In global procurement, a flange being “code-compliant” does not guarantee it is “plug-and-play.” Many procurement managers have faced the frustration of receiving flanges that perfectly meet the ordered American (ASME) or European (EN) standard, only to find they cannot mate with valves or equipment from other suppliers on site. The issues typically lie in these hidden points of divergence:
- The “Ghost” of Code Edition: You specified “ANSI B16.5,” but the supplier defaults to producing the latest edition. The existing equipment interface on your site might be from a decade-old edition. While core dimensions are stable, minor revisions to facing finish or bolt hole chamfers can affect sealing performance.
- The Metric-Imperial Confusion: The order states “Class 150 Flange,” and the supplier provides metric bolt holes. Yet, the bolts on site are imperial. This stems from the ASME standard’s “dual description” of bolt holes. It is essential to explicitly specify “Imperial Bolt Holes” or “Metric Bolt Holes” during procurement.
- The “Manufacturer Standard” End: Flanged ends on equipment from many pump and compressor manufacturers, while nominally following a standard, often feature “special designs” in dimensions like raised face height or bolt circle diameter. Purchasing off-the-shelf standard flanges may lead to a failed connection.
- The Hidden Requirements of Surface Treatment: Codes may not explicitly specify the thickness or type of anti-corrosion coating. An overly thick epoxy coating can alter the effective thickness of the flange, resulting in bolts that are too short.
Mitigation Strategy: Develop an “Enhanced Technical Inquiry Sheet.” Beyond the standard number, it must specify: the standard publication year, precise bolt hole details (thread type, size), detailed drawings of the mating end (if applicable), and exact treatment requirements for the facing and all non-contact surfaces. A clear schematic of the mating interface is often more effective than ten pages of text.