SSINS No.: 6830 Accession No.: 8005050067 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 June 27, 1980 IE Circular No. 80-16 OPERATIONAL DEFICIENCIES IN ROSEMOUNT MODEL 510DU TRIP UNITS AND MODEL 1152 PRESSURE TRANSMITTERS Description of Circumstances: The NRC has recently been advised through a 10 CFR 21 report that operational deficiencies exist in Rosemount Inc. Model 510DU trip units and Model 1152 pressure transmitters as follows: MODEL 510DU TRIP UNITS The 510DU trip units have common mode failures of two switches; S1 in the trip status output, LED logic circuit and S2 in the trip output logic circuit. The trip units involved are those with serial Numbers 3001 to 4203. The 510DU units having serial numbers within this range that are not trip units are not affected (i.e., Card Files, Readout Assemblies, Calibration Units, etc.). Malfunction of these switches appears as an open circuit in the output logic upon receipt of an actual trip signal. Switch (S2) failure could result in failure to automatically activate a safety function. MODEL 1152 PRESSURE TRANSMITTERS The model 1152 pressure transmitters have a common mode failure of a capacitor when the transmitter operating environmental temperature is greater than 175F, and when the damping potentiometer is rotated clockwise. The failure results in a decrease in transmitter output current of up to 10 percent of the correct current. For example, when the transmitter is used in an indication circuit, the parameter indication would be correspondingly lower than the correct value if the capacitor failure occurred. The failure potentially involves all pressure transmitters with the following model designations: Rosemount Pressure Transmitter Models: 1152 _ _ _ E _ _ T0280 1152 _ _ _ E _ _ T0445 1152 _ _ _ E _ _ T0400 Available information indicates that the problems outlined above have been reported to each customer who was furnished the Model 510DU trip units and Model 1152 pressure transmitters. . IE Circular No. 80-16 June 27, 1980 Page 2 of 2 RECOMMENDED ACTION FOR LICENSEES AND HOLDERS OF CONSTRUCTION PERMITS All licensees of nuclear power reactors and holders of construction permits should be aware of the potential problems discussed above. It is recommended that the following actions be taken: 1. Determine if your facility has installed or plans to install the Rosemount Model 510DU trip units and/or the pressure transmitters described herein in any safety-related equipment. 2. If it is determined that your facility has installed or plans to install any of the affected units described herein, contact the supplier for performance of the required modifications to the units to resolve the problems. 3. Modifications should be performed on all affected units prior to plant operation. If the affected units are installed in plants that are operating, the following actions are recommended for continued operation until the units are modified. a. 510DU Trip Units A functional test verifying proper operation of the trip units should be performed. b. Model 1152 Pressure Transmitters On pressure transmitters that are affected and that may be subjected to operating environmental temperatures greater than 175xF, the transmitters should be operated with the damping potentiometer (R12) in the fully counterclockwise position. CAUTION The circuit output should be monitored to assure that no action detrimental to operation results from placing R12 in the counter clockwise position, such as spurious tripping caused by unstable operation. No written response to this circular is required. If you require additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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