There are several potential causes for leakage in a globe valve:
Seat and Disc Wear: Over time, the sealing surfaces of the valve seat and disc can wear due to friction and repeated operation. This wear can create gaps or uneven surfaces that allow fluid or gas to leak through the valve.
Improper Installation: Incorrect installation procedures, such as insufficient tightening or improper alignment of the valve components, can lead to leaks. If the valve is not properly aligned, the seating surfaces may not make adequate contact, resulting in leakage.
Damaged or Defective Seals: Globe valves often utilize seals or gaskets to ensure a tight seal between the valve body, bonnet, and other components. If these seals become damaged, worn, or deteriorated, they may fail to provide an effective seal, causing leaks.
Over- or Under-Tightening: Incorrect adjustment of the valve packing or gland can contribute to leakage. If the packing is too loose, the valve may leak when closed, while excessive tightening can lead to excessive friction and premature wear, also resulting in leaks.
Corrosion or Erosion: Corrosive fluids or environments can cause damage to the valve body, seat, or disc, leading to leaks. Similarly, erosion from high-velocity flows or the presence of solid particles in the fluid can wear away the sealing surfaces, compromising the valve's integrity.
Thermal Expansion and Contraction: Extreme temperature changes can cause the valve components to expand or contract at different rates, affecting the tightness of the seal. This can result in leakage, especially if the valve is not designed to handle thermal expansion properly.
High Operating Pressure: Excessive pressure within the system can cause the valve to leak, particularly if it exceeds the valve's rated pressure capacity. The increased force exerted on the sealing surfaces may overcome the valve's ability to maintain a tight seal.
It's important to identify the specific cause of leakage in a globe valve to determine the appropriate corrective actions. Regular maintenance, proper installation, and selecting valves suitable for the operating conditions can help minimize the risk of leaks.
