Knowledge · Hydraulics
What is a two-way cartridge valve? Function, nominal sizes and control covers
A two-way cartridge valve is a poppet valve without a housing of its own: sleeve, poppet and closing spring sit in a standardised cavity of the manifold block, and only the bolted-on control cover turns them into a blocking, pressure or flow valve. That is why these valves carry the large flows of compact manifolds, from 320 l/min in nominal size 16 to over 30,000 l/min in nominal size 160. This article answers the three questions that come before the order: how the valve works, what the cover decides, and which nominal size matches the flow.
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How the valve works
The cartridge element consists of a sleeve, a poppet with its seat and a closing spring. It sits in a cavity whose dimensions ISO 7368 defines, long known in Germany as DIN 24342. Two main ports open into the cavity: A axially at the seat, B laterally at the annulus. On the back of the poppet lies the pilot port X, on which the spring and the pilot pressure present there act. Whether the poppet opens or stays closed is decided by the balance of forces alone: the pressure at A and B pushes on the seat and annular areas and wants to lift the poppet, spring and pilot pressure at X hold it on the seat.
Because the element itself contains no pilot control, it is a pure actuator. The logic sits in the control cover, which closes the cavity to the outside and supplies port X: with drillings, a mounted directional valve, a pressure valve or a stroke limiter. From the same element, different valve functions arise, and the manifold stays compact because the element needs no pipes, flanges or subplates. As a poppet valve it closes leak-free, and the short paths between cavity and cover give short switching times.
Which function the control cover determines
- Blocking and directional function: a directional valve in the cover pressurises or relieves port X. With X under pressure the element stays closed; with X relieved, the pressure at A or B opens the poppet. That is how the cartridge valve switches large flows with a small pilot valve.
- Pressure function: a pressure valve in the cover limits or regulates the pressure at X. If the pressure at the main port rises above the set value, the poppet lifts and passes flow to tank or into the second port. In the range these elements are listed as pressure-relief cartridge valves; electrically adjustable covers carry the proportional technology.
- Flow function: a stroke limiter in the cover restricts the poppet stroke and with it the released cross-section. The element then acts as a throttle or flow valve; the adjustment sits externally accessible on the cover.
- Check function: the cover routes the pilot oil so that the poppet opens in one flow direction only. In a pilot-operated version this becomes a load-holding valve.
Nominal sizes and flow
ISO 7368 grades the cavities into ten nominal sizes from 16 to 160. The nominal size names the seat diameter in millimetres and with it the cross-section the poppet releases. Which flow passes at an acceptable pressure drop additionally depends on the poppet version: seat poppets with or without damping and with different area ratios carry different maximum values per nominal size. The table therefore states, per nominal size, the span of maximum flows across the versions carried; the value of the specific version is in the data sheet.
| Nominal size | Max. flow (l/min) | Max. operating pressure (bar) |
|---|---|---|
| 16 | 320 to 430 | 420 |
| 25 | 700 to 900 | 420 |
| 32 | 1,130 to 1,500 | 420 |
| 40 | 2,050 to 2,500 | 420 |
| 50 | 2,950 to 3,500 | 420 |
| 63 | 5,000 to 6,500 | 420, individual versions 450 |
| 80 | 6,050 to 8,500 | 420, individual versions 450 |
| 100 | 9,200 to 13,000 | 420, individual versions 450 |
| 125 | 13,000 to 19,000 | 420 |
| 160 | 26,250 to 32,500 | 420 |
Selection in four steps
- Define the function: blocking, pressure limiting, flow throttling or check. That yields the cover type, and the cover determines which element version fits it.
- Choose the nominal size from the flow: look up the largest operating flow in the table and take the nominal size whose span covers it with reserve. Too small raises the pressure drop, too large grows the block without benefit.
- Poppet version and spring per data sheet: damping against pressure surges on closing, area ratio and spring rate per the switching task. These values are version-specific and appear only in the manufacturer data sheet.
- Fluid and seal material: the standard version is released for mineral oils HL, HLP, HLPD, HVLP, HVLPD and the fire-resistant fluid HFC, the V version with FKM seals for HETG, HEES, HEPG, HFDU and HFDR. Source: Bosch Rexroth manufacturer data, LC series.
Cartridge valves, control covers and seal kits from stock
PTS hydraulics carries two-way cartridge valves and control covers in nominal sizes 16 to 160 with price and availability and no login. Name function, flow and fluid, and engineering assembles element, cover and seal kit.
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