How do I select a gasket for a flanged joint?

Select based on: flange rating (class 150/300/600 etc.), pipe size (NPS), service conditions (temperature, pressure, media), and gasket type (spiral wound, PTFE, rubber, metallic). ASME B16.20 defines standard gasket dimensions.

What is the difference between raised face and ring-type joint flanges?

Raised face (RF) flanges use flat or spiral wound gaskets seated on a raised surface. Ring-type joint (RTJ) flanges use metallic ring gaskets in a machined groove. RTJ provides superior sealing at higher pressures.

What is gasket seating stress?

Seating stress (y) is the minimum bolt stress required to initially seat the gasket and create a seal. It varies by gasket type: rubber ≈ 1.4 MPa, spiral wound ≈ 69 MPa, solid metal ≈ 180 MPa.

What bolt torque is needed for a flanged joint?

Bolt torque depends on bolt size, number of bolts, gasket type, and required seating stress. T = K × d × F/n, where K is nut factor (≈0.2 for lubricated), d is bolt diameter, F is total bolt load, n is number of bolts.

When should I use a spiral wound gasket?

Spiral wound gaskets (ASME B16.20) are the most versatile choice for raised face flanges in process piping. Suitable for temperatures from -200°C to 600°C (depending on filler), pressures up to Class 2500, and most chemical services.

Free Engineering Tool — #153

Flange Gasket Calculator

Select flange class, pipe size, and gasket type to get gasket dimensions (ID, OD, thickness) and bolt load requirements.

ASME B16.5ASME B16.20Class 150–600

Gasket Data

Gasket Description

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Gasket ID

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Gasket OD

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Thickness

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Number of Bolts

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Bolt Diameter

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Gasket Seating Stress

W_m2 — minimum bolt load for gasket seating
y — gasket seating stress (varies by type)
A_g — gasket contact area

Gasket Factors

Gasket Type	m factor	y (MPa)
Rubber sheet (1.6 mm)	0.50	0
PTFE sheet	2.00	6.9
Spiral wound + graphite	2.50	68.9
Spiral wound + PTFE	2.50	68.9
Metal ring (soft iron)	5.50	124.1

⚠️ Note: This is a reference tool for standard gasket dimensions. For critical applications, perform full ASME PCC-1 bolt load calculations and verify with gasket manufacturer data.

Flange Gasket Calculator | Gasket Sizing | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Gasket Data

Gasket Seating Stress

Gasket Factors