Information Notice No.80-08 – The States Company Sliding Link Electrical Terminal Block
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 7, 1980
Information Notice No. 80-08
THE STATES COMPANY SLIDING LINK ELECTRICAL TERMINAL BLOCK
Description of Circumstances:
On July 19, 1979, the Consumers Power Company notified the Nuclear
Regulatory Commission of a defect found in the sliding link electrical
terminal block manufactured by the States Company, a subsidiary of Multi Amp
Corp. The defective terminal blocks were found at the Midland plant.
The connection between the two slotted bars on the terminal block is made by
a U-shaped sliding link and spacer located between the two bars. The top of
the U-shaped link and the spacer are drilled and the bottom of the link is
threaded to accept a 8-32 screw. When the screw is tightened it binds the
link, spacer and bar together to make electrical connection. Loosening the
screw and sliding the link from between the bars breaks the connection. The
purpose of the link is to provide easy insertion of test instruments, etc.
into the circuit.
The defect, which has been identified in 5% of the terminal blocks checked,
occurs in the form of a crack between the threaded screwhole and the side of
the U-shaped link. When the screw is tightened the crack widens and a poor
or intermittent electrical connection can result. A defective link is
impossible to cinch tightly in place and is difficult to detect visually.
Enclosure 1 shows the States Company terminal block. The defect, a crack in
the bottom portion of the metal U-shaped link, is displayed in the exploded
view of the terminal block assembly. These terminal blocks are widely used
in the nuclear industry and may be used as permanent installations in safety
related systems. The defective mechanical connection can cause an electrical
This Information Notice is provided to inform licensees of a potentially
significant matter. It is expected that recipients will review the
information for applicability to their facilities. No written response to
this Information Notice No. is required. However, the reporting requirements
as set forth in the regulations must be met. If you require additional
information regarding this matter, contact the Director of the appropriate
NRC Regional Office.
Graphic Display of Terminal
Page Last Reviewed/Updated Thursday, March 25, 2021