Straw minnows:

Hydraulically driven pusher, which pushes the material from the dosing hopper through the water-cooled channel into the boiler box. A mixer mounted on the pusher ensures that the material is evenly spread. The pusher runs at a variable speed depending on the boiler load, which ensures even feeding of the fuel.

The water-cooled duct should ensure a "straw plug" between the pusher and the combustion grate, thus preventing false air intake. The pusher piston is equipped with emptying pistons, which are used at STOP of the plant, to ensure that the pusher is emptied of material and backfire is prevented.

The straw pusher is driven by a hydraulic unit which also operates fire dampers. The unit is equipped with an accumulator, so the fire damper can close in the event of a power failure.

Fire dampers:

The fire damper is installed between the pusher and the water-cooled duct for shut-off between the combustion on the grate and the pusher system. The function of the fire damper is to close in case of alarms or shutdown of the system, which could cause fire to migrate from the boiler to the pusher. The fire damper closes by means of two hydraulic cylinders pulling a heavy steel plate between the pusher and the water-cooled duct (1).

Water cooling and fire dampers:

The fire damper is equipped with water cooling which is activated by alarms after a set time when the fire damper must close for safety reasons. The water cooler is mounted down into the extension piece (3) and will spray water in via nozzles. Note: When working in the pusher or the water-cooled duct, red safety bolts must be fitted (2), as the fire damper hydraulics are equipped with accumulator and therefore have pressure on the cylinder of the fire damper. Furthermore, the pressure from accumulator to tank must be equalized by opening the valve from accumulator to tank at the hydraulic station.