flange gasket basics gf

7/28/2019 Flange Gasket Basics GF

http://slidepdf.com/reader/full/flange-gasket-basics-gf 1/8

39605 Independence, Shawnee, OK, 74804 | 1.800.654.3872 | www.gfcp.com

RP01/2013

Wy Gasks A Us:

Gt r d t rt tti btw tw ttiry mmbr f mhi mby

d t miti tht dr prtig diti whih my vry dpdt p hg i

pressures and temperatures. If it were possible to have perfectly mated anges and if it were possible

to maintain an intimate contact of those perfectly mated anges throughout the extremes of operating

diti, gt wd t b rqird. Thi i virty impibiity b f:

1. The size of the vessel and/or the anges

2. The difculty in maintaining such extremely smooth ange nishes during handling

d mby

3. Corrosion and erosion of the ange surfaces during operations.

As a consequence, relatively inexpensive gaskets are used to provide the sealing element in these

mechanical assemblies. In most cases, the gasket provides a seal by external forces owing the

gt mtri it th imprfti btw th mtig rf. It fw th, tht i prpry

digd gt r, thr mjr idrti mt b t it t i rdr fr

tiftry t b hivd.

1. Sufcient force must be available to initially seat the gasket. Stating this another way,

adequate means must be provided to ow the gasket into the imperfections in the gasket

tig rf.

2. Sufcient forces must be available to maintain a residual stress on the gasket under operating

diti t r tht th gt wi b i itimt tt with th gt tig rf

t prvt bw-by r g.

3. The selection of the gasket material must be such that it will withstand the pressures exerted

git th gt, tiftriy rit th tir tmprtr rg t whih th r wi b

exposed and withstand corrosive attack of the conned medium.

As a consequence, relatively inexpensive gaskets are used to provide the sealing element in thesemechanical assemblies. In most cases, the gasket provides a seal by external forces owing the

gt mtri it th imprfti btw th mtig rf. It fw th, tht i prpry

digd gt r, thr mjr idrti mt b t it t i rdr fr

tiftry t b hivd.

ProdUct SPecificAtionS Sheet

FlanGe InsulaTIon

GaskeT BasIcs

Product Specications Sheet




RP01/2013

eg A Sal:

A seal is effected by compressing the gasket material and causing it to ow into the imperfections on

th gt tig rf tht itimt tt i mtd btw th gt d th gtseating surfaces preventing the escape of the conned uid. Basically there are four different methods

tht my b d ithr ig r i mbiti t hiv thi br brrir.

1. cmpss: This is by far the most common method of effecting a seal on a ange joint and

the compression force is normally applied by bolting. See gure A.

2. A: attriti i mbiti f drggig ti mbid with mpri h i

pr pg gt whr th pr pg i trd dw gt tht i bth mprd

and screwed into the ange. See gure B.

3. By ha: h i th f ig b d pigt jit t ir pip by m f

mt d. nt, hwvr, tht ftr th mt d i prd, it i tmpd it p ig

tmpig t d hmmr.

4. Gask lp xpas: Thi i phm tht wd r d t dg wig wh th

gasket would be affected by conned uid, as in the case of electrometric compounds affected

by conned uids, such as solvents, causing the gasket material to swell and increase the

interaction of the gasket against the ange faces.

I gr, it i idrd tht y th gt rf prvid th i th jit. It i md tht

the gasket material is impervious and will not permit any passage of uid through the gasket seal.





RP01/2013

Gask Sag:

There are two major factors to be considered with regard to gasket seating. The rst is the gasket

material itself. The ASME* Unred Pressure Vessel Code Section VIII, Division 1 denes minimumdig tig tr fr vrity f gt mtri. Th dig tig tr rg frm

zr pi fr -d f-ig gt typ h drmtr tmr d o-Rig t 26,000

psi to properly seat solid at metal gaskets. Between these two extremes there are a multitude of

materials available to the designer enabling him/her to make a selection based upon the specic

prtig diti dr ivtigti.

fs Ag a Gask J:


1. t ial Pssu: Th r th fr tiy tryig t gtd jit by

exerting pressure against the gasket (blowout pressure) and against the anges holding the

gasket in place (hydrostatic end force).

2. t flag La: Th tt fr mprig th gt t rt , i.. th fftiv

prr rtig frm bt dig.

3. tmpau: Temperature creates thermo-mechanical effects, expanding or contracting the

metals, affecting the gasket material by promoting “creep relaxation" which is a permanent

strain or relaxation quality of many soft materials under stress. The effect of certain conned

uids may become increasingly degrading as temperature rises and attack upon organicgasket materials is substantially greater than at the ambient temperatures (about 75° F). As a

r, th highr th tmprtr, th mr riti th ti f th prpr gt.

4. Mum: Th iqid r g git whih th gt i t .

5. Gal cs: The type of ange, the ange surfaces, the type of bolt material, the

pig d tight f th bt, t.

*asMe – amri sity f Mhi egir




RP01/2013

Each of these factors require consideration before an effective gasket material is nally chosen.

Hwvr, th prpr gt my ft b rjtd b fir rrd d t pry d

ange face or improper bolting-up practice. These details require careful attention, but if complied with,

wi hp imit gt bwt r fir.

Thr r thr priip fr tig y gtd jit. Thy r:

1. Bl La and/or other means of applying the initial compressive load that ows the gasket

mtri it rf imprfti t frm .

2. t ysa , that tends to separate anges when the system is pressurized.

3. ial pssu acting on the portion of the gasket exposed to internal pressure, tending to

bw th gt t f th jit d/r t byp th gt dr prtig diti.

Thr r thr h fr tht my b rtd d t dd hg i tmprtr d

pressure. Creep relaxation is another factor that may come into the picture. The initial compressionfr ppid t jit mt rv vr prp.

1. It must be sufcient to initially seat the gasket and ow the gasket into the imperfections on the

gt tig rf rgrd f prtig diti.

2. Iiti mpri fr mt b grt gh t mpt fr th tt hydrtti d

fr tht wd b prt drig prtig diti.

3. It must be sufcient to maintain a residual load on the gasket/ange interface.

From a practical standpoint, residual gasket load must be “X" times internal pressure if a tight joint is to

be maintained. The unknown quantity “X" is what is known as the “m" factor in the ASME Unred

Pressure Vessel Code and will vary depending upon the type of gasket being used. Actually the “m"value is the ratio of residual unit stress (bolt load minus hydrostatic end force) on gasket (psi) to

internal pressure of the system. The larger the number used for “m", the more assurance the designer

h f btiig tight jit.

Slg Pp Gask Maal:

Th ptimm gt mtri wd hv th fwig hrtriti. It wd hv th hmi

rit f PTFe, th ht rit f grphit, th trgth f t, rqir zr tig tr

such as soft rubber and be inexpensive. Obviously there is no known gasket material that has all these

hrtriti d h mtri h rti imitti tht rtrit it . It i pib t vrm

imitti prtiy by vr mthd h idig th f rifrig irt, mbiig it

with thr mtri, vryig th trti r dity, r by digig th jit itf t vrmm f th imitti. obviy, mhi ftr r imprtt i th dig f th jit bt th

primary selection of a gasket material is inuenced by three factors.

1. the temperature of the uid or gas to be contained

2. the pressure of the uid or gas to be contained

3. the corrosive characteristics of the uid or gas to be contained





RP01/2013

Some of the factors that can inuence the corrosion resistance of a particular material at operating

diti r:

1. ca sv ag. (full sg slus a ssaly msv a s lu pps a, us, vs s als u.)

2. t puy sv ag. f xampl, sslv xyg ws pu

wa may aus ap xa sam ga qupm a g mpaus.

3. t mpau sv ag. i gal, g mpaus sv

ags wll ala sv aak.

As a consequence, it is often necessary to “eld-test" materials for resistance to corrosion under

rm prtig diti t dtrmi if th mtri td wi hv th rqird rit t

rri.

evmal csas:

obviy, mtri ti dpd th tt virmt ptrm i whih y giv wi

prfrm. Thrgh yi f fti hd wy bgi with idrti f th fr mjr

virmt diti.

1. Ma: awy idr mdi tht my m i tt with th d rtir.

Example: if the system is to be cleaned or purged periodically, be sure to anticipate what

cleaning uids will be used. These secondary uids will play as much a role in selecting the

mt mptib mpd wi th priip prtig mdi.

2. Pssu: Prpr rtir dig pd with d hi f mtri wi prvid

molded elastomer seal capable of withstanding extremely high pressures (e.g. some moldedelastomer seals have been tested over 100,000 psi). Similarly, reliable molded elastomer seals

congurations can be achieved for extremely low pressure levels that is, ultra hard vacuums

dw i th 10-9 rg. It i ti tht mpt prr dt b bmittd with

inquires to assure optimum seal design. This includes maximum and minimum presusures,

prf prr, brt prr, yig diti d pti.

n: exmly g pssu suas ma aqualy suu mag

assemblies to maintain metal to metal contact and prevent extrusion of the elastomer.

3. tmpau: Tmprtr, thgh migy mtry i ft th mt midrtd

and exaggerated of the environmental parameters. Hence, it is all too often OVER

SPECIFIED. It should always be born in mind that temperature at the seal itself may vary

widely from the ambient condition (sometimes by hundreds of degrees).

For example: The seal surrounding a water cooling port may never get over 200º F, whereas

the temperature in a combustion chamber a mere ¼" away may easily exceed 1,000º F! Low

tmprtr prfrm, th thr hd, ivv mwht diffrt idrti…

namely the inherent exibility of the chosen material and its ability to maintain an adequate line

f tt.

4. tm: The fourth major determinant in material selection is time. Brief temperature excursions up

to a temperature level higher than those recommended in the material specications are often

tolerable. Example: The standard Buna-N (Nitrile) is recommended normally for service up to

225º F. However, Nitrile can withstand a much higher temperature for brief periods of time.





RP01/2013

typs o Gasks:

typ e – full fa Gasks

Full face gaskets completely cover the ange face from ange bed to outside diameter. Full face

gaskets are used on at faced anges, however, can be used with a raised at face ange to

imit dbri bidig p i rid r ig hrt.

typ f – rg Gask

Rig Gt r digd t t iid th bt ir d r mt mmy d with rid

face anges.


typ "e" full fa Gasks

typ "f" flag a Gask




RP01/2013

typ d – rg typ J (rtJ)

The RTJ is an oval phenolic gasket designed to work specically with RTJ grooved Flanges. RTJ

gt r izd by R-mbr.

A neoprene ller gasket is sometimes used to set on the I.D. of the RTJ gasket to the I.D. of the

ange bore. This is to eliminate debris bridging across and causing a short. TheRTJ’s are made

frm pt f phi, thrfr, th g prr wd b prd t th gri wig th

RTJ to work with pressures up to 2,500 PSI.

typ d – BX

BX gaskets are an octagonal shape phenolic gasket designed to work specically with a BX

grooved ange. BX gaskets are machined from phenolic tubing; therefore, the gas pressure wouldbe perpendicular to the grain, allowing the gasket to withstand pressures up to 15,000 PSI.

BX gaskets are supplied with an asbestos-ll gasket which is placed from the O.D. of the BX to

iid th bt ir.


rtJ Gask

BX Gask




RP01/2013

“Jk" o-rg typ

The “Jock" O-Ring gasket can be a full face (Type E) or ring gasket (Type F) conguration. The

“Jock" has a high-energy O-Ring elastomer seal that compresses and expands to ll any voids as

the ange is tightened. The totally encapsulated sealing element prevents gasket blow-out. Theo-Rig prvid pitiv, tt with zr virmt g. cmpt tt f

ange and retainer prevents re failure and reduces exposure of the seal to service uids and

environment. The conned O-Ring seal allows zero “m" and “y" factors to be achieved.

On special request, the “Jock" gasket can replace most sizes of RTJ and BX gaskets. With the

versatility of changing the sealing element or the retainer material, the “Jock" can be utilized in

mt y ppiti.

isulag Wass

Central’s standard insulating washers are manufactured from CE Phenolic. The maximum

operating temperature is approximately 225º F with a compression strength of 36,400 PSI and a

dielectric strength of 300 VPM. Our high temperature insulating washer has a maximum operating

temperature of 450º F.

isulag Slvs

ctr ffr itig v i vrity f mtri. or mt tdrd id Myr, High

Density Polyethylene, Phenolic and Nomex. They are designed to easily be inserted in the bolt

h vig mp rm fr th bt, v wh th bt h r miigd. Th w thi

is 1/32" and can be provided for bolt sizes from ½" to 3-1/2".

Ml o-P Slv & Was

The one-piece sleeve and washer reduces handling (many loose parts) and make-up problems in

the eld. One glance and an inspector can easily tell if the ange has been properly insulated.

a Mi mtri hd b d b f it high mpri trgth d prir

toughness. A one-piece sleeve and washer is most generally used for one-side ange insulation in

that we mold it in a sleeve length, that is on an average, signicantly longer than the thickness of a

single ange. They can be cut to size for twoside insulation. The maximum operating temperature

is 250º F, dielectric strength 420 VPM and compression strength 19,000 PSI.


“Jk" Gask

flange gasket basics gf

Documents