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Inflatable seals

Garlock expand their range of products Denise Fröhlich
Inflatable seals

Garlock have taken over the French company Cefilac, thereby supplementing their range of products as a result of this integration. New to this range are inflatable seals which are particularly suitable for mobile components that need to be separated or opened frequently.

They have never become unfashionable: inflatable armchairs, settees or stools are experiencing a comeback after 20 years. Such items are not just used for fun and entertainment, however – developed back in the Fifties, inflatable seals are today being used in more and more applications than ever. By taking over Cefilac – a French company of sealing specialists based in St. Etienne – Garlock have now also added inflatable special seals to their existing range of metal and mechanical seals. The products, which are marketed under the brand name Cefil’Air, provide a leak-proof seal, are simple in design and do not give.

Separating layer between supporting and contact surfaces
An inflatable seal consists of a concave, spiral or flat elastomer hose, which when inflat-ed forms a solid and leak-proof sealing layer between the supporting and contact surfaces. Owing to its long service life, the inflatable seal represents a viable alternative to conventional solid seals, particularly for sealing mobile components which need to be separated or closed at any time,. Garlock offer Cefil’Air seals for temperatures ranging from -110 to + 250 °C depending on the material (see Table), as well as for pressures of 10-3 mbar (low-pressure seals) and up to 10 bar (high-pressure seals). The elastomer materials which are used offer a high elastic modulus and tensile strength, so that they may be subjected to minor stresses when installed. For this reason, therefore, the specified installation dimensions must be observ-ed.
The high-pressure seals are available with a toothed or comb profile with dimensions from 16 x 12 mm to 35 x 32 mm. When the inflatable seals are installed, the grooves must surround them on all four sides. The low-pressure seals can only be attached at the base and must be allowed to inflate freely. They are available with dimensions from 30 x 200 mm to 150 to 80 mm.
The ends of straight seals can be designed as solid pieces. In this case, the seals cannot expand or contract in this area. The profile end which is used may provide a seal in either the expanded or the contracted state. For applications which require expansion over the entire length of the seal, Garlock supply special, expandable end pieces.
Expansion by means of elastic arms
Thanks to the special shape of the side walls, which act like two elastic arms, the medium (generally compressed air or optionally a liquid or a gel) expands in the direction of the contact surface so as to provide a tight fit. The seal is contracted in the same way – after discharging the medium, it contracts and returns to its initial shape.
When not installed, the seals can only be inflated to a maximum pressure of 0.8 to 1.5 bar (depending on the profile). The required degree of tightness is achieved after inserting the seal into the groove and inflating it to a pressure of 2 to 2.5 bar at room temperature.
High and low-pressure applications
The inflatable seals in the Cefil’Air range have been developed for a variety of sealing, handling and locking applications, for example:
• mobile partition walls,
• storage and transport vessels,
• heated chambers,
• clean rooms,
• sliding and quick-closing doors,
• autoclave and sterilisers,
• centrifuge filters.
Cefil’Air seals are particularly well suited for pressurised chambers. If excess pressure prevails in the chamber, its tightness will depend on the sealing gap J, on the surface characteristics of the sealing face itself and on the pressure Pi within the inflatable seal. In order to keep the free surface area as small as possible, the sealing gap needs to be reduced to a minimum for this application. Cefil’Air products are capable of sealing off a dynamic vacuum down to 10-3 mbar.
Cleanness is an absolute must
All components in immediate contact with the seal should have a clean surface. Rolled metal sheets can be used for the grooves; however, they need to be freed of dirt or scale residues. The best results can be achieved with an average surface roughness of Ra = 0.8 to 1.6 µm. If tightness is not an abso-lute requirement, a value of 3.2 µm is permissible. Before the seal is fitted, it must be completely deflated. The air connection must be fitted first.
In the non-active state, the seal only rests in the groove and is protected against damage by the groove flanks. Sealing gap J can be reduced to zero without any risk of shearing the seal. (Fig. 2).
The Cefil’Air inflatable seals manage without additional fixing. In order to ensure tightness at all times, the pressure needs to be maintained in the seal. Possible positive or negative pressure conditions must be compensated by a pressure controller.
Garlock
Fax: ++49/231/34 92 22
Further information cpp-206
Mr. Plaisier, Garlock have taken over the French sealing specialists Cefilac. What were the goals of this take-over?
Plaisier: Garlock are one of the international market leaders for high-quality and sophisticated sealing technology, and have been expanding for years. Alongside the US, Europe is of course our most important market. By integrating Cefilac we were able to kill three birds with one stone. Firstly we have reinforced our profile with new or supplementary products. Inflatable, metallic and mechanical seals according to European specifications have been added to our range. Finally, we have been able to strengthen our position on the important French market and expand our production capacity in Europe.
For Garlock, inflatable seals are an entirely new category of products. Which materials and designs do you offer?
Plaisier: We have seals made of all common elastomer compounds. We offer low-pressure and high-pressure profiles for internal pressures up to 10 bar as standard. Many special profiles are available to meet specific customer requirements.
What are the areas of application for inflatable seals, especially in chemical apparatus, and where are their limits?
Plaisier: In chemical apparatus the seals can be found in docking systems for bulk materials, as gas-tight seals for gate and butterfly valves and as door seals for drying cabinets, clean rooms and heated or air-conditioned chambers. They are well suited for large flange joints which need to be opened and closed frequently, or when large components need to be pressed. There are practically no limits to the potential uses.
Where can these seals present an alternative to conventional systems?
Plaisier: Especially in the case of large flange joints which need to be separated and joined frequently, inflatable seals represent a good alternative. The flanges must simply be locked – for example by means of a bayonet – and then the seal is inflated. Time-consuming assembly and disassembly work is a thing of the past. If inflatable seals in connection with gate valves, they are not exposed to any dynamic loads, which has a positive effect in the form of a longer service life. The gate valve moves to its end position with the seal deflated and only then is the seal activated.
What is the market share for these products and what opportunities do you see for the future?
Plaisier: In Germany our inflatable seals have a market share of about 70%.
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