Westinghouse Electric Corporation

Allen J Baum

Robert Draper

Gregg D Auld

Donald G Lorentz

George C Economy

William J Stenger

Judith B Esposito

William M Cox

An improved method for cleaning heat exchangers, wherein a first cleaning liquid is used to remove a majority of the accumulated sludge and deposits from the surfaces of the heat exchanger, and a second cleaning liquid is used to remove deposits from the crevice regions of the heat exchanger. Boiling may be induced in the crevices between the tubes and the tube support plates by venting of the secondary side while heating through the primary side of the heat exchanger. Repeated venting as the water level is lowered results in crevice boiling at each tube support plate. Mechanical cleaning techniques such as pressure pulse cleaning may be utilized with either or both of the cleaning liquids. Additional liquids may be introduced into the heat exchanger to provide further cleaning action or to facilitate flushing of the previous cleaning liquids.

Two-step chemical cleaning process

An improved method for cleaning heat exchangers, wherein a first liquid containing a cleaning agent is used to remove substantially all of the accumulated sludge and deposits from the surfaces of the heat exchanger, and a second liquid containing a cleaning agent is used to remove deposits from the crevice regions of the heat exchanger. The concentration of cleaning agent in the second liquid and/or the duration of exposure for the second liquid are preferably greater than those of the first liquid, because the risk of corrosion is reduced as a result of a lower concentration of ferric ions in the second liquid. Furthermore, improved crevice region cleaning is obtained with the second liquid because the available cleaning agent is not depleted by the large volume of sludge and deposits removed by the first liquid. Mechanical cleaning techniques such as pressure pulse cleaning may be utilized with either or both of the cleaning liquids. Additional liquids may be introduced into the heat exchanger to provide further cleaning action or to facilitate flushing of the previous cleaning liquids.

Cleaning method for heat exchangers

A device for creating a corrosive condition and monitoring that condition, adapted for use in active fluid heat exchangers, has a sealed tube having corrosion sites spaced apart on its exterior. Structure positioned on the outside of the tube at the corrosion sites provide crevices for retaining corrosive sludges in contact with the corrosion sites. The interior of the tube is pressurized with a gas to stress the tube thereby accelerating corrosion of the surface. Heat is provided to the corrosion sites from within the tube when placed within a fluid reservoir, such as the secondary side of a fluid heat exchanger. The heat concentrates corrosive chemicals at the corrosion sites, also accelerating corrosion. Electronic probes can be mounted in proximity to the corrosion sites for real time monitoring of the progress of corrosion.

Tube corrosion accelerator

An improved method for removing sludge and corrosion products from the interior of a heat exchanger vessel, such as a nuclear steam generator, which comprises the steps of generating a series of pressure pulses within a liquid chelate-containing chemical cleaning agent after the agent has been introduced into the interior of the vessel to create shock waves in the liquid for dislodging, dissolving and fluidizing sludge and corrosion products. The liquid chemical cleaning agent is removed from the vessel after only about 10 to 70 percent of what would have been its normal residence time without the pressure pulses. The method further includes the steps of simultaneously recirculating the chemical cleaning agent through a filter assembly during the pressure pulsing operation in order to remove fluidized sludge and corrosion products dislodged by the pressure pulsing, thereby affording them no opportunity to resettle back onto the surfaces of the heat exchanger vessel and interfere with the chemical cleaning of the vessel. The method reduces not only the time required for a particular chemical cleaning agent to effectively clean the vessel, but further reduces the number of times such chemicals need to be introduced into the vessel, which in turn results in the production of less radioactive liquid waste products.

Chemical cleaning method for steam generators utilizing pressure pulsing

An improved, compact model steam generator having multiple primary systems is described herein. The model steam generator of the invention is capable of simultaneously simulating a plurality of thermo-hydraulic conditions which may exist in various areas of a full-scale nuclear steam generator in order that the effect of these various conditions on the heat exchange tubes within the full-scale generator may be separately monitored. The model steam generator of the invention generally includes a boiler vessel having a primary side which houses a plurality of individually controllable primary systems, a tubesheet, a secondary side, and a plurality of sample heat exchange tubes for transferring heat between each of the individual primary systems and the secondary side of the boiler vessel. A heat flux control system connected to each of the heat sources within the primary systems allows the operator to separately adjust the heat fluxes of each of the ends of the sample tubes disposed within the secondary side of the boiler vessel. In order to reduce the longitudinal and diametrical dimensions of the primary side of the boiler vessel, the heat source used in each of the individual primary systems is preferably a single, high-intensity electrical heater formed from a coil or other high density configuration of electrical resistance wire. Moreover, each of these primary systems may be housed within the tube-receiving bores of the tube sheet of the boiler vessel in order to minimize the longitudinal dimensions of the primary side even further.

Compact model steam generator having multiple primaries

A process for cleaning out deposits collected in the restricted areas of the secondary side of a steam generator of a nuclear power plant system, where the concentration of an aqueous organic cleaning agent solution is increased in the restricted areas, relative to the remainder of the solution. The solution is heated, at an initial pressure which prevents boiling of the solution, and the pressure is reduced to effect localized flashing and boiling of the solution in the restricted areas. After a period of time, the pressure is increased and the cleaning agent solution, containing solubilized deposits, is withdrawn from the secondary side of the steam generator. The heating temperature and pressure will vary depending upon the type of deposit to be removed, either ferrous-type or copper-type deposits.

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Pittsburgh, PA, United States of America

Allen J Baum