Diesel Engine Water Pump

Types of Units
A. Horizontal single-stage centrifugal pumps, double-suction pumps, and multi-stage pumps use a foot valve to fill the system with water before starting the diesel water pump unit. (Filling the system with water is cumbersome, and after use, the connection between the foot valve and the pipeline is filled with water, making disassembly difficult.)  
B. Self-priming pumps: Add a small amount of water to the pump chamber, then start the diesel engine water pump to expel air from the pipeline before filling with water. (During operation, air purging is often delayed to achieve rapid water supply.)  
C. Centrifugal pump or double-suction pump combined with a vacuum priming pump set, using two diesel engines to establish two independent systems: ① diesel engine centrifugal pump or double-suction pump; ② installing a small single-cylinder diesel engine vacuum pump set on the basis of the diesel centrifugal pump or double-suction pump to serve as a vacuum priming device to achieve rapid water supply. (Advantages include fast water supply speed, etc., with two systems operating.
D. Centrifugal pumps or double-suction pumps with built-in vacuum priming devices use a single diesel engine to drive the water pump and vacuum priming device. After rapid water supply, the priming device can be quickly shut off with a single button. This water supply system eliminates the need for a single-cylinder diesel engine while effectively saving space.
E. The self-propelled diesel engine water pump is modified from a standard agricultural vehicle, enhancing the mobility and flexibility of the pump truck. This addresses the drawbacks of conventional trailer-mounted systems, such as poor manoeuvrability and limited mobility. The system is based on a vacuum priming power unit driven by the vehicle's engine, providing vacuum assistance to enhance water intake speed.

Machine Selection
1. Fixed diesel engine water pump
When selecting a fixed diesel engine water pump unit, it is generally recommended to choose a standard centrifugal pump unit with a horizontal inlet and vertical outlet. Ensure proper alignment and use a base with reinforcement devices to prevent vibration during operation. During pipeline installation, the weight should not be placed on the pump. When using a clutch-type system, install a check valve to prevent reverse rotation and impeller detachment when the pump stops. In special operating conditions, it is recommended to use larger pump shafts and bearings to extend the service life of the pump set.
2. Towed mobile diesel engine water pump  
When selecting a mobile diesel engine water pump set, it is advisable to avoid using a horizontal inlet and vertical outlet configuration. While horizontal inlet and vertical outlet centrifugal pumps and self-priming pump sets maintain good concentricity when the unit is not in operation, However, the mobile trailer itself has a height difference between the upper and lower sections. When the suction pipe is full of water during use, it can cause uneven stress on the suction and discharge pipes, leading to excessive stress on the coupling during operation and accelerating pump set damage. It is recommended to use a horizontal inlet and outlet diesel engine water pump unit.
3. Self-propelled diesel engine water pump  
The self-propelled diesel engine water pump is modified from a standard agricultural vehicle, enhancing the mobility and flexibility of the pump truck. This addresses the limited manoeuvrability of conventional trailer-mounted systems.

Installation and Use Instructions
The proper installation of a diesel engine water pump has a significant impact on the pump's operation and lifespan, so it must be installed with great care. The installation of a diesel engine water pump unit must follow the following steps:  
1. Installation
(1) After the diesel engine water pump unit is positioned, (before positioning the unit, the following checks must be conducted on the foundation elevation and orientation of the diesel engine water pump) leveling and alignment must be performed first (coupling alignment should be based on the pump shaft centreline, with the engine position adjusted for alignment). The coaxiality deviation at the coupling interface should be within 0.05 millimetres, and the axial clearance between the shaft couplings (Note: For multi-stage pumps, the clearance should be adjusted after radial positioning) should be 4–8 millimetres. The parallelism deviation of the coupling can be measured using a feeler gauge, with the end face clearance tolerance within 0.05 millimeters.
(2) Pipe connections: Whether fixed or mobile, diesel engine water pumps should have their own pipe supports. Avoid placing the weight of the pipes on the pump to prevent misalignment of the unit and resulting faults. When the diesel engine water pump is shut down, backflow can cause the pump to reverse, so a check valve must be installed. Installing an outlet gate valve during the operation of the diesel engine water pump effectively prevents the pump from operating under overload conditions, ensuring normal flow and parameters. The valve assembly sequence is: pump outlet – gate valve – check valve. Flexible connectors must be installed at the inlet and outlet ends of the diesel engine water pump. The inlet end is installed at the pump inlet, and the outlet end is connected after the gate valve and check valve.
2. Starting, Stopping, and Operation
(1) Check whether the diesel engine water pump rotates smoothly. Open the gate valve on the discharge pipeline by 1/4, fill the pump with priming water (except for vacuum priming), start the engine, and after the engine reaches normal speed, gradually open the gate valve on the discharge pipeline and adjust to the required operating conditions. When the gate valve on the discharge pipeline is closed, the pump must not operate continuously for more than 3 minutes.