sealing solutions for communications equipment

Sealing solution for Communication Equipment

Communications sealing applications present many unique challenges. Environmental sealing is not as simple as just keeping water out of an enclosure. Due to varying environmental conditions, chemical reactions between the environment and the enclosure must also be considered. Harsh environmental conditions such as corrosive coastal air or flooding make sealing sensitive electronic components of prime importance. The long life expectancy of equipment also mandates that premium sealing grade elastomers be used.

Mechanical Design
Seals are often required to compensate for large manufacturing variances in the dimensions and flatness of enclosures. Dense (non-foam) hollow extrusions perform well in these situations because of their ability to accommodate larger cross sectional squeeze percentages without incurring large reaction forces or overfilling the gland. Depending on the configuration of the seal and sealing surfaces, a hollow seal can function when being squeezed to 50% of its original height. The chart below shows the dramatic effect wall thickness has on closure force. The low closure force properties of a hollow spliced seal allow it to be used in areas where a solid dense seal cannot perform. Enclosures manufactured from plastic or thin metal tend to warp or crack when subjected to large seal loads. Fasteners and hinges used to hold the enclosure shut may also be excessively stressed by seal closure loads. Die cast enclosures can have large tolerance stack-ups or porosity in the groove which is often difficult to seal. A hollow spliced ring in these applications will solve most tolerance stack-up and porosity problems because of its ability to be compressed more than solid cross-sections and better conform to imperfections of the groove.

Friction Fit
Another key advantage of dense hollow spliced seals is that they can be designed to self retain or “friction fit” in a seal gland. The void of dense material created by the hollow core allows the outer diameter of the seal to be larger than the width of the seal gland without overfill.

Special Considerations: Often communications equipment must be sealed from environmental conditions and shielded against electromagnetic interference. In such cases Parker can provide a “dual seal” solution, with TechSeal’s hot vulcanized spliced gasket as the outer environmental seal and a Parker Chomerics Division seal inboard to provide the required level of shielding. The dual seal approach is becoming more common as electronic enclosures are placed in more severe environments.