JPS62237319A - Impeller flow meter - Google Patents

Abstract

PURPOSE:To stably measure the flow rate of fluid with high accuracy for a long period by forming a pivot bearing on one side of the rotating shaft of an impeller and forming a spiral groove bearing on the other side. CONSTITUTION:A shaft 32 on a fluid inflow side is fixed to the impeller 31 and the pivot bearing is formed in a boss 33; ad a flat plate 56 made of ceramic is fixed to the end surface of the boss 34 on an outflow side and the spiral groove bearing (flat plates 56 and 57) which is fixed to the end surface of the rotating shaft of a rotor 31 is formed. The rotor 31 is supported with a slight margin in a right-left direction, so when fluid flows in, the boss 34 on the outlet side moves slightly and rotates, so that the tip of the shaft 32 leaves a flat plate precious stone 55. Then a fluid film is formed on the bearing (flat plates 56 and 57) as well, so the rotor 31 rotates substantially without contacting. Thus, the flow rate is measured stably with high accuracy for a long period.

Description

[Detailed Description of the Invention] [Object of the Invention] "Industrial Application Field" The present invention relates to an impeller flowmeter that can measure the flow rate of a liquid with high precision and stably over a long period of time. It is.

``Prior art'' An impeller flowmeter places an impeller in a fluid, rotates it using the fluid's dynamic pressure, and measures the instantaneous flow rate based on its rotational speed and the cumulative flow rate based on its rotational speed. It was designed to be measured.

These impeller flowmeters include tangential flow impeller flowmeters, which are often used as water meters, axial flow impeller flowmeters (Waltmann type water meters), and turbine make, which are often used as industrial meters.

FIG. 8 is a longitudinal sectional view showing an example of a conventional tangential flow type impeller flowmeter. Water flowing in from the inlet 2 passes through the filter 12 and enters the inlet side 1a of the main body 1 partitioned by the partition wall 4, and enters the case 14 of the metering unit 13, which is fitted and fixed in the main body 1.
It enters the case 14 through the hole 15 provided in the hole 1 of the case 14.
6 to the outlet side 1b of the partition wall 4 and flows out from the outlet 3.

The impeller 6 is rotated by the water flowing in and out of the case 14, and the rotating shaft 17 to which the impeller 6 is fixed rotates. The lower end of the rotating shaft 17 has a conical shape and is supported by a pivot bearing 18 screwed into the case 14, and the rotating shaft 17 extends upward and is attached to the case 1.
The shaft is sealed by the shaft sealing device 21 provided in the instrument box 19 of the measuring unit connected to the instrument box 19 connected to the instrument box 19.
The conical shaft end provided at the upper end is supported by a pivot bearing 1) screwed into the shaft. Therefore, the rotation of the impeller 6 is guided to the instrument box 19 by the rotating shaft 17, and inside the instrument box 19, a gear train 24 interlocked with a gear 25 fixed to the rotating shaft 17 rotates, passing through the scale plate 22 and moving upward. Each shaft of the gear train provided with the pointer 23 extending thereon rotates to rotate the pointer 23. Corresponding to the pointer 23, each digit of the water amount is displayed on the scale plate 22 as an analog amount. A glass 26 seals the instrument box 19.

FIG. 9 is a longitudinal sectional view of the turbine meter.

The main body 1 has a cylindrical shape, and the one shown is the flange 3.
It is attached to piping (not shown) by 0. An inlet 2 and an outlet 3 are provided at both ends of the main body 1, and a rotor 51 is rotatably supported at the center. A shaft 32 is fixed to the rotor 31 passing through its center.
The tip portions of are supported by bearings formed on an inlet side boss 33 and an outlet side boss 34, respectively. This bearing is composed of a sleeve bearing 35 made of a ceramic ring and an end stone 36 made of a plate-shaped artificial sapphire, and is designed not to deteriorate even if it is immersed in water for a long time.

In addition, plate-shaped spiders 6 and 7 are formed radially on the bosses 53 and 34, respectively, to rectify the water flow and to adjust the rotor 31.
to hold it in place. g31a of the rotor 31 is twisted with respect to the shaft 32, but this is because the water flow is rectified by the spider 67 so that it is parallel to the shaft 62;
It is also possible to give a certain twist to the spider 37 to guide the water flow as a swirling flow to the rotor 31, and to rotate the rotor 31 with its blades 31a parallel to the shaft 32. The inner wall 40 in the main body 1 has a spider 67 on the inlet side and a spider 3 on the outlet side.
In order to push in and fix 7, the inner diameter is from the inlet 2 side to the outlet 3 side.
The rotor 31 is rotatably supported at a predetermined position by pressing and fixing the spider 37 on the inlet side with the clip 41, which becomes smaller stepwise toward the side.

Small permanent magnets 42 are embedded in the outer peripheral edges of the blades 3ja of the rotor 31, and when the rotor 31 rotates, the permanent magnets 42 move toward the coil 4 provided in the pickup section 43.
4, an electric signal corresponding to the rotational speed of the rotor 31 is generated in the coil 44, and an instantaneous value and an integrated value of the water flow are calculated and displayed on a measurement display section (not shown).

The type of pickup shown is called an inductive pickup, but instead of the coil 44, a Hall element,
A magnetoresistive element can be used, and the rotor 5
1. A carrier modulation type pickup that does not require a permanent magnet is also used.

10(a), (1)), and (C) are enlarged cross-sectional views of the main parts showing various bearing systems in impeller flowmeters, and FIG. 10(a) is a ball bearing system with shaft 32. is the boss! ! (34), and the rotor 31 is rotatably supported on the shaft 32 by a ball 45 provided inside the rotor 31.

FIG. 10(1)l shows a journal bearing system in which a journal 46 is fixed to the boss 33 (34), a sleeve 47 is fixed to the inner circumference of the rotor 31, and a thrust washer 48 is fixed to the boss 33 (34). 31
It is designed so that it rotates. Furthermore, Figure 10 (
C) is a pivot bearing type, in which both ends of the shaft 32 are rotatably supported by bearings 49 made of a gemstone such as sapphire or ruby.

``Problems to be solved by the invention'' Impeller flowmeters have a simpler structure than positive displacement flowmeters, can measure large flow rates, can be used for liquid gases, and can be applied over a wide temperature range. However, since the rotation speed of the rotor is not necessarily directly proportional to the flow rate, an accurate mass flow rate cannot be obtained unless it is corrected for temperature, viscosity, flow velocity, etc. 1Basically, a positive displacement flowmeter is used to obtain an accurate mass flow rate. This must be corrected.

Furthermore, in the region of small flow rate, the rotation of the rotor is extremely reduced, so there is a drawback that accurate flow rate cannot be determined.

In particular, the mechanical impeller flowmeter shown in Figure 8 has an impeller (
Since the rotation of the rotor directly drives the gear of the indicator needle, it is not possible to accurately measure the flow rate in the region of small flow rates, nor can it be corrected. On the other hand, the electronic turbine meter shown in Fig. 9 has small instrumental error even in the region of small flow rates, and can be electrically corrected in some cases (Sensor Technology, Vol. 6, No. 3, pp. 53-59 (1985) 0, 2007 Therefore, as a conventional technique for improving the performance of impeller flowmeters, the main method has been to convert the mechanical rotation detection of the rotor to an electronic detection method.

However, in principle, an impeller flowmeter has an impeller (
Since the impeller is rotated according to the flow rate by immersing the rotor), the solid particles contained in the fluid to be measured and the liquid quality of the fluid itself (pL humidity temperature redox potential, etc.)
Therefore, there were various difficulties in maintaining stable performance over a long period of time.

In particular, in impeller-type water meters, which are one of the most widely used flowmeters, when magnetic rotation detection means are used, iron in the water adheres to the permanent magnet embedded in the rotor, causing the indicated value to be distorted. It was pointed out that there is a gradual decline and that the inter-instrument difference increases as a result.

The present invention was made in view of these circumstances, and aims to provide an impeller flowmeter that can maintain stable performance over a long period of time, and to more accurately grasp the flow rate. The purpose is to provide an impeller flowmeter that can perform

[Structure of the invention]

"Means for Solving the Problems" The present invention provides an impeller flow rate that measures the flow rate of a fluid by measuring the rotation of an impeller rotatably disposed in a flow path of a fluid whose flow rate is to be measured. This is an impeller flow meter in which a pivot bearing is formed on one side of the rotating shaft of the impeller, and a spiral group bearing is formed on the other side.

Further, in the present invention, it is a preferred embodiment that the pivot bearing is arranged on the fluid inflow side and the spiral group bearing is provided on the fluid outflow side, or that the spiral group bearing is made of ceramics. be.

"Function" In the impeller flowmeter of the present invention, the impeller is supported by a pivot bearing and a spiral group bearing, so when the impeller is pushed toward the spiral group bearing and rotates, the tip of the pivot bearing does not come into contact with the impeller. The thrust force applied to the impeller is supported only by the spiral group bearing, but fluid dynamic pressure is generated in the spiral group bearing, and the impeller rotation axis is supported by the fluid film and is essentially fixed. Rotates without making contact with the sides.

The rotation of the impeller is detected by conventionally known means, but since the impeller is rotated at a fixed position by a spiral group bearing, the accuracy cannot be improved if magnetic rotation detection or optical rotation detection is used. This allows for high detection.

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an example of an impeller flowmeter of the present invention, and shows a longitudinal sectional view of a turbine meter. 2 is an enlarged cross-sectional view of the main part of FIG. 1, and FIG. 3 is a partially enlarged view of the bearing section of FIG. 2.

In FIG. 1, a shaft 32 is fixed to an impeller (rotor) 31 on the fluid inflow side, a pivot bearing is formed inside the boss 33, and a ceramic material is attached to the end face of the boss 34 on the fluid outflow side. A spiral group bearing is formed by a ceramic plate (not shown) in which a spiral groove is formed and a ceramic plate (not shown) fixed to the end face of the rotating shaft of the rotor 31 to which a flat plate 56 serving as a bearing plate made of aluminum is fixed.

The support means for the bosses 55 and 54 are the same as the conventional means described above, but in FIG. A lead wire 53 for guiding a signal from a rotation detection probe (not shown) housed in the boss 34 to the outside is passed through the boss 34 .

A through hole 5 is provided in the portion where the protective tube 50 penetrates the peripheral wall 1C.
4 is formed, and the space between the through hole 54 and the protective tube 50 is filled with resin to maintain airtightness. 62 is a small ball used as a part of the spiral group bearing. Impeller (
side 1 facing the boss 34 on the downstream side of the rotating shaft of the rotor) 61
A permanent magnet (not shown) is provided here, and different magnetic poles are formed along the annular shape. A rotation detection probe (not shown) attached to the end of the lead wire 53 is buried in a position facing the permanent magnet, and transmits the rotation of the impeller (rotor) 31 to an external measurement display (not shown). .

Figure 2 shows the impeller (rotor) 31 and boss 55 in Figure 1,
34. Inside the boss 33 on the fluid inflow side, a pivot bearing is formed by a flat jewel 55 that supports the tip of the shaft 32 fixed to the rotating shaft of an impeller (rotor) 51. Ceramic flat plates 56 and 57 are respectively fixed to the boss 34 and the rotor 51 on the opposite side from which the fluid flows out, and a spiral groove is formed on the surface of one of the flat plates (56 or 57). It is formed.

In the figure, a spiral groove 58 is formed on the surface of a ceramic flat plate 57 fixed to a rotor 61, and a boss 3
The surface of the ceramic flat plate 56 fixed to 4 is a smooth plane.

Furthermore, hemispherical recesses 59 and 61 are formed in the centers of the two flat plates 56 and 57, respectively, and a small sphere 62 made of ceramic is accommodated in the space formed by the two recesses 59 and 61.

Furthermore, a plastic magnet 6 is attached to the inner circumferential side of the spiral group 58 of the ceramic flat plate 57 on the rotor 61 side.
3 are provided in an annular shape and are magnetized with different magnetic poles. Further, a hole 64 is formed in the ceramic flat plate 56 on the boss 54 side facing the plastic magnet 6S, and a sensor 65 is housed in the hole 64. The hole 64 that accommodates the sensor 65 is filled with resin to maintain airtightness on the lead wire 53 side. The storage tube 5o is inserted into the guide port 67 of the conductive path 66 formed in the boss 54, and the periphery thereof is similarly fixed with resin, so that the fluid to be measured does not flow into the lead wire 53.

Here, the rotor 31 is supported with a slight margin in the left and right directions in the figure, so when fluid flows in, it moves slightly toward the boss 54 on the outlet side and rotates.At this time, the tip of the shaft 32 is a flat plate. It is in a non-contact state with the jewel 55. And spiral group bearings (
Since a fluid film is also formed on the flat plates 56, 57), the rotor 31 rotates in a substantially non-contact state. Therefore, in this state, contact between the rotating body and the stationary side occurs at the sleeve bearing 35 and the small ball 62, but since the resistance is small in both cases, the rotation of the impeller (rotor) 31 is caused by the fluid It is easy to follow the flow velocity.

FIG. 6 is a front view of the end face of the rotating shaft on the downstream side of the rotor 31, and the rotor 31 rotates in the direction of an arrow 70 during forward rotation. 31 is a plastic rotor, rotor 3
A ceramic flat plate 57 is embedded and fixed so as to slightly protrude from the end face of the ceramic plate 1 . The flat plate 57 is attached to the rotor 3 in advance.
A hemispherical recess 59 is formed at a position corresponding to the rotational axis of 1, and an annular groove 71 is formed around the recess 59. The formed body is fired to form a hard ceramic flat plate, and then lapping is performed. to create a flat surface with few undulations. In this state, the parts other than the hemispherical recess 59 and the annular groove 71 have a mirror surface. A tape 72 of a plastic magnet 63 is embedded and fixed in the annular groove 71, and different magnetic poles are alternately magnetized along the annular shape. In the figure, it is magnetized to 16 poles, and the plastic magnet is a tape-shaped mixture of rare earth permanent magnet powder and plastic, so a strong magnetic field can be obtained. In addition to elements, sensors that require strong magnetic force for switching, such as reed switches, can be used.

A spiral resin mask is attached to the flat plate 57 which has been finished smoothly, and the spiral grooves 58 and the central pressure equalizing portion 74 are processed and formed by shot blasting. The surface processed by this shot blasting has a satin finish. The pear-shaped surfaces 74 and 58 are approximately 3 to 50 μm deeper than the surface of the spiral land 75, and the surface of the plastic magnet tape 72 is slightly deeper than the surface of the land 75 so that it does not protrude. It is desirable to leave it there. When the fluid flows in the normal direction, the rotor 31 rotates in the direction of arrow 70, and the rotor 31
is caused by the pressure of the fluid that the blade 51a receives from the downstream boss 3.
Pressed to the 4th side. The rotation of the rotor 31 exerts a force that causes the fluid to flow in the inner circumferential direction along the spiral groove 58, and as a result, the rotor 31 rotates without substantially directly contacting the end surface of the boss 34 on the downstream side.

FIG. 4 is a front view showing the surface of a flat plate 56 that serves as a ceramic receiving plate fixed to the end face of the boss 34 on the downstream side. A recess 61 is formed, and a hole 64 is formed at a position facing the tape 72 of the plastic magnet described above, and a sensor 65 is embedded inside the hole 64. Furthermore, since the sensor 65 is fixed with resin, the fluid will not leak out.

Furthermore, if the flow direction of the fluid is reversed, the rotor 31 will be pressed against the pivot bearing side and rotate.
A point contact is made at the tip of the shaft 32. On the other hand, since the spiral group bearing side is in a non-contact state, the resistance accompanying the rotation of the rotor 31 is small.

FIG. 5 is a longitudinal sectional view showing another embodiment of the present invention,
It is a drawing when the present invention is applied to a wet-type illuminated impeller flowmeter. Portions that overlap with those of the known example shown in FIG. 8 are given the same numbers, and their explanation will be omitted.

In the figure, the lower part of the impeller 6 is supported by a pivot bearing formed by a ceramic support pin 76 fixed to the bottom of the case 14 and a sapphire disc 77 fixed inside the impeller 6, and the upper part A flat plate 79 that serves as a ceramic receiving plate with a smooth surface is fixed to the inside of the lid 78 of the case 14, and a flat ceramic plate FIt with a spiral groove formed therein is fixed to the tip of the rotating shaft of the impeller 6. It is supported by formed spiral group bearings. If fluid flows in from the normal direction, the impeller 6 will receive an upward force depending on the flow rate, and when the impeller 6 begins to rotate, the pivot bearing will be out of contact in the low flow velocity region, causing the impeller to The thrust force that 6 receives is applied to the spiral group bearing provided above. However, since a fluid film is formed between the flat plates 79 and 81 as the impeller 6 rotates, the impeller 6 receives less resistance when it rotates.

In addition, a ceramic flat plate 8 on which a spiral groove is formed
Since a permanent magnet is embedded in the surface of the impeller 6 in the same manner as described above, the rotation of the impeller 6 can be detected by the sensor 83 embedded in the center of the outer cover 82.

In addition, in FIG. 5, the detailed structure of the spiral group bearing is shown in FIGS. 3 and 4, and will therefore be omitted.

FIG. 6 is an enlarged cross-sectional view showing the main parts of another embodiment of the spiral group bearing section which is the bearing on one side of the impeller. In FIG. 6, an annular ceramic flat plate 57 is fixed to the downstream rotating shaft end of the impeller (rotor) 31, and a spiral groove 58 is formed on its surface. Further, an annular permanent magnet 60 is provided on the inner circumference thereof, and different magnetic poles are annularly magnetized.

In this embodiment, the sensor 65 is covered and fixed by the flat plate 56, which serves as a ceramic receiving plate, which is fixed to the end face of the boss 34, so there is an advantage that the sensor 65 is hard to be damaged.

FIG. 7 is a front view of the downstream end face of the rotating shaft shown in FIG. 6, and the annular permanent magnet 60 is magnetized with eight annular magnetic poles, and a spiral groove 58 is formed on its surface. It is about 0.1 to 0.5 times lower than the surface of the ceramic flat plate 57.

Ceramics are the most suitable material for forming the spiral group bearing in the present invention, and are chemically stable against a wide range of fluids and stable even at high temperatures. Furthermore, if the thrust force is small, a thin layer of metal spirally coated on the surface of the plastic may function, but the operating temperature range will be narrow.

In addition, in the present invention, materials constituting the rotor (impeller) include, if the impeller flowmeter is used at room temperature,
It is best to use plastic, and metal ceramics are suitable when used at high temperatures. In particular, when using in high temperature conditions where permanent magnets cannot be used, the entire structure should be made of a material that can be used at high temperatures, such as metal or ceramics, and for example, a glass optical fiber may be connected to the sensor section shown in Figure 2 from the outside. The spiral groove should be irradiated with a narrow beam of light, and the rotation of the impeller should be detected from the reflected light intensity based on the difference in light reflectance between the land and the groove.

Furthermore, in the present invention, in the case of an impeller flowmeter in which the rotation axis of the impeller is mainly installed horizontally as shown in FIG. It should be designed to be a bearing, and in this way, the thrust force for normal fluid flow will be supported by the dynamic pressure bearing, so there will be virtually no wear on the bearing part.

Of course, it goes without saying that it functions in the same way as a normal flowmeter for fluid flow in the opposite direction.

If the rotary shaft is mounted vertically as shown in Figure 5, the spiral group bearing should be at the top so that an upward thrust force is generated by the fluid flow. This is advantageous because the weight of the impeller is offset. In addition, in the impeller flowmeter of the present invention as well as in known impeller flowmeters, it is important to reduce the weight of the rotating part, and parts made of high-density materials such as ceramics used in the rotating part. The smaller the value, the better, and the embodiment shown in FIG. 6 is preferable. Further, when embedding a permanent magnet in a rotating part, only one or two small pieces may be embedded if the accuracy of the instantaneous value is not so required.

Furthermore, in the present invention, if a magnetoresistance effect element is used as a rotation sensor, it is activated by a change in magnetic field strength of about 30 Gauss, so a small permanent magnet is sufficient, which is advantageous compared to a reed switch or a Hall element. becomes.

In the present invention, as a means for detecting the rotation of the impeller, mechanical detection means can be used in addition to magnetic and optical detection means, as described above, and in particular, magnetic detection means and optical detection means are possible. When using a spiral group bearing, the clearance between the impeller rotation axis and the end face of the boss is extremely small in the range of several μm to several tens of μm, and shaft runout is suppressed, so accurate You can understand the rotation.

〔Effect of the invention〕

In the impeller flowmeter of the present invention, the impeller is rotatably supported by a pivot bearing and a spiral group bearing, and when the impeller rotates, the spiral group bearing is in a substantially non-contact state. Since it supports the load applied to the impeller, it has the advantage that its performance does not change over a long period of time. In addition, since the pivot bearing, which is one of the bearings, has low resistance when the impeller rotates from a stopped state, it can easily operate even in a low flow rate range. Furthermore, since the spiral group bearing supports the rotating body on the surface of an extremely thin fluid film, the rotation of the rotating body, that is, the impeller, is stable, so rotation can be detected even when measuring the instantaneous value of the flow rate. can be performed accurately, and a more accurate flow rate can be determined. In particular, when detecting the rotation of the impeller magnetically or optically in the spiral group bearing section, the gap is narrower than in the conventional structure of the detection section, making it possible to read with significantly higher accuracy.

In this method of optically detecting the rotation of the impeller, it is preferable to attach the member on the side that forms the spiral group of the spiral group bearing to the impeller, but if you use the method of magnetically detecting the rotation, it is preferable to attach the spiral group bearing to the impeller. A member formed with this can also be used on the boss side.

In addition, if ceramics are used as the material for spiral group bearings, they will not be worn out by solid particles such as iron splinters or sand, and are not only extremely stable chemically, but also have excellent performance as hydrodynamic bearings. Therefore, dynamic pressure can be generated even in a region where the rotation speed of the impeller is extremely low, and the impeller rotates smoothly. In this case, the thickness of the ceramic plate may be 1) 1E or less, so the weight of the impeller does not increase significantly.

As described above, according to the present invention, since the bearing of the impeller flowmeter has been improved as described above, there is an advantage that accurate flow rate can be determined over a long period of time without deterioration of performance.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, FIG. 2 is a partially enlarged vertical cross-sectional view of FIG. 1, and FIG. 6 is a front view of the bearing portion of FIG. 2.
FIG. 4 is a front view of a flat plate placed opposite to the spiral group flat plate of FIG. 3, FIG. 5 is a longitudinal sectional view of another embodiment, and FIG. 6 is an enlarged sectional view showing the bearing portion of still another embodiment. 7 is a front view of the bearing part in FIG. 6, FIGS. 8 and 9 are vertical sectional views showing a conventional impeller flowmeter, and FIGS. 10(a) and (1))
, (C) is an enlarged sectional view showing the bearing structure of a conventional impeller flowmeter. 1...Body 1a...Inlet side 1b...Outlet side 1C...
・Peripheral wall 2・・Inflow port 3・Fist outlet 4・・Partition wall 6
・・Impeller 1)・・Pivot bearing 12・・Filter 13・・Measuring unit 14・e case 15.16
... Hole 17 ... Rotating shaft 18 ... Pivot bearing 19
・・Measure tray box 21・・Shaft sealing setting 22・・Scale plate 23・
・Pointer 24・・Gear train 25・・Gear 26・・Glass 30・・Flange 31@・Rotor 31a・・Blade
32..Shaft 33゜341)・Boss 35..Sleeve bearing 66.e End stone 37..Spider 4d..Inner wall 41..Clip 421).Permanent magnet 43..Pickup section 44-.Coil 4
5.Fist hole 46.Journal 47.Sleeve
4B...Thrust washer 49...Jewel bearing 50...
Protection tube 53...Lead wire 54...Through hole 55...
Flat jewelry 56.57...Flat plate 58...Spiral group 59...Recess 60...Permanent magnet 61...Recess 62...Small ball 63...Plastic magnet 6
4... Hole 65... Sensor 66... Conduction path 67... Induction port 70... Arrow 71... Groove 72... Tape 74
・・Pressure equalization part 75・・Land 76・φ support pin 77・
Fist sapphire disk 78＠・Lid 79・・Flat plate 8
1・e flat plate 82・・outer cover 83・ro sensor.

Claims (3)

[Claims] (1) In an impeller flowmeter that measures the flow rate of a fluid by measuring the rotation of an impeller rotatably disposed in a flow path of a fluid whose flow rate is to be measured, the rotation axis of the impeller is An impeller flowmeter characterized in that a pivot bearing is formed on one side and a spiral group bearing is formed on the other side. (2) The impeller flowmeter according to claim (1), wherein the pivot bearing is provided mainly on the fluid inflow side. (3) Claim (1) or (3) wherein the spiral group bearing is made of ceramics.
2) The impeller flowmeter described in any of the above.