What Is the SYP Hydraulic Reversing Valve
The SYP hydraulic reversing valve is a mechanically self-actuated switching layer for dual-line lubrication systems. It changes which main line receives flow using line pressure alone: no external signal, no solenoid, no PLC command. When pressure in the active line reaches the preset value, the valve shifts and the other line becomes active. Two models cover the common range: SYP-220 and SYP-455, both rated to 40 MPa. The body integrates what is traditionally a two-component arrangement, a pressure indicator plus a separate directional valve, into one housing. It suits dual-line lubrication systems where reliable mechanical changeover matters more than electronic control.
Within the family, each device has a distinct role. The YCK pressure valve senses pressure and signals. This SYP valve switches mechanically on pressure. The electric directional valve switches on controller command. The end-of-line pressure unit displays end-of-line pressure.
Technical Specifications
Both models share the same operating principle and pressure rating, and differ mainly in flow capacity, port size, minimum switching pressure, and weight. Switching pressure is adjustable across the stated range on each unit.
| Parameter | SYP-220 | SYP-455 |
|---|---|---|
| Type | 4-way 2-port two-position | 4-way 2-port two-position |
| Max operating pressure | 40 MPa (400 bar) | 40 MPa (400 bar) |
| Rated flow | 220 ml/min | 455 ml/min |
| Minimum flow | 50 ml/min | 100 ml/min |
| Switching pressure range | 1-35 MPa, adjustable | 1.5-35 MPa, adjustable |
| Pressure loss at rated flow | No more than 0.3 MPa | No more than 0.3 MPa |
| Ports | G1/2 inch BSP | G3/4 inch BSP |
| Medium | Grease or oil, NLGI 0-2 | Grease or oil, NLGI 0-2 |
| Operating temperature | -20°C to +80°C | -20°C to +80°C |
| Body material | High-strength steel | High-strength steel |
| Seals | NBR standard, FKM optional | NBR standard, FKM optional |
| Weight | 6.8 kg | 11.7 kg |
| Mounting | Inline or 4-bolt flange | Inline or 4-bolt flange |
How the Valve Switches
Operation follows four phases. First, Line I is active and pressure builds as lubricant fills the line and injectors discharge. Second, when line pressure overcomes the spring preload, the spool shifts and flow is redirected. Third, Line II becomes active and pressure builds there in the same way. Fourth, the return switching occurs when Line II reaches the preset value, shifting back to Line I.
The handwheel sets the switching pressure. Turning it clockwise increases the preset pressure; turning it counterclockwise decreases it. Two pressure gauges on the body show both line pressures, so you can watch the switching event directly and confirm the setting. An optional proximity switch or stroke switch bracket provides a signal for PLC cycle monitoring, while the switching action itself remains purely mechanical.
SYP-220 vs SYP-455
Select by flow first. Sum the maximum simultaneous metering valve output in one main line, add 20 percent margin, then pick the model whose rated flow exceeds that figure. If the total lands under 220 ml/min, SYP-220 is the match, with G1/2 inch BSP ports and a 6.8 kg body. Above that, SYP-455 covers up to 455 ml/min with G3/4 inch BSP ports and an 11.7 kg body. Minimum switching pressure is 1 MPa on SYP-220 and 1.5 MPa on SYP-455, which matters on low-pressure systems.
| Selection Point | SYP-220 | SYP-455 |
|---|---|---|
| Rated flow | 220 ml/min | 455 ml/min |
| Minimum flow | 50 ml/min | 100 ml/min |
| Minimum switching pressure | 1 MPa | 1.5 MPa |
| Ports | G1/2 inch BSP | G3/4 inch BSP |
| Weight | 6.8 kg | 11.7 kg |
Installation
Connect the P port to the pump outlet, the R port to the reservoir, and the I and II ports to the two main lines. Mount the valve so the handwheel stays accessible and both gauges can be read. After connecting, set the switching pressure roughly 10 to 15 percent above normal operating pressure, then run three to five switching cycles to verify that changeover occurs cleanly in both directions and that no connections weep. Full system guidance is available in the dual-line lubrication systems section.
What Is Supplied
Each order includes the reversing valve in the selected model, SYP-220 or SYP-455, with NBR seals fitted as standard and FKM available as an option. The proximity switch or stroke switch bracket for PLC cycle monitoring is optional and must be confirmed at ordering.
Frequently Asked Questions
How do I choose between SYP-220 and SYP-455?
Compare your calculated flow against rated flow, port size, and minimum switching pressure. SYP-220 suits lower flows with G1/2 inch ports.
How does it switch without electricity?
A spring-loaded spool holds position until line pressure overcomes the preload. The shift then redirects flow to the other line.
Can it integrate with a PLC?
An optional proximity switch or stroke switch bracket provides a cycle signal to a PLC. The mechanical switching action stays fully independent.
What switching pressure should I set?
Set it 10 to 15 percent above normal operating pressure. Too low leaves lubrication points starved; too high overworks the pump.
Are maximum system pressure, switching pressure, and minimum flow the same value?
No, they are three separate values. Max pressure is 40 MPa, switching pressure is adjustable, minimum flow 50 or 100 ml/min.
What happens if the valve sticks?
One line keeps pressurizing while the other starves of lubricant. Inspect for blockage and relieve pressure before servicing.
How does the handwheel work?
Clockwise raises the preset switching pressure and counterclockwise lowers it. Set it unloaded first, then fine-tune while the system runs.
What do the dual gauges show?
They display pressure in both main lines at once. You can watch the switching event and confirm the setting directly.
What does it save compared with a pressure unit plus directional valve pair?
It removes wiring between components, reduces joints, and needs one adjustment. Commissioning is simpler and the footprint smaller.
Who builds the SYP reversing valves?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
For model selection or switching pressure setup, contact us for a quote. You can also request a quotation with your flow figures.
