Stuffing box packings:
- braided with threads made of natural fibers, synthetic fibers (for example PTFE, aramide, polymer, polybenzimide azole), graphite, glass, ceramic or pressed from expanded graphite resp. moulded fibrous composites
- available forms: meter goods, closed and open sealings ready to be installed applications: centrifugal and piston pumps, ventilators, agitating devices and fittings
- lids and flap sealings: wrapped with tissue made of natural fibers, synthetic fibers (for example aramide, glass, ceramic) pressed out of expanded graphite
- available forms: meter goods, closed and open sealings ready to be installed
Applications:
tissue: hand and manhole cocers, boiler bottoms and doors, tank dome lids and lever flaps. graphite: self-sealing closures (for example according to the Bredtschneider principle)
| Media |
Resistant against most
media, also suited for food
Not applicable against
alkaline metals in melted or dissolved form, as well as elementary fluorine
and fluoride compounds at higher temperature and pressures
|
| Design |
Euraflex®-diagonal plaiting of expanded, microporous PTFE (GFO®)-yarn with incorporated graphite and high temperature resistant lubricant.
|
| Conditions
of application |
|
circulating pump |
piston pump |
armature |
| Vg |
20 m/s |
2 m/s |
2 m/s |
| pressure |
20 bar |
250 bar |
250 bar |
| temperature |
-200
bis +280°C |
| pH-range |
0
- 14 |
|
| Notes |
Concerning the packing
1681 of GFO®-yarn the graphite incorporated in the PTFE does not abrase.
The good distribution of the graphite furthermore enables a considerable
improvement of the heat conductivity.
Due to the microporous
structure of the yarn, the packing is very elastic.
This quality is applicable
in the food industry and is released by the FMPA (Forschungs- und Materialprüfungsanstalt
Baden-Württemberg).
|
| Density |
1,5 g/cm3 |
During
the last years Stuffing box packings for sealing of rotating shafts have
increasingly been ousted by mechanical sealings. In applications with low
circumferential speed or with abrasive media nevertheless stuffing box
packings represent a technically and economically better alternative to
the costly and expensive mechanical seals.
The most important requests to stuffing box packings are good heat-conductivity, high resistance to galling and sufficient chemical resistance. Dry packing materials consisting of carrying yarns like cotton, aramide or polyimide, cannot fulfil all these requests alone. In all cases the application of lubricants in form of an impregnation is necessary. This impregnation can be found on the packing or on the yarn outside. Test bed and practice tests have shown, that these deposited impregnations are soon washed out by the leakage and so they aren't available for the packing. The reasons for the washout are heat up and mechanical abrasion. Leakage, firstly remedied by adjusting the stuffing box gland, results in damage of shaft and the protection sleeve.
In applications with abrasive media, leakage as lubrication or as heat removal between packing and shaft is often not possible. In these cases, the impregnation of a packing has a quite special meaning.
Bad heat conductivity of the dry yarn also supplies, beside the damage of the protection sleeve like written before, the burn up of the packing.
These typical failure modes of stuffing box packings are avoided by use of packings made of full yarns. In full yarn packings, components with heat conductivity and greasing components are incorporated homogeneous into the yarn (see picture 1). Impurities of the medium through bleeding are minimised.
Using packings made from full yarn, like the "Hecker packing 1681" (see picture 2), the lifetime, compared with conventional carrying yarn packings, is multiplied.
The packing 1681 is a Euraflex(r)-diagonally plaited packing out of GORE-GFO(r)-yarn with incorporated graphite and a high temperature lubricant.
In the case of packing 1681 the incorporated graphite can not be rubbed off. The high content of graphite causes a very high heat conductivity of the packing and at the same time an extremely low leakage. Through the diagonally plaited way, the packing is very elastic.
The advantages of this packing are:
- high heat conductivity
- good starting and good emergency behaviour
- minimised shaft abrasion
- no hydrolysis
- no hardening
- easily to cut
- extremely low leakage
- strongly increased lifetime
The packing 1681 is suitable as a universal pump and agitator sealing in the chemical industry, the paper manufacture or in the sugar-industry.
Stuffing box packings - catalogue: table of content
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