Westinghouse Electric Corporation

John M Driggers

William E Pirl

Thomas J Saska

Lyman J Petrosky

Bruce W Bevilacqua

Paul J Boone

Donald R Stoner

Arnold S Kitzes

Stephen M Ira

Michael D Hecht

Chris W Bach

James C Yeh

Steve J Orbon

A component maintenance system having a network linked to a data acquisition system, a data analysis system, a historical file of component design and inspection information, and a diagnostic system having the capability to perform structural analysis of discontinuities identified by the data acquisition system. The network nodes may be located apart from each other; for example in the maintenance of a nuclear power plant steam generator, the data acquisition system may be located in a high radiation area while the data analysis system is safely located away from the radiation areas. Furthermore, the diagnostic system and the file of component design and inspection history information may be centrally located and shared to support component evaluations being conducted in numerous geographic locations. Network communication facilitates the rapid evaluation of discontinuities, thereby permitting the inspection plan to be modified as the inspection results are obtained.

Component maintenance system

A process for using an eddy current probe to precisely locate the edges of a baffle plate or support plate which surrounds a tube of a heat exchanger is disclosed herein. The process generally comprises the steps of moving the eddy current probe through the interior of the tube in the vicinity of the plate with the axis of rotation of the coil oriented parallel to the longitudinal axis of the tube. The rate of change of coil impedance is monitored as a function of the position of the coil along the longitudinal axis of the tube. When the rate of change of current flow through the coil attains its first maximum, the mid-plane of the coil is parallel to the bottom edge of the plate. This process is particularly useful in implementing maintenance procedures wherein heat exchanger tubes are selectively expanded along certain portions of their longitudinal axes in order to eliminate or reduce unwanted clearance between the tubes and the bores in the support plates through which they extend. The process may also be used to confirm whether or not a tube expansion has been performed in proper position in a tube relative to a particular support plate.

Process for accurately determining the position of the edges of support

A flexible radiant tube heater is disclosed herein which is particularly useful in thermally stress-relieving the U-bend sections of the heat exchange tubes within nuclear steam generators. The apparatus generally comprises an elongated, flexible mandrel formed from a spring composed of a heat-resistant alloy, a flexible electrical resistance heating element wound around the mandrel spring, and a flexible insulating sleeve formed from braided alumina fibers disposed around the heating element for electrically insulating the heating element from both the metallic spring and the inner walls of the tube. A nosepiece assembly and an endpiece are disposed on the front and back ends of the spring, respectively. A flexible reinforcing member which may be a thin rod of Inconel.TM. is mounted to both the nosepiece assembly and the endpiece and disposed through the windings of the mandrel coil in order to lend more tensile and compressive strength to the mandrel coil. A push rod formed from a stainless steel cable is connected to the endpiece for sliding the heater to a desired location in a tube.

Flexible radiant tube heater

An improved heater assembly and method for applying a brazing heat across a selected longitudinal section of a tube is disclosed herein. The heater assembly generally comprises a heater mandrel having an electrical resistance heating element coiled thereabout, and a support mandrel for supporting and centering this heating element. The heater mandrel further includes a means for directing a flow of inert gas in the space between the coiled heating element and the inner walls of the tube being brazed in order to purge this space of ambient atmospheric oxygen and prevent the heater mandrel from oxidizing. The support mandrel includes a centering means in the form of two roller assemblies, each of which has three spring-loaded rollers equidistantly spaced 120.degree. around its diameter. In the method of the invention, the heater mandrel is inserted into the tube and slid across the longitudinal section to be brazed. The heater then applies a brazing heat while a purging flow of inert gas is directed in the annular space between the coiled heating element and the inner walls of the tube. After the brazing operation has been completed, the flow of purge gas may be increased to cool down the heater assembly. The heater assembly is particularly useful for brazing reinforcing sleeves across sections of corrosion-damaged heat exchange tubes in nuclear steam generators.

Braze heater assembly and method

Both an apparatus and a process for accurately applying a correct amount of brazing heat to a conduit are disclosed herein. The apparatus generally comprises a mandrel including an electrical resistance wire heating element and a heat sensor for sensing the temperature of the inside walls of the conduit which were heated. The mandrel is preferably formed from a refractory material, and the heat sensor is located beneath the surface of the mandrel in order to insulate it from heat radiated from the electrical resistance wire wound about the mandrel body. The mandrel further includes an opening in the portion of the mandrel which surrounds the heat sensor in order that the sensor may be selectively exposed to a section of conduit to which heat was applied by sliding the mandrel to a position which aligns the opening with the wall of the heated conduit. The temperature of the conduit may then be determined as a function of the radiant heat received by the heat sensor. The invention is particularly useful in producing high quality braze joints between reinforcing sleeves inserted within damaged heat exchange tubes of a nuclear steam generator since the heat sensor allows the operator to determine whether or not a proper amount of brazing heat was applied to the sleeve/tube configuration.

Radiant brazing temperature sensing apparatus and process

A brazing apparatus and process which utilizes a dual function heating and eddy current probe coil is disclosed herein. The apparatus generally includes a radiant heater assembly having a coil which is capable of both generating radiant heat to effect a braze joint between a reinforcing sleeve and a surrounding tube, as well as serving as an eddy current probe which locates the sections of this sleeve to which the brazing heat should be applied to effect the desired joint. A switching means selectively connects the coil to either a relatively high, heat-generating current, or to the aforementioned alternating current which induces eddy currents within the metal forming the reinforcing sleeve. The apparatus further includes eddy current detection circuitry for monitoring changes in the coil impedance which result from these eddy currents while the coil is slid along the longitudinal axis X of the reinforcing sleeve. In the process of the invention, the edges of the sleeve are accurately located by noting the position of the coil when the coil impedance attains its first and last local maximum values. Both the apparatus and process of the invention are particularly useful in effecting high-quality braze joints in reinforcing sleeves which are brazed within damaged or corroded heat exchange tubes in nuclear steam generators.

Brazing apparatus having a dual function heating and eddy current probe

Small portable electrical resistance heated radiant heating unit useful for insertion in tube bores to effect localized high temperature heating. Useful for the internal heating of tubes and tube/sleeve assemblies in steam generators, having bores as small as 0.75 cm. or less, for brazing, stress relieving, and other applications.

Small diameter radiant tube heater

A process for brazing a sleeve within a tube which is resistant to longitudinal expansion is disclosed herein. In the first step of the process, a thermally induced radial expansion is induced in the tube in a first longitudinal section of the tube which does not include the ring of brazing alloy which circumscribes the sleeve. In the second step of the process, a brazing heat is applied across the longitudinal section of the tube which does include this ring of brazing material. The residual tensile stress created by the thermally induced radial expansion in the tube avoids the creation of gaps in the braze joint between the sleeve and the inner walls of the tube. This process is particularly useful in creating high-quality braze joints in sleeving operations in nuclear steam generators, where the heat exchange tubes which need to be sleeved may be partially or completely prevented from expanding in the longitudinal direction due to sludge deposits in the generator.

Two-position sleeve brazing process

Small portable electrical resistance heated radiant heating unit useful for insertion in tube bores to effect localized high temperature heating. Useful for the internal heating of tubes and tube/sleeve assemblies in steam generators, for brazing, stress relieving, and other applications. Has a machined mandrel of boron nitride and electrical resistance wire leads that have reduced electrical resistance for reduced heat generation by the leads. The leads preferably are braided, to permit the use of cramped connectors.

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Pittsburgh, PA, United States of America

John M Driggers