Slip On Flanges are widely used in pipeline systems of the chemical, water supply, and drainage industries due to their convenient installation and controllable cost. However, mistakes are often made under pressure, medium, and installation environment during selection, leading to safety issues. Below are key points to avoid pitfalls from three dimensions:
1. Pressure Dimension: Do Not Ignore Operating Condition Redundancy
Common pitfalls: Selecting flanges based on rated pressure while ignoring pressure fluctuations, without reserving 10%-20% redundancy; confusing nominal pressure (PN) with working pressure and neglecting temperature impact-for example, a PN16 flange at 20°C will have its allowable working pressure reduced to PN10 at 150°C; choosing low-cost, thin-walled flanges for medium-low pressure pipelines, ignoring the matching of neck strength.
Solutions: Determine the allowable pressure according to GB/T 9124, accounting for pressure fluctuations and temperature. Select materials based on pressure levels-carbon steel is suitable for PN16 and below, while stainless steel is appropriate for PN25.
2. Medium Dimension: Prevent Material-Medium Incompatibility
Common pitfalls: Assuming carbon steel is compatible with all media, while acidic media or media containing chloride ions easily cause corrosion (e.g., carbon steel flanges for hydrochloric acid transportation and 304 stainless steel flanges for seawater transportation both tend to corrode); neglecting temperature impact on corrosion resistance-for instance, 316L flanges are prone to intergranular corrosion when exposed to alkalis above 200°C; mismatching sealing surfaces with media.
Solutions: Select materials with reference to GB 50235 based on the chemical properties and temperature of the medium-316L for acidic media and carbon steel with anti-corrosion coating for alkaline media; choose sealing surfaces according to medium characteristics.
3. Installation Environment Dimension: Adapt to the Environment to Prevent Hidden Risks
Common pitfalls: Inadequate protection against climatic corrosion for outdoor flanges (carbon steel flanges without anti-corrosion treatment tend to rust, and plastic insulation layers age easily under sun exposure); selecting flanges with inappropriate dimensions for narrow spaces, leading to difficult installation and uneven bolt torque; no anti-loosening measures for vibrating environments (flanges at pump outlets without anti-loosening are prone to leakage within 3-6 months).
Solutions: Apply hot-dip galvanizing and anti-corrosion paint to outdoor carbon steel flanges. For high-temperature environments, use PTFE insulation layers. Choose compact flanges for tight spaces, ensuring to reserve an operational gap of at least 50 mm. In vibrating environments, utilize anti-loosening bolts with thread-locking adhesive, and install elastic gaskets simultaneously.
In summary, slip on flange selection requires comprehensive consideration of pressure, medium, and environment, as well as accurate matching of parameters and protective designs to ensure stable operation of the pipeline system.
