In Brief
Schwing uses an open hydraulic circuit with an S-valve controlled by a directional valve – simpler than Putzmeister’s closed circuit, but requiring precise diagnostics when pressure faults occur. The most common issues are hydraulic valve failure, main pump leakage and oil overheating. The BP 600 is the workhorse for mid-size sites; the BP 1400 is built for high-pressure, large-volume projects. PHS Magnum offers mobile Schwing service up to 200 km – tel. +48 602 716 551.
Schwing Hydraulic System – How It Works
Effective diagnostics of Schwing pump faults requires a clear understanding of the hydraulic architecture. What sets Schwing apart from Putzmeister or Cifa is, above all, its control philosophy.
Open Hydraulic Circuit
Schwing trailer pumps and many boom pumps use an open hydraulic circuit. In simple terms:
- Hydraulic oil circulates from the tank through the hydraulic pump to the directional control valve, then to the actuators or motor, and back to the tank
- Working pressure is generated on demand by a piston or gear pump
- S-valve switching is controlled by a separate hydraulic circuit (typically pilot-operated or electro-hydraulic)
The open circuit has one clear diagnostic advantage: pressure can be measured at several key points in each sub-circuit, making it straightforward to pinpoint which side of the system has lost pressure.
Closed Hydraulic Circuit (Putzmeister HSP) – For Comparison
Putzmeister’s BSF series uses a closed hydraulic circuit with a multi-piston Hydrostatic Servo Pump (HSP). In this arrangement the oil circulates in a closed loop between the pump and the hydraulic motor, with no contact with the tank during operation. This is more energy-efficient and allows more precise flow control, but demands higher oil cleanliness and is more costly to overhaul – HSP service is specialist work.
Variable-Displacement Hydraulic Pumps on Newer Schwing Models
Newer Schwing machines are fitted with variable-displacement hydraulic pumps controlled either by a frequency inverter or a hydraulic servomechanism (load-sensing). The system adjusts pump output to match instantaneous demand – lower energy consumption at idle, less heat build-up in the oil.
This matters for servicing: wear patterns in load-sensing circuits differ from those in fixed-displacement systems, and diagnostics require knowledge of the specific control characteristics.
Common Schwing Pump Faults
1. Hydraulic Valve Failure – S-Valve Control Circuit
The S-valve (S-tube) changes the direction of concrete flow between the cylinders. Switching is driven by two hydraulic actuators. The most common problems:
- Valve fails to switch – possible causes: loss of pilot pressure (check control circuit pressure), faulty solenoid valve, mechanical blockage (a piece of concrete or stone lodged in the switching zone)
- Slow switching – leaking control actuator, contaminated oil, blocked control filter
- Noise during switching – cavitation in the control circuit, low oil level, or blocked suction filter
Diagnostics: measure pilot pressure at the test points near the S-valve (Schwing labels these M1, M2, etc.) and compare against the service manual values.
2. Main Pump Leakage (Hydraulic Pump)
The piston hydraulic pump fitted to Schwing machines (Rexroth, Sauer-Danfoss, Linde) develops internal leakage after many operating hours or if the oil becomes contaminated.
Symptoms:
- The concrete pump fails to reach rated pressure even though the actuators are intact
- Hydraulic oil heats up rapidly (the thermal energy equals the pressure loss through internal bypass)
- Irregular, pulsating piston movement at low engine speed
Diagnostics: carry out a pump pressure test at the dedicated test port. Pressure below specification indicates irreversible wear or damaged pump pistons.
3. Hydraulic Oil Overheating
The Schwing BP 600 can develop oil temperature problems under intensive operation (high pressures, dense concrete, continuous pumping). Typical permissible operating temperature is 60–70°C (80°C maximum under extreme conditions).
Causes of overheating:
- Blocked oil cooler (fins clogged with dust or concrete residue)
- Fault in the thermostatic circuit (hydraulic oil thermostat valve opening too early or too late)
- Internal leakage in the pump or hydraulic motor (energy converted to heat rather than movement)
- Low oil level (insufficient heat dissipation through the tank)
- Overpressure operation caused by a faulty relief valve
Diagnostics: use an infrared thermometer on the cooler inlet and outlet hoses. A temperature difference across the cooler of less than 5–8°C under normal load indicates an ineffective cooler.
4. Uneven Cylinder Wear
Like other manufacturers, Schwing uses replaceable cylinder liners. Highly abrasive concrete mixes (granite aggregate, TR0 class) accelerate liner wear. Tell-tale signs: increasing clearance between the piston and cylinder, and milky water in the water box.
Schwing BP 600 vs BP 1400 – Which Model for Which Application?
| Parameter | BP 600 | BP 1400 |
|---|---|---|
| Max. output | approx. 60–70 m³/h | approx. 100–140 m³/h |
| Concrete pressure | up to ~85 bar | up to ~130 bar |
| Typical use | 1–4 storey buildings, foundations, slabs | high-rise, bridges, long pipelines, SCC |
| Kerb weight | approx. 2,800 kg | approx. 4,500 kg |
| Drive | diesel or electric | diesel or electric |
The BP 600 is the workhorse for small and medium contractors. The BP 1400 is a project machine for main contractors on large-scale contracts.
Mobile Schwing Service – PHS Magnum
PHS Magnum services Schwing pumps (trailer-mounted and boom-mounted) both on site and at the workshop in Chorula near Opole. Scope of service:
- Hydraulic system diagnostics (pressure measurement, oil analysis)
- Repair and replacement of hydraulic valves, actuators and main pumps
- Piston, cylinder liner and S-valve replacement
- TDT inspections
- Mobile service within 200 km: Opole, Katowice, Wrocław, Kraków, Legnica, Częstochowa
ISO 9001:2015 certified. Phone availability: +48 602 716 551 – response within 2 hours of your call.
Related: Pump service and maintenance · Pump repairs · TDT inspections · Putzmeister vs Cifa
