What a Dual-Line Metering Valve Does
The SDPQ is a dual-line metering valve. It mounts on the two distribution mains of a dual-line system and doses grease to each outlet on every pressurization cycle. When one main pressurizes, the piston strokes and every outlet on that side discharges its set volume in parallel; when the reversing valve swaps the mains, the piston strokes back and the outlets on the other side discharge. This differs from a progressive divider, where outlets feed one after another in sequence. A visible indicator pin rises and falls with the piston stroke so an operator can confirm the valve cycled.
Code note: dual-line metering valves in this family appear under several letter codes — SDPQ and SSPQ both circulate in parts lists for dual-line metering valves of this type. If your list cites SSPQ, the dual-line metering valve on this page is the match to check first.
SDPQ Specifications
| Item | Declared value |
|---|---|
| Outlet counts | 2, 4, 6, 8, or 12 outlets |
| Adjustable discharge | 0.2-6.0 mL per outlet per cycle |
| Operating pressure range | 40-400 bar |
| Temperature range | -20°C to +80°C |
| Inlet connection | G3/8 |
| Outlet connections | G1/4 |
| Grease grades | NLGI 0 to 2 |
| Body | carbon steel, zinc plated |
| Seals | NBR standard, FKM optional |
The 400 bar maximum sits above the 31.5 MPa (315 bar) output of the SDRB-N grease station, so the valve ceiling clears the pump output it is commonly paired with.
How the Two Mains Alternate
A dual-line system has two distribution mains that a reversing valve pressurizes in turn. While main one carries pressure, the SDPQ pistons stroke toward the vented side and the outlets on the pressurized side discharge in parallel. When the line finishes, pressure rises and the reversing valve swaps the mains; main two pressurizes and the opposite outlets discharge on the return stroke. Each outlet therefore receives one dose per full cycle of both mains. The 40 bar minimum matters: the pump must reach at least 40 bar to generate the shift force that strokes the piston.
Setting Outlet Volumes and the Indicator Pin
Each outlet adjusts independently across 0.2-6.0 mL per cycle, so heavy and light points on the same valve can receive different volumes. Set an outlet with its adjusting screw, catching and measuring the discharge over counted strokes until the delivered volume matches what the point needs. The indicator pin rises and falls with the piston stroke: it proves the valve stroked, not how much volume moved, so treat it as a cycle witness rather than a flow meter.
Choosing Outlets and Connections
Order the valve with the number of outlets you need, from 2 up to 12, rather than planning to blank unused ports in the field. The inlet is G3/8 while the outlets are G1/4: the supply side bore is larger than the delivery side, matching a single supply line feeding several delivery lines. Confirm the port thread forms on both sides when ordering, and consider one size up if future points are likely, since spare outlets avoid a second manifold later. If you are unsure which outlet count fits your point count, ask through our quote request page.
Related Dual-Line Components
The mains are alternated by the DR4-5 hydraulic reversing valve, with the SYP reversing valve covering the family principle. Because a cycling valve does not prove delivery, an end-of-line YCK pressure switch closes the loop. Electrically shifted systems use the 24EJF-P valve. For single-line systems, the metering injector principle lives on the metering unit page.
Frequently Asked Questions
How do the two mains work?
The reversing valve pressurizes the two mains in turn. While one main pressurizes, its side of the valve discharges; then the mains swap.
Can each outlet be set separately?
Yes, each outlet adjusts across 0.2-6.0 mL per cycle. Set each screw to the volume its lubrication point needs.
What does the indicator pin prove?
It proves the piston stroked, so the valve cycled. It does not show how much volume moved past the seal faces.
Can unused outlets be blanked?
Order the outlet count you need: 2, 4, 6, 8, or 12. Choosing one size up leaves spare outlets for future points.
Which grease grades can it handle?
The valve handles NLGI 0 through NLGI 2. Grade 0 is softer than grade 2, and softer grades stroke more easily.
How is dual-line feeding different from progressive feeding?
Dual-line outlets discharge in parallel when a main pressurizes. Progressive dividers feed one point after another in sequence; see the metering unit page.
Why are the inlet and outlet bores different?
The inlet is G3/8 and the outlets are G1/4. The supply side is larger, matching one supply line feeding several deliveries.
Why is there a 40 bar minimum pressure?
The pump must reach at least 40 bar to shift the piston. Below that, the valve does not stroke and no outlet discharges.
Can the valve meter oil too?
It is declared for grease NLGI 0 to 2. For oil service, confirm suitability when ordering through our quote request page.
Who builds the SDPQ?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
