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Hydraulic Gear Pump Applications in Walking Beam Furnaces

 

 

Hydraulic gear pumps provide several important functions for the fuel delivery and dispensing systems of walking beam furnaces. As a fuel oil transfer device, gear pumps send fuel oil that’s stored in the day tanks located in the processing facility’s yard to the heating and pumping unit (HPU) of the walking beam furnace. From the HPU, hydraulic gear pumps dispense fuel to the furnace’s burner where the oil is mixed or atomized with air and finally sprayed into the furnace compartment. In addition, gear pumps have a secondary function as an excess oil pump. Any excess oil at the furnace’s burner is fed back to the suction line of the pump where it is first filtered and then redirected back to the burner.

Furnace Operation

In general, walking beam furnaces are a type of continuous, reheating furnace used in the steel industry. They get their name from the moving or walking beams that transport the steel stock from the charge side to discharge end of the furnace. The walking beams are cycled by means of a hydraulic drive system that uses both lifting/lower hydraulic cylinders as well as travel hydraulic cylinders to hydraulically move the support beams. The lifting cylinder raises the steel stock to rest on fixed beams/ridges while a travel cylinder moves the beam forward a distance equal to the length of the cylinder’s stroke, which is generally about one meter. After this is accomplished, the lifting cylinder lowers the steel stock to the fixed beam as the traveling cylinder retracts to its original position to start the transport cycle again.

Gear Pumps: Types and Features

Hydraulic gear pumps are positive, fixed displacement pumps that employ a meshed gearing system that increases pressure to force fluid through the pump. They are known for being simple in design and inexpensive to maintain and operate. Gear pumps are a very common type of hydraulic pump and noted for their ability to withstand high pressures and to pump fluids of high viscosity. They are commonly used for fluid transfer, lubrication, pressure boosting, filtering, pressure spraying, among other applications. There are two basic types of gear pumps: internal and external. External gear pumps are often used in fluid transfer applications because they have the benefits of high speed, no overhanging bearing loads, and quiet operation. Since external gear pumps are machined with close tolerances and designed with bearings to support the unit on both sides of the pump, they can handle pressures of about 3,000 psi. Internal gear pumps are typically used for thin fluids, such as solvents and fuel oil. They have the benefits of a wide viscosity and temperature range (up to 750°F / 400°C) few moving parts, smooth discharge, bi-directional, and self-priming. They also can run dry for limited periods of time. Constructed with spur, helical, herringbone gears, they pump by carrying fluid from the intake to the discharge end of the pump. Spur gear pumps are most suited to pumping light oils and they are the most cost-effective. Herringbone gear pumps are most suited for viscous fluids. Some gear pumps have built-in pressure relief valves for pump or motor protection.