A solid ledge seal is the most simple ‘mechanical stop’ seal. This consists of an annular steel ring, which is welded around the inside periphery of the vane and which mates with the vane edge in the fully-closed position. A ledge seal gives a reasonably good seal (compared to no seal at all) and is very robust and maintenance-free.
In order to increase the sealing efficiency beyond that of a solid steel on steel contact, Flowrite offers a range of more sophisticated seals.
A flexible metallic seal consists of a twin layer of 0.5mm stainless steel seal elements which are clamped to the vane periphery and mate with a landing bar welded around the inside periphery of the damper body. The flex in the seal elements compensates for any slight fabrication tolerances and ensures a firm contact around the full periphery of the seal.
A rubber ‘P’-section compression seal is clamped to an angle welded around the inside of the damper body. As the vane closes is compresses the bulk of the rubber ‘P’-section. Several rubber materials are available including nitrile, silicone, Viton and PTFE. This type of seal provides an excellent (single seal row) sealing efficiency but has temperature limitations to the properties of the rubber material.
The ‘P’-section compression type seal can also be made from ceramic fibre if higher temperatures are involved. This material is suitable up to around 900⁰C.
A rubber wiper seal can also be fitted which consists of a flexible rubber strip which is clamped around the vane periphery and which wipes against the inside of the damper body in the fully closed position. This type of seal is particularly useful on small dampers where the air stream contains some non-abrasive traces of particulates, as there is no edge for dust to build up against.
Whereas a shut-off damper usually incorporates a single seal row, our isolation dampers incorporate a double seal row and a ‘pressure barrier’ between the two seal rows (the seal interspace).
A small vent damper is fitted to the main damper body and allows air to flow either into or out of the seal interspace. The small vent damper is fitted with its own actuator, or can be linked to the main actuator, such that the vent damper opens as the main damper vane closes, and vice versa.