The stability of a pressure vessel flange sealing system directly determines equipment operation safety. Seal failure is the most common type of fault in chemical and petroleum equipment. Under actual working conditions, flange sealing performance is affected by multiple factors including assembly parameters, accessory performance, flange body precision, structural rigidity, and working conditions. The five core influencing factors are analyzed in detail as follows:
1. Bolt Preload
Bolt preload is the core prerequisite for ensuring flange gasket sealing pressure. Proper preload enables the gasket to continuously maintain effective sealing specific pressure under equipment operating conditions, preventing medium leakage. If the preload is excessive, it will directly cause gasket extrusion deformation, crushing, or even extrusion failure, completely destroying the sealing structure. Meanwhile, the uniformity of preload distribution on the gasket end face also directly determines overall sealing performance. During actual installation, uniform preload distribution can be achieved by reasonably arranging the number of bolts and ensuring sufficient space for bolt disassembly, assembly, and tightening operations, avoiding sealing leakage problems caused by excessive local pressure or insufficient pressure.
2. Gasket Sealing Performance
The gasket is the core sealing component of the flange sealing system. Its material, elasticity, and compression resistance directly determine sealing reliability. A high-quality gasket suited to the working conditions can produce controllable elastic deformation under standard bolt preload, neither being crushed nor damaged, while fully filling the flange end face gaps. During equipment operation, under the influence of medium pressure, the flange sealing surface spacing undergoes slight changes. A gasket with excellent elasticity can adaptively deform, always fitting tightly against the flange end face, continuously maintaining a stable sealing state, and effectively preventing leakage faults caused by working condition fluctuations.
3. Flange Sealing Surface Characteristics
The structural type, machining precision, and surface quality of the flange sealing surface play a decisive role in sealing performance. Among these, the overall flatness of the flange end face and the coaxiality and perpendicularity of the sealing surface relative to the flange centerline directly affect the uniformity of gasket stress and determine the tightness of fit between the gasket and the sealing surface. Meanwhile, the surface roughness of the sealing surface must strictly match the usage requirements of the gasket material. Radial tool marks, scratches, cracks, and other defects are strictly prohibited on the end face to avoid poor gasket fit and local pressure loss caused by sealing surface defects, which ultimately lead to medium leakage.
4. Flange Rigidity
Insufficient rigidity of the flange body will cause bending and deformation under high-pressure operating conditions of the equipment, resulting in misalignment of the sealing surface contact and uneven stress distribution, ultimately leading to sealing failure. Flange rigidity is greatly affected by structural dimensions. Optimization methods such as increasing flange thickness and enlarging flange outer diameter can effectively improve the overall stiffness of the flange and reduce deformation deviation under working loads. A high-rigidity flange can evenly transfer bolt preload to the entire gasket face, forming uniform and sufficient sealing specific pressure, greatly improving the overall sealing stability of the flange joint.
5. Operating Conditions
The equipment operating temperature, operating pressure, and physical and chemical properties of the medium are key external factors affecting the long-term reliability of flange connections. As the operating temperature increases, the medium viscosity decreases and fluidity increases, greatly raising the probability of medium permeation and leakage; at the same time, high temperature intensifies the chemical activity of the medium, accelerating corrosion, dissolution, and aging of the gasket and flange sealing surface. In addition, high-temperature and high-pressure conditions can also cause creep deformation and stress relaxation of bolts, flanges, and gaskets, leading to attenuation of the previously precise preload and insufficient sealing specific pressure, making sealing failure highly likely after long-term operation.
