Use condition of gasket material

There are many types of flange gasket,their materials and use conditions are different.

Materials of flange gasket:

1. Natural rubber and synthetic rubber, such as natural rubber, neoprene rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, fluorine rubber, etc.
2. Asbestos rubber sheet (XB350, XB450 of GB 3985) and wear-resistant asbestos rubber sheet (NY400 of GB539)

3. Synthetic fiber rubber pressing board (inorganic, organic)
4. Modified or filled PTFE sheet
   Note: When the use of asbestos is prohibited due to harmful health and other reasons, the non-asbestos materials listed in 3 and 4 or flexible graphite composite pads can be used.

Use conditions of flange gasket:

The use conditions of non-metallic flat gaskets should meet the requirements of Table 1.1

Table 1.1 Conditions of use for non-metallic gaskets
Type	Name		Code	Conditions of use
				P.Class（MPa)	t.Temperature（℃）
Rubber	natural rubber		NR	≤1.6	‘-50～﹢90
	Neoprene		CR	≤1.6	‘-40～﹢100
	NBR		NBR	≤1.6	‘-30～﹢110
	Nitrile rubber		SBR	≤1.6	‘-30～﹢100
	Ethylene propylene rubber		EPDM	≤1.6	‘-40～﹢130
	fluororubber		Viton	≤1.6	‘-50～﹢200
Asbestos rubber	Asbestos Rubber Sheet		XB350	≤2.5	≤300
			XB450	P.t≤650MPa ℃
	Oil-resistant asbestos rubber sheet		NY400
Synthetic fiber rubber	Synthetic fiber rubber pressing plate	Inorganic	﹣	≤4.0	‘-40～﹢290
		Organic			‘-40～﹢200
PTFE	Modified or filled PTFE sheet		﹣	≤4.0	‘-196～﹢260

Note: There is no corresponding product standard for synthetic fiber rubber pressed plates and modified filled PTFE, and the recognized manufacturer brand should be indicated when using.

The nominal pressure range of gaskets for flanges with different sealing faces is shown in the standard Table 1.2

Table 1.2 Nominal pressure range of gaskets for flanges with different sealing surfaces
Type（Code)	Class PN,MPa(bar）
（FF）	0.25～1.6（2.5～16）
（RF）	0.25～4.0（2.5～40）
（FMF）	1.0～4.0（10～40）
（TG）	1.0～4.0（10～40）

Gasket type and size

Gaskets are divided into FF.RF.FMF. And TG types according to the sealing surface type, which are suitable for all planes, protrusions, uneven surfaces, tongue and groove surface flanges, as shown in Figure 2.0.1

Gasket size

1.Type FF for full-plane flanges, the size of the gasket is in accordance with Table 2.0.2-1.

2.RF type for raised flange, gasket size according to Table 2.0.2-2, as required, asbestos rubber sheet, oil-resistant asbestos rubber sheet or synthetic fiber rubber pressed sheet RF type gasket can be stainless steel (304) inner package The edge (RF-E type), the size of the hemming is shown in Table 2.0.2-2.

3.FMF type for concave-convex flanges, gasket size according to Table 2.0.2-3.

4.Type TG for tongue and groove face flanges, the size of the gasket is in accordance with Table 2.0.2-4.

5.The gasket sizes listed in Table 2.0.2-1 ～ 4 are applicable to the steel pipe flanges of the two steel pipe outer diameter series listed in HG20592.

6.The inner diameter D of the gasket according to Table 2.0.2-1 ～ 3 is applicable to the inner diameter of the general gasket, but it can also be modified as needed, and the modified inner diameter size should be indicated when ordering.