ASME B16.5 covers pipe flanges and flanged fittings in sizes NPS ½" through NPS 24" and pressure classes 150 through 2500. This is the most common flange standard and covers the vast majority of oil & gas and process piping applications.

ASME B16.47 covers large-diameter steel flanges from NPS 26" through NPS 60" and is divided into two series: Series A (formerly MSS SP-44), which has the same bolt circle and bolt sizing as B16.5 extended, and Series B (formerly API 605), which is a more compact (and lighter) design with a different bolt circle. When specifying large-diameter flanges, always confirm whether Series A or Series B is required — they are not interchangeable.

A raised face (RF) flange has a flat circular face raised 1.6mm (1/16") or 6.4mm (1/4") above the pipe flange face. A soft or semi-metallic gasket (spiral wound, CAF, PTFE) sits between the two raised faces and is compressed when the bolts are tightened. RF flanges are suitable for Class 150 through 900 in most standard service applications.

A ring type joint (RTJ) flange has a precisely machined groove machined into the flange face. A solid metal ring gasket (oval or octagonal) seats into this groove and creates a metal-to-metal seal. RTJ flanges are used for Class 900 and above, and wherever a more positive, reliable seal is required — such as high-temperature steam, sour gas service, or high-pressure oil & gas systems. RTJ flanges cost more and require more careful installation, but provide superior sealing integrity. API 6A wellhead flanges always use RTJ (6B or 6BX groove).

A spectacle blind (also called a figure-8 blind) is a single plate component that combines a solid blind disc and an open ring (spacer) connected by a solid bridge — like a figure 8. It is installed between two flanges and can be rotated 180° to select either the blind position (solid disc, blocking flow — positive isolation) or the open position (ring, allowing flow).

Spectacle blinds are specified to ASME B16.48 and are used extensively in oil & gas plants, refineries, and petrochemical facilities for positive process isolation during maintenance, turnarounds, and equipment isolation — providing a visible, auditable, and lockable method of isolation that is safer than relying on a closed valve alone. The figure-8 shape means the blind plate and spacer ring are permanently connected, reducing the risk of the wrong item being installed.

The selection depends on the flange facing type, pressure class, and service conditions. As a general guide:

Spiral wound gaskets are used with raised-face (RF) flanges and are suitable for Class 150 through 2500 in most standard service. They are the most common gasket in refinery and process plant piping and offer a good balance of sealing performance, reusability, and cost. They require a defined bolt load to achieve the correct compression — critical to avoid over or under-compression.

Ring type joint (RTJ) gaskets are used with RTJ-faced flanges only and are preferred for Class 900 and above, high-temperature steam, sour gas service, and wherever a highly reliable metal-to-metal seal is required. RTJ gaskets are not reusable after compression — a new ring must be used each time the joint is opened. If in doubt for a critical oil & gas connection, specify RTJ at Class 600 and above — the incremental cost of RTJ over RF is small compared to the cost of a leak.

Yes. Metal Junction FZE supplies flanges pre-qualified and documented for ADNOC (Abu Dhabi National Oil Company), Saudi Aramco, PDO (Petroleum Development Oman), QatarEnergy, KNPC, and other major Middle East operator specifications. We maintain relationships with flange manufacturers who carry these operator approvals and can provide compliance documentation. For ADNOC and Aramco projects, we also support full Approved Vendor List (AVL) registration and pre-qualification (PQ) submissions on behalf of our clients. Contact our technical team with your project's operator specification number — such as ADNOC specifications, Aramco SAMSS, or PDO PGEPS — for specific compliance confirmation.

Yes. Metal Junction FZE supplies ASME B16.36 orifice flanges in all pressure classes and materials as matched pairs — including the jack screws, ½" NPT tapping plugs, and orifice plate carrier/holder. We can also supply the companion orifice plate (to AGA-3 / ISO 5167), differential pressure (DP) transmitters, impulse tubing, and manifold valve sets as a complete flow measurement package. Orifice flanges are available in carbon steel (A105), stainless steel (A182 F316), and alloy steel (F11/F22) — contact us with your pipe size, pressure class, and material specification for a complete package quotation.

EN 1092-1 is the European standard for steel flanges (and companion EN 1092-2 for cast iron). Instead of ASME pressure class designations (150#, 300#, etc.), European flanges use PN (Pressure Nominale) ratings — PN 6, PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, PN 160, PN 250, and PN 400. EN 1092-1 and ASME B16.5 flanges are NOT interchangeable — they have different bolt circle diameters, bolt sizes, flange ODs, and facing dimensions. You would need EN 1092-1 flanges when connecting to European-designed equipment (compressors, pumps, heat exchangers manufactured in Germany, Italy, France, etc.) or when the project engineering specification calls for metric/European design codes. Metal Junction FZE supplies both ASME and EN 1092-1 flanges — specify the standard clearly on your enquiry.