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Hydraulic Power Packs Used in Walking Beam Furnaces

Hydraulic power packs are the source of pressurized hydraulic fluid that powers the operation of hydraulic valves and actuators used in the operation of walking beam furnaces. They primarily provide hydraulic power to drive for the vertical and lateral movement of the beam structure that carries the steel slabs, sheets or billets through the furnace for processing. In some walking beam furnace designs, the power packs will provide power to hydraulic motors that drive the steel billet ejector mechanism.

Construction

Hydraulic power packs are built in several configurations. Some are simply a pump-and-motor unit with a reservoir. Others are self-contained units that can be attached the rear of the furnace. Hydraulic power packs generally consist of a storage tank, a hydraulic piston pump and its drive (i.e., an electric motor), a strainer at the pump inlet, a relief/shut off valve, a pressure gauge, filters, a manifold block at the pressure outlet, and return & drain line piping. In some applications, the pump is mounted within the reservoir to provide improved suction as well as a reduction of audible noise. The pump can also be mounted externally, which provides greater convenience for servicing. Another variation of hydraulic power pack construction is having a redundant, spare pump that upon failure of the main pump will automatically be switched on. Hydraulic power packs are typically rated for up to 500 bar (7,250 psi) with flow rates up to 1,200 lpm. The storage tank can hold capacities up to 12,000 liters. It is worth noting that hydraulic power packs have a wide range of applications beyond walking beam furnaces including steel mills, machine tools, hydraulic presses, material-handling, pipe mills, hot & cold rolling industries, and construction.

Hydraulic System

The present day designs of walking beam furnaces use a hydraulic positioning system to move the steel slabs or billets through the furnace. Steel billets rest on stationary beam of the charge side of the furnace. The billets are conveyed through the furnace in a "walking” motion by first powering hydraulic lift cylinders that pivot bell cranks to lift the billet above the stationary beams of the walking beam furnace. Then a lateral movement, hydraulic cylinder pushes the billets for the distance of the cylinder’s stroke, generally no more than a meter. In the next part of the “walking” cycle, the vertical movement cylinder then lowers the moving beam. When the stationary and moving beams are of equal height, the steel billet now rests on the fixed beams or one stroke ahead of where it had been located. The lateral movement cylinder is retracted and the transport cycle is repeated again. The hydraulic cylinders or actuators used in walking beam furnaces vary with furnace design. But they can single- or double- acting cylinders capable of withstanding high temperatures and pressures. They are typically made of sharpening steel, medium hardened steel or cast iron. The hydraulic power packs of walking beam furnace are fairly easy to maintain. The primary maintenance task of powder packs is the cleaning or replacement of the oil filters. Topping of the power’s packs storage tank is another regular maintenance task along with verifying the proper operation of the power pack’s thermostat and cleaning the blowers of the pumps.