in a conventional hydraulic lift circuitThe load drives fluid from the cylinder through the metering lowering valve back to tank. The check valve blocks the reverse route through the pump. The bypass remains open with no pump flow.DOWN123456

The load drives fluid from the cylinder through the metering lowering valve back to tank. The check valve blocks the reverse route through the pump. The bypass remains open with no pump flow.

  1. Tank. Stores the fluid and receives the return flow.
  2. Pump. Delivers fluid during ascent. It is stopped in the holding and gravity-lowering states shown.
  3. Check valve. Opens for supply towards the cylinder; reverse pressure seats the ball in this simplified picture.
  4. Bypass path. Returns pump delivery to the tank when open. It is shown shut during steady ascent. Opening it progressively can reduce cylinder flow during levelling; it is a different function from pressure relief.
  5. Lowering path. Meters the cylinder’s return flow. Shut for ascent and hold; open by a controlled amount for descent.
  6. Cylinder. Incoming fluid extends the actuator. During descent, the supported load pushes fluid back through the lowering path.
Read the lines: solid orange lines with arrowheads carry the flow shown. Dashed grey lines have no through-flow in that state; they may still contain pressurised fluid. A thick bar closes a valve path; a gap opens it, and opposed points indicate a metering restriction. These are simplified teaching pictograms, not a complete ISO hydraulic schematic. Relief protection, pilot passages and installation-specific protective devices are omitted so the journey paths remain clear. They remain essential parts of the real design; see hydraulic rupture protection.

Why the bypass matters: pump delivery divides between the cylinder and any open bypass path. Reducing cylinder flow reduces actuator speed. During conventional descent the energy comes from the lowering load, and controlling the return flow controls the speed.

Connect it to the lift.

Blocks may use mechanical adjustment, electronic feedback or a combination. A symptom such as rough stopping can involve the command, fluid condition, valve response or load. Individual adjustments cannot be understood independently of the whole circuit.

A closer look

Two blocks that look similar can have different internal functions and control sequences. Identification and the correct hydraulic schematic are essential for engineering work.

Check your understanding

Is a valve block just a single large on/off valve?

Reveal the explanation

No. It commonly integrates several interacting functions and passages.

Further reading.

Optional reading to explore this lesson in more detail.

  • Blain: service manual (PDF)

    Technical example: compare the EV100 cross-section on pages 4–5 with the component layout on page 12.

  • Blain: EV / KV service manual (PDF)

    Compare the check, bypass and lowering functions labelled on pages 4–5 with the EV100 journey curves on page 8. The teaching circuit simplifies these functions; it does not reproduce the installed schematic.