Walvoil SD25/2/AC(XG-250)/28L/18L/RC is a 2 spool hydraulic control valve sectional valve from the Walvoil SD25 high-flow series.It integrates a pilot operated relief valve within the inlet section and provides dual working spools.Rated at 240 L/min nominal flow and 315 bar maximum pressure,this directional control valve targets hydraulic systems in metallurgical industry,marine vessels,earth-moving equipment,and mobile hydraulic applications.

　　What Is a Sectional Hydraulic Control Valve?

　　A sectional hydraulic control valve is a modular directional control valve assembly that combines an inlet element,multiple working sections,and an outlet element bolted together with tie rods.Each working section controls a specific hydraulic function such as cylinder extension or motor rotation.Sectional valves allow system designers to build custom valve stacks by selecting the exact number of spools and auxiliary functions required for a given application.

　　The SD25 series is a high-flow sectional valve platform manufactured by Walvoil in Italy.The model designation SD25/2/AC(XG-250)/28L/18L/RC identifies a 2-spool configuration with an AC-type inlet section equipped with a pilot-operated main pressure relief valve,two working spools with specific spool flow codes(28L and 18L),and an RC-type outlet section with carry-over capability.The SD25 platform supports up to 12 working sections per assembly.

　　Key Specifications

　　Nominal Flow Rating:240 L/min(63 US gpm)

　　Maximum Operating Pressure:315 bar(4,600 psi)

　　Number of Spools:2

　　Inlet Element Type:AC with Pilot-Operated Relief Valve

　　Main Relief Valve Setting:250 bar(per XG-250 designation)

　　Spool 1 Flow Code:28L

　　Spool 2 Flow Code:18L

　　Outlet Element Type:RC(with Carry-Over Port)

　　Spool Pitch:62 mm(2.44 inches)

　　Hydraulic Connection Threads:G 3/4 inch(inlet/outlet/service ports)

　　Control Method:Manual Lever Operation with Spring Return

　　Maximum Number of Sections:12(per assembly)

　　Circuit Configuration:Type Y Free Flow Gallery(Parallel Circuit)

　　Internal Leakage:Approximately 4 cm³/min at 100 bar

　　Hydraulic Fluid Temperature Range:-15°C to+80°C

　　Contamination Level Compliance:-/19/16 per ISO 4406

　　Material Housing:Special Cast Iron

　　Material Spool:Nickel-Plated Carbon Steel

　　Material Seals:NBR(Nitrile Butadiene Rubber)

　　Tie Rod Tightening Torque:50 N·m

　　Mounting Orientation:Any Position

　　Weight(Assembled):Approximately 16 to 18 kg(estimated per 2-spool configuration)

　　Technical Highlights

　　The SD25 platform utilizes a modular sectional architecture with 62 mm spool pitch for compact hydraulic manifold integration.The inlet,working sections,and outlet elements are secured via through-bolts with tie rods,enabling field-configurable valve assemblies.This design supports the addition or removal of spool sections without replacing the entire valve block,reducing downtime during system reconfiguration.

　　Each working section incorporates an independent load check valve.This prevents reverse flow and load drift when multiple actuators operate simultaneously under varying load pressures.Load check valves ensure that a lightly loaded cylinder does not move unintentionally when a heavily loaded function is activated.

　　The inlet section features a pilot-operated main relief valve set to 250 bar(XG-250 designation).Pilot-operated relief valves provide more stable pressure regulation and lower pressure override compared to direct-acting relief valves.This characteristic is essential in high-flow systems where pressure spikes during valve shifting must be minimized to protect downstream components such as hoses,cylinders,and hydraulic motors.

　　The RC outlet element provides a carry-over port for power beyond functionality.This allows hydraulic flow to continue downstream to additional valve stacks or auxiliary circuits when the SD25 spools are in neutral position.Systems without power beyond would require a separate pump for downstream functions,increasing cost and installation complexity.A common question from system integrators is whether the carry-over port can be plugged for closed-center applications—yes,the RC outlet may be configured for closed-center operation with a blind plug.

　　The spool flow codes 28L and 18L define specific metering characteristics.These alphanumeric codes correspond to spool configurations optimized for double-acting cylinder control with spring return to neutral.The SD25 series offers interchangeable spools with multiple spool types—parallel circuit,series circuit,float position,and regenerative spools—allowing custom flow characteristics per working section based on actuator requirements.

　　Applications

　　Metallurgical industry hydraulic systems:Controls hydraulic cylinders on furnace doors,tilting mechanisms,and material handling manipulators.The pilot operated relief valve maintains stable pressure regulation under high-temperature operating conditions typical of steel mill environments,while the 240 L/min flow capacity supports rapid movement of heavy furnace charging equipment.

　　Marine hydraulic systems:Manages winches,steering gear,and deck machinery aboard vessels and offshore platforms.The valve body is constructed from special cast iron with nickel-plated spools,providing corrosion resistance in saltwater environments.Walvoil hydraulic components are specified in marine equipment applications including sea platform cranes and vessel steering systems.

　　Earth-moving equipment hydraulics:Directs flow to boom lift,bucket tilt,and auxiliary attachment circuits on wheel loaders,all-terrain cranes,and large agricultural loaders.The Type Y free-flow gallery enables parallel circuit operation,allowing simultaneous actuation of multiple functions with independent speed control.

　　Mobile hydraulic equipment:Operates hydraulic functions on garbage compactors,drain machines,and material handling forklifts and stackers.The compact sectional design with 62 mm spool pitch reduces overall valve envelope,facilitating installation in space-constrained mobile equipment chassis.

　　Construction machinery:Provides directional control for excavator attachments,concrete pump booms,and drilling rig feed systems.The SD25 series supports manual,pneumatic,hydraulic,and electro-hydraulic control options,enabling integration with both basic lever-operated systems and advanced proportional control architectures.

　　Industrial presses and compactors:Controls hydraulic clamping,pressing,and ejection cylinders.The 315 bar maximum pressure rating supports high-force applications,while the internal leakage specification of 4 cm³/min at 100 bar minimizes energy loss during load-holding phases.

　　Selection Guidance

　　Suitable applications:

　　Hydraulic systems requiring 240 L/min nominal flow and up to 315 bar operating pressure with manual lever control

　　Open-center hydraulic circuits where parallel spool operation with load check protection is required

　　Mobile and industrial equipment demanding field-configurable valve stacks with power beyond capability

　　Systems operating within-15°C to+80°C hydraulic fluid temperature range with ISO 4406-/19/16 contamination control

　　Applications requiring pilot-operated main relief valve performance with 250 bar pressure setting

　　Not recommended for:

　　Closed-center load-sensing systems requiring pressure-compensated flow control.Select the Walvoil SDS150 or SDS180 series instead—these platforms provide pressure compensation for load-independent flow sharing across multiple functions.

　　Applications requiring flow rates below 45 L/min.The SD25 is optimized for high-flow applications.For lower flow requirements,consider the Walvoil SD8 series with 80 L/min nominal flow or the SD6 series with 45 L/min capacity.

　　Electro-hydraulic proportional control without manual lever backup.The SD25 series supports electro-hydraulic actuation options,but the SD25/2/AC(XG-250)/28L/18L/RC is configured for manual lever operation only.Specify alternative spool actuation codes when proportional control is required.

　　AC power switching or pneumatic control signals.This hydraulic valve requires hydraulic pilot pressure or manual mechanical input.For pneumatic actuation,specify pneumatic control kit configurations.

　　FAQ

　　1.What are the dimensions and weight of the Walvoil SD25/2/AC(XG-250)/28L/18L/RC?

　　The assembled valve measures approximately 90 mm in height,62 mm spool pitch per section(total width approximately 124 mm for two spools),and 200 mm in depth.Weight is approximately 16 to 18 kg for the complete 2-spool assembly.Contact Beijing Zhongping Technology for exact dimensional drawings and certified shipping weight.

　　2.What is the delivery time and lead time for the Walvoil SD25/2/AC(XG-250)?

　　Manufacturer standard lead time is 6 to 8 weeks for built-to-order sectional valve assemblies.Beijing Zhongping Technology maintains inventory of common SD25 configurations and components for expedited assembly and shipping within 2 to 3 weeks.

　　3.Is the Walvoil SD25/2/AC(XG-250)/28L/18L/RC in stock?

　　We stock the inlet,spool,and outlet components required to assemble this configuration.The complete valve is assembled to order with component availability confirmed at time of quotation.Contact Beijing Zhongping Technology for current stock status and assembly lead time.

　　4.How much does the Walvoil SD25/2/AC(XG-250)/28L/18L/RC cost and what is the price range?

　　The Walvoil SD25 sectional valve assembly typically ranges from$1,200 to$2,200 USD depending on configuration complexity,spool selection,and order quantity.Prices fluctuate due to exchange rates,tariffs,and factory adjustments.For an accurate quotation,contact Beijing Zhongping Technology directly.

　　5.What do the spool codes 28L and 18L indicate on the Walvoil SD25?

　　The 28L and 18L codes are Walvoil spool type designations indicating specific flow metering characteristics for double-acting cylinder control.The 28L spool provides higher nominal flow capacity;the 18L spool provides lower flow capacity.Exact spool performance curves are available in the Walvoil SD25 technical catalog.

　　6.What payment terms do you accept for purchasing the Walvoil SD25/2/AC(XG-250)?

　　We accept bank wire transfer(T/T)and major credit cards.For qualified corporate accounts,Beijing Zhongping Technology offers net 30 payment terms upon credit approval.

　　7.How do I install the Walvoil SD25/2/AC(XG-250)and what hydraulic connections are required?

　　The valve mounts in any orientation using the integrated mounting brackets.Hydraulic connections are G 3/4 inch BSPP threads for inlet,outlet,and service ports.Tie rods must be torqued to 50 N·m during assembly.Beijing Zhongping Technology provides installation documentation including port identification diagrams and torque specifications.

　　8.What is the return policy and warranty period for the Walvoil SD25 sectional valve?

　　We provide a 1-year warranty against manufacturing defects for Walvoil hydraulic valves.Returns require prior authorization and are evaluated on a case-by-case basis.Valves assembled to customer-specific spool configurations are non-returnable except for warranty claims.Beijing Zhongping Technology processes RMA requests within 48 business hours.

　　9.What are the spare parts availability and service support for the Walvoil SD25 series?

　　We maintain inventory of SD25 series components including inlet elements,working sections,outlet elements,tie rod kits,seal kits,and replacement spools.Beijing Zhongping Technology provides technical support for valve troubleshooting,spool identification,and field service recommendations.

　　10.What is the HTS code,customs duty,and import tariff for importing the Walvoil SD25/2/AC(XG-250)?

　　The HTSUS code is 8481.20.00 for hydraulic directional control valves.International shipments are dispatched under Incoterms CPT(Carriage Paid To),with duties,customs fees,and applicable VAT payable by the buyer at time of delivery.Beijing Zhongping Technology provides commercial invoices and packing documentation required for customs clearance on all export orders.