Control

Control system

The hydraulic system pressure, which is proportional to the scroll torque and can be directly used as a control variable. For this reason, it is possible to achieve very high operational readiness and operating safety of the drive using suitable control engineering measures.

There are two control models:

Digital control enables a manually adjustable, fixed differential speed that boosts the differential speed to the maximum value when the previously set pressure (scroll torque) is exceeded. The point at which the differential speed increases, known as the pressure threshold P1, is infinitely adjustable.

Analogue control enables a manually adjustable, fixed differential speed (base differential speed ∆n) and a gradual increase in the differential speed as the pressure (scroll torque) rises. The point at which the differential speed increases, known as the pressure threshold P1 is variable and the regulation stiffness α can also be adjusted.

The hydraulic system pressure is also used as a direct and precise control variable.

Both analogue and digital control units are equipped with safety shutdown mechanisms in cases of high torque P2 and very high torque P3. These situations are reported by pressure switches (adjustable) and set to boost pump shutoff at P2 and bowl drive shutoff at P3.

A pressure relief valve protects the system from overloads to prevent damage to the scroll drive due to overtorque. This happens at a value higher than P3, and the maximum torque at the scroll is retained. In this situation, the bowl drive is switched off, the rotational speed of the bowl drive is reduced and the decreasing G-forces cause the scroll to start rotating again. This can prevent the machine from getting blocked or unblock it.

Electronically controlled drive systems

Depending on the type of electronic equipment used, the following operating parameters are either only displayed or displayed and controlled. It is also possible to process the measured operating parameters using an interface device and to control the transmitted data using a PLC control system. This enables simple integration into a larger control system via standardised fieldbus interfaces.

The operating parameters are as follows:

• Hydraulic system pressure in bar (pressure sensor)
• Bowl speed in rpm (speed sensor)
• Differential speed in rpm (speed sensor)
• Additional measured values (oil temperature, level, vibration etc.)

<br/> The benefits of having an electronic control system are manifold:

• When the differential speed is returned, extremely low differential speeds are possible (differential speed monitoring in a closed control loop)
• Operating hours of the ROTODIFF, maintenance interval indicator
• Utilization of additional regulation parameters is possible (vibration, feed rate, flocculation and so on)
• Integration capability into a superior control system.

There are two different electronic regulation systems available

VFD pump unit

VFD control system => Automatic, analogue control, electronic with frequency converter

An electronic pressure sensor is mounted on the control block of the pump unit with frequency converter (VFD). This sensor transmits the measured system pressure (torque) to the electronic display, control or interface unit.

Among other components, the system includes a pump with constant displacement. The necessary variation in the displacement (and, as a result, the rotational speed) to the ROTODIFF scroll drive, is achieved by adjusting the pump speed. The pump speed is regulated using a suitable frequency converter. As the differential speed is proportional to the conveyed oil quantity, automatic control is possible without any problems. The measured system pressure is proportional to the torque and can be directly used as a control variable. Similarly to the delivery torque of the scroll and, as a result, the solids loading of the bowl, the differential speed can be automatically adapted with a high degree of accuracy.

B/C pump unit

B/C control system => Automatic, analogue control, electronic with proportional throttle valve

An electronic pressure sensor is mounted on the control block of the B/C pump unit. This sensor transmits the measured system pressure (torque) to the electronic display, control or interface unit.

A proportional throttle valve, also mounted on the control block of the B/C pump unit, controls the oil flow to the ROTODIFF scroll drive. Actuation to the proportional throttle valve corresponds directly with the oil flow, which is directed to the ROTODIFF drive motor.

Hydrostatic regulation systems

The hydrostatic regulation control block uses the direct feedback of the pressure or torque into the system as a control variable. The default control values are set using 3 hydrostatic adjusting components. The two emergency functions P2 and P3 are set at the manometer pressure gauge switch. Hydrostatic regulation systems are easy to operate and extremely durable.

C pump unit

C control system => Automatic, analogue control, hydraulic

Decanter bowl and scroll drive system

Control system

In the fully hydraulic pump units, we work with two working circuits that are independent of each other.

In the case of the scroll drive circuit, the control unit corresponds to that of the standard scroll drive. There are two control models, digital and analogue. Depending on the application, the control system is also available in an electronic or hydraulic version.

The working circuit of the bowl drive is equipped with an infinitely variable rotational speed control system, which can be designed as an electronic or a hydraulic version.

VH-E-B/C fully hydraulic units

Control chart

VH-E-VFD fully hydraulic units

Control chart