Technical Bulletin TB-004

PP-260SC with seal plug installed

Typical power secured to a pump discharge pipe

Technical Bulletin

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Tri Nuclear Corp.

TECHNICAL BULLETIN
TB-004A 08/01/08

SUBJECT: Failure of two Tri Nuclear PP-260SC pump pigtails at McGuire Nuclear Power Plant.

Applicability: All Tri Nuclear ‘sea con’ pumps (PP-100SC, PP-260SC, PP-600SC, PP-1000SC)

Background:

McGuire station recently broke two PP-260SC pump pigtail connectors. The first connector broke on a system that had been in service for approximately 5 years. The connector broke while attaching the cable. The second connector broke while removing the cable on a system that had been used one time.

Tri Nuclear set up a test pump in our shop and was able to duplicate the break in the electrical connector.

Fractured PP-260SC Pump Pigtial connector

Conclusions

The fracture in the pigtail connectors occurred in the threaded portion of the connector in vicinity of the keyway.

We believe there are two main contributing factors causing the pigtail connector to fracture:

The first contributing factor comes from over-torquing the connector during installation of the power cord. This over-torquing could occur when channel lock pliers are used to tighten the power cable to the pigtail connector.

The second contributing factor occurs when there is a bending moment put on the connector while it is installed and over torqued. This bending could cause excessive stress in the connector in the vicinity of the threaded portion and key way. If a fracture occurs under these conditions, it can quickly spread out in a half moon shape.

Even if the threads have fractured on a pigtail connector, we believe this will not affect the electrical seal integrity of the electrical connection. The connection has two internal sealing o-rings that are located well below the threaded portion of the connector.

Recommended Customer Action

· A visual inspection of all pump pigtail connections should be performed to ensure that there are no stress fractures in the vicinity of the keyway and threads. If fractures are found the pump should be removed from service and the pigtail replaced. Please contact Tri Nuclear for the procedure, price and availability of replacement pig tail assemblies.

· When installing and removing the power cord, do not move the power cable connector with side to side motion in an attempt to install or remove it.

· If difficulty is encountered during installation ensure that the keyway is lined up and that the male end of the PSC-100 power cord is properly lubricated with a non conductive electrical lubricant (Dow Corning #4).

· If difficulty is encountered during removal ensure the power cable has been unthreaded fully and pull in the vertical direction ONLY to remove the power cable from the pump.

· Install the power cord to pump pigtail HAND TIGHT ONLY. Do NOT use any tools (pliers, channel locks etc.) to tighten the connection.

· Eliminate the possibility of a bending force on the connector by using cable ties to fasten the pump power cable to the vertical discharge pipe of the pump.

The pump pigtail threads must be protected at all times when the pump power cable is not installed. A special sealing plug (P/N: SC-P) should be installed in place of the power cable when it is removed. This plug protects the threads and seals the pump pigtail connection from moisture and other contamination. Please contact Tri Nuclear for price and availability for seal plugs.