ASME B16.30-1969 scan — Unfired Pressure Vessel Flange Dimensions

🏭 ASME B16.30-1969 is the USA Standard published in 1969 under the title Unfired Pressure Vessel Flange Dimensions. Developed by the ASME B16 Committee (Standardization of Pipe Flanges and Fittings), the Standard provides standardized dimensions for unfired pressure vessel flanges that are based on the formulas and specifications of the ASME Unfired Pressure Vessel (UPV) Code and on proportions established by the design practices of many large industrial users. Its purpose is to give enough size and pressure choices to cover the majority of vessels in use, to establish interchangeability between loose-type (similar to ASME UPV Code illustration UA-48-1a) and welded-type (similar to illustration UA-48-8a) flanges for equivalent vessel diameters and operating pressures, and to permit the use of a wide variety of gasket materials.

1. Scope and Applicability 📌

Section 1 of the Standard states five objectives:

• To provide dimensions for unfired pressure vessel flanges based on the ASME UPV Code formulas and specifications and on established design practices;
• To provide enough size and pressure choices to include the majority of vessels used;
• To provide the most economical flanges consistent with satisfactory installation and operation;
• To provide a design that permits the use of a wide variety of gasket materials;
• To establish interchangeability between loose-type (e.g., illustration UA-48-1a) and welded-type (e.g., illustration UA-48-8a) flanges for equivalent vessel diameters and operating pressures.

Section 2 defines the size and pressure ranges. Flanges are listed for vessels with outside diameters (in inches) of 26, 27, 28, 30, 32, 33, 34, 36, 38, 39, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90, 93, 96, 99, 102, 105, 108, 111, 114, 117, and 120 — some 37 diameter steps — and for working pressures of 50, 100, 150, 200, 250, 300, 400, 450, 550, 600, 650, 700, 750, and 800 psi, plus 25 and 75 psi for vessels 48 inches in outside diameter and larger.

2. Design Basis and Allowable Stresses 📐

Section 3 establishes the design stress basis of the Standard:

• Allowable working stress for the flange material: 13,750 psi;
• Allowable working stress for the vessel material: 11,687 psi (13,750 psi × 85% weld factor);
• Vessel shell thicknesses are calculated by the formulas of ASME UPV Code UG-27;
• Materials matching these stresses include commonly used plate materials such as SA-201A and SA-285C, and bar material A-306 Grade 55, over the temperature range of -20°F to 650°F; some carbon-silicon and stainless alloys are higher in these temperature ranges.

Where special alloy or temperature conditions markedly affect strength, the difference must be considered when choosing a flange. Corrosion allowances are normally carried in the vessel shell and are not included in the flange calculations.

3. Bolting and Gasket Design 🔩

Section 4 establishes the bolting design rules:

• The number of bolts is taken as the largest multiple of 4 contained in the number of inches in the vessel outside diameter (for example, a 42-inch vessel takes 40 bolts, since 40 is the largest multiple of 4 contained in 42);
• The bolt circle is selected considering: a 1/8-inch clearance between the centered gasket and centered bolts; no interference between the outside diameter of the wrench socket on a centered bolt and the toe of the ASME UPV Code minimum weld on welded-type flanges (UA-48-8a); and at least a 1/8-inch clearance between the centered socket wrench and the corner of the nut on the next centered bolt;
• Threading is specified as UNC-2A for 1 inch and smaller and 8N-2A for larger sizes, per USA Standard B1.1 (Unified Screw Threads); if other threading is used, the variation in net effective cross-sectional area must be considered;
• Nuts are to be A 194 Class 2H or equivalent; the use of washers is optional, with clearance provided for high-strength structural washers per ASTM A 325 (medium carbon steel, quenched and tempered);
• The flange design bolt load is calculated from UA-49 formula 4, which recognizes that bolts are usually slightly oversize and provides a margin against abuse of the flange from over-bolting.

Section 5 defines the gasket design requirements: the Standard is based on a gasket factor m = 2.5 and a minimum design seating stress y = 2,900 psi; gaskets have inside diameters equal to the vessel inside diameter and outside diameters equal to the outside diameter of the raised face, leaving a 1/8-inch clearance between the gasket outside diameter and the inside edge of the centered bolt.

4. Flange Types and Interchangeability 🛠️

The Standard gives dimensions for two basic flange types:

• Loose-type flanges: similar to ASME UPV Code illustration UA-48-1a; the flange ring is not welded integrally to the vessel shell, which eases assembly, disassembly, and alignment; limited to vessel wall thicknesses of up to 0.50 inches.
• Welded-type flanges: similar to illustration UA-48-8a; the flange is welded directly to the vessel shell for direct load transfer and a compact structure; flange thickness is limited to 6 inches.

For the same vessel outside diameter and working pressure, the two types are interchangeable — this is the concrete realization of the interchangeability objective in para. 1.5. For flanges subject to other stresses, such as bending due to wind load on a tower or in ductwork applications, stress calculations must be made and an appropriately heavier flange selected.

5. Engineering Practice Essentials 📋

• 🔍 Selection workflow: determine the vessel outside diameter → determine the working pressure → select the type (loose or welded) and dimensions from the Standard’s tables → verify wall thickness, flange thickness, and bolt diameter limits → check additional loads.
• 🔧 Material consistency: vessel and flange materials must satisfy the respective allowable stress premises (13,750 / 11,687 psi); re-verify when temperature falls outside -20°F to 650°F or when special alloys are used.
• 📊 Testing and assembly: hydrostatic test pressure must not exceed the flange’s allowable working pressure at the test temperature.
• 📋 Historical reference: although this Standard is based on the 1965 edition of ASME Section VIII and modern design has largely migrated into the ASME BPVC system, its dimension tables remain a useful historical reference for rapid vessel flange selection.

6. Frequently Asked Questions ❓