What Is a KCB Gear Pump?

What the KCB Design Consists Of

KCB is a classic designation for external gear pumps used widely in oil transfer, covering a family of similar machines rather than one manufacturer's model. The standard construction:

• The casing — a close-fitting housing, usually cast iron for clean oil service, carrying the suction and discharge ports.
• Two external gears — a driven gear coupled to the shaft and a matching idler, running with small controlled clearances.
• Bearings and shafts — the driven shaft transmits motor power while the idler shaft rotates freely.
• Shaft seals — mechanical seals or packed glands keep oil inside the pump.
• An integral relief valve — fitted on many KCB-type pumps to protect the pump and piping if the discharge line is closed while running.

How a KCB Gear Pump Works

The operating principle is positive displacement. As the gears rotate out of mesh on the suction side, the tooth spaces open and oil is drawn in, then carried around the gears in the tooth pockets — trapped between the teeth and the casing wall — and squeezed out through the discharge port as the teeth mesh again at the centre. Flow is proportional to speed and almost independent of discharge pressure, and the pumped oil itself does the internal sealing, which is why gear pumps suit naturally lubricating liquids. The KCB gear pump working principle article covers these phases in more detail.

Where KCB Gear Pumps Are Used

KCB-style external gear pumps appear wherever clean, lubricating liquids must be moved at moderate pressure with a compact, simple machine:

• Lubricating oil systems — circulating lube oil to bearings, gearboxes and machine tools.
• Fuel oil supply — feeding burners and boilers and transferring diesel and light fuel oils.
• Heavy and viscous oil transfer — moving heated fuel oil and heavy oils that must stay fluid at the suction.
• Hydraulic and process oil duties — oil transfer and circulation where the liquid is clean and solids-free.

Duty-specific guidance sits in the fuel oil, lubricating oil and heavy-oil articles, and the step-by-step KCB gear pump selection procedure ties them together.

Strengths and Limits of the KCB Type

The KCB gear pump earns its place through simplicity, compactness and cost: few moving parts, high pressure in a small package, self-priming within its vacuum limit, and steady flow as discharge pressure rises.

The limits matter just as much. Gear pumps need clean liquid — abrasive solids wear the gears and casing, and free water destroys internal sealing and corrodes parts. They shear the product more than lobe or screw rotors, and the meshing gears should not run dry. For gentle or solids-laden duties a rotary lobe pump fits better; for very high viscosity and large flows an industrial screw pump competes; for thin, non-lubricating liquids a centrifugal pump is the wrong family entirely.

Model Availability: Confirm the Current Range

KCB-type pumps are covered on this site as a technical-reference topic rather than a listed product series, so specific flow, pressure and motor figures are not published here. Where a number would be needed — required flow, discharge pressure, viscosity at pumping temperature — confirm current model availability and specifications with Qingdao Green Power before procurement, and request the performance curve for the exact duty point.

Frequently Asked Questions