Concrete pump S-valves (S-tubes, S-transfer tubes) · the swinging pipe in a two-cylinder piston pump that connects each delivery cylinder to the outlet in turn, changeover cylinders, wear adjustment, and alternative valve designs
In a two-cylinder piston pump, an S-valve is the S-shaped pipe inside the hopper. It swings between the two delivery cylinders so that the cylinder on its pressure stroke always feeds the outlet and delivery line, while the other cylinder draws material from the hopper. Before ordering one, know three things: which pump model and hopper it must fit, what material it will carry and at what pressure, and which wear parts come with it.
S-shaped transfer tubes (S-valves) and their wear parts for two-cylinder piston pumps that move concrete and similar thick materials. Complete pumps, booms, delivery pipe and other valve types are outside this page except where compared.
01
CIFA, a concrete pump maker, explains that concrete is discharged from the mixer truck into the pump hopper; from there, two cylinders working alternately draw the material in and push it through the delivery pipeline to the pouring point. Schwing, another maker, writes that “The most important component of a two-piston concrete pump is the concrete valve”: under high pressure it switches between the two delivery cylinders and should make the flow from the cylinders into the outlet as friction-free as possible. [1] [2]
Putzmeister describes its KOS pump, a two-cylinder piston pump for thick materials with a high solids content. The pump has a hopper, two hardened delivery cylinders with one piston each, and an S-transfer tube that connects the delivery cylinders to the outlet flange. Two plunger cylinders switch the S-tube over, and two hydraulic cylinders drive the delivery pistons. That page covers sludge and waste pumping, but its description of the S-tube arrangement matches the concrete-pump layout described above. [3]
Give the supplier the pump make, model and serial number, the hopper and outlet flange, the delivery cylinder size, the material pumped and its maximum aggregate size, the delivery pressure, the changeover cylinder and shaft details, and which wear parts you need with the tube.
02
Schwing writes that wear is particularly high in the concrete valve because concrete passes through it into the outlet under high pressure. For the S-tube on its KOS pump, Putzmeister states that the tube can be adjusted for wear so that the wear parts last longer, and that all moving parts are connected to a central grease lubrication system. [2] [3]
Putzmeister also lists reinforced S-pipes, and S-pipe pistons that shear off foreign bodies, as features for materials containing foreign bodies. It adds an automatic reverse-pumping function that prevents and clears blockages. [3]
03
SANY's trailer concrete pump pages give maximum output pressure and output, with two paired values for some models. The HBT5008C-6Y has 66 kW engine power, 8 MPa maximum output pressure and 55 m³/h maximum output. The electric HBT6013C-5 has 90 kW and lists 8/13 MPa with 65/40 m³/h, the higher output going with the lower pressure. The HBT9028CH-5S has 2 × 180 kW and lists 19/28 MPa with 95/70 m³/h. [4] [5] [6]
The SANY pages do not state which valve type each model uses; they show the pressure and output range a valve on such pumps must handle. Compare with the S-tube and ROCK valve descriptions and the wear notes above. [1] [2] [3]
Editorial calculation: 28 MPa is 280 bar, 3.5 times the 8 MPa of the smallest model; on the HBT9028CH-5S, switching from 95 to 70 m³/h raises pressure from 19 to 28 MPa, so pressure × output stays between 1,805 and 1,960 MPa·m³/h across the two listed pairs.
| SANY trailer pump | Engine power | Max. output pressure | Max. output |
|---|---|---|---|
| HBT5008C-6Y | 66 kW | 8 MPa | 55 m³/h |
| HBT6013C-5 (electric) | 90 kW | 8/13 MPa | 65/40 m³/h |
| HBT9028CH-5S | 2 × 180 kW | 19/28 MPa | 95/70 m³/h |
Give the valve supplier the pump model, its maximum concrete pressure and output, cylinder diameter and the concrete mix, and ask which S-tube, wear plate and cutting ring set is rated for that pressure.
04
Not every two-cylinder concrete pump uses an S-tube. Schwing says its pumps use its ROCK valve, which it developed after negative experiences with the S-pipe. Schwing states that at the most heavily loaded point the ROCK valve has concrete sliding on concrete rather than on steel, that its straight design makes cleaning easier, and that it has fewer wear parts than other concrete valves. These are one maker's claims about its own design. [2]
Wear parts are specific to the valve type, so confirm which valve your pump uses before ordering spare parts.
05
Putzmeister's KOS pump description supplies the changeover and lubrication rows; Schwing and CIFA add the wear and hopper context.
| Part | Role | Fix in the order |
|---|---|---|
| S-transfer tube | Connects the active delivery cylinder to the outlet. [3] [2] | Pump model; outlet flange. |
| Changeover (plunger) cylinders | Swing the S-tube between cylinders. [3] | Cylinder and linkage fit. |
| Delivery cylinders and pistons | Draw in material and push it out alternately. [1] [3] | Bore; stroke. |
| Hopper | Receives the material that is fed in. [1] [3] | Hopper type. |
| Wear parts | High wear at the valve; the tube is adjustable for wear. [2] [3] | Parts included; replacement interval. |
| Lubrication | Central grease system for the moving parts. [3] | Manual or automatic. |
06
Only the pressure-and-output row carries numbers, from SANY's trailer pumps; the other rows say what to confirm against your pump's drawing.
| Field | What it means and published information | Ask the supplier for |
|---|---|---|
| Pump fit | The tube sits between the hopper, the delivery cylinders and the outlet. [3] | Model and serial number; drawing. |
| Material | Concrete; also sludge and waste on KOS pumps. [1] [3] | Aggregate or particle size. |
| Pressure | The valve switches under high pressure. [2] | Rated delivery pressure. |
| Wear | Wear in the valve is high; the tube can be adjusted for wear. [2] [3] | Wear-part list; material. |
| Valve type | S-tube, or alternatives such as Schwing's ROCK valve. [2] | Confirm the valve type. |
| Pump pressure and output | Examples: 8 MPa, 55 m³/h (HBT5008C-6Y); 19/28 MPa, 95/70 m³/h (HBT9028CH-5S) (SANY). [4] [6] | Max. concrete pressure the valve must hold. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Pump: [make; model; serial number] Fit: [hopper; outlet flange; cylinder bore] Material: [concrete mix; maximum aggregate size; other media] Duty: [delivery pressure; output] Parts: [tube; wear ring/plate; seals; bearings] Documents: [drawing; material certificate]
1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.
Its website lists S-tube assemblies, S valves and spectacle plates for concrete pumps.
Product scope checked 2026-10-12
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It connects whichever delivery cylinder is on its pressure stroke to the outlet, so that two cylinders working alternately keep material moving into the delivery line. [3] [1] [2]
On Putzmeister's KOS pump, two plunger cylinders switch the S-tube between the delivery cylinders. [3]
No. Schwing says its pumps use its ROCK valve, a different design. [2]
Sources checked 2026-10-12. CIFA, Schwing and Putzmeister make concrete pumps and describe their own equipment; their statements are maker descriptions, not independent tests. SANY's three trailer pump pages supply the pressure and output figures.
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