A filing with the U.S. Nuclear Regulatory Commission (NRC) by Weschler Instruments, a division of Hughes Corp., identified a potential defect in its KX-241 axial, VX-252 and VC-252 instrument models.

The condition could result in the instrument's inability to perform its safety-related function, which is accurate indication of a measured process. The company filing said the symptom of this inability to perform its safety-related function is changing indication, which is not accurately reflective of the monitored process. This symptom may exhibit as a wandering indication or difficulty in maintaining a stable zero scale setting.

The company said the condition is due to a dimension of a component of the assembly being beyond lower tolerance limits. The part, known as the insulating bushing, is part number 186N051H01. It is used as one of two anchor and centering points for the part of the instrument that the pointer is attached to.

The subject instrument models are and have been sold as commercial, nuclear designated and nuclear safety-related.

The affected production period is from Aug. 15, 2018, when the non-compliant bushings were received from the supplier, through Jan. 11, 2019, when the condition was discovered by production personnel.

The company said that an initial analysis of the movement of bushings through inventory suggests that non-conforming bushings may not have been used on safety-related instruments, or were used in a quantity of less than 10 units.