The ASLD 2200 is a fully automatic sludge blanket level detector primarily designed for the water and waste water industry but could be applied to other types of process. It utilises a servo-driven sensor which continually tracks the settled interface and produces a 4-20 mA output which is proportional to the depth of the blanket.

A range of sensors are available to allow the ASLD to work on a variety of settlement tanks. All the sensors are of the infrared gap type, the normal sensors selections are:

  Nominal Range 0-1,500 mg/l: Final or Secondary Settlement Tanks
  Nominal Range 0-10,000 mg/l: Primary Settlement Tanks
  Nominal Range 0-30,000 mg/l: Sludge Thickeners.

The use of infrared attenuation as the principle of operation for the sensor allows Partech to ensure sufficient sensitivity to monitor sludge blankets in a wide variety of applications. It should be noted that sensor selection can be site dependent, Partech are happy to provide full support in the selection of the correct sensor.

Provision must be made for transmission of the output signal to the control system; this is normally possible via spare slip rings. Where this is not possible a radio telemetry option is available, allowing transmission directly to the control system without the need for installation of cables.

The ASLD 2200 has a number of key parts that are integrated into a single system that must to be mounted on the bridge of the settlement tank to ensure reliable operation.

The basic principle of operation is that the sensor cable is wound on a motorised drum. Initially the sensor will be in the clear supernatant at the top of the tank. The electronics will direct the motor to move the sensor downward to find the interface. Once the sensor meets the interface the sensing path becomes obscured which in turn causes the motor to withdraw the sensor until the sensor is just clear of the interface. The sensor will now follow the top of the interface as it rises and falls.

In application where the scraper or Picket Fence moves independently of the bridge the ASLD 2200 can accept control input to automatically raise and lower the sensor. Specific application advice from Partech is recommended before carrying out this type of installation.

Compatible Sensors

  Soli-Tech 20 Sensor
  Infrared Sensors