The main components are impeller, pump shell and shaft seal device.

1 the impeller
The impeller's role is to transfer the mechanical energy of the prime mover directly to the liquid, so as to increase the static pressure energy and kinetic energy of the liquid mainly to increase the static pressure energy.
The impeller generally has 6~12 backward curved blades.
 
The open impeller has no cover plate on both sides of the blade, which is simple to manufacture and convenient to clean. It is suitable for conveying materials containing a large number of suspended solids, with low efficiency and low liquid pressure.
Semi-closed impeller has no cover plate on one side of the suction inlet, and a cover plate on the other side. It is suitable for conveying materials that are easy to precipitate or contain particles, and the efficiency is low.
The closed impeller has front and rear cover plates on both sides of the impeller blade, which has high efficiency and is suitable for conveying clean liquid without impurities.
The general diesel pump impeller is this kind.
Impeller has single suction and double suction two suction methods.

2 the pump
The function is to close the impeller in a certain space, so that the action of the impeller inhalation and pressure out of the liquid.
Pump shell made of volute shape, it is also known as the volute.
As the cross-sectional area of the flow passage gradually expands, the velocity of the high-speed liquid thrown around the impeller gradually decreases, so that part of the kinetic energy is effectively converted into static pressure energy.
The pump shell not only collects the liquid thrown out by the impeller, but also serves as an energy conversion device.

3 Diesel pump shaft seal device
The function is to prevent the liquid in the pump shell from leaking along the shaft or the outside air from leaking into the pump shell.
The commonly used shaft seal device has two kinds of packing seal and mechanical seal.
The packing is usually made of asbestos rope soaked in oil or coated with graphite.
The mechanical seal mainly depends on the movable ring installed on the shaft and the static ring fixed on the pump shell between the end face for relative movement to achieve the purpose of sealing.