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This post was last edited by liuquan1100 on 2018-5-23 at 14:13. The feed water pump is an important auxiliary device for boilers, responsible for supplying water to the boiler during its operation. In the event of a leakage issue, the inspection process can be quite complicated. To address this problem, we will below introduce the common problems related to leakage in boiler feed water pumps and the methods for dealing with them. Solutions to leakage in the control valve of a boiler pump: 1. The method of adding sealing grease – For valves that do not currently use sealing grease, it is possible to add such grease to improve the sealing performance of the valve stem. 2. Adding packing: To improve the sealing performance of the packing around the valve stem, the method of adding more packing can be employed. Typically, a dual-layer or multi-layer mixed packing structure is used; simply increasing the number of elements, for example from 3 to 5, does not yield significant results. 3. Graphite packing replacement method: The widely used PTFE packing has an operating temperature range of –20 to +200°C. When the temperature fluctuates significantly between these limits, its sealing performance declines markedly; it ages quickly and has a short lifespan. Flexible graphite fillers can overcome these disadvantages and have a long service life. As a result, some factories have replaced all PTFE packing with graphite packing; even the control valves of newly purchased boiler pumps have their PTFE packing replaced with graphite packing before use. However, the hysteresis is large when using graphite fillers, and some systems even exhibit crawling behavior at first; this must be taken into consideration. 4. Change the flow direction, with P2 located at the end of the valve stem. When △P is large and P1 is also high, sealing P1 is clearly more difficult than sealing P2. Therefore, the method of changing the flow direction can be adopted, by moving P1 to the valve stem end and P2 to the other end; this is particularly effective for valves with high pressure and large pressure differences. For example, with bellows valves, sealing P2 should usually be taken into consideration. 5. Use the lens gasket sealing method for the sealing of the upper and lower covers, as well as for the sealing between the valve seat and the upper and lower valve bodies. In the case of a flat seal, its sealing performance is poor under high temperature and pressure, leading to leaks; using a lens gasket for sealing can yield satisfactory results. 6. Replace the gaskets: To this day, most gaskets are still made of asbestos sheets; under high temperatures, they have poor sealing performance and a short lifespan, which leads to leaks. In such cases, wound gaskets or ring gaskets can be used as alternatives; many factories are already adopting them. 7. Tighten the bolts symmetrically and use thin washers for sealing. In the structure of boiler pump control valves with ring seals, when thick gaskets with significant deformation (such as wound gaskets) are used, uneven compression and force distribution can easily lead to damage, misalignment, and deformation of the seal, severely affecting its sealing performance. Therefore, when maintaining or assembling such valves, the compression bolts must be tightened symmetrically (be careful not to tighten them all at once). It would be better if thick gaskets could be replaced with thin ones, as this makes it easier to reduce the inclination and ensure a good seal. 8. A method to increase the width of the sealing surface in order to prevent the flat valve core from jumping during closure and to reduce leakage. Leakage in flat-type valve cores: Flat-type valve cores (such as those used in two-position valves or sleeve valves) lack guiding and positioning surfaces within the valve seat. As the valve operates, lateral forces act on the valve core, pushing it from the inlet side toward the outlet side. The greater the clearance between the valve core and the valve seat, the more severe this one-sided movement becomes. Additionally, deformation, misalignment, or a small chamfer on the sealing surface of the valve core (usually a 30-degree chamfer is used for guidance) can cause the chamfered end of the valve core’s sealing surface to come into contact with the valve seat’s sealing surface when the valve is nearly closed. This results in the valve core jumping during closure, or even failing to close properly, thereby increasing leakage. The simplest and most effective solution is to increase the size of the sealing surface on the valve stem, so that the minimum diameter of the end face of the valve stem is 1–5 mm smaller than the diameter of the valve seat; this provides sufficient guidance to ensure that the valve stem fits into the valve seat and maintains good contact between the sealing surfaces. There is a leak in the outlet section of the high-pressure feed water pump for the boiler. The mechanical seal is the main cause of leakage in such pumps, but it is itself a highly precise component that requires high standards in terms of design, machining, and assembly quality. When using mechanical seals, it is necessary to analyze various factors related to their use, so that the seals can meet the technical requirements of different pumps as well as the requirements of the fluids being handled, and have adequate lubrication conditions; only in this way can long-term reliable operation of the seals be ensured. Leakage at the outlet section is a common issue with boiler feed water pumps. If it’s not a leakage in the pump casing, then it’s likely that the pump’s mechanical seal is damaged and cannot maintain a sealed environment for the water. In such cases, the solution is to repair or replace the mechanical seal; in most cases, it is the damaged mechanical seal that causes the pump to leak. In fact, mechanical seals are not that easy to damage – they tend to get damaged due to sand present in the water. Another reason could be the failure to release air from the pump during its first operation, as air inside the pump can also lead to damage to the mechanical seal. Solution: 1. There is a leak at the pipe connection; if it’s a newly installed unit, the issue is likely minor. Measure: Remove and reinstall. 2. When the water pump pumps water, leakage occurs; usually it is the water seal that leaks. Solution: Disassemble the water pump and replace the water seal. 3. If the water pump leaks continuously, it may be because a check valve has not been installed on the water inlet side of the pump. Measure: Install a check valve. Leakage at the shaft end of the boiler feed water pump: 1. Replace the packing. As mentioned earlier, since leakage at the shaft end is mainly caused by wear of the shaft sleeve, replacing the packing does not resolve the leakage problem fundamentally. Its function is merely to fill and compress the worn part of the shaft sleeve with filler, which can only provide a temporary solution to the water leakage problem. 2. Wear-resistant shaft sleeves are used; the removed pump is disassembled and replaced with shaft sleeves made of wear-resistant materials. However, these shaft sleeves require a long processing time and are expensive, so in light of the company’s efforts to reduce costs, this solution is not the preferred option. How to prevent leaks in boiler feed water pumps: 1. Clean the water pipes before starting up the pump, and check whether the water quality is suitable for its operation. 2. Be sure to open the vent hole before starting up the pump in order to remove air from inside it. Finally, there’s another clever trick: when installing a mechanical seal, adding an additional O-ring can also extend its lifespan.