SANS 1123 Table 1000/3 Flanges: Complete Specification Guide — Dimensions, Materials & Cross-Standard Comparison

A critical specification error occurs when engineers treat the nominal pressure of 1000 kPa as the maximum allowable working pressure at all temperatures. The 1000 kPa figure is the nominal design class - the actual working pressure depends on the material grade and operating temperature. For carbon steel flanges at ambient temperature, the working pressure can approach or equal the nominal class, but it decreases significantly with temperature elevation. For stainless steel grades, the allowable stress values differ from carbon steel and the pressure rating must be checked against the material's allowable stress at the design temperature.

Do not read 1000 kPa as the maximum working pressure. For elevated temperature service, confirm the allowable working pressure against the material's yield strength and allowable stress at your design temperature. For South African projects, refer to SANS 10144 (piping codes) for guidance. 

The following dimension table covers nominal bore sizes NB10 through NB600 for SANS 1123 Table 1000/3 flanges with raised face. All dimensions are in millimetres unless otherwise noted. Column definitions: d1 = pipe OD; D = flange OD; b = flange thickness (plain/plate); b1 = flange thickness (slip-on/weld-on); b3 = flange thickness (weld neck); h = hub height (weld neck); d4 = raised face diameter; f = raised face height; No. = number of bolt holes; d2 = bolt hole diameter; k = bolt circle diameter; Bolt = bolt designation.

• 3.1 Weld neck vs slip-on vs plate: which thickness column applies?

The SANS 1123 dimension table provides different thickness values depending on the flange type. Column 'b' is the minimum thickness for a plain plate flange (no hub). Column 'b1' applies to slip-on (weld-on) flanges, which have a short hub to accommodate the two fillet welds. Column 'b3' applies to weld neck flanges, which have a longer tapered hub for butt welding. When specifying flanges to Table 1000/3, always confirm the flange type in addition to the table number, because the same table covers multiple types with different load-carrying capacities.

SANS 1123 specifies dimensions and pressure classes but is not prescriptive about material grades - it defines that flanges shall be manufactured from appropriate steel, with the grade selected by the engineer based on service conditions. In practice, the following material categories cover the vast majority of Table 1000/3 applications in South Africa.

• 4.1 The stainless steel question: when to upgrade from carbon steel

The single most common material upgrade decision on SANS 1123 Table 1000/3 projects is from carbon steel to SS316L. This decision is typically driven by one of four factors: (1) the process fluid contains chlorides above a threshold that accelerates carbon steel corrosion; (2) the piping handles demineralised water or steam condensate, where iron pickup from carbon steel flanges contaminates the fluid; (3) the project is in a coastal or marine environment with atmospheric chloride exposure; (4) the project is in a food, beverage, or pharmaceutical facility where hygiene regulations require corrosion-resistant materials in contact with product.

For most South African municipal water supply applications, carbon steel flanges with appropriate internal lining or coating are the economic choice. For mine process water, wastewater, and reagent handling, SS316L is the most commonly specified stainless grade. For seawater cooling systems and brine circuits, duplex 2205 should be evaluated.

South African projects frequently involve equipment and piping from European, American, and local suppliers. Engineers need to understand whether a SANS 1123 Table 1000/3 flange can be bolted to an EN 1092-1 PN10 or an ASME B16.5 Class 150 counterpart - the answer is not always straightforward.

• 5.1 The bolt circle compatibility issue - the most common on-site problem

When a South African water treatment plant imports a European pump with EN 1092-1 PN10 flanged connections, the engineer's first instinct is that PN10 and SANS 1123 Table 1000/3 - both rated 10 bar nominal - should bolt up directly. This is often correct for smaller sizes (NB50 to NB200) where SANS 1123 and EN 1092-1 bolt circles are identical or compatible. However, at larger sizes, differences in flange OD, bolt circle diameter, and bolt hole count mean the flanges cannot be directly bolted together.

Before any cross-standard flange connection, always compare the bolt circle diameter (k), number of bolt holes (No.), and bolt hole diameter (d2) from both standards' dimension tables for the specific NB size. If they match, the flanges can be bolted. If they differ, an adapter spool or custom-drilled transition flange is required.

⚠ Never assume that same nominal pressure + same NB size = bolt-compatible flanges. SANS 1123 Table 1000/3 and EN 1092-1 PN10 do NOT use identical bolt circles across all sizes. Verify dimension by dimension for every non-standard connection.

• 6.1 Municipal water supply and wastewater infrastructure

This is the dominant application domain for SANS 1123 Table 1000/3 in South Africa. Bulk water supply pipelines connecting reservoirs, pump stations, water treatment works, and distribution networks are almost universally flanged to SANS 1123 Table 1000/3 in the 1000 kPa pressure class. The nominal 10 bar pressure class provides sufficient margin for most gravity-fed distribution systems and pump station headers. Carbon steel with coal tar epoxy lining or cement mortar lining is the standard material for large-diameter trunk mains; stainless steel is used at smaller bore connections in the treatment works itself where corrosion from process chemicals is a concern.

• 6.2 Mining - process water, slurry and reagent piping

South Africa's mining industry - gold, platinum, coal, iron ore, chromite - is one of the largest consumers of SANS 1123 Table 1000/3 flanges outside of municipal infrastructure. Process water supply lines, slurry transport circuits, flotation plant pipework, tailings return lines, and reagent dosing headers all operate in the 600 kPa to 1600 kPa range. Table 1000/3 is the standard workhorse for this pressure range. Material selection is driven by the specific chemistry: SS316L for acidic reagent lines and chloride-containing mine water; duplex 2205 for high-chloride or high-strength requirements; carbon steel with sacrificial anodes and cathodic protection for large-diameter mine water mains.

• 6.3 Petrochemical, refinery and general process industries

Petrochemical plants and refineries in South Africa (Sasol, Engen, Astron Energy) use SANS 1123 flanges alongside ASME B16.5 and EN 1092-1 components - often within the same facility - because the plant was constructed over multiple decades with different codes. Table 1000/3 flanges appear in utility service lines (cooling water headers, instrument air, plant water), non-critical process lines, and condensate return systems. For process lines carrying hydrocarbons at pressure, ASME B16.5 is typically the engineering standard; SANS 1123 is more common in the utility and water handling circuits.

• 6.4 Marine, shipbuilding and coastal infrastructure

South African port infrastructure, desalination plants, and marine engineering projects specify SANS 1123 Table 1000/3 for non-critical seawater service where EN 1092-1 is not specifically required. For seawater cooling headers and open-circuit cooling water systems, carbon steel is inadequate without cathodic protection; SS316L is the minimum for flanges in direct seawater contact, and duplex 2205 is preferred for higher chloride concentrations or higher flow velocities.

• 7.1 Required markings on SANS 1123 Table 1000/3 flanges

SANS 1123 requires permanent marking on each flange to enable traceability and receiving inspection. Markings are typically applied by steel stamping on the flange OD or hub face. For stainless steel flanges, low-stress electro-etching is preferred over hard stamping to avoid creating stress concentration points that can initiate crevice corrosion.