IMPROVED APPARATUS FOR MEASURING VARYING DENSITY OF A SLURRY FLOWING IN A PIPELINE

Abstract: An improved apparatus is disclosed which employs hy­ drostatic bearings for measuring varying density of a fluid, usually of a slurry of coal or minerals, flowing in a transport pipeline. A first pipe section is fixedly interposed in the fluid carrying pipeline. A second or centre pipe section is horizon­ tally mounted within the first pipe section substantially co­ axially therewith and to be in fluid communication with the fluid or slurry transporting pipeline whereby the transported fluid flows through the second or centre pipe section. Ends of the second or centre pipe section and adjacent ends of the trans­ port pipe, or of intermediate pipe pieces conventionally cou­ pled to the transport pipe, are machined and configured to be capable of functioning as hydrostatic bearing surfaces in a di­ rection normal to the longitudinal axis of the centre pipe sec­ tion. A substantially ring-shaped chamber is disposed be­ tween the first and second pipe sections into which hydro­ static fluid is pumped under pressure through an inlet port pro­ vided in the first pipe section. The hydrostatic fluid flows through suitable ducts inwardly to the hydrostatic bearing sur­ faces, whereby motion of the centre pipe section is substan­ tially frictionless in the vertical direction. Weight of the centre pipe section and of the fluid contained therein is measured by load cells, or strain gauges or the like. Preferably, the weight is obtained by accurately measuring vertical displacement of the centre pipe section against the force of preloaded tension rods which mount the centre pipe section to the enveloping first pipe section.

Description: IMPROVED APPARATUS FOR MEASURING VARYING DENSITY OF A SLURRY FLOWING IN A PIPELINE ¯¯¯¯¯ ¯¯¯¯¯¯¯¯ The present invention is directed to an imr)roved apparatus for accurately measuring the density of a fluid flowing through a pipeline. More particularly, the present invention is directed to an al)paratus which has an improved construction and hydrostatic bearings for measuring the varying density of a slurry flowing through a pipeline. Pipelines for transporting slurries of coal and other minerals have been known for a long time. In order to determine the amount of coal (or other mineral) transported through the pipeline, it has been customary in the prior art to measure the density of the coal or mineral slurry flowing through a )rfdtermined portion of the pipeline. As is known the density of the slurry usually varies in t ime . The amount of coal or mineral transported in th pipeline is usually calculated from the density verbs time function which must be known as a result of continuous measurements. Devices used in the prior art for measuring the density of the coal or mineral slurry include nuclear densitometers, and weight measuring devices. The latter measure the weight of a predetermined section of the pipeline wherethrough the slurry flows. Density of the slurry is then readily calculated from the measured weight. Most weight measuring densitometer devices of the prior art are relatively inaccurate, because, in these "early" devices a flexible joint mounts the pipe section, the weight of which is measured-, to the pipeline. Disclosures relating to such devices are found in United States Patent Nos. 3,503,267, 3,320,791, 68S,388, 2,039,997, 2.613,530, 2,669,1181 3,8127723, 7.143,87, and 1,905,558. Another type of fluid densitometer device is disclosed in United States Patent No. 4,285,259. The densitometer of this relatively recent patent employs a substantially horizontally disposed pipe section which is coupled to the pipeline through precisely machined interfacing surfaces adapted to function as hydrostatic bearings. The pipe section is held ben two end flanges of the pipeline by a predetermined force attained by precise adjustment of t tension of bolts mounting the pipe section to the 4i;nes of the pipe ends. The pipe section is surrounded b5r a suitable liquid tight envelope, such a a bellows. During operation of the slurry densitometer disclosed in United States Patent No. 4,285,239, 1 q d, usually water, is pumped under pressure to the interfacing, bearing surfaces. When the force generated on the interfacing surfaces by the pressure of the pumped liquid equals the predetermined mechanical force holding together the interfacing surfaces, a hydrostatic bearing is created. Liquid flows out of the hydrostatic bearings into the interior o the pipeline, and also to the exterior, wherein it is collected in the bellows. Because the hydrostatic bearings "suspend" the pipe section in a substantially frictionless manner, its weight together with the weight of the slurry flowing therein can be accurately measured by load cells, strain gauges or the like. The above summarised fluid or slurry densitometer of United states Patent No. 4,285,239 functions well. Nevertheless, a need has arisen in ti art for a densitometer, which, although still incorporates hydrostatic bearings and provides their adv;-ntEe-- Ela., a relatively simplified and less expensive construction, minimises outflow or loss of th hydrostftic liquid from the bearing surfaces, and therefore requires less pump power to operate. According to the present invention there is provided a device for measuring the weight of a pipe section having a fluid or slurry flowing therethrough, the device comprising a first substarltially horizontally disposed pipe section having two ends. each end of the first pipe section being fixedly coupled to a fluid or slurry transport pipe a second substantially horizontally disposed pip section, smaller in diameter than the first pipe section, being substantially concentrically disposed within the first pipe section so as to define a chamber between the outer surface of the second pipe section and the inner surface of the first pipe section, the second pipe section having a transport cavity which is in fluid communication with the fluid or lury transport pipe, and a machined surface proved at each end of the second pipe section which interface complementary machined surfaces provided in respective ends of the fluid or slurry transport pipe, with a gap being located between ends of the second pipe section and respective ends of the fluid or slurry transport pipe, said machined surfaces being configured for functioning as hydrostatic bearings; first means operatively associated with the first pipe section for supplying a hydrostatic fluid under pressure to the chamber between the first and second pipe sections, second means provided in the second pipe section for permitting passage under pressure of the hydrostatic fluid from the chamber to the machined surfaces at each end of the pipe section and for permitting passage of the hydrostatic fluid into the gaps between the respective machined surfaces of the second pipe section and the ends of the fluid or slurry transport pipe whereby a hydrostatic bearing is created between the machined surfaces to permit substantially frictionless movement of the second pipe section in the direction parallel with the earth's gravitational field, third means operatively associated with the second pipe section for sensing a physical parameter, comprising an inlet to a transducer, from which weight of the second pipe section and of the fluid or slurry momcntarily contained therein may be calculated. According to the present invention there is further provided a device for measuring varying density of a slurry such as a coal or mineral slurry flowing through a transport pipe, the device comprising: two intermediate pipe pieces, each intermediate pipe piece having a first end adapted to be (coupled to the transport pipe, and a second end, a first pipe section fixedly mounted between the second ends of the two intermediate pipe pieces; a second pipe section smaller in diameter than the first pipe section and mounted within the first pipe section in a substantially horizontal position between the two second ends of the two intermediate pipe pieces, the second pipe section being In fluid communication with the second ends of the intermediate pipe pieces, whereby the second pipe section comprises an intermediate portion of the transport pipe a chamber being disposed between the inner periphery of the first pipe section and the outer periphery of the second pipe section, interfacing hydrostatic bearing ures formed in the ends of the second pipe section and in the second ends of the intermediate pipe pieces, the bearing surfaces comprising means for permitting substantially frictionless movement of s,c,o,d pipe section in a direction parallel with Li, o'rtt '.; gravitational field, pump means for providing a hydrostatic liquid through the first pipe section into the chamber at a pressure higher than tyle pressure of the slurry flowing in the transport r)is,c, for substantially filling the chamber with the hydrostatic liquid, duct means provided in the second ryre section for conducting hydrostatic liquid from t chamber to the hydrostatic bearings; spring means for limiting movement of the second pipe section in a direction parallel with the earth's gravitational field and for rendering said movement proportional to the gravitational force acting on the second pipe section and on the slurry contained therein; and sensing means for sensing position of the second pipe section in the direction parallel with the earth's gravitational field. According to the present invention there is still further provided a densitometer for measuring varying density of a slurry, such as a slurry of coal or mineral flowing in a transport pipe, the densitometer comprising: two intermediate pipe pieces, a first section of a pipe fixedly attached to the intermediate pipe pieces coupled to be in fluid communication with a transport pipeline; a centre pipe section disposed substantially horizontally and substantially concentrically within the first pipe section, the centre pipe section being in fluid communication with the intermediate pipe pieces whereby slurry transported in the transport pipeline flows through the centre pipe section, a substantially ring-shaped chamber being formed between the first pipe section and the centre pipe section, hydrostatic bearing means formed in the ends of the centre pipe section and in adjacent ends of the intermediate pipe pieces for permitting .lab < itantially frictionless movement of the centre pipe section within the chamber, pump means including at least one inlet port provided in the first pipe section for supplying a hydrostatic liquid into the chamber at a pressure greater than the pressure of the slurry flowing in the transport pipeline; spring means mounted to the first pipe section and the centre pipe section for limiting movement of the centre pipe section and for rendering movement of the centre pipe section in a vertical direction indicative of the weight of the slurs momentarily contained in the centre pipe section, and position sensing means for sensing the position of the centre pipe section in the chamber in the vertical direction Densitometer apparatus embodyIng the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a partial cross-sectional view of a first embodiment of a densitometer; Figure 2 is a partial cross-sectional view of a second embodiment of a densitometer, Figure 7 is an enlarged view of an area shown on Figure 1 Figure 4 is a graph showing pressure distribution in a hydrostatic bearing of the densitometer, the graph being keyed to the enlarged view of Figure 5 Figure 5 is another cross-sectional view of the first preferred embodiment of the densitometer, the cross-section being taken on lines 5,5 of Figure 1 Figure 6 is still another cross-sectional view of the first preferred embodiment of the densitiometer, the cross-section being taken on lines 6,() of Figure 1, Figure 7 is an enlarged plan view showing a displacement or position sensor incorporated into the densitometer te p figure iJ is arL enlarged cross-sectional JiXw showing tension rods incorporated into the densitometer, figure 9 is a partially exploded perspective view of the first and second preferred emi,orliment of the densitometer, and Figure 10 is a perspective view of the first and second preferred embodiments of the densitometer. Referring now to the drawing Figures, and particularly to Figures 1, 9 and 10, a first preferred embodiment 20 of the densitometer of the present invention is disclosed. It is noted at the outset that the densitometer of the present invention is in many respects similar in construction, operation and utility to the densitometer disclosed in United States Patent No. 4,285,239. For this reason the densitometer of the present invention is described in detail in its novel aspects. However, for general background and for general description of the operation of the hydrostatic bearings employed in the densitometer of the present invention, reference is made to United States Patent No. 4,285,259, the specification of which is expressly incorporated herein. Thus, the densitometer of the present invention is adapted for continuously or intermittently measuring the density of a fluid flowing in a pipeline. The fluid may be gas or liquid, and the stream of fluid may carry suspended solid particles. As is known, measurement of the density of slurries of coal or other minerals has great practical importance, because it is customary to calculate the amount of coal or mineral transported in a slurry pipeline from the measured densities. Furthermore, the liquid medium tr;orlsporting tile slurries is usually water, although on occasions hydrocarbon liquids are used to transport coal. The foregoing comprise a summary of the environment in which the present invention is most frequently used. However, the invention is neither limited by the nature of the fluid transported in the pipeline nor by the presence or nature of the solid particles suspended in the fluid, nor by the dimensions of the pipeline. Nevertheless, it is noted that coal or mineral slurry transporting pipelines are usually two to twenty-four inches in diameter. In the ensuing description, the pipeline is usually referred to as a slurry transport pipeline or pipe 22, and the liquid medium is described as water with the understanding that these references are intended to serve as examples rather than limitations. Referring now again to Figures 1, 9 and 10, the first preferred embodiment 20 of the densitometer of the present invention is shown coupled to a slurry transport pipe 22. The densitometer 20 includes two intermediate pipe pieces 24, each of which has one flanged nd 26 which is conventionally mounted to the pipeline. Thus, in effect, the densitometer 20 is inserted into the pipeline 22. Second ends 28 of the intermediate pipe pieces 24 incorporate flat, precisely machined surfaces 30 disposed normally to the longitudinal axis of the pipeline 22. The flat surfaces 50 are disposed on flange type enlargements of the ends 28 of the intermediate pieces 24 and are designed to interface with the densitometer 20 and to function as hydrostatic bearings. For this reason, the flat surfaces 30 include a cladding 51 of a higher grade steel than the ordinary carbon steel Df the transport pipe 22. ireL(rtbly a 0.250" (6.35 inn) thick SS-304 steel. cladding 1, shown on Figure 1 is incorporated in the first preferred embodiment 20 A first or exterior pipe section 52 of the densitometer 20 is fixedly mounted between the intermediate pipe pieces 24. This is accomplished by driving threaded bolts 54 into axially disposed internal bores provided in the first pipe section 32. As is shown on Figure 1, internal diameter of tee first pipe section 52 is larger than the internal diameter of the intermediate pipe pieces 24. except through the hereinafter described hydrostatic bearings, the first or exterior pipe section 52 is not in fluid communication with the intermediate pipe pieces 24 or with the transport pipe 22. A second, or centre pipe section 38 is disposed within the interior of the first pipe section 52. The second or centre pipe section 52 has an internal diameter which is substantially equal to the internal diameter of the intermediate pipe pieces 24. Preferably, as in the herein shown embodiment, the internal diameter of the intermediate pipe pieces 21 is the same as that Of the transport pipe 24. The second, or centre pipe section 38 is horizontally disposed, substantially concentrically with the first pipe section 72, and in substantial alignment with the interior transport cavity 40 of the intermediate pipe pieces 24. In effect, the slurry (not shown) transported in the pipe 22 flows through the second or centre pipe section 38. As is further shown on Figures 1, 5 and 5, ends 42 of the second or centre pipe section 58 are machined to form hydros-tatic bearing surfaces 44 which interface with the precision machined complementary surfaces 46 provided on the ends 28 of the intermediate pipe pieces 24. The entire second pipe section 58 is preferably made of stainless steel, such as SS-504 steel. Ducts 48 are incorporated in the second or centre pipe section 38 to lead from its outer periphery 50 to the bearing surfaces 44. The hydrostatic bearing surfaces 44 of the second pipe section 58 incorporate a plurality of indentations or pockets 52. This is standard in the construction of hydrostatic bearings and is described in more detail in the specification of United States Patent No. 4,285,259. As is further known in the arts relating to hydrostatic bearings, at least one duct 48, including a nozzle 49 having a precision orifice 49a leads to each indentation or pocket 52. The pockets 52 and the nozzles 49, the precision orifices 49a and the ducts 48 are shown on Figures 1, 2, 5 and 5. Referring now principally to Figures 1 and 5, a chamber 54 is shown disposed between the outer periphery 50 of the second pipe section 58, and the interior surface 55 of the fixedly mounted first pipe section 52. it is an important feature of the present invention that a llydrostatic fluid (not shown) is pumped by a suitable pump into the chamber 54 at a pressure which is higher than the pressure of the fluid or slurry (not shown) flowing in -the transport pipe 22. The hydrostatic fluid (not shown) is preferably the same as the fluid medium of the slurry (not shown), in case of aqueous slurries the hydrostatic fluid is water. The pump is indicated only schematicaliy on Figure 1, and bears the reference numeral 56. Only a single inlet port 57 is necessary in the first pipe section 52 to conduct the hydrostatic fluid (not shown) into the chamber 54. in the first preferred embodiment of the present invention, the first pipe section 32 and the second pipe section 58 are of equal length. Gaps 58, which are necessary for -the operation of the hydrostatic bo±ri ngs , tre maintained between the complementary bearing surfaces 44 and 46 by shims 60 placed between the first pipe section 52 and the intermediate pipe pieces 4 Tn the herein described first preferred embodiment 20, the shims 60 are approximately 0.0005" (0.017 mm) thick. Thins, in the first preferred embodiment 20, the hydrostatic bearing surfaces 44 and 46 are separated from one another by a permanent gap 58 of approximately 0.0005" (0.0127 mm) thickness. Generally speaking, the shims 60, and therefore the gaps 58, are in the order of approximately 0.0003" to 0.0007" (0.0076 to 0.0178 mm) within the scope of the present invention. For operation, the densitometer 20 of the present invention is carefully levelled so that the second or centre pipe section 58 occupies a horiontal position. hydrostatic fluid, usually Water (not ShOWrl), is pumped into -the chamber 54. From the chamber 54 the water passes through the ducts 48 and through the gaps 58 to create hydrostatic bearings between the complementary surfaces 44 and 46. Distribution of hydrostatic fluid (water) pressure in the bearings is shown on the graph of Figure 4 for an example where the water pressure in the slurry flow (not shown) is 1000 PSI (6.89 MPa) and the pump 56 maintains 1500 PSI (10.34 MPa) pressure in the chamber 54. O-rings or like seals 62 are incorporated in seal glands 64 to seal the first pipe section 52 to the intermediate pipe pieces and to prevent leakage of pressurized fluid to the exterior. The hydrostatic bearings enable the second or centre pipe section 38 to move in a substantially frictionless manner in any direction normal to the longitudinal axis of the pipe section 58. This, of course, means, that the centre pipe section 38 moves substantially without friction in the direction of the earth's gravitational field. Thus, the second pipe section "floats" in the chamber 54. The second or centre pipe section 38, is however, unable to move freely in axial direction in the chamber 54. This is because when the gap 58 is narrowed at either end of the second pipe section 38, then the fluid pressure increases significantly in the "narrowing" hydrostatic bearing while pressure decreases in the "widening" bearing. As a consequence, the second or centre pipe section 38 is maintained in a fixed axially centred position in the chamber 54. Because the centre pipe section 38 is capable of frictionless movement in the chamber 54 in the direction of the earth's gravitational field, weight of this "floating" centre section 38, including weight of the slurry (not shown) contained therein, can be measured accurately, as is described below. Important dimensions of an exemplary densitometer constructed in accordance with the first preferred embodiment of the present invention are as follows. The first pipe section 52 is 12" (304.8 mm) long, and the second or centre pipe section is of equal length therewith. External diameter of the first pipe section 32 is 18" (457.2 mm), and its internal diameter is 14.25" ()61.95 mm). Each intermediate pipe piece 24 is 12" (304.8 mm) long. External diameter of the second or centre pipe section is 14" (555.6 mm), and its internal diameter is 12" (304.8 mm). Consequently, the chamber or substantially ring-shaped space 54 which is filled with hydrostatic fluid under pressure, has a nominal width of 0.125" (5.175 mm). Walls of the second or centre pipe section 38 may be hollow, as shown on Figure 1, in order to save weight and materials. Holes 66 are provided in the centre section 38 to permit the hydrostatic fluid (not shown) to enter the hollow interior 68. The hollow centre pipe section 38 having the above noted exemplary dimensions weighs approximatey 75 lbs (52.02 kg). A centre pipe section 58 having hollow walls is incorporated in the densitometer of the present invention primarily for applications where the pressure of the slurry in the pipeline is low, up to approximately 220 PSI (1.38 MPa). Referring now to Figure 2, a second preferred embodiment 70 of the densitometer of the present invention is disclosed. The second preferred embodiment 70 differs from the first preferred embodiment 20 in that the "floating" second or centre pipe section 78 is solid, rather than hollow. Moreover, no shims are disposed between the first pipe section 52 and the intermediate pipe pieces 24. As in the first preferred embodiment the second pipe section 58 is still equal in length with the first pipe section 52 Therefore when the densitometer of the second preferred embodiment 70 is not in operation there is no gap between the complementary bearing surfaces 44 and 46 of the intermediate pipe pieces 24 and of the second or centre pipe section 58 respectively However when the densitometer 70 is in operation with a significant pressure differential between the hydrostatic fluid (not shown) in the chamber 54 and the fluid (not shown) transported in the pipe 22 then a significant, axial compressive force acts on the "floating" second or centre pipe section 38 For example when the dimensions of the bearing surface 44 are as follows (with particular reference to Figure 3) b1 = 0 292" (7 417 mm) a = 0-292" (7 417 mm) and b2 = 0292" (7 417 mm) the pressure of the hydrostatic fluid in chamber 54 is maintained by the pump 56 at Po (PSI) pressure in the slurry 'flow (not shown) is P2 (PSI) and the pressure in the indentation or pocket 52 is maintained at P1 (PSI) by appropriate design and selection of the precision orifice 49a then the compressive axial force (Faxial ) acting on the centre pipe section 58 is calculated by Equation 1 EMI14.1 <tb> P <SEP> axial <SEP> - <SEP> 0+ <SEP> " <SEP> (142-13-4162) <SEP> < <SEP> + <SEP> Equation <SEP> 1 <tb> <SEP> 1 <SEP> 2 <tb> EMI14.2 When P0 = 1500 PSI P1 1550 PSI 1000 00 Then i%'xial = 51000 ib (23133 2 kg) Deformation (#l1) of the solid "floating" second or centre pipe section 38 I?ndOr this compressive force is calculated as shown in Equations EMI15.1 = 87 19 X 106 lb/inch (1 5269 1010 N/m) Equation 2 Where K1 is the spring constant A is area (square inch) E is Young's modulus and 1 is the length of the centre section 58 EMI15.2 <tb> F <SEP> - <SEP> F <SEP> 51000 <SEP> 0.0006" <SEP> (0 <SEP> 01524 <SEP> mm) <tb> <SEP> 87.19 <SEP> x <SEP> 10 <SEP> Equation <SEP> 5 <tb> <SEP> 7. <SEP> Equatlon <SEP> 3 <tb> The hydrostatic pressure in the bearings also causes a tension force to act on the first pipe section 32 This force (F2) and elongation (A12) caused thereby are approximated as follows with reference to the relevant dimensions of the first pipe section 32 Faxial2 = P2 (122#) + 4 axial = 164000 lb (74589 kg) Lquation 4 EMI15.3 = 230 x 106 lb/inch (4 0279 x 1010 N/m) EMI15.4 Equation 5 Equation 6 Thus under the above noted circumstances a gap 58 is created on each side of the second or centre pipe section 38 by the hydrostatic pressure acting in the bearings Tite width (w) of the gap 58 is calculated b <RTI ID=15.14> Equatioit 7 EMI15.5 Equation 7 The gap 58 of approximately 0.00065" (0 0165 mm) is well suited for operation of the hydrostatic bearings Generally speaking, a gap width of at least ().0003" (O (iG70 mm) is necessary for the operation of the hydrostatic bearings utilising a water as a fluid In the above described first preferred embodiment, a much small gap is created by the hydrostatic pressure than in the second preferred embodiment because the second or centre pipe section 38 is hollow and because the operative pressures are usually much lower in the application of the first embodiment: for example P2 usually does not exceed 200 PSI (1 .579 MPa) Therefore, only a much smaller compressive force acts on the centre pipe section 38, and only a much smaller tension force acts on the first pipe section 52 Significant advantages of the herein described densitometer 20 and 70 of the present invention include the following. Construction of the densitometer and particularly of the hydrostatic bearing surfaces 44 and 46 is relatively simple Except for the indentation of pockets 52. the surfaces 44 and 46 are simply machined flat. Furthermore the densitometer of the present invention requires less pump power to operate than the densitometer described in United States Patent No- 4 285,259 This is apparent from the fact that flow of hydrostatic fluid occurs only inwardly, toward the interior of the transport pipe 22. There is no loss of hydrostatic fluid outwardly, towards the exterior of the first pipe section 52 as in the prior art. Referring now to Figures 1 2, 6 and 7 of the drawings the manner of measuring the weight of the "floating" second or centre pipe section 58 and mounting of the same in the interior of the enveloping first pipe section 52 is disclosed Generally speaking. the centre pipe section 38 may be mounted on one or several load cells or strain gauges (not shown) Requirements in this regard are only that the load cells or strain gauges must not permit excessive displacement of the centre pipe section 38. in other words the centre pipe section 38 must be maintained in operative position and must not come into contact with the interior walls of the enveloping first pipe section 52 Output of the load cells or strain gauges may be recorded continuously and may be wised to compute the density of the slurry (not shown) flowing in the pipeline The load cells or strain gauges (not shown) must of course be protected from the hydrostatic fluid (not shown) which surrounds the "floating" centre pipe section 58 A preferred alternative to tile use of load celts or strain gauges is however to mount the centre pipe section 58 on a plurality of preloaded tension rods 72 or tension wires (not shown) Preferably three preloaded tension rods 72 are used which are equally spaced (at 120 apart from one anotller) about the periphery of the centre pipe section 58 as is best shown in Figure 6. Each tension rod 72 engages a threaded bore 74 provided in the centre pipe section 38 and is attached to the enveloping first pipe section 52 by a suitable nut 76 as is shown on Figure 6 and 8. The tension rods 72 have known strain characteristics (spring constants). It can be shown by relatively simple calculations that when as in the herein described preferred embodiments there are three equally spaced tension rods 72 having identical spring constants (K) the actual spring constant acting in the vertical direction (Kv) (or any direction for that matter) is double of the spring constant (K) of the individual t ens ori rods. (Equation 8) Kv = 2K Equation 8 Advantages of this arrangement are that it is not necessary for any of the tension rods to be aligned with the vertical direction and only one of the three equal tension rods needs to be adjusted or tightened thereby automatically creating equal tension force on all three tension rods. Since the spring constant (K) of the tension rods 72 is known. movement or displacement of the centre pipe section 58 in the gravity vertical direction is measured by a suitable instrument such as 2 displacement or position monitoring device operating on optical principles, or on the principle o capacitance varying as a function of distance. Such position or displacement measuring devices are well known in the art and are commercially available. "Fotonic Sensors" of KD 300 series and the "Accumeasure System 1000" of Mechanical Technology Incorporated of Latham ew York serve as examlpes. Thus in the preferred embodiments 20 and 70 of the present invention, a small mirror 78 is embedded in the outer surface 50 of the centre pipe section 58 A fibre optics containing sensor 80 is mounted into the first pipe section 52. Operation of the sensor and of associated electronics need not be described here, since such sensors and electronics are well known It is sufficient to note that a light is cast on the mirror 78, and the reflected light triers a signal in the sensor which is indicative of the position of the mirror 78. The above noted "Fotonic Sensors" of Mechanical Technology Incorporated (and like fibre optics containing displacement sensors known in the art) are accurate to the 10-6 inch (25.4 x 10-6 mm) magnitude. The weight of the second or centre pipe section 38 and of the slurry momentarily contained therein, is readily calculated from the accurately measured displacement of the centre pipe section 38, in a mariner well known in the art. In fact, a readout or recorder device (not shown) used in conjunction with the densitometer of the present invention may include the necessary computing means to perform the calculations, and may directly display and record, the calculated weights, and also the hurry densities calculated from the weights. In a modification or alternative embodiment of the slurry densitometer of the present invention, the intermediate pipe pieces may be omitted. In this embodiment, the corresponding ends of the transport pipe have fixed direct connection to the first pipe section 32, and also have precision machined surfaces to form the hydrostatic bearings.

Claims: CLAIMS 1. A device for measuring the weight of a pipe section having a fluid or slurry flowing therethrough, the device comprising: a first substantially horizontally disposed pipe section having two ends, each end of the first pipe section being fixedly coupled to a fluid or slurry transport pipe, a second substantially horizontally disposed pipe section, smaller in diameter than the first pipe section, being substantially concentrically disposed within the first pipe section so as to define a chamber between the outer surface of the second pipe section and the inner surface of the first pipe section, the second pipe section having a transport cavity which is in fluid communication with the fluid or slurry transport pipe, and a machined surface provided at each end of the second pipe section which interface complementary machined surfaces provided in respective ends of the fluid or slurry transport pipe, with a gap being located between ends of the second pipe section and respective ends of the fluid or slurry transport pipe, said machined surfaces being configured for functioning as hydrostatic bearings; first means operatively associated withthe first pipe section for supplying a hydrostatic fluid under pressure to the chamber between the first and second pipe sections; ; second means provided in the second pipe section for permitting passage under pressure of the hydrostatic fluid from the chamber to the machined surfaces at each end of the pipe section and for permitting passage of the hydrostatic fluid into the gaps between the respective machined surfaces of the second pipe section and the ends of the fluid or slurry transport pipe whereby a hydrostatic bearing is created between the machined surfaces to permit substantially frictionless movement of the second pipe section in the direction parallel with the earth's gravitational field; third means operatively associated with the second pipe section for sensing a physical parameter, comprising an Input to a transducer, from which weight of the second pipe section and of the fluid or slurry momentarily contained therein may be calculated. 2. The device of Claim 1 wherein the first means are adapted for supplying the hydrostatic fluid into the chamber at a pressure which is higher than the pressure of the fluid or slurry flowing through the fluid transport pipe. 5. The device of Claim 1 or Claim 2 wherein each of the machined surfaces of the second pipe ee ti on comprise at least one pocket, and wherein the second means include a duct leading to each of the pockets for conducting flow of hydrostatic fluid through the duct to the respective pocket. 4. The device according to any preceding claim wherein each of the machined surfaces of the second pipe section comprise a plurality of pockets, and wherein the second means include a plurality of ducts, each duct leading to one pocket for conducting flow of hydrostatic fluid through the duct to the respective pocket. 5. The device according to any preceding Claim 2 wherein the first means includes pump means for supplying hydrostatic fluid under pressure to the chamber, and at least one inlet duct means disposed in the first pipe section for permitting flow of hydrostatic fluid from the pump means to the chamber. 6. The device of Claim 5 wherein the inlet duct means includes only a single inlet duct into the first pipe section. 7. The device according to any preceding claim wherein the first pipe section includes a plurality of internally threaded bores, the fluid or slurry transport pipe includes a flange substantially at each of its ends adjacent to the first pipe section, and wherein the first pipe section is stationarily mounted to the flanges of the fluid or slurry transport pipe with a plurality of bolts engaging the threaded bores. 8. The device according to any preceding claim further comprising fourth means for permitting limited movement of the second pipe section in the direction of the earth's gravitational field in response to varying weight of the fluid or slurry momentarily contained in the second pipe section, and wherein the third means comprise means for sensing location of the first pipe section in the direction of the earth's gravitational field. 9. A device for measuring varying density of a slurry such as a coal or mineral slurry flowing through a transport pipe, the device comprising: two intermediate pipe pieces, each intermediate pipe piece having a first end adapted to be coupled to the transport pipe, and a second end; a first pipe section fixedly mounted between the second ends of the two intermediate pipe pieces, a second pipe section smaller in diameter than the first pipe section and mounted within the first pipe section in a substantially horizontal position between the two second ends of the two intermediate pipe pieces, the second pipe section being in fluid communication with the second ends of the intermediate pipe pieces, whereby the second pipe section comprises an intermediate portion of the transport pipe a chamber being disposed between the inner periphery of the first pipe section and the outer periphery of the second pipe section; interfacing hydrostatic bearing surfaces formed in the ends of the second pipe section and in the second ends of the intermediate pipe pieces, the bearing surfaces comprising means for permitting so-UsLantially frictionless movement of the second pipit section in a direction parallel with the earth's gravitational field; ; pump means for providing a hydrostatic li(1flid through the first pipe section into the chamber at a pressure higher than the pressure of the slurry flowing in the transport pipe, for substantially filling the chamber with the hydrostatic liquid; duct means provided in the second pipe section for conducting hydrostatic liquid from the chamber to the hydrostatic bearings, spring means for limiting movement of the second pipe section in a direction parallel with the earth's gravitational field and for rendering said movement proportional to the gravitational force acting on the second pipe section and on the slurry contained therein; and sensing means for sensing position of the second pipe section in the direction parallel with the earth's gravitational field. 10. A densitometer for measuring varying density of a slurry, such as a slurry of coal or mineral, flowing in a transport pipe, the densitometer comprising. two intermediate pipe pieces, a first section of a pipe fixedly attached to the intermediate pipe pieces coupled to be in fluid communication with a transport pipeline; a centre pipe section disposed substantially horizontally and substantially concentrically within the first pipe section, the centre pipe section being in fluid communication with the intermediate pipe pieces whereby slurry transported in the transport pipeline flows through the centre pipe section, a substantially ring-shaped chamber being formed between the first pipe section and the centre pipe section, hydrostatic bearing means formed in the ends of the centre pipe section and in adjacent ends of the intermediate pipe pieces for permitting substantially frictionless movement of the centre pipe section within the chamber, pump means including at least one inlet port provided in the first pipe section for supplying a hydrostatic liquid into the chamber at a pressure greater than the pressure of the slurry flowing in the transport pipeline; spring means mounted to the first pipe section and the centre pipe section for limiting movement of the centre pipe section and for rendering movement of the centre pipe section in a vertical direction indicative of the weight of the slurry momentarily contained in the centre pipe section; and position sensing means for sensing the position of the centre pipe section in the chamber in the vertical direction. 11. The device of any one of Claims 8 to 10 wherein the fourth or spring means comprise a plurality of tension rods mounting the second pipe section within the first pipe section. 12. The device of any one of Claims 8 to 11 wherein the fourth means comprise three tension rods spaced equally about the circumference of the second pipe section, the tension rods having substantially identical spring constants. 13. The device according to any preceding claim wherein the first pipe section and the second pipe, section are of equal length, and wherein a shim is stationarily disposed between ends of the first pipe section and adjacent ends of the fluid or slurry transport pipe. 14. The densitometer of Claim 13 wherein the shims Eire approximately 0.0003" to 0.0007" (0.0076 to ;D.0178 mm) thick. 15. The device according to any preceding claim wherein the third or sensing means comprises a mirror fixedly attached to the second pipe section, means for casting light on the mirror, and transducer means responsive to light reflected from the mirror for transmitting a signal indicative of the position of the mirror. 16. The device according to any preceding claim wherein the third or sensing means comprise a proximity sensor adapted for measuring varying capacitance of a condenser as a function of distance. 17. The device according to any preceding claim wherein the first pipe section and the second or central pipe section are of equal length, and wherein, the hydrostatic fluid is supplied by the first means at a sufficiently high pressure into the chamber to cause a pressure differential between the pressure of the hydrostatic fluid transport pipe, which differential is sufficient to axially compress the second pipe section to create the small gaps of the hydrostatic bearings. 18. The densitometer of Claim 17 wherein the pressure applied to the second or centre pipe section is sufficient to axially compress the second or centre pipe section by at least 0.0003" (0.0076 mm). 19. The device of Claim 17 wherein the hydrostatic fluid is supplied by the first or pump means to the chamber at least at 1500 PSI (10.34 MPa) pressure. 20. The device according to any preceding claim comprising two intermediate pipe pieces, each intermediate pipe piece being fixedly coupled to the fluid or slurry transport pipe, and incorporating the pipe ends which have the machined surfaces complementary to the machined surfaces provided at each end of the second pipe section.

Inventors: HEINE, OTTO R., RIEDE, PETER M.
Applicants: SLURRY TECHNOLOGY LIMITED
Application year: 1984
Main classification: G01G11
IPC codes: G01G11, G01N9