What Is the YCK Differential Pressure Switch
The YCK-P5/SG-A is a differential pressure switch built for dual-line centralized lubrication systems. It watches the pressure difference between the two main lines and closes an electrical contact when that difference reaches the set value. That contact signal tells the pump controller it is time to reverse the flow direction. The switch is the sensing layer of the system: it senses and signals, but it does not move any flow by itself. In the same family, the SYP hydraulic reversing valve switches mechanically on pressure, the 24EJF-P electric directional valve switches on a controller command, and the YKQ unit displays end-of-line pressure.
Technical Specifications
The table below lists the declared data for this model. Only these figures are published; anything not shown here should be confirmed with the supplier before an order is placed. The switch works with both grease and oil, and it is installed between the two main lines near the end of the run.
| Item | Value |
|---|---|
| Type | Differential pressure switch |
| Max pressure | 40 MPa (400 bar) |
| Output | Electrical switch signal |
| Lubricants | Grease and oil |
| System type | Dual-line centralized lubrication |
| Installation | Between the two main lines, near the end of the run |
| Model | YCK-P5/SG-A |
How It Works
In a dual-line system, one line carries pressure while the other is relieved. As lubricant travels through FL33 injectors and the rest of the circuit, the pressure in the active line rises and the difference between the two lines grows. The YCK-P5/SG-A monitors that difference continuously. When the difference reaches the set value, the switch closes its contact and sends an electrical signal to the pump controller. The controller then reverses the directional valve, so the previously active line becomes the relieved line and the other line takes over. The same signal also confirms that the cycle has completed. Because the switch reacts to the difference between the lines rather than to one absolute line pressure, it reflects the real condition of the circuit at the moment reversal is due.
Signal Wiring and System Matching
Wire the switch output to the pump controller so the signal both reverses the directional valve and confirms cycle completion. The switch is a discrete device: it reports that the set difference has been reached, not a continuous pressure value. Match it with the rest of the circuit so the reversal point suits the injectors and line length in use. In a full dual-line lubrication system, the switch works alongside the reversing valve and the end-of-line unit. Review the whole dual-line lubrication systems range to see how the parts combine.
Installation Notes
Mount the switch between the two main lines, toward the end of the run, where the pressure difference best represents the far side of the circuit. Keep the connection to each line short and direct so the switch reads the true difference. Route the wire output back to the pump controller along a protected path. After mounting, confirm the set differential when ordering, since the correct value depends on the circuit. Check that the switch body and fittings are seated correctly before pressurizing. Once the system runs, watch the first few reversal cycles to confirm the signal arrives at the expected point.
What Is Supplied
Each order includes the YCK-P5/SG-A differential pressure switch unit. Mounting fittings are confirmed at ordering, because the correct connections depend on the lines and the installation point in your circuit. Tell us your line arrangement when you request a quotation so the supplied parts match your system.
Frequently Asked Questions
How does the YCK differ from a regular pressure switch?
It measures the difference between the two main lines, not single-line pressure. A regular switch reacts to one line only.
Can it replace a pressure transmitter?
No, it provides a discrete contact signal rather than a continuous measurement. Use a transmitter where you need a live pressure value.
Where does the switch install?
It installs between the two main lines, toward the end of the run. That reflects the difference across the far side.
Is the differential value the absolute line pressure?
No, it is the difference between the two lines, not the absolute pressure. Confirm the set differential when ordering.
What happens if the switch fails?
Fail open: the controller keeps pumping past cycle end. Fail closed: a false confirmation masks a blocked line.
How does it differ from the YKQ monitoring unit?
The YCK signals reversal, while the YKQ displays end-of-line pressure. They serve different roles and can be used together.
Why do dual-line systems need this switch?
Dual-line systems must reverse flow at the right moment in each cycle. The switch provides the signal that sets that reversal timing.
Does it work with both grease and oil?
Yes, the declared compatibility covers both grease and oil. Confirm your lubricant when ordering.
What if the signal is left unwired?
Then there is no end-of-cycle confirmation and cycle control is lost. The controller cannot reverse on pressure difference.
Who builds the YCK-P5/SG-A?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
To confirm the set differential for your circuit, contact us for a quote or request a quotation with your line layout and controller type.
