Inflatable seal

Door seals if the door is equipped with a seal that provides tightness both in the vacuum and overpressure ranges, the door locking system must ensure that there is no gap between the door and the door flange at the lower areas of the door. This danger must be reckoned with if double seals are used, e.g. inflatable seals. Con-... 

The major penetration inthe RB containment are the main airlock, emergency airlock and fuelling machine airlock. They provide entry into and exit from the RB for personnel and equipments. Each airlock has two doors with an interlock between them such that only one door can be opened at any time. Two inflatable seals are provided for better reliability for sealing between each door and its frame. 

The empty canister is raised and inserted into the transfer cask. The annulus is filled with plant water and the canister is filled with SFP water or plant demineralized water. An inflatable seal is installed in the upper end of the annulus between the canister and the transfer cask to prevent SFP water from contaminating the exterior surface of the canister. The transfer cask with the empty canister is then lowered into the SFP for fuel loading using the overhead crane. Pre-selected assemblies are loaded into the canister and a visual verification of the assembly identification is performed. 

During a pressure transient the cap will be blown off when the pressure reaches about 2 pslg. After the steam has escaped, the butterfly valve will close. Should the butterfly valve fail to seal completely the Inflatable seal can be manually released from the control room to effect the seal. 

A fabric reinforced seal is a completely molded seal that is built with the same operating principles as a homogeneous inflatable seal. The addition of fabric helps increase the amount of internal pressure under which the seal can operate, where higher pressures are required in a non-enclosed environment (Figure 3.3). 

Depending on the conditions that the seal will encounter, we can use nearly any fabric available to reinforce an inflatable seal. Some fabrics used will have limitations in the thickness that can be applied within the part, and what temperatures they can withstand during operation. The following are some of the fabrics used ... 

Typical application areas for inflatable seals in the nuclear industry... 

Inflatable seals are operated through a medium of air or water. Either medium pressurizes the internal chamber in the seal via a valve which, in turn, forces the expansion of the seal profile to its designed shape (Figure 3.4). In addition to air or water, other fluids can be used, such as helium, nitrogen or, in some cases, mineral oils. An inflatable seal can be used in delicate systems. 

Inflatable seals are molded in different planes radially in, radially out, axially and combinations thereof (Figures 3.5-7). They wiU conform to many different contours. They can be made in strips with closed ends or in continuous loops. The bend radius will vary from seal to seal and the seal can be molded to exact configurations, even of very sharp corners. 

Figure 3.6 Inflatable seal with sharp corner...

Figure 3.7 Inflatable seal with bend radii...

Non-reinforced inflatable seals are homogenized seals manufactured only from rubber without any reinforcement but having thicker wall sections. These inflatable seals can be used for a variety of applications where sealing two surfaces that move in relation to each other is required. By introducing a medium such as air or fluid, the seal will expand at a specified rate until a determined size is achieved. The rates and sizes of expansion of an inflatable seal are determined by its shape (Figure 3.8). Nearly all inflatable seals, reinforced or non-reinforced, are custom fabricated for a specific application. 

Butyl rubbers, unlike many other rubbers, do not break down easily during the normal mixing process in the mill. The compound viscosity can be controlled by selection of the proper grade of butyl rubber, the type of carbon black and the type and loading level of oil. Relatively high loading levels of paraffinic or naphthenic oils are employed for typical butyl applications, such as inflatable seals, tubes or sealing bladders and solid body items. 

The dome valve is a more recent addition to the list of valves available, but it has been specifically designed for this type of duty, and is now being widely used in industry. The valve has moving parts, but these move completely out of the path of the conveyed material when the valve is open. On closing, the valve first cuts through the material and then becomes airtight by means of an inflatable seal. The valve can be water-cooled and so it is capable of handling hot materials. 

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