Flange Marking And Marking Examples

1.  National standard marking:

Flanges shall be marked according to nominal diameter, nominal pressure, sealing surface form code, mating steel pipe series code (mating metric pipe code is "series 2", mating inch pipe is not marked) and standard number.

Marking example: 

· Convex butt-welded steel pipe flanges with nominal diameter 80mm and nominal pressure 4.0MPa(25bar) (with metric pipe)

   Flange DN80-PN40 M(Series 2) GB/T9115.2-2000

·  Nominal diameter 100mm, nominal pressure 5.0MPa(25bar) raised face flat welded steel pipe flanges with neck (with inch pipe)

   Flanges DN100-PN50 RF GB/T9116.1-2000

2.The Ministry of Machinery standard mark:

Marking examples : nominal diameter 500mm, nominal pressure 1.6MPa, series 2 of the cornice flat welding steel pipe flange flange 500-16 JB/T81-94

Nominal diameter 300mm, nominal pressure 6.4MPa, series 1 concave butt-welding steel pipe flange flange 300-64B (series 1) JB/T82.2-94

(Note: Ministry of Machinery standard default pipe O.D. for series 2, Butt-welding flange classification: A-type convex surface, B-type concave surface, C-type tongue and groove surface, D-type groove surface)

3. Ministry of Chemical Industry standard marking:

· Flanges shall be marked according to the following provisions (this marking method is recommended)

a. Standard No.: All types of pipe flanges are uniformly marked with the standard No. of this standard: HG20592.

b. Flange type code according to the provisions of Table 5.0.1.

When the threaded flange adopts tapered pipe thread according to GB/T7306, it is marked as "Th(Rc)" or "Th(Rp)";

When the threaded flange adopts the conical pipe thread according to GB/T12716, it is marked as "Th(NPT)";

Threaded flange is Rp (GB/T7306.1) if the thread code is not marked.

c. Nominal diameter of flange DN (mm) and applicable steel pipe OD series: integral flange, flange cover, lined flange cover, threaded flange, applicable steel pipe OD series marking can be omitted;

   Applicable to the international common series of steel pipe (commonly known as imperial pipe) flange, mark "DN (A)";

   Apply to the domestic series of steel pipe (commonly known as metric pipe) flange, labeled "DN (B)".

d. Nominal pressure of flange PN,MPa.

e. Sealing surface form code according to the provisions of Table 6.0.1, protruding flange such as car system dense waterline, then marked as "RF (A)".

f. The wall thickness of steel pipe shall be provided by the user. Butt-welding flanges with neck, butt-welding ring loose flanges shall be labeled with wall thickness of steel pipe.

g. Material grade.

h. Others. The use of inconsistent with the provisions of this standard series of requirements or additional requirements, such as the surface roughness of the sealing surface.

Marking examples:

· Nominal diameter 1200mm, nominal pressure 0.6MPa, with metric pipe protruding panel type flat welded steel pipe flange, material Q235A

   HG20592 Flange PL1200(B)-0.6 RF Q235A

· Flat welded steel pipe flanges with raised face and neck, with nominal diameter 300mm, nominal pressure 2.5MPa, for inch pipes, made of 20 steel

  HG20592 Flange SO300(A)-2.5 M 20