Fire pumps are now widely used in many fields. Although there are many applications, many people feel that the fire pump is broken when they have some failures, and they will be helpless. The following is a brief summary of some common fault inspections of fire pumps.
First, the fire pump is not provided with liquid or the liquid supply and pressure are insufficient. This situation may occur because of the following places:
1. Check whether the pump casing of the fire pump and inlet pipeline is not filled with liquid, which causes the fire pump to not be filled with water or not properly vented first.
2. Check if there is air pocket or air leakage in the inlet pipeline
3. Check if the speed is too low due to incorrect motor wiring
4. Check whether the position of the outlet nozzle or pipeline pressure gauge is correct
5. Check whether the gap between the impellers is unqualified
6. Check whether the net pressure head currently used by the fire pump is worn.
7. Check the system’s water head for any loss caused by friction
8. Check whether the immersion depth of the foot valve or inlet pipe reaches the standard
9. Check the impeller and pipeline for obstacles
10. Check if there is an error in the direction of rotation
The impeller is an important component of the fire pump. The performance of the impeller directly determines the quality of the fire pump. In the routine maintenance of fire pumps, the maintenance of impellers is an important task. How should the impeller be maintained? The pump industry will explain the relevant knowledge of impeller maintenance.
1. When the impeller is found to have corrosion or trachoma, if the impeller is not severely corroded or there is not much trachoma, it can be repaired by repair welding. Copper impellers are repaired with brass, and cast iron impellers can also be repaired with brass.
2. The single-ring mouth ring hub of the impeller wears out groove marks, or when the phenomenon of partial wear is not serious, it can be polished with gauze, and it can also be polished if the thickness allows. Or you can use metal spraying to restore the original size.
3. The impeller’s double-ring-shaped inner ring sealing edge wears out, or if the uneven wear phenomenon is not serious, you can also use gauze to polish, if the thickness allows, you can also light. In case of severe wear or partial wear, the inner ring can be replaced with a new one.
4. The new impeller or repaired impeller shall be subjected to a static balance test. The spray pump impeller is balanced by the method of removing the fire pump weight. The experimental impeller can be placed on a milling machine, and the heavier side can be milled to the same weight as the object sandwiched by the lighter side during the balance test. However, the thickness milled on the impeller cover cannot exceed 1/3 of the thickness of the impeller cover, and it is allowed to be cut on the front and back covers. The cutting marks should be smoothly over the cover disc.
5. If the impeller has cracks, when repair welding is required, the method of repair welding is to clean the parts to be welded before welding to remove oil, rust, scale, etc. It can be preheated locally or globally at 250 ~ 450℃. Welding powder generally uses powder 30I +. Welding wire usually uses wire 224 silicon brass welding wire. Gas welding flame should use a slight oxidation flame or neutral flame. Pressure welding method is generally used during operation to reduce direct contact with the weld metal to avoid welding. Air holes are created in the seam metal. Insulation is slowly cooled after welding to eliminate stress and improve performance. After cooling, it can be machined.