Gouges can be caused by objects—such as a screwdriver, flange jack or chisel. All the paths of leakage are effectively blocked between the gasket and flange. This is accomplished when the bolt load compresses the gasket to a level of tightness that allows it to fill the gap between the mating faces and fill the small imperfections in the sealing surfaces. However, depending on the force that created them, they can be deep. Protrusions above the serrations are not permitted anywhere on the raised face. The acceptance criteria are based upon a comparison against ASTM reference radiographs, which are rated 1 through 5 (best to worst). The RPL of the imperfection shall not exceed the values given in Table 3. Flange Dimension Tolerances, Dimension Table, ASME B16.5 Flanges. With regular maintenance and removing old, stuck-on gasket\debris, flanges with scratches, pits, dents and dings are a common site in many a plant. Subscribe to OILMAN Today, our industry newsletter covering oil and gas business news, events, information and trends shaping the market, delivered to your inbox. exceed the O-ring quality acceptance criteria for grade N of ISO 3601-3. the in-service inspection of flanges to identify corrosion on the flange face. Also: There's usually a good reason why everyone does it that way. “Sealing Sense” in the April 2008 Pumps & Systems discussed the importance of ensuring that the choice of gasket and surface finish work together to maintain the appropriate level of sealing stress on the gasket. I have used different criteria for flange face (gasket surface) damage evaluation at several different refineries throughout the U.S. Often, pits occur in clusters or groups. 4) Analyze criteria #3: 4.1) If the depth of that imperfection in the flange is deeper than the serration and radial length smaller than 4 mm, then the imperfection is acceptable. We have a WNRF Flange of Dia 20" of which the serration face is damaged (Approximately 3mm Depth and Length 60mm) due to the improper handling. What are the permissible imperfections or acceptance criteria in Flange facing finish for RAISED FACE FLANGE? Some common types of flange surface damage, their characteristics and possible causes are listed below: This type of damage is narrow and elongated with sharp, shallow bottoms. Table – 3: Maximum Radial Project Length for Various. An imperfection crossing the borderline of the GASKET SEATING WIDTH from the inner side of the serrated face and having a depth less than 0.005” below the serrations shall have the RPL measured only with respect to the portion occurring within the GASKET SEATING WIDTH. or larger radius. The American National Standards Institute (ANSI) code for flanges and flanged fittings (ANSI B16.5) requires that the flange face has a specific roughness to ensure that this surface be compatible with the gasket and provide a high quality seal. If a defect is large (especially across the radial direction of the flange face) or several defects are grouped in a small area, the leakage path can exceed the ability of the gasket to block it, and leakage can occur. If these defects are small and few, the leak tightness of the bolted connection will not be significantly impacted. These objects may include the bristles of a wire brush or a tool, such as a chisel. All Right Reserved. - Flange의 Serration API ST’D 600(Steel Gate Valves, Flanged or Buttwelding Ends) 또는 ANSI B16.34에 따른 Valve의 Flange는 ASNI B16.5(Pipe Flanges and Flanged Fittings)에 따른 평면좌(Raised Face) 및 Large Male and Female Flange의 Gasket 접촉면에 Serration 가공을 할 필요가 있다. He is currently working as Field Engineer in an LNG Liquefaction Project in Southwest Louisiana. 63 AARH : 32 to 63µ in AARH. Whether the gasket can successfully seal these damaged areas depends on their size, depth, orientation and number. Below are the standard surface finish types as determined by ASME. With regular maintenance and removing old, stuck-on gasket\debris, flanges with scratches, pits, dents and dings are a common site in many a plant. This allows different surface grades to be used with various types of gasket s to ensure … (FSA) and the Flange Gasket Division of the European Sealing Association (ESA). What are the permissible imperfections or acceptance criteria in Flange facing finish for RAISED FACE FLANGE? , or students posting their homework and depth of the same defect D used... Below are the standard includes information that specifically addresses issues of flange surface condition, damage can occur flange... 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