Hydraulic Solenoid Valve
Precise Load Control with the Hydraulic Solenoid Valve PPDB-LDN Hydraulic systems that lift and lower heavy loads need special protection. Without proper control, a falling load can outrun the pump, causing cavitation, loss of control, or dangerous dropping. The hydraulic solenoid valve from Flying Bull (Model PPDB-LDN) is a pilot-operated balance valve – also known as a motion control valve or over-center valve – designed to prevent over-speeding of loads in construction machinery and industrial equipment. The PPDB-LDN hydraulic solenoid valve allows free flow from the directional valve to the load (port 2 to port 1). However, it controls flow in the opposite direction (port 1 to port 2) using a direct-acting, pilot-assisted relief valve. The pilot assist at port 3 reduces the effective setting of the relief valve at a rate determined by the pilot ratio. This means when the load tries to run away, the valve creates back pressure to hold it back – but when the operator commands lowering, the pilot pressure opens the valve proportionally. Key technical features: Load control – The valve prevents over-speed of the load during lowering. It acts as a counterbalance valve, holding the load in place when the directional valve is in neutral. Setting recommendation – The balance valve setting should be at least 1.3 times the maximum induced pressure from the load. This ensures the valve stays closed when it should, without creeping. Adjustment – Turn the adjustment clockwise to reduce the setting and release the load. The valve is set clockwise to less than 200 psi (14 bar) from the factory. Back pressure effect – Any back pressure on port 2 (tank line pressure) increases the effective relief setting by a factor of 1 plus the pilot ratio multiplied by the back pressure. Keep tank lines unrestricted. Reset percentage – When set to standard, the valve resets (re-seats) at more than 85% of the set pressure. Setting below standard may result in a lower reset percentage – meaning the valve may not close fully after opening. Leakage – The valve does not have a forward seal in the pilot section. A small amount of leakage (1000 psi at 70 bar, 45 ml/min) passes between ports 2 and 3 during normal operation. This is normal and does not indicate a defect. Seal compatibility – Spools equipped with EPDM seals are for systems containing phosphate ester fluids (fire-resistant hydraulic fluids). Do not use EPDM seals with petroleum-based oils – the seals will swell and fail. For standard mineral oil, use standard seals. Installation options: The valve can be installed directly into a cavity machined into the actuator housing (cylinder or motor). This provides better protection and increases circuit stiffness by eliminating external hoses between the valve and actuator. Two types of check valve opening pressure are available: use 25 psi (1.7 bar) for general applications unless you are concerned about cavitation in the actuator. All three-port counterbalance, load control, and pilot-operated check valves are physically interchangeable for a given cavity size (same flow path, same cavity). Corrosion-resistant versions are available: suffix /AP (external stainless steel parts) for corrosive environments, or suffix /LH (external galvanized nickel parts) for moderate corrosion protection. Flying Bull’s hydraulic solenoid valve PPDB-LDN is 100% brand new, manufactured in Zhejiang, China, and backed by a 1‑year warranty. Delivery takes 5–7 working days. Choose Flying Bull for reliable load control in hydraulic systems.
Product Introduction
Products Description
OE NO.: PPDB-LDN |
Media: Oil |
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Warranty: 1 YEAR |
Condition: New, 100% Brand-new |
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Place of Origin: Zhejiang, China |
Power: Hydraulic |
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Brand Name: FLYING BULL |
Quality: High-Quality |
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Delivery: 5-7 Working Days |
Pressure: Ordinary Pressure |
Pressure guiding check valve PPDB-LDN
Balance valves with pilot AIDS are used to control overloading. The hydraulic Solenoid Valve allows free flow from the direction valve to the load, while the direct acting pilot auxiliary relief valve controls the flow from port 1 to port 2. The pilot auxiliary device at port 3 will reduce the effective setting of the safety valve to rotate at a rate determined by the pilot ratio.
Other names for the valve include motion control valves and eccentric valves.
The setting value of the balance valve should be at least 1.3 times the induced pressure of the large load.
Rotate the adjustment clockwise to reduce the setting and release the load.
The hydraulic solenoid valve PPDB-LDN is set clockwise to less than 200 psi (14 bar).
The back pressure on the oil port 2 increases the effective pressure relief setting by a ratio of 1 plus the lead ratio multiplied by the back pressure.
When the valve is set to standard, reset more than 85% of the set pressure. Setting below the standard setting pressure may result in a reduced reset percentage.
The valve does not have a forward seal in the pilot section and will operate at 1000 psi (45 ml/min) between ports 2 and 3. @70 bar) pressure through 3in³/ min. When pass. And leak test of valve cylinder assembly.
Spool equipped with EPDM seal can be used in systems containing phosphate ester solution. Exposure to petroleum-based liquids, oils and lubricants can damage seals.
The hydraforce Valve Replaced the counterweight box can be installed directly into the cavity machined in the actuator housing to increase protection and increase the stiffness of the circuit.
There are two types of check valve opening pressure. Use 25 psi (1.7 bar) pressure for inspection unless there is concern about cavitation in the actuator.
All three-port counterweight, load control, and pilot open check spool are physically interchangeable (i.e., same flow path, same chamber for a given rack size).
Corrosion resistant cartridge valves are intended for use in corrosive environments and are identified by type code suffix/AP (for external stainless steel parts) or by type code suffix/LH (for external galvanized nickel parts).
Company Introduction
Frequently Asked Questions (FAQ)
1. What is the model number and basic function of this valve?
The model number is PPDB-LDN. This is a pilot-operated balance valve (also called a motion control valve, over-center valve, or counterbalance valve). It controls over-speed of a falling load while allowing free flow in the opposite direction.
2. How does the PPDB-LDN hydraulic solenoid valve work?
The valve allows free flow from the directional valve to the load (port 2 to port 1). Flow in the opposite direction (port 1 to port 2) is controlled by a direct-acting, pilot-assisted relief valve. Pilot pressure at port 3 reduces the relief setting proportionally, so the valve opens only when the operator commands lowering – preventing the load from running away.
3. What is the recommended setting for a balance valve?
The valve setting should be at least 1.3 times the maximum induced pressure from the load. For example, if the load creates 2000 psi of pressure in the cylinder, set the valve to at least 2600 psi. This prevents load creep and ensures the valve stays closed when it should.
4. How does back pressure on port 2 affect the valve?
Back pressure on port 2 (tank line) increases the effective relief setting by a factor of 1 plus the pilot ratio multiplied by the back pressure. For example, if the pilot ratio is 3:1 and back pressure is 100 psi, the effective setting increases by 400 psi. Always keep tank lines as unrestricted as possible.
5. What is the difference between EPDM seals and standard seals?
EPDM seals are resistant to phosphate ester fluids (fire-resistant hydraulic fluids). They will be damaged by petroleum-based oils and lubricants – swelling and failing. Standard seals (nitrile or FKM) are for mineral oil. Always match the seal material to the hydraulic fluid. If unsure, consult your fluid supplier.
6. Can I install this valve directly into the cylinder housing?
Yes. The valve can be installed directly into a cavity machined into the actuator housing (cylinder or motor). This eliminates external hoses between the valve and actuator, increasing circuit stiffness and providing better protection against damage.
7. What is the normal leakage through this valve?
The valve does not have a forward seal in the pilot section. Normal leakage is 1000 psi (70 bar) at 45 ml/min (3 in³/min) between ports 2 and 3. This is not a defect – it is a design feature of pilot-operated balance valves.
8. Does the hydraulic solenoid valve PPDB-LDN come with a warranty?
Yes. Flying Bull provides a 1‑year warranty against manufacturing defects. Damage caused by contaminated fluid, incorrect seal selection (e.g., EPDM in mineral oil), improper adjustment, or overpressure is not covered. Always use the correct seal material for your hydraulic fluid.
9. Are corrosion-resistant versions available?
Yes. Use suffix /AP for external stainless steel parts in highly corrosive environments (marine, chemical, outdoor coastal). Use suffix /LH for external galvanized nickel parts for moderate corrosion protection.
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