Sealing material
Sealing materials are materials and aids that are used for sealing.
Vegetable fibers
Especially the tensile and weather-resistant fibers of the hemp plant are traditionally used for sealing against liquids and gases. In order to seal and preserve the pores of the organic fibers in an airtight and liquid-tight manner, the hemp is often soaked with waterproof, non-volatile liquids, some of which harden after use.
In the renovation of old buildings and ecological construction, coconut and hemp fibers in particular are used as thermal insulation and stuffing material for airtight sealing of joints. Coconut fiber is similarly weatherproof as hemp fiber, but more brittle and less pliable.
For caulking wooden hulls, hemp and other fiber materials are used, which are soaked with wood tar or pitch .
Sealing material for pipe connections
Sealing hemp
Sealing hemp (also tow ) consists of hemp or flax fibers (linen) and is a sealing agent for threads . It is used in combination with a mostly paste-like sealant for water and gas installations . A sealing paste approved for this purpose must be used for drinking water installations, as well as for solar installations, where increased temperatures and pressures can occur. Pipe threads are actually supposed to provide a metallic seal or a form fit by tightening the thread tight enough that the thread flanks pressed onto one another are plastically deformed. The hemp provides additional security. The sealing paste protects the hemp from chemical and biological decomposition, makes it easier to screw in and fills the remaining cavities in the threads.
advantages
- Sealing hemp swells when it comes into contact with water, which can compensate for slight movement in the sealing joint as well as the imprecise fit of the conical screw connection of steel installation pipes. A screw connection can usually be opened a quarter turn after screwing for adjustment without the connection becoming leaky.
- The temperature resistance is given as 140–160 ° C. Hemp can scale at higher temperatures. Occasionally, hemp is also used successfully at higher temperatures. Even if the hemp can withstand brief exposure to heat, threads in the area of pipe connections that are soldered or welded should only be sewn after this work.
- In contrast to hardening sealing compounds, the connection can be loosened again later.
disadvantage
- The processing is more complex than with sealing tape: First, the thread should be roughened before the application of the hemp so that the hemp layer adheres well and does not slip when screwed together. For this purpose, special pliers with three corrugated rollers can be used, which roll across the threads. Often instead, the fine teeth of the metal saw blade of a hand hacksaw or, alternatively, a wire brush are used to brush across the threads. The resulting grooves in the longitudinal direction of the pipe are intended to prevent the hemp fibers from slipping on the thread. Start at the outer end of the pipe thread (which is first screwed into the inner thread of the socket) so that the hemp fibers follow the direction in which the socket thread is then screwed on. It is advantageous to work with a long, thin fiber strand that is wrapped tightly around the thread. Only enough hemp should be used that the thread tips can still be seen. It is also occasionally recommended to leave the first thread and the last two threads free so that the thread can be joined together more easily and not too much hemp prevents the desired metallic contact between the internal and external threads. The fibers can then be brushed firmly into the thread using a wire brush. As a rule, a paste-like sealant is applied to the thread both before the hemp is inserted and again coated with the agent after the hemp has been inserted.
- Some manufacturers prohibit the use of hemp to seal plastic threads (made of PVC ). Hemp fibers slip easily on plastic threads and, due to their volume, can cause deformation of the threads in the plastic.
Thread sealing tape
Sealing tape (also known colloquially as Teflon tape or Fluflex) is usually made of PTFE (Teflon). In contrast to sealing hemp and lead wool, it is processed from the roll without additional aids. Sealing tape is available in different versions, for example with approval for gas installation or high temperature resistant.
Some manufacturers prescribe the use of Teflon sealing tapes to seal plastic threads (especially also for threads made of PVC ), as Teflon tape is very thin and the plastic thread is less stressed when it is screwed in. Since screwing with Teflon tape requires less force, an increase in the torque when tightening the thread can also be better perceived. The process can then be canceled before the thread breaks.
advantages
- chemically resistant, can therefore be used with almost all media
- Pressure resistant up to 20, sometimes even up to 30 bar
- Temperature range −60 ° C to +240, sometimes up to 260 ° C
- metallic threads do not need to be roughened, as the thin Teflon tape does not usually shift when screwing together
- Easy to process
- In contrast to hardening sealing compounds, the connection can be loosened again later.
disadvantage
- does not swell and does not seal elastically, so that the threaded screw connection can no longer be turned back without risking a leak
- At higher temperatures, for example in solar installations , leaks can also occur.
- only seals reliably with narrow and even gaps. If wider gaps are to be bridged, the tape would have to be wrapped in several layers on top of one another. However, there is then the risk that it will shift when it is screwed together, since it develops little frictional resistance. By using Teflon thread instead of Teflon tape, the material can possibly be applied in a slightly thicker layer.
- Some manufacturers of piping systems made of stainless steel advise against the application, as there is concern that thread sealing tape could release chloride ions, which attack the steel under unfavorable conditions.
Aluminum hemp
Aluminum hemp is used in a similar way to hemp and can be used at temperatures of up to 640 ° C, if necessary in conjunction with graphite paste, which, depending on the composition, is temperature-resistant up to 300 ° C in heating and sanitary areas or as a graphite compound up to 1000 ° C can.
Lead wool
Lead wool is used as a sealant wherever sealing hemp is unsuitable. It is particularly important for the fire brigade (e.g. lead wool can be used as a seal in tanker accidents with leaking oil). Lead wool also plays a certain role in radiation protection .
fiberglass reinforced plastic
GRP systems are offered for emergency repairs . Usually, epoxy resin is first applied from the outside to a leaking pipe. By wrapping with fiberglass mats , a high compressive strength can be achieved.
Guidelines
- DIN EN 751: Sealant for metal threaded connections in contact with gases of the 1st, 2nd and 3rd family and hot water
- Part 1: Anaerobic Sealants
- Part 2: Non-hardening sealants
- Part 3: Unsintered PTFE tapes
Sealing profiles, tapes and pads
Flexible sealing profiles made of elastomers for sealing joints are offered in a large number of cross-sections as hollow or solid profiles. Often, laterally protruding lips are formed with which the profile can jam in a correspondingly shaped joint .
Some sealing profiles, like adhesive pads, are self-adhesive so that they can be attached to flat surfaces. Otherwise, the sealing material can also be fastened with screws, nails or staples .
Sealing profiles are also referred to as sealing cords in some areas of application . Oven sealing cords consist of refractory fibers that are inserted or glued into grooves in the body of the oven or in the oven flap. Sealing cords which are applied directly to a component in liquid form and then harden or cross-link as sealing foam are also referred to in industry as formed in-place foam gaskets .
Compriband
Compression tape (also known as stop tape or joint tape) is a pre-compressed, impregnated foam sealing tape based on polyurethane , which slowly expands after being introduced into a joint and lies close to the joint edges. Compriband is usually available as an inner and outer band.
Window sealing tape
In addition to Kompriband , special sealing tapes are also used when installing windows .
Adhesive tapes and films
Adhesive tapes and foils are suitable for protecting sensitive surfaces against environmental influences and for sealing cracks, crevices and holes on surfaces that allow sufficient adhesion.
Self-amalgamating tape
Self-amalgamating tape can be used as corrosion protection for the outside of pipes and instead of shrink tubing to seal repair points on electrical cables.
Fire and rescue services
In addition to the above sealing materials, the following products are used in particular by fire departments: Manhole covers and gully quick-release fasteners can be used to seal road gullies and similar sewer inlets . Binders are also sometimes used. Means for sealing leaks are also leak sealing sleeves and bandages, as well as made of wood or plastic sealing plug .
Individual evidence
- ↑ a b c d Information on the website of the manufacturer of sealing materials - Fermit. Accessed February 2016
- ↑ a b Information ( memento of the original from March 25, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. in the catalog of the manufacturer of sealing materials - Fermit, accessed February 2016
- ↑ a b c discussion in the forum on Haustechnikdialog.de, accessed in February 2016
- ↑ Neo-Fermit Universal - Technical Data Sheet , In: Fermit.de; accessed in November 2019.
- ↑ Installation of PE-HD cold water pipe, Marley.de
- ↑ Installation of PE-HD cold water pipe, Marley.de
- ↑ Technical product and assembly information ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. from the manufacturer Sanha, accessed in February 2016
- ↑ The graphite paste Helvosyt GPO 80 according to the manufacturer Voelkel for application to aluminum die casting molds and intended thermally and mechanically stressed conveyor chains, gear racks, guide rails and other stressed machine elements and can be used up to 1000 ° C; accessed in February 2020
