Large-diameter forged flange production photo
30 Июль 2026

Как выбрать класс 150, 300, 600, 900 или 1500 Фланцы

Technical guideReviewed: 30 July 2026Prepared by SASA FLANGE Technical Content Team

Direct answer

Select flange class by locating the flange material in the applicable ASME pressure-temperature table, then confirming that the allowable pressure at the design temperature meets or exceeds the required design pressure. Also check size limits, тип фланца, лицом к лицу, gasket, запирание, piping code and project design margin. Сорт 150 does not simply mean 150 psi.

Key takeaways

  • Use pressure and temperature simultaneously.
  • Use the correct material group and current project-approved standard edition.
  • Confirm the entire joint rating; the lowest-rated compatible component governs.

Step 1: define design conditions

Start with design pressure and design temperature, not normal operating values. Include upset, steam-out, regeneration, shutdown and external-fire cases where the design basis requires them. Vacuum or external pressure may introduce separate checks.

The fluid category, cyclic service and leakage consequence can also influence flange type, facing and assembly requirements even when the numerical class is adequate.

Step 2: identify material group and rating table

ASME B16.5 assigns listed materials to groups with pressure-temperature ratings by class. Find the exact ASTM grade and confirm any notes. Do not use a table for A105 when ordering F22 or F91.

Read the edition specified by the project. Online charts may omit notes, use an older edition or apply to a different material.

Step 3: verify size, class and flange configuration

ASME B16.5 covers NPS 1/2 through NPS 24 within defined class ranges. Сорт 2500 has a more limited size scope than lower classes. Large-diameter flanges are addressed separately by ASME B16.47.

Then verify weld neck, без шнуровки, blind or other type restrictions, the required facing, pipe bore and any project-specific dimensions.

Step 4: check the complete bolted joint

A flange rating does not independently qualify the gasket, bolts, nuts, attached pipe or nozzle. Check gasket temperature and chemical compatibility, bolting allowable stress, differential thermal expansion, external loads and assembly method.

Document the selected class in the line list and valve/flange data sheets so all mating components are purchased consistently.

Часто задаваемые вопросы

Does Class 300 mean 300 psi?

Нет. Class is a designation. Allowable pressure varies with material and temperature and must be read from the applicable standard table.

Can a higher-class flange replace a lower-class flange?

Not without review. Размеры, bolt pattern, thickness, mating equipment, gasket and system design may differ.

Which class is best for F22?

There is no universal best class. It must be selected from the F22 material rating and the project design conditions.

Related alloy flange guides

Flange Pressure Temperature Ratings Asme B16 5 Alloy Steel Flange Dimensions

Primary standards referenced

Always verify the edition specified by the purchase order and obtain the complete controlled standard for design and acceptance.

Request an alloy steel flange quotation

Send the material grade, стандартный, НПС, класс давления, тип фланца, лицом к лицу, pipe schedule, требования к количеству и проверке. SASA FLANGE will review the technical description before quotation.

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