Analysis of the causes of packing leakage in piston compressors and solutions

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It is normal for there to be leaks in the packing of piston compressors; a small amount of leakage is carried away by the nitrogen sealing system. However, when the leakage volume exceeds what can be handled by this system, the packing material can enter the crankcase along with the piston rod. Since the crankcase is equipped with a breather cap that allows air exchange, this creates an environment within the crankcase where hydrogen can accumulate and explode, posing serious safety hazards. I. Causes of leakage
1. Issues with the assembly of packing seal rings
1) Incorrect installation sequence: Packing seal rings include radial rings, tangential rings, flow-restricting rings, etc. If these are installed in the wrong order, it can lead to seal failure. 2) Improper clearance: An excessive clearance between the seal ring and the end face of the stuffing box can lead to gas leakage ； If the gap is too small, the packing seal ring expands due to heat generated by friction during operation, and it becomes impossible to form a sealing chamber; in addition, abnormal wear can lead to failure of the seal. 2. Packing gland installation issues: 1) Inadequate tightening: If the packing gland is not properly tightened within the chamber, it can lead to leakage between the packing gland and the chamber. 2) Installation skew: An incorrect installation of the stuffing box can also lead to leakage between the stuffing box and the chamber. 3. Issues with the packing ring itself
1) Inappropriate material and configuration: Using an unsuitable material or an unreasonable configuration for the packing ring may result in poor sealing performance. For example, the three-stage packing seal of a new hydrogen compressor experienced multiple leaks in succession due to issues with the material of the packing rings and their arrangement. 2) Prolonged storage time: If the packing ring is stored for too long, the primary seal made of non-metallic materials may deform, resulting in a poor fit with the piston rod and thus leakage. 3) Fatigue corrosion: Under the influence of periodic alternating loads such as high temperature and pressure, the impact from the reciprocating motion of the piston, and friction over a long period, the packing seal ring is prone to fatigue failure and malfunction. 4. Piston rod issues 1) Surface roughness: A high surface roughness of the piston rod increases frictional wear with the packing seal, thereby affecting the sealing performance. 2) Ovality: Ovality in the piston rod may result in poor contact between the packing ring and the piston rod, thereby causing leakage. 5. Cooling system issues 1) Blockage in the cooling water channels: A blockage in the cooling water channels of the stuffing box prevents heat from being dissipated promptly, resulting in failure of the packing seal. 2) Incorrect machining dimensions of the cooling water jacket: The chamfer dimensions of the inner hole of the cooling water jacket do not match those specified in the design drawings, which may affect the cooling effect of the packing seal and thus lead to leaks. 6. Lubrication issue: Insufficient oil supply to the packing ring prevents effective lubrication and cooling of the packing ring and piston rod, which leads to accelerated wear of the packing ring and a decline in its sealing performance. 7. Other factors: 1) Excessively long maintenance intervals: Packing seals are vulnerable components; if the maintenance interval for the compressor is too long, the packing seal will exceed its service life, leading to leaks. 2) Abnormal gas pressure: Excessively high gas pressure or large pressure fluctuations increase the load on the packing seal, which may lead to leaks. II. Solutions 1. Proper assembly of the packing seal rings 1) Install the radial ring, tangential ring, flow-blocking ring, etc., in the correct order to ensure good fit between all the seal rings. 2) Strictly control the gap between the sealing ring and the end face of the packing box to meet the design requirements. 2. Proper installation of the stuffing box: 1) Ensure that the stuffing box is firmly secured within the cavity to prevent it from loosening. 2) When installing the stuffing box, ensure its coaxiality with the chamber to avoid skewing. 3. Optimize the material and combination of the packing ring: 1) Select an appropriate material for the packing ring based on the specific operating conditions of the compressor. For example, the material of the pressure reduction ring can be changed from a single PTFE ring to a combination of a more wear-resistant PEEK ring and a bronze ring. 2) Reasonably adjust the combination of packing rings to improve sealing performance. 4. Inspection and repair of the piston rod 1) Check the surface roughness of the piston rod; if it does not meet the requirements, it must be ground or replaced. 2) Check the ellipticity of the piston rod; if it exceeds the allowable range, correction or replacement is required. 5. Maintenance of the cooling system: 1) Regularly clean the cooling water channels in the stuffing box to prevent blockages. 2) Check the machining dimensions of the cooling water jacket to ensure they meet the design requirements. 6. Adjust the oil injection amount appropriately: Based on the operating conditions of the compressor, adjust the amount of oil injected into the packing ring so that it meets the requirements for lubrication and cooling without causing waste of lubricating oil. 7. Shorten the maintenance cycle: Perform maintenance on the compressor according to the specified schedule, and replace the vulnerable packing seal components in a timely manner. 8. Control the gas pressure to ensure it remains within the designed range, avoiding excessive pressure or large fluctuations.