1. Field of the Invention
This invention relates generally to an improved mechanical snubber apparatus and, more particularly, to such a snubber which may be tested in place within a snubber system.
2. Description of the Prior Art
Shock absorbing or damping snubbers are widely used in electric power plants, particularly nuclear power plants, in which pipes or other structures are yieldably attached, by, for example, pipe hangers or other supports, to relatively fixed supporting structure, for example, power plant walls or ceilings. In such applications, the snubbers are operatively connected, usually as part of a strut assembly, between the pipe and the supporting structure. The snubber operates to permit relatively unrestricted motion or movement of the pipe relative to the supporting structure in response to normal slow movements of the pipe, such as might be induced by routine thermal expansion or contraction during plant start-up or shutdown, but to resist or damp rapid vibratory relative motion of the pipe, such as might be induced by seismic or other transient shock or vibration. A typical state-of-the-art snubber of the mechanical type is disclosed and claimed in my U.S. Pat. No. 4,286,693, issued Sept. 1, 1981, and entitled "Mechanical Snubber". While the service life of high quality mechanical snubers of the type described in the aforementioned U.S. patent should be on the order of several decades, their function and proper operation are so important to the safety of the power generating plants that such snubbers must be periodically tested to ensure that they are operating properly. Accordingly, in the past, it has been the general practice in the industry to have technicians periodically remove each snubber, or the snubber and strut assembly, from the system for examination and testing. If the snubber is located in a radiation contaminated area, such as in or near the reactor of a nuclear power plant, the technicians must wear protective clothing and the snubber must be decontaminated to reduce the absorbed radiation to a safe level prior to the testing thereof. Following testing, if the snubber is determined to operate within the limits of the applicable operating specification, the snubber is replaced in the system. If the testing indicates that the snubber is not performing properly, it must be replaced or repaired.
With large snubbers and large snubber and strut assemblies weighing hundreds of pounds, and with some power plants employing hundreds of snubbers, it is evident that the present test procedures are highly cumbersome, time-consuming, and extremely expensive to perform. The problems involved in current snubber test practices are overcome by the present invention which provides an improved mechanical snubber that lends itself to in-place testing. The present invention further provides an apparatus which may be retro-fitted to existing snubbers for testing such snubbers in their normal, operational location in a snubber system. In addition, the present invention is useful for positioning and aligning snubbers, particularly large sized snubbers having high drag forces, to facilitate their proper installation within a snubber system.