PTFE envelope flange gaskets

A PTFE envelope gasket is a composite gasket, and consists of an envelope of PTFE with an insert. The envelope gasket is mainly used as a flange gasket in applications where high chemical and pressure resistance is required.

Because of the cold flow affinity of unfilled PTFE, PTFE composites are primarily used because PTFE wrapped gaskets are more resistant to stress relaxation.

Due to their high chemical resistance and excellent sealing properties, PTFE-wrapped gaskets have proven excellent in use at fluctuating pressures and temperatures from -195 °C to +250 °C.

Applications of PTFE envelope gaskets

In chemically aggressive environments, where contamination of the medium is not allowed, it is complicated to apply a standard gasket. Here PTFE envelope gaskets are applied as flange gaskets, for example in the (petro)chemical industry and in the process industry.

Envelope gaskets are also ideal for application in the food industry. PTFE is physiologically inert and can be used in direct contact with food.

Types and profiles of PTFE envelope gaskets

U-envelope	For average and high pressures.
C-envelope with diffusion stop	Specially designed gasket with a so-called 3 mm‎‏ thick diffusion stop.
Double U-envelope	Suitable for high pressures. A sealed gasket with a linear upper side. Is applied in places where the medium may contact the upper side of the seal.
Donut envelope	Suitable for high pressures. A sealed gasket with a round upper side. Is applied in places where the medium may contact the upper side of the seal.
C-envelope	For average and high pressures, but is suitable for a more flexible inlay (for example rubber).
Y- or V-envelope	A low cost solution for lower pressures. The inlay material is up to 2 mm thick.

There are many more types and profiles available, and the above versions are only examples of commonly used envelope gaskets....

Reference(s):

	klinger-awschultze.de
	ridderflex.com

Dimensions PTFE envelope flange gaskets conform‎‏ ASME B16.21

Class 150

	STD	FF
NPS	OD x ID	OD x ID	NBH	DBH	PCD
1/2	48 x 21	89 x 21	4	16	60
1/2	48 x 21	89 x 21	4	16	60
3/4	57 x 27	95 x 27	4	16	70
1	67 x 33	108 x 33	4	16	79
1.1/4	76 x 42	117 x 42	4	16	89
1.1/2	86 x 48	127 x 48	4	16	98
2	105 x 60	152 x 60	4	19	121
2.1/2	124 x 73	178 x 73	4	19	140
3	137 x 89	191 x 89	4	19	152
3.1/2	162 x 102	216 x 102	8	19	178
4	175 x 114	229 x 114	8	19	191
5	197 x 141	254 x 141	8	22	216
6	222 x 168	279 x 168	8	22	241
8	279 x 219	343 x 219	8	25	298
10	340 x 273	406 x 273	12	25	362
12	410 x 324	483 x 324	12	29	432
14	451 x 356	533 x 356	14	29	476
16	514 x 406	597 x 406	16	32	540
18	549 x 457	635 x 457	16	32	578
20	606 x 508	699 x 508	20	32	635
24	718 x 610	813 x 610	20	35	749

sSTDStandard Envelope Gasket FFFull Face Envelope Gasket NPSNominal Pipe Size OD x IDOutside Diameter x Inside Diameter NBHNumber Of Bolt Holes DBHDiameter Of Bolt Holes PCDPitch Circle Diameter

Class 300

	STD	FF
NPS	OD x ID	OD x ID	NBH	DBH	PCD
1/2	54 x 21	95 x 21	4	16	67
3/4	67 x 27	117 x 27	4	19	83
1	77 x 33	124 x 33	4	19	89
1.1/4	83 x 42	133 x 42	4	19	98
1.1/2	95 x 48	156 x 48	4	22	114
2	111 x 60	165 x 60	8	19	127
2.1/2	130 x 73	191 x 73	8	22	149
3	149 x 89	210 x 89	8	22	168
3.1/2	165 x 102	229 x 102	8	22	184
4	181 x 114	254 x 114	8	22	200
5	216 x 141	279 x 141	8	22	235
6	251 x 168	318 x 168	12	22	270
8	308 x 219	381 x 219	12	29	330
10	362 x 273	445 x 273	16	29	387
12	422 x 324	521 x 324	16	25	451
14	486 x 356	584 x 356	20	32	514
16	540 x 406	648 x 406	20	35	572
18	597 x 457	711 x 457	24	35	629
20	654 x 508	775 x 508	24	35	686
24	775 x 610	914 x 610	24	41	813

Class 600

	STD	FF
NPS	OD x ID	OD x ID	NBH	DBH	PCD
1/2	54 x 21	95 x 21	4	16	67
3/4	67 x 27	117 x 27	4	19	83
1	77 x 33	124 x 33	4	19	89
1.1/4	83 x 42	133 x 42	4	19	98
1.1/2	95 x 48	156 x 48	4	22	114
2	111 x 60	165 x 60	8	19	127
2.1/2	130 x 73	191 x 73	8	22	149
3	149 x 89	210 x 89	8	22	168
3.1/2	162 x 102	229 x 102	8	25	184
4	194 x 114	273 x 114	8	25	216
5	241 x 141	330 x 141	8	29	267
6	267 x 168	356 x 168	12	29	292
8	321 x 219	419 x 219	12	32	349
10	508 x 273	445 x 273	16	35	432
12	559 x 324	521 x 324	20	35	489
14	603 x 356	584 x 356	20	38	527
16	686 x 406	648 x 406	20	41	603
18	743 x 457	711 x 457	20	44	654
20	813 x 508	775 x 508	24	44	724
24	791 x 610	940 x 610	24	51	838