US3116977A

US3116977A - Method and apparatus for screening corrosion inhibitors in boiler water

Info

Publication number: US3116977A
Application number: US48471A
Authority: US
Inventors: Hilary A Grabowski; Peter F Santoro
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1960-08-09
Filing date: 1960-08-09
Publication date: 1964-01-07
Anticipated expiration: 1981-01-07

Description

H. A. GRABOWSKI ETAL v 3,116,977 METHOD AND APPARATUS FOR SCREENING coRRosIoN Jan. 7, 1964 Filed Aug. 9, 1960 Fig. l.

INI/ENToRs Hilary A. Grubowski Peter F. Santen BY (2.1... ZZ@

TTORNE Y United States Patent METHD AND All ATUS FR S REENENG CllROSlN INHHBITRS iN BLER WAER Hilary A. Grahowsiri, Sinsliury, and Peter F. Santoro,

Thompsonviile, Conn., assigner-s to Combustion Engineering, inc., Windsor, Conn., a corporation et lleiaware Filed Aug. 9, 196i?, Ser. No. @,471

Claims. (Cl. 231-230) This invention pertains generally to a method and apparatus for testinfy the electiveness of corrosion Water treatment or inhibitors and particularly for testing or screening corrosion inhibitors employed in the steam generating art.

It is the purpose of the invention to provide an apparatus and process for testing a substantial number of specimens in a short time to determine the eilectiveness of a corrosion inhibitor for use with steam generators under the conditions that prevail in the steam generator. In steam enerators various inhibitors are employed to prevent or deter corrosion of the metallic parts of the steam generator and in the operation of steam generators the conditions under which corrosion is a problem include the intermittent wetting of the metallic tubes and other elements in the evaporating region. In this region these metallic elements are intermittently wet and dry and as a result of the evaporating action concentrations oi boiler water constituents build up or accumulate on these elements.

The method and apparatus of the present invention provides a relatively simple and effective way to duplicate, relatively accurately, these operating conditions and so test the effectiveness of the inhibitors that are dissolved in the boiling water to inhibit corrosion of the parts of the steam generator. The invention is particularly well adapted to test the electiveness of water treatments or inhibitors to prevent or inhibit stress corrosion cracking of austenitic stainless steel employed with steam generators particularly in the evaporating region. This problem, with regard to stress corrosion cracking of this type of material, is an extremely serious one, with it having been found that austenitic stainless steel, when under stress and disposed in boiler water which contains chlorides, which all boiler Water does, is very susceptible to this particular deterioration or corrosion.

In accordance with the invention there is provided a pressure container or vessel which includes electric heating elements disposed about the vessel to heat water disposed therein and in which extends a rod which is provided with a read at its end or inner extremity. A suitable motor drive is connected at the upper end of the rod to move the saine up and down at a predetermined rate or period of reciprocation. The head carries the specimens which are to be immersed in the boiler water that contains the particular inhibitor being tested and the lower region of this vessel contains this water with the water being heated by the aforementioned electric heaters 4to the desired temperature. The head is moved up and down so as to raise and lower the specimens above and below the water level. Accordingly, the specimens are intermittently wetted.

lt is desirable to dry the specimens when they are located in the region above the water level so as to produce the evaporating effect in the steamgenerator. Furthermore, since the action that takes place in a steam generator is to have the metallic elements heat the water or be at a higher temperature than the water such is the condition which prevails in the organization of the invention. In order to heat the specimens, there is provided a source of electrical potential which is connected to the specimen so as to pass a high current through them and arias?? Patented dan. 7, ltl

ICC

accordingly heat them Wherefore when the specimens are withdrawn from and are above 'the liquid the liquid will quickly evaporate.

The head is designed so that a large number of specimens may be mounted thereon and accordingly a large number of specimens may be simultaneously tested and the operation of the organization is such that the conditions in the steam generator are closely duplicated and an accurate and satisfactory test may be effected in a short time.

Accordingly, it is the object of this invention to provide an improved method and apparatus for testing corrosion inhibitors as employed in boiler water and under the conditions existing in the steam generator.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in View, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as 'to attain the results desired as hereinafter more particularly set forth in the following detailed description of the invention as shown by the accompanying drawings wherein:

FlG. l is a somewhat diagrammatic representation of the organization of the invention with this representation being in the nature of a vertical section;

FIG. 2 is a transverse section taken generally along line 2 2 of FIG. l;

FlG. 3 is a fragmentary sectional View through one portion oi the rim that forms part of the head of the organization ot the invention.

Referring now to the drawing, wherein like reference characters are used to designate like elements throughout, the illustrative and preferred embodiment of the invention depicted therein includes a pressure vessel or container l@ which is comprised of an inner cylindrical member 1?., preferably made of Monel metal or the like, and provided at its upper end with threaded collar 14. Disposed about member l2 are a plurality of electric strip headers le which are connected with an electric potential 13 through electric control device 2t). These heaters are effective to heat the boiler water 2l which partially lills vessel l@ with 22 being the level of this boiler water.

Disposed about cylindrical member l2 and heater elements ld is a layer of thermal insulation 24 with this insulation layer being contained within the shell or casing 26.

The upper end of vessel l@ is provided with a removable closure in 'the form of a threaded nut 25S which is threadably received on collar le and which is provided with a radially inwardly extending flange that overlays a complementary outwardly extending flange on the cover member 3i? as disclosed. A iluid tight seal is provided by the gasket 32 disposed intermediate cover member 3@ and the upper end of cylindrical member l2.

Extending downwardly through and generally coaxial of cover member 3l) is the drive rod 343- and in order to insure a iiuid tight seal a suitable stuffing box 36 is provided which is secured to and extends up from member Sil as shown.

At the lower end of rod 34 there is mounted a head member 38 which includes a hub portion and a rim portion that is supported from the hub. This rim portion is of laminated construction as disclosed in FIG. 3 and includes outer and inner metallic annuluses d@ and 42 respectively which are separated by a layer of electrical insulation ed. The metallic specimens are supported from this rim and the specimens are preferably U bent as shown in FIG. 3, having their upper ends connected with the annuluses il and d2.

The head member 33 with its attached specimens is periodically reciprocated so that the specimens are moved up and down to and from a position above the

liquid level

2,2 and a position below the liquid level. This latter position being depicted in FiG. 1. In order to provide this reciprocating action a suitable motor drive is connected to the upper region of rod 3d with this drive, as illustrated, including reversible electric motor lil which has connected with its shaft 42 a pinion and with this pinion engaging suitable teeth le formed on the rod 34. The operation of motor 4d is preferably controlled by timer 43 and the resulting drive that is produced is eiective to maintain the specimens in the position shown in FiG. l for a predetermined time, such as live minutes, and thereafter elevate the specimens into a region above level 22 for another predetermined time, again such as five minutes, and continuously repeat this operation.

Each of the specimens 39 is heated by having a rela- 'tively high current pass therethrough and for this purpose there is provided a source of electrical potential SG which is electrically connected with these specimens by means of insulated conductors S2 and Srl that extend centrally down through drive rod 34 with one of these connectors being connected with annulus d@ and the other with annulus 42. The potential source t? is of low voltage, high current capacity and is adjusted so that the elements 39 will be heated to a temperature that is above the temperature of the boiler water in vessel l0. For eX- ample the value of this potential source may be set to raise the temperature of the specimens 16 to 20 above the temperature of the water while the specimens are in the water phase and when the specimens are raised above the water level the temperature will increase because of the poorer heat dissipation qualities of steam as compared to water. When thus raised, the liquid adhering to the specimens will quickly evaporate.

At the beginning of a run, current will be supplied to the strip heaters 16 and to the specimens 39, when the desired Water temperature is reached and which temperature is detected by the thermocouple 56 the strip heaters 16 will be energized intermittently to maintain the water temperature at its desired value while the specimens will be heated continuously.

By forming specimens 39 in the manner disclosed the U bent portion thereof which is immersed intermittently in the body of water is, of course, under stress as a result of bending the metal strip and accordingly the effect of the inhibitor to prevent corrosion of this stressed region will be determined.

It will be appreciated that a relatively large number of specimens can be simultaneously tested, i.e. l2 to 18 and as previously mentioned, the organization is well adapted for testing the effectiveness of chloride stress corrosion Water treatments. in testing these treatments or inhibitors the specimens 39 would be austenitic stainless steel of various types and make ups and the production of stress corrosion cracks at the stressed U bend portions of the specimens would be determined with this determination representing the actual conditions prevailing in the steam generating region of a boiler.

Accordingly a relatively simple, yet eitective method and apparatus is provided in accordance with the invention for screening corrosion inhibitors for use in the boiler Water of steam generators.

While we have illustrated and described a preferred embodiment of our invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. We therefore d0 .1,101 Wish to be limited to the precise details 4 set forth but desire to avail ourselves of such changes as tall within the purview of our invention.

What is claimed is:

1. The process of screening corrosion inhibitors for boiler water comprising providing in an enclosed container a heated bath of water having the inhibitor dissolved therein, periodically immersing a plurality of metallic test specimens into the bath and withdrawing the same into the space thereabove, passing a current through said specimens and thereby heating the same to a temperature above said bath and so the specimens quickly become dry when moved from the Water bath into said space, and continuing the periodic emersion and withdrawal for a substantial period.

2. The process of testing the effectiveness of inhibitors of stress corrosion cracking of austenitic stainless steel in boiler water comprising providing a heated bath or" boiler water having the inhibitor dissolved therein, provid-.ing a bent specimen of austenitic stainlesssteel so that stresses are developed at said bend, for a predetermined time, pcriodically immersing the bent portion or" the specimen in said bath and withdrawing the same into the space and passing a current through said specimen to heat the same to a temperature above said bath and so it will quickly become dry when moved from the water bath into said space.

3. An organization of the type described comprising a generally tluid tight vessel partially iilled with boiler water having a corrosion inhibitor dissolved therein, means for heating said water to a desired temperature, means operative to support a metal specimen in said vessel and periodically move the same into and out of said water, a source of electric potential and means connecting said source to said specimen so as to pass current therethrough, said source being such as to heat said specimen to a desired temperature above the temperature of the water.

4. A device for testing the effectiveness of a stress corrosion cracking inhibitor in boiler water comprising a pressure vessel partially iilled with boiler water having said inhibitor dissolved therein, support means exten(- ing through the upper end of the vessel, a plurality of bent strips of austenitic stainless steel supported by said means within said container, means operative to periodically move said support to move the bent portion of the strips into and out of the water, a source of electric potential connected with said strips to pass current therethrough, said source being such as to heat said specimen to a 'desired temperature above the temperature of the water.

5. Testing apparatus for testing the effectiveness of corrosion inhibitors in boiler water comprising a pressure vessel, partially filled with boiler water having the inhibitor dissolved therein, electric heater means disposed about the vessel to heat the water therein, a vertically disposed shaft extending through the upper end of the vessel in a generally fluid tight manner, a head secured to the lower end of the shaft, a plurality of metal specimens supported on said head for periodic immersion in the water, motor means connected with the upper end of the shaft and operative to periodically reciprocate the same to effect said periodic immersion, a source of electric potential, means connecting this source with said specimens to pass current therethrough, said source being such that the specimens are heated to a temperature above that of the water.

References Cited in the file of this patent UNITED STATES PATENTS 2,405,52 Todd Aug. 6, 194s

Claims

1. THE PROCESS OF SCREENING CARROSION INHIBITORS FOR BOILER WATER COMPRISING PROVIDING IN AN ENCLOSED CONTAINER A HEATED BATH OF WATER HAVING THE INHIBITOR DISSOLVED THEREIN, PERIODALLY IMMERSING A PLURALITY OF METALLIC TEST SPECIMENS INTO THE BATH AND WITHDRAWING THE SAME INTO THE SPACE THEREABOVE, PASSING A CURRENT THROUGH SAID SPECIMENS AND THEREBY HEATING THE SAME TO A TEMPERATURE ABOVE SAID BATH AND SO THE SPECIMENS QUICKLY BECOME DRY WHEN MOVED FROM THE WATER BATH INTO SAID SPACE, AND CONTINUING THE PERIODIC EMERSION AND WITHDRAWAL FOR A SUBSTANTIAL PERIOD.