A rotary shear directional control valve changes the route taken by hydraulic oil when the operator moves the handle. This allows flow to be directed to the required side of a hydraulic actuator or returned to the valve’s centre condition.

The 180 and 280 Series use a manually operated rotary handle and are available with different centre conditions and operating actions to suit a wide range of hydraulic actuator control applications. 

A zero or near-zero leakage directional valve is useful where pressure needs to be maintained when the valve is closed, or where internal leakage could contribute to unwanted actuator movement or gradual pressure loss.

This can be particularly important where a hydraulic actuator needs to remain in a controlled position after the operator has released the control.

The 180 and 280 Series use PDP® technology to minimise leakage between the valve’s internal flow paths, helping remove one possible source of pressure decay. Other components, including cylinders and seals, should also be considered when diagnosing unwanted movement or pressure loss. 

PDP® stands for Pressure Decay-Proof and is Webtec’s rotary shear valve technology designed to prevent the pressure decay associated with internal valve leakage.

Conventional sliding spool valves require a small clearance between the spool and bore so that the spool can move. This clearance creates a potential internal leakage path and can also make the valve susceptible to contamination causing the spool to stick or jam.

PDP® rotary shear valves instead use a precision-engineered rotary shear design that creates a positive metal-to-metal shut-off. In the 180 and 280 Series, an optically flat rotary spool works with pressure-loaded seats to provide zero or near-zero leakage between the valve’s flow paths. 

One of the main differences is how the valve seals internally.

A sliding spool valve requires clearance between the spool and bore so that it can move freely. This creates a potential leakage path and can allow contamination to interfere with movement of the spool.

PDP® rotary shear technology instead uses positive metal-to-metal shut-off. The design is intended to resist wear, contamination and high differential pressures while maintaining pressure-tight operation over repeated duty cycles.

For the user, this can provide more predictable hydraulic performance, fewer leakage-related problems and reduced maintenance and downtime. 
 

The 180 and 280 Series are designed to provide zero or near-zero leakage, but measured leakage depends on the selected flow size and internal configuration.

Closure testing for both ranges using low-pressure air at approximately 5.7 bar (82 psi) found:

• the 15 L/min (4 US gpm) non-interflow version had no visually detectable leakage during the 60-second test; 
• the 26.5 L/min (7 US gpm) and 38 L/min (10 US gpm) interflow versions recorded leakage of approximately 1.67 × 10⁻⁴ L/min, equivalent to less than one drop of water every ten minutes. 

Both datasheets also note that reduced fluid viscosity can adversely affect leakage performance. 
 

The main difference is the construction and the environment for which each range is intended.

The 180 Series has an aluminium body and is designed for mobile and industrial hydraulic actuator control where internal leakage needs to be minimised.

The 280 Series uses a 316L stainless steel body and is intended for more arduous operating environments. It is also compatible with water-glycol hydraulic fluid and has an ATEX rating stated in the datasheet.

Both ranges use the same rotary shear principle and are available with maximum flow ratings up to 38 L/min (10 US gpm) and maximum working pressures up to 700 bar (10,000 psi), depending on the selected flow size and configuration. 

The 280 Series is intended for arduous environments where a 316L stainless steel valve construction is preferred to the aluminium construction of the 180 Series.

This provides an alternative for applications where the valve may be exposed to more demanding environmental conditions while still requiring the zero or near-zero leakage characteristics of a rotary shear directional valve.

The 280 Series also extends the available fluid and application options through its stated water-glycol compatibility and ATEX rating. 

Yes. The 280 Series datasheet specifically states that the valve is compatible with water-glycol hydraulic fluid.

Mineral hydraulic oils meeting ISO 11158 are also listed as compatible. For other hydraulic fluids, the datasheet recommends contacting Webtec. 

The 280 Series datasheet states that the valve has been designed, manufactured and tested to the ATEX directive referenced as BS EN 13463-1:2009 and is rated II 3G TX.

Standard documentation listed for the 280 Series includes a manual, Certificate of Conformity, performance test certificate and Declaration of Conformity to ATEX.

The suitability of the complete hydraulic system for a particular hazardous-area application should still be assessed against the requirements of that installation. 

A manually operated valve provides a simple, direct control point where the operator is positioned close to the hydraulic equipment.

Both ranges offer standard, panel and manifold mounting arrangements, although the available connections and manifold options differ between the 180 and 280 Series.

Straight and bent handles are also available, allowing the valve arrangement to be adapted to different machine layouts and operator positions. 

A detented valve remains in the selected position until the operator moves the handle again. This can be useful where a hydraulic function needs to remain selected without the operator continuously holding the control.

A spring-centred valve automatically returns to its centre position when the handle is released. This can be more suitable where the hydraulic function should only remain selected while the operator is actively holding the control.

There are some pressure limitations to consider.

For the 180 Series 15 L/min (4 US gpm) version, spring-return performance can be compromised above 207 bar (3,000 psi).

For the 280 Series, spring-return performance can be compromised above 138 bar (2,000 psi) on the 15 L/min (4 US gpm) version and above 207 bar (3,000 psi) on the 26.5 and 38 L/min (7 and 10 US gpm) versions. 

A position-lock option is available for detented versions of the 180 Series. It can secure the valve in any of its three operating positions.

Two versions are available:

• push-button position lock; 
• removable-key position lock. 

The position-lock option cannot be combined with the pressurised tank-port option.

A position-lock option is not listed in the 280 Series datasheet, so it should not be assumed to be available for the stainless steel range. 

Yes, on selected flow sizes.

For both ranges:

• the 15 L/min (4 US gpm) version does not have throttling capability; 
• the 26.5 L/min (7 US gpm) version has throttling capability; 
• the 38 L/min (10 US gpm) version has throttling capability. 

Throttling allows flow to be progressively restricted as the handle is moved between positions, which may be useful where the hydraulic circuit requires a more gradual actuator response.

The centre condition determines which hydraulic ports are connected or blocked when the handle is in its centre position.

This affects what happens to the actuator and the rest of the hydraulic circuit when neither operating direction is selected.

Different valve models are available to provide different centre conditions. The correct model should therefore be selected by comparing the required circuit behaviour with the hydraulic symbols in the relevant datasheet rather than treating the hydraulic symbol as a separate product feature.

Yes. Both ranges can provide standard three-position operation or two-position operation where the application only requires the centre position and one operating direction.

The available two-position arrangements are:

• centre and right positions only; 
• centre and left positions only. 

This can make the valve better suited to a machine function that only needs one selected direction of hydraulic operation.

Yes, although the way the options are specified differs between the ranges.

The 280 Series can be configured as a standard four-port valve or as a three-port valve with either port A or port B plugged.

The 180 Series also includes three-port configurations. Models 180 and 181 have port B plugged, while the other valve models provide different four-port circuit arrangements.

The required configuration should be selected from the hydraulic circuit rather than simply by the number of physical connections required. 
 

The main flow and pressure ratings are the same for the 180 and 280 Series and must be considered together:

• 15 L/min (4 US gpm): up to 700 bar (10,000 psi), without throttling capability. 
• 26.5 L/min (7 US gpm): up to 350 bar (5,000 psi), with throttling capability. 
• 38 L/min (10 US gpm): up to 207 bar (3,000 psi), with throttling capability. 

The highest-pressure and highest-flow ratings therefore do not apply to the same configuration. Required system flow and pressure should always be checked together when selecting a valve. 

The standard maximum tank-port pressure for both ranges is 17 bar (250 psi).

An optional pressurised tank-port arrangement allows the T port to operate at full system working pressure, subject to the pressure rating of the selected flow size.

This option includes an additional 1/8 in NPTF drain connection. The normal tank-line pressure limit then applies to the separate drain port, and the drain port must not be plugged.

On the 180 Series, this option cannot be combined with a position lock. 
 

The available options differ between the two ranges.

The 180 Series includes:

• 9/16 in-18 UN #6 SAE ORB; 
• 3/8 in NPTF; 
• 3/8 in BSPP; 
• 014 O-ring connections; 
• 014 O-ring manifold mounting; 
• CETOP3 and D03 manifold interfaces. 

An eight-port version with four side ports and four additional bottom ports is also available on selected 180 Series configurations.

 

The 280 Series includes:

• 1/4 in NPTF;
• 9/16 in-18 UN #6 SAE ORB;
• 3/8 in NPTF;
• 3/8 in BSPP;
• 014 O-ring connections;
• 014 O-ring manifold mounting.

The 280 Series uses a separate stainless steel adapter kit where a BS ISO 4401-03 or NFPA T3.5.1-D03 mounting pattern is required.

Suitable thread sealant should be used with NPTF connections as specified in the datasheets.

Yes. On both ranges, the handle can be reassembled through 180° to help reduce the space required between adjacent valves.

The minimum spacing differs because of the construction of each range.

For the 180 Series:

• approximately 16 mm (0.63 in) with a straight handle; 
• approximately 14 mm (0.55 in) with a bent handle. 

For the 280 Series:

• approximately 28 mm (1.10 in) with a straight handle; 
• approximately 21 mm (0.83 in) with a bent handle. 

These dimensions can be useful when planning a compact manual control station containing several hydraulic functions. 

Yes, but the mounting method differs.

The 180 Series has dedicated CETOP3 and D03 interface versions. The datasheet notes that the overall valve width exceeds the maximum width normally required by those standards, so clearance around neighbouring components should be checked. 

The 280 Series uses a 316L stainless steel adapter kit to adapt the 014 O-ring manifold-mounted valve to either a BS ISO 4401-03 or NFPA T3.5.1-D03 mounting pattern. The maximum pressure is 350 bar for the BS ISO 4401-03 adapter and 3,000 psi for the NFPA T3.5.1-D03 adapter
 

Both ranges are compatible with mineral hydraulic oils meeting ISO 11158. Other fluids should be discussed with Webtec before use.

The 280 Series datasheet additionally states that it is compatible with water-glycol hydraulic fluid.

The media temperature range for both ranges is:

• -30 to 120 °C (-22 to 248 °F). 

The ambient temperature ranges differ:

• 180 Series: -20 to 50 °C (-4 to 122 °F). 
• 280 Series: -30 to 50 °C (-22 to 122 °F). 

Fluid viscosity should also be considered because reduced viscosity can adversely affect leakage performance. 
 

No. PDP® rotary shear technology is designed to resist contamination-related problems associated with conventional sliding spool valves, and the 180 Series datasheet specifically describes the valve as having excellent tolerance to contaminants. 

This does not remove the need for appropriate filtration, good installation practices and routine hydraulic maintenance.

Neither datasheet specifies a particular fluid-cleanliness code for these valves, so filtration requirements should be determined by the needs of the complete hydraulic system and its most contamination-sensitive components.
 

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