Pvbs, Main Spools For Flow Control (Standard); Pvbs, Main Spools For Flow Control (With Linear Characteristics); Pvbs, Main Spools For Pressure Control - Danfoss PVG 32 Service Manual
Proportional valve group
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- Technical information (76 pages) ,
- Service manual (15 pages) ,
- Application manual (13 pages)
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Service Manual
PVG 32 Proportional Valve Group
Operation
PVBS, main spools for flow control (standard)
PVBS, main spools for flow control (with linear characteristics)
PVBS, main spools for pressure control
12 |
©
Danfoss | February 2017
PVMF
P
B
F
(Standard assembly)
P
A
F
(Optional assembly)
When using standard flow control spools, the pump pressure is determined by the highest load pressure.
This is done either via the pressure adjustment spool in open center PVP (fixed displacement pumps) or
via the pump regulator (variable displacement pumps).
In this way the pump pressure will always correspond to the load pressure plus the stand-by pressure of
the pressure adjustment spool or the pump regulator.
This will normally give optimum and stable adjustment of the oil flow.
PVBS main spools with linear characteristic have less dead band than standard spools and a completely
proportional ratio between control signal and oil flow in the range beyond the dead band.
W
Warning
PVBS with linear characteristic must never be used together with PVEM electrical actuators.
The interaction between the small dead band of the spools and the hysteresis of the PVEM actuator of
20% involves a risk of building up a LS pressure in neutral position.
In a few systems load sensing pump pressure may result in unstable adjustment of the oil flow and a
tendency towards system hunting. This may be the case with working functions that have a large
moment of inertia or over-center valves. In such systems main spools for pressure control can be
advantageous. The spools are designed in such a way that the pump pressure is controlled by the spool
travel. The main spool must be displaced until the pump pressure just exceeds the load pressure before
the working function is applied.
If the main spool is held in this position, the pump pressure will remain constant – even if the load
pressure changes – giving a stable system.
The use of pressure control spools, however, also means that:
•
the oil flow is load dependent
•
the dead band is load dependent
•
the pump pressure can exceed the load pressure by more than is usual.
11039167 | AX00000031en-US0301
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Troubleshooting
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Questions and answers
После нескольких поворотов катка гидравлика уходит в аварию при перезагрузке снова срабатывает несколько раз и останавливается в аварии.
The Danfoss PVG 32 hydraulic system could go into fault mode after several turns of the roller due to the following possible causes:
1. Contamination in Hydraulic Oil – Dirt or debris in the oil can affect valve operation.
*Check*: Take an oil sample.
*Corrective Action*: Flush the system and refill with clean, filtered fluid per OEM specifications.
2. Air in Hydraulic Pilot Lines – Air trapped in the signal lines can cause unstable operation.
*Check*: Inspect for air in the signal lines.
*Corrective Action*: Bleed air from the hose connection at the valve section.
3. Low Hydraulic Oil Supply – Insufficient oil can cause pressure drops and improper function.
*Check*: Verify fluid level in the reservoir.
*Corrective Action*: Refill with clean, filtered fluid per OEM specifications.
4. Faulty Hydraulic Remote Actuator – A malfunctioning actuator can lead to inconsistent valve response.
*Check*: Measure signal pressure from the remote hydraulic controller.
*Corrective Action*: Repair or replace the actuator.
5. External Hydraulic Pilot Pressure Too Low – If pressure is too low, the main spool may not function properly.
*Check*: Measure external pilot pressure from the pilot pump and check for restrictions.
*Corrective Action*: Ensure the pilot pressure meets the required specifications.
6. Leaking or Burst Supply Hose – A damaged hose can lead to pressure loss and system faults.
*Check*: Inspect supply lines to the valve stack.
*Corrective Action*: Repair or replace damaged hoses.
These potential causes should be systematically checked and corrected to restore proper system operation.
This answer is automatically generated