ASME · API · MSS · ASTM

Codes & Standards

Not the full text — that’s what the standards themselves are for. This is what a piping designer actually needs to understand about each one and why it matters on a real project.

ASME B31.3
Process Piping — the designer’s primary code
+

B31.3 is the code you live in. It covers design requirements, materials, fabrication, examination, and testing for process piping — the type of piping found in refineries, chemical plants, and petrochemical facilities.

Key areas a designer must understand: wall thickness calculation (304.1), allowable stress tables, the concept of design conditions vs operating conditions, branch connections and reinforcement, and the examination requirements that affect how you detail welds.

What it means in practice
When you pick a pipe schedule, you’re implicitly applying B31.3. When you specify a branch connection type, B31.3 determines whether you need a reinforcing pad. Know Chapter III (Fluid Service Requirements) cold — it’s where most project-specific deviations come from.
ASME B31.1
Power Piping — utilities and steam systems
+

B31.1 applies to steam, water, oil, gas and air services associated with electric power generating stations, industrial and institutional plants, and central and district heating plants. If you’re designing a steam header on an industrial site, B31.1 likely applies.

What it means in practice
Many sites run both B31.3 (process) and B31.1 (utilities) simultaneously. Confirm which code applies to each system before you start — the allowable stress values and examination requirements differ significantly.
API 570
Piping Inspection Code — in-service inspection
+

API 570 covers the in-service inspection, rating, repair, and alteration of metallic piping systems. On brownfield projects, this is critical — it defines what the plant owner’s inspection regime looks like and what constraints that places on your modifications.

What it means in practice
When you’re tying into existing piping on a revamp, understanding API 570 tells you what the inspection history of that line is and whether your modification triggers a re-rating. Always ask for the Piping Inspection Records before designing a tie-in.
ASME B16.5
Pipe Flanges and Flanged Fittings — ratings and dimensions
+

B16.5 is your go-to for flange pressure-temperature ratings, dimensions, facing types, and bolting requirements for NPS ½” through 24”. It defines the six pressure classes: 150, 300, 600, 900, 1500, and 2500.

What it means in practice
Class selection is one of the most consequential decisions in piping design. Understand that Class 150 at elevated temperatures drops significantly in allowable pressure. The material group (Group 1.1 for A105, Group 2.1 for 316SS) changes everything — don’t assume the same class gives the same rating across materials.
MSS SP-58 / SP-69
Pipe Hangers and Supports — the support designer’s bible
+

SP-58 covers the types, design, manufacture, selection and application of pipe hangers and supports. SP-69 covers the selection and application of those supports. Together they define the standard support types (Type 1 through 59) that appear in every piping spec.

What it means in practice
When a stress engineer says “add a Type 38 guide at this location”, they’re speaking SP-58. Know the common types cold: Type 1 (adjustable clevis), Type 3 (eye rod), Type 37 (pipe clamp), Type 38 (double bolt pipe clamp guide).