US3342064A - Erosion indicator - Google Patents

Description

p 19, 1967 E. w. BLATTNER EROSION INDICATOR Filed May 15, 1964 N E N 4 m J .55 l H tzn 5213mm Al 2:453 M255; 93 53 United States Patent 3,342,064 ERQSION INDICATOR Ernest W. Blattuer', Trenton, N.J., assignor to De Laval Turbine Inc., Trenton, N.J., a corporation of Delaware Filed May 15, 1964, Ser. No. 367,722 11 Claims. (Cl. 7386) This invention relates to erosion indicators particularly for the checking of erosion characteristics of fluids which are passing to apparatus to be protected.

While the invention is applicable widely, its nature and use may be best made clear by reference to a particular example of a system in connection with which it has major advantages.

Various catalytic processes involve deposition of carbon or carbonaceous materials on a catalyst which may be of granular form and subject to agitation during use. Regeneration of the catalyst is achieved by burning of the carbon or other material in a stream of air or oxygencontaining gas. The resulting combustion gases contain sufiicient energy, by reason of elevated pressures and temperatures, to make it economical to recover this energy. For this purpose gas turbines are used. The mechanical power developed by such turbines may be used for current generation, operations of compressors, or the like.

A serious problem is presented, however, by reason of the fact that the combustion gases leaving the catalyst carry abrasive particles in the form of dust resulting from attrition of the catalyst granules against each other. The abrasive gas would be highly detrimental to the nozzles and blading of gas turbines because of the very high velocities of relative flow which are involved in the turbine. Accordingly, it is usual to interpose between the catalyst and the turbine a dust separator designed to remove, as far as possible, the abrasive dust particles which would be responsible for erosion in the turbine. The dust particles range through a wide band of sizes, and it will be evident that the major erosion is due to large particles which dust collectors are best suited to remove. For normal operating conditions, dust collectors are chosen which are capable of reducing erosion in the turbine to acceptable values.

However, manlfunctions in the system preceding the turbine may result in very abnormal increases in the erosive properties of the gas by increase in its erosive dust content or increase of the sizes of the dust particles. This situation is particularly insidious because it may occur without any apparent change in the thermodynamic properties of the gas. Even when the gas is highly erosive, its dust content is so low that measurement of this content is impractical. Erosion may easily increase without being detectable to a point where the turbine parts may be destroyed in the matter of a few weeks or months. Shut down and dismantling to examine a turbine from time to time would be prohibitively costly.

It is one object of the present invention to provide an indicating device serving as a continuous monitor of erosion characteristics of a gas in a system such as that just indicated. In brief, the erosion indicator provided in accordance with the invention is responsive to an actual erosion produced by a sample of the gas continuously withdrawn from the main stream. The erosion is not directly observed as such, but practical operation is achieved by observation of a pressure change. This pressure change is produced by the differential enlargement of a pair of orifices through which the sample of gas passes, the pressure being measured in a chamber between the orifices.

As will become apparent from what follows, the invention is not limited to the detection of erosive properties of a gas due to abrasive particles therein, but is more broadly applicable to the detection of erosive properties of fluids generally, including liquids. It is applicable, for example, to the monitoring of abrasion which may be produced in pumps handling liquids containing abrasive solid particles.

The general objects of the invention have to do with the provision of erosion indicators of the general type mentioned above, and these and other objects relating to details of construction and operation will become apparent from the following description, read in conjunction with the accompanying drawing in which FIGURE 1 shows the detector and indicator in section and associated with a system which is illustrated in block diagram, and FIGURE 2 is a graph showing illustrative curves which are indicative of erosion rates.

A catalytic and power recovery system is indicated. A catalytic unit of conventional type is diagrammed at 2. This is conventional and need not be described in detail. When on-strearn, the catalytic unit will receive vapors or gases at proper temperatures and pressures and will produce products which are taken off and handled in suitable fashion. It may be assumed that in such operation, as is usual, carbon or carbonaceous materials are produced which coat or are intermingled with the catalyst particles, and in a regeneration cycle these are burned 01f by the introduction of air or other oxygen-containing gas at 4, products of combustion at high temperature and elevated pressure being delivered in such cycle at 6. Normal operation involves a condition in which by far the major amount of catalyst remains in the catalytic unit. But due to mutual abrasion, catalytic dust is produced of such fine particle size that it is carried by the combustion gases. Most catalytic materials are quite hard, and if these gases were passed directly into a gas turbine the result would be rapid destruction of the expensive turbine.

Accordingly, the gases are first delivered to a dust separator 8 which is so chosen that there are eifectively removed such particles as would be primarily detrimental to the gas turbine. While the dust separator will even normally not remove all of the dust, what passes from it through the connection 10 to the gas turbine unit 12 will have sufliciently low erosive properties to be acceptable and consistent with a long life of the gas turbine. The exhaust from the gas turbine is indicated at 14. The exhaust gases may be discharged into the air or may pass the heat exchange units for recovery of residual heat. The problems which arise are due to the possible malfunctioning of the portion of the system preceding the turbine. If the catalystic unit operates under conditions giving rise to higher than usual concentrations of dust, or the presence in the dust of abnormal concentrations of large particles, the dust separator which is used may have its dust-removing capabilities exceeded so that delivered to the gas turbine unit may be a gas which has much higher than normal erosive properties. Or the dust-separator itself may be functioning improperly so that the gases therefrom would be highly detrimental to the gas turbine. The monitoring provided by the present invention is to atford rapid detection of abnormal conditions so that steps may be taken for their rectification.

For this purpose a small sample of the gas passing through the connection 10 is extracted continuously through a passage 16. To be sure that the sample thus extracted is typical of what is entering the gas turbine unit, the inlet to the connection 16 is desirably arranged, as indicated at 17, to receive the sampled gas in the direction of main flow at the point of sampling, thus insuring that any large particles pass with the sample. This sampling may, of course, be effected through a tube having its entrance either in a connecting line such as It) or in the gas chest, or other suitable portion, of the turbine. The gas sample taken may be only a very small percentage of the combustion gas stream, so that the energy loss involved is negligible.

The indicator itself is of simple mechanical construction and, in a preferred form, comprises the inlet member 18, an intermediate tube 20 and an outlet member 22 which may be provided by castings bolted together. The inlet member 18 provides the inflow passage 24. The tube 20 provides a chamber 26. The outlet member 22 provides the outlet passage 28. This outlet passage 28 may exhaust its gases to the atmosphere or, if desired, it may communicate with the outlet 14 from the gas turbine so that the sampled gasses may be commingled with the main exhaust passing to a heat exchanger or the like.

The chamber 26 is connected by tubing 30 to a pressure gauge 32. This tubing may be extended in length so that the pressure gauge may be protected from the high temperature normally existing in the chamber 26, the tube providing for heat dissipation.

The left-hand end of chamber 26 is partially closed off by a plate 34- provided with an orifice opening 36. This plate is desirably formed of very hard material such as a tool steel or an alloy or composition which is highly resistant to abrasion and such as may ordinarily be used for a machine tool cutter. A suitably shaped tip 38 of a needle valve 40 projects into the opening 36 to provide an annular orifice. The size of the orifice is adjustable by reason of the threaded engagement of the needle valve in the member 18, there being provided suitable packing at 42, and a wrench socket 44 for adjustment of the needle valve.

The right-hand end of the chamber 26 is associated with similar elements comprising the hard plate 46 provided with the opening 48 into which there extends the tip 50 of the needle valve 52 threaded in the member 22 and provided with packing 54 and a wrench socket 56.

Because of the provision of the inlet and outlet orifice associated with the chamber 26, it Will be evident that the pressure in this chamber, indicated by the gauge 32, will lie intermediate the pressures in the passages 24- and 28. The value of the pressure in the chamber 26 will depend on the relative sizes of the orifices. Several alternative types of operation are possible.

Assuming that the needle valve tips 38 and 50 have the same composition, desirably in this instance a composition considerably more readily eroded than the erosion-resistant material of the plates 34 and 46, adjustment of the needle valves may be made so that one of them provides an orifice substantially less in effective cross-section presented to flow than the other. Assume, for explanation, that the needle valve 40 is adjusted so that the annular clearance about its tip 38 is considerably less than that provided about the tip 50. Initially the pressure gauge 32 will then indicate a pressure more nearly that existing in the passage 28 than that in the passage 24. This is, of course, due to the relative pressure drop across the orifices. Since the higher pressure drop occurs across the inlet orifice, erosion of the tip 38 will be correspondingly greater than the errosion of the tip 50. As operation proceeds, therefore, the pressure in the chamber 26 will rise, and by observation of the pressure indicated at 32 from time to time a curve may be drawn showing pressure variation with time. The slope of such a curve will indicate the erosion rate of the needle valve tip 38 (relative to that of the tip 50) and thus the erosive properties of the combustion gas may be estimated. This is illustrated by the curve A in FIGURE 2.. It may here be noted that what has just been stated assumes a usual condition, namely, that the pressure in the connection is constant. This pressure is normally iridicated by instrumentation, but if this pressure varies, what would be significant would be the pressure drop from the connection 10 to that in the chamber 26.

lternatively, the needle valve 40 may be adjusted to provide a larger orifice and the needle valve 52 to provide a smaller orifice which would then be subject to the major wear. As erosion proceeded, the reading of pressure in the chamber 26 would then drop as the crosssection of the discharge orifice increased. This is illustrated by the curve B in FIGURE 2.

While operation in accordance with the foregoing may be used, it will be evident that the change of pressure with erosion is reduced by the fact that both needle valve tips were of the same hardness. In a preferred form of the invention, therefore, it is desirable to have one of the valve tips of very hard material of the type described above for the plates 34 and 46, so that erosion at the orifice delimited by this tip will be relatively quite small. The other tip in such case is desirably of a material easily eroded in comparison with that first mentioned. For example, a soft steel may be used. Or there may even be used a non-ferrous metal such as brass, aluminum or the like. When the tips are thus relatively hard and soft, the soft tip may be either at the inlet orifice or at the outlet orifice as above described. Relative adjustments of the needle valves may be made to set initial valves of the pressure in the chamber 26 or to reset this pressure repeatedly after periods of wear.

The indicator may be used either for qualitative measurements or quantitative measurements. In the latter case, for a given turbine and structural materials thereof, and for particular materials and settings of the needle valve tips, observations may be made of the pressure drops in the chamber 26 with respect to time intervals, and these may be correlated with the wear actually found in the turbine in question when it is, for example, taken out of operation for overhauling or replacement of bearings or the like. Information is thus obtained which could be applied to similar turbines to give a close estimation of the wear which may have occurred at any particular time.

It may be noted that the tips 38 and 5d of the needle valves may be formed of materials differing from the valve bodies, and these tips may be made replaceable.

It will be evident from the foregoing that the erosion indicator is quite simple in construction and capable of very easy adjustments to secure desired characteristics of operation. It also utilizes a negligible percentage of the gas which is passing to the turbine. Despite these advantages, it provides an indication directly based on what is of interest, namely the erosion characteristics of the fluids.

While, as indicated, the invention has its primary utility in determination of the erosion characteristics of a gas ladened with abrasive dust, it will be evident that the same principles may be applied to measure or indicate the erosion characteristics of liquids which may contain abrasive particles.

It will be evident that various details of the invention may be changed without departing from the principles thereof as defined in the following claims.

What is claimed is:

1. A device for the indication of the erosive properties of a fluid containing abrasive particles comprising means providing a chamber, first orifice defining means providing an inlet orifice, second orifice defining means providing an outlet orifice, means for leading fluid containing abrasive particles at a known pressure condition through said inlet orifice into said chamber for flow therefrom through said outlet orifice whereby said fluid erodes both said orifice defining means to vary the orifice size thereof, said chamber providing unimpeded flow from said inlet orifice to said outlet orifice, one of said orifice defining means presenting to the fluid flow a surface of material which is eroded more easily than the material forming the other orifice defining means, and means to measure a change of pressure in said chamber which pressure change is indicative of the relative erosion of said orifices.

2. A device according to claim 1 including means co operable with one of said orifice defining means and movable for the adjustment of the size of said one orifice.

3. A device according to claim 1 including means cooperable with said orifice defining means having the more easily eroded surface and manually movable for adjusting the orifice size thereof.

4. In a gas system comprising a gas turbine and means providing the gas turbine with gases containing abrasive particles, a device for the indication of the erosive properties of the gas containing abrasive particles comprising means providing a chamber, first orifice defining means providing an inlet orifice, second orifice defining means providing an outlet orifice, means for leading a sample of the particle containing gas from said turbine gas providing means at a normally constant pressure through said inlet orifice into said chamber for flow therefrom through said outlet orifice whereby said gas erodes both said orifice defining means to vary the orifice size thereof, said chamber providing unimpeded flow from said inlet orifice to said outlet orifice, one of said orifice defining means presenting to the fluid flow a surface of material which is eroded more easily than the material forming the other orifice defining means, and means to measure a change of pressure in said chamber which pressure change is indicative of the relative erosion of said orifice by said particle containing gas passing therethrough.

5. A device according to claim 4 including means cooperable with one of said orifice defining means and movable for the adjustment of the size of said one orifice.

6. A device according to claim 4 including means cooperable with said orifice defining means having the more easily eroded surface and manually movable for adjusting the orifice size thereof.

7. A device according to claim 1 including means for supplying fluid at a normally constant pressure to said means for leading fluid to said inlet orifice.

8. A device for the indication of the erosive properties of a fluid containing abrasive particles comprising means providing a chamber, first orifice defining means providing an inlet orifice, second orifice defining means providing an outlet orifice, the effective cross-section presented to flow of one of said orifices being initially substantially less than that of the other orifice, means for leading fluid containing abrasive particles at a known pressure condition through said inlet orifice into said chamber for flow therefrom through said outlet orifice so that said fluid erodes said orifice defining means providing said smaller orifice to vary the orifice size thereof, said chamber providing unimpeded flow from said inlet orifice to said outlet orifice, and means to measure a change of pressure in said chamber which pressure change is indicative of the relative erosion of said orifices.

9. A device according to claim 8 including means for supplying fluid at a normally constant pressure to said means for leading fluid to said inlet orifice, and means cooperable with the means defining one of said orifices and manually movable for the adjustment of the size of the orifice defined thereby.

10. In a gas system comprising a gas turbine and means providing the gas turbine with gases containing abrasive particles, a device for the indication of the erosive properties of the gas containing abrasive particles comprising means providing a chamber, first orifice defining means providing an inlet orifice, second orifice defining means providing an outlet orifice, the effective crosssection presented to flow of one of said orifices being initially substantially less than that of the other orifice, means for leading a sample of the particle containing gas from said turbine gas providing means at a known pressure condition through said inlet orifice into said chamber for flow therefrom through said outlet orifice so that said particle containing gas erodes said orifice defining means providing said smaller orifice to vary the orifice size thereof, said chamber providing unimpeded flow from said inlet orifice to said outlet orifice, and means to measure a change of pressure in said chamber which pressure change is indicative of the relative erosion of said orifices.

11. The system according to claim 10 in which the gas is supplied at a normally constant pressure to said means for leading fluid to said inlet orifice, and means cooperable with the means defining one of said orifices and manually movable for the adjustment of the size of the orifice defined thereby.

References Cited UNITED STATES PATENTS 2,839,071 6/1958 Rosch 137-37 3,066,912 10/1962 Soheper 235-76 3,165,924 1/1965 Wolif 73-86 3,229,498 l/1966 Oakes 73-7 OTHER REFERENCES Etamic catalog: Mar. 20, 1951, 2 pages. JAMES J. GILL, Acting Primary Examiner. RICHARD C. QUEISSER, J. J. SMITH, Examiners.

Claims (1)

1. A DEVICE FOR THE INDICATION OFTHE EROSIVE PROPERTIES OF A FLUID CONTAINING ABRASIVE PARTICLES COMPRISING MEANS PROVIDING A CHAMBER, FIRST ORIFICE DEFINING MEANS PROVIDING AN INLET ORIFICE, SECOND ORIFICE DEFINING MEANS PROVIDING AN OUTLET ORIFICE, MEANS FOR LEADING FLUID CONTAINING ABRASIVE PARTICLES AT A KNOWN PRESSURE CONDITION THROUGH SAID INLET ORIFICE INTO SAID CHAMBER FOR FLOW THEREFROM THROUGH SAID OUTLET ORIFICE WHEREBY SAID FLUID ERODES BOTH SAID ORIFICE DEFINING MEANS TO VARY THE ORIFICE SIZE THEREOF, SAID CHAMBER PROVIDING UNIMPEDED FLOW FROM SAID INLET ORIFICE TO SAID OUTLET ORIFICE, ONE OF SAID ORIFICE DEFINING MEANS PRESENTING TO THE FLUID FLOW A SURFACE OF MATERIAL WHICH IS ERODED MORE EASILY THAN THE MATERIAL FORMING THE OTHER ORIFICE DEFINING MEANS, AND MEANS TO MEASURE A CHANGE OF PRESSURE IN SAID CHAMBER WHICH PRESSURE CHANGE IS INDICATIVE OF THE RELATIVE EROSION OF SAID ORIFICES.

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