HS Code for Flanges and Gaskets

Quick Answer

The HS code for flanges falls under heading 7307 (tube or pipe fittings of iron or steel), specifically 7307.21 for stainless steel flanges and 7307.91 for carbon steel and alloy steel flanges. Gaskets are classified under heading 8484 (gaskets and similar joints of metal sheeting combined with other material).

Correct HS code classification for flanges and gaskets is critical for customs duty calculation and trade compliance. Flanges and gaskets are always shipped together in piping material orders, but they belong to different HS chapters and attract different duty rates in most countries.

HS Codes for Flanges

HS Code	Description	Product
7307.21	Flanges, of stainless steel	All SS flange types (WN, SO, BL, SW, THD, LJ)
7307.91	Flanges, other than stainless steel	CS, alloy steel, low-temp steel flanges
7307.19	Other cast fittings	Cast flanges (if classified as cast fittings)
7326.90	Other articles of iron or steel	Spectacle blinds, spacers, paddle blinds

Flanges are classified by material first (stainless vs. non-stainless), not by type (weld neck, slip-on, blind). A carbon steel blind flange per ASME B16.5 and a carbon steel weld neck flange share the same HS heading 7307.91.

HS Codes for Gaskets

HS Code	Description	Product
8484.10	Gaskets of metal sheeting combined with other material	Spiral wound gaskets, kammprofile
8484.20	Mechanical seals	Shaft seals (not pipe gaskets)
8484.90	Other gaskets and similar joints	Ring joint gaskets, flat metal gaskets
4016.93	Gaskets of vulcanized rubber	Rubber gaskets, EPDM, Viton
6812.99	Compressed fiber gaskets	CNAF sheet gaskets
3926.90	PTFE gaskets	Solid PTFE, PTFE envelope gaskets

The HS classification for gaskets depends on the gasket construction material. Spiral wound gaskets (metal + graphite/PTFE filler) fall under 8484.10, while solid metallic RTJ gaskets are classified under 8484.90.

HS Codes for Bolting

HS Code	Description	Product
7318.15	Other screws and bolts (with or without nuts)	Stud bolts (ASTM A193)
7318.16	Nuts	Heavy hex nuts (ASTM A194)
7318.22	Other washers	Hardened washers
7318.19	Other threaded articles	Threaded rod, anchor bolts

Classification Examples

Product	Material	HS Code (6-digit)
Weld neck flange ASTM A105	Carbon steel	7307.91
Blind flange ASTM A182 F316	Stainless steel	7307.21
Slip-on flange ASTM A350 LF2	Low-temp CS	7307.91
Spectacle blind A516 Gr. 70	Carbon steel	7326.90
Spiral wound gasket (SS/graphite)	Metal + filler	8484.10
RTJ gasket (soft iron)	Solid metal	8484.90
Stud bolt A193 B7 + 2H nut	Alloy steel	7318.15 (bolt) / 7318.16 (nut)
CNAF gasket	Compressed fiber	6812.99
PTFE envelope gasket	PTFE + filler	3926.90

Common Mistake

Classifying spectacle blinds and paddle blinds under 7307.91 (flanges). While spectacle blinds look similar to flanges, customs authorities in many countries classify them as “other articles of iron or steel” under 7326.90 because they are not tube or pipe fittings. This distinction can significantly affect duty rates. Verify the classification with the destination country customs before shipping.

For a full reference on HS codes for all piping materials including valves, pipes, and structural steel, see the detailed guide.

Read the full guide to HS codes