For measuring or checking pressure

90.26 - Instruments and a paratus for measurin or checking the flow, level, pressure or other variables o liquids or gases ( or example, flowmeters, level gauges, manometers, heat meters), excluding instruments and apparatus of heading 90.14, 90.15,90.28 or 90.32. i' f - For measuring or checking the flow or level of liquids 9026.20 - For measuring or checking pressure 9026.80 - Other instruments or apparatus 9026.90 - Parts and accessories 9026.10 Apart fiom instruments or apparatus more specifically covered by other headings of the Nomenclature, such as : (a) Pressure-reducing valves and thermostatically controlled valves (heading 84.81); (b) Anemometers (wind gauges) and hydrological level gauges (heading 90.15); (c) Thermometers, pyrometers, barometers, hygrometers and psychrometers (heading 90.25); (d) Instruments and apparatus for physical or chemical analysis, etc. (heading 90.27), this heading covers instruments and apparatus for measuring or checking the flow, level, pressure, kinetic energy or other process variables of liquids or gases. The instruments and apparatus of this heading may be fitted with recording, signalling or optical scale-reading devices or transmitters with an electrical, pneumatic or hydraulic output. Measuring or checking a paratus general1 incorporates an element sensitive to variations in the uantity to be measure (e.g., Bourdon tu e, diaphragm, bellows, semiconductors) moving a nee e or a pointer. In some devices the variations are converted into electrical signals. S ll Measuring or checkin instruments or ap aratus of this heading combined with taps, valves, etc., are to be classifie as indicated in the xplanatory Note to heading 84.81. f ! (l) APPARATUS FOR MEASURING OR CHECKING THE FLOW OR RATE OF PLOW OF LIQUIDS OR GASES (A) Flowmeters. These indicate the rate of flow (in volume or weight per unit of time) and are used for measurement of flow both through open channels (nvers, waterways, etc.) and through closed conduits (piping, etc.). Some flowmeters use the principle of the fluid meters of heading 90.28 (turbinepiston-type, etc.), but the majority are based on the principle of differential pressure. T ese include : Pep (1) Differential pressure (fixed aperture) flowmeters. These comprise essentially : (i) a primary device (e.g., Pitot or Venturi tube, simple diaphragm, orifice plates, shaped nozzle) to set up a differential pressure, and (ii) a differential pressure gauge (float, diaphragm, differential pressure, oscillating ring balance or flow transrmtters, etc., type). (2) Variable area (variable aperture) flowmeters. These usual1 consist of a graduated cone-shaped tube containing a heavy float which is carried Jong by the current until the flow of the liquid between the float and the wall reaches equilibrium. For high ressure liquids, use is made either of magnetic flowmeters (the position of an iron Roat in s non-magnetic tube being shown externally by a magnet), or of valve flowmeters (an iris diaphragm fitted inside the tube being connected in parallel with a small flowmeter). (3) Flowmeters which operate by using magnetic fields, ultrasound or heat. This heading excludes : (a) Hydrometric addle-wheels for measuring the rate of flow in rivers, canals, etc., which fall in heading 90.1 as hydrological instruments. g (b) Apparatus which merely indicate the total amount of liquid delivered over a period, which are classified as supply meters in heading 90.28. (B) Anemometers of the special types used for recording the rate of flow of air currents in mines, tunnels, chimneys, furnaces and conduits in eneral, and consisting essentially of a bladed fan and a calibrated dial. In some devices e measured values are converted into electrical signals. C (11) INSTRUMENTS AND APPARATUS FOR MEASURING OR CHECKING THE LEVEL OF LIQUIDS OR GASES Level indicators for liquids and indicators for the content of gasometers. Level indicators for liquids include : e. These may give a direct reading on a graduated column mounted on the float, or the e ect may be transmitted to a dial needle by means of a cable and drum or be converted into an electrical signal. (2) Pneumatic and hydrostatic type. These are used to measure the level in pressure tanks, by means of a differential pressure gauge. (3) Po-colour Light type, for boilers. These are based on the difference in the refractive indices of water and steam. They consist of a set of Iamps, coloured screens, an optical system and a level which indicates in different colours the respective heights of the water and the steam. (4) Electrical-type, based, for example, on the variations of resistance, capacitance, ultrasound, etc. This heading covers not only level indicators for closed reservoirs or tanks, but also those for open basins and canals (hydroelectric works, irrigation systems, etc.). To ascertain the content of a gasometer, the level of the " bell " is measured, either directly or from a dial needle to which the bell is connected by means of a cable and drum. Instruments for measuring or checking the level of solid materials are excluded (heading 90.22 or 90.31, as the case may be). (111) INSTRUMENTS AND APPARATUS FOR MEASURING OR CHECKING THE PRESSURE OF LIQUIDS OR GASES Pressure au es (e.g., manometers), a paratus for measuring the pJessure of a li uid or gas. These di er om barometers in that $e latter measure atmospheric pressure w h e pressure gauges indicate the pressure of a liquid or gas in a closed space. The main types of pressure gauges are as follows : (1) Liquid-t e pressure gauges (mercury, water or other liquids, or two non-miscible li uids). R e 11 uid is contained in a lass or metal tube; these gauges may be of the single co umn type, 8-tube type, inclinecftube or multitube type, or be in the form of an oscillating ring balance. (2) Metallic pressure au es. Like aneroid barometers, these may have a single or multiple diaphragm, a ca su&e,iourdon tube or spiral metal tube or some other pressure sensitwe element which &ectly moves a pointer or varies an electrical signal. (3) P.iston-type pressure gau es. In these, the ressure is applied either directly or via a diaphragm on to a piston w ich is weighted or eld by a spnng. h R (4) Electrical pressure auges based on variations of an electrical phenomenon (e.g., resistance, capacitanceT or using ultrasound. Vacuum gauges for low pressures, including ionisation auges using thermionic vacuum positive ions produced by co lision of the electrons with the gas are attracted towards a negative late. Thermionic vacuum tubes (triodes) presented separately are excluded (heading 85.40f f The heading also covers the maximum and minimum type pressure au es. Differential pressure gauges, used to measure differences in pressure, include t fe ollowing types : two-liquid, float, oscillating ring balance, diaphragm, capsule, ball (without liquid), etc. f (IV)HEAT METERS Heat meters measure the quantities of heat consumed in an installation (e.g., a hot water type heatin system). They consist essentially either of a liquid suppl meter, two thermometers place respectively at the intake and outlet of the conduit, an a counting and totalising mechanism. This group also covers thermocouple heat meters. CP d' Small heat meters of the types mounted on radiators in blocks of flats so that central heating costs can be fairly divided resemble thermometers and contain a liquid which evaporates under the effect of heat. PARTS AND ACCESSORIES Subject to the provisions of Notes 1 and 2 to this Chapter (see the General Explanatory Note), separate1 presented parts and accessories of apparatus or ap liances of this heading remaxn classifieJhere. Examples include separate graphcal recording &vices (includin those m which the indications supplied by several measuring or checking instruments are recor ed), whether or not fitted with devices for signalling, pre-selection or control. d 90.27- Instruments and apparatus for physical or chemical analysis (for example, nolarimeters. refractometers. saectrometers. gas or smoke analvsis auuaratus): ,, instruments and apparatus for measuring or ch%ckingviscosity, pofosity, surface tension or the like; instruments and apparatus for measuring or c eckmg quantities of heat, sound or light (including expiiure meters); microtomes. ern Tpn9 9027.10 9027.20 9027.30 9027.50 9027.80 9027.90 - Gas or smoke analysis apparatus - Chromatographs and electrophoresis instruments - Spectrometers, spectrophotometers and spectrographs radiations (UV, visible, IR) using optical - Other instruments and apparatus using optical radiations (UV,visible, IR) - Other instruments and apparatus - Microtomes; parts and accessories This heading includes : (1) Polarimeters. Instruments for measuring the angle throu h which the plane of olarisation of a ray of li t is rotlnd in assing throu h an optica y active substance. &ey consist essentially o a source of liggf an optica device comprisin polarising and analysing prisms, a tube holder in which the substance to be analyse is placed, an observation eyepiece and a measuring scale. 8" i B B In addition to the essential o tical elements of a conventional polarimeter, electronic polarimeters are also fitted wit a photoelectric cell. \ (2) Half-shadow polarimeters for analysing plane or elliptically polarised light. (3) Saccharimeters. These are special polarimeters designed for determining the strength of sugar solutions. (4) Refractometers. These are instruments for determining the refractive index of li uids or solids (one of the most important constants in dete-g the purity of substance$. They consist essentially of a system of prisms, observing and reading eyepieces, and a device for controlling the temperature (since this eatly affects the refractive index). They are widely used, particularly m food industries &r testin oils, butter and other fatty substances, analysing jam, fruit juices, etc.), in the lass in ustry, in oil refineries and in biology (for measuring the protein content of blood p asrna or discharges, etc.). f k Most refractometers are mounted on a base or stand; others are of the hand type, while yet another type is intended for fixing on the side of manufacturing vats. (5) Sfectrometers. These instrumen& are used to measure the wave-lengths of emission and a sorption s ectra. They consist essentially of an adjustable slit collimator (through which the beam o light to be analysed passes), one or more ad'ustable prisms, a telesco e and a prism table. Some spectrometers (particularly those use for infra-red or ultra-vio et rays) ? are fitted with prisms or with diffraction gratings. P d This oup includes : spectroscopes for the observation of spectra; spectrographs for ing the spectrum on a photo a hic plate or film (spectro rams ;monochromators, recorcf= instruments for isolating a particu ar me m a line spectrum or or iso ating certain parts of a continuous spectrum. rf r-? But the heading excludes spectrohelio aphs and spectrohelioscopes, used for solar observation (heading 90.05); specbun projectors, R r examining m enlarged spectrogram projected on to a screen (heading 90.08); mcrornetric microscopes and spectrocomparators incorporatin microscopes (for comparative examination of specbograms by optical observation) (heading 90.14 and spectrum analysers for measuring or chechng electrical quantities (heading 90.30). (6) Mass s ectrogra hs and similar apparatus for analysing the isotopic constitution, etc., of materia s. But the eading excludes calutrons for isotopic separation (heading 84.01). P (7) Colorimeters. The tern " colorimeter " is applied to two distinct classes of instruments. One class is used to detennine the colour of a substance (li uid or solid b matchin its primary colours (re , green an b ue) mixe in d7 f The other class of calorimeters is used in chemical or of a substance present in a solution by (or of the colour of the substance after treatment with a reagent) with that of coloured standard plates or of a standard liquid. In one type of colorimeter of the latter class, the solution under test and a standard solution are contained in two glass tubes which are viewed by means of two prisms through an eyepiece. Certain of these instruments are based on the use of a photoelectric cell. In some instruments of this e a paper tape is used with a reagent changing its colour afier reaction with a gas. T ese Instruments use two photoelectric cells measuring the colour before and after reaction with the gas. % This oup also covers other optical analysis apparatus such as nephelometers and turbi imeters (for determining the cloudiness of solutions), absorptiometers, fluorimeters (for determining fluorescence, widely used for analyses of vitamin, alkaloid contents, etc.), blancometers and opacimeters (special1 used for measuring the degree of whiteness, opacity or brilliance of paper pulp, paper, etc.r f (8) Gas or smoke analysis apparatus. These are used to analyse combustible gases or combustion by-products (burnt gases) in coke ovens, gas producers, blast furnaces, etc., in articular, for determining their content of carbon dioxide, carbon monoxide, oxygen, Rydrogen, nitrogen or hydrocarbons. Electrical gas or smoke analysis a paratus are manly for determinin and measuring the content of the following gases : car on dioxide, carbon monoxide and ydrogen, oxygen, hydrogen, sulphur dioxide, ammonia. ! Some of these instruments or apparatus determine volumetrically the gases absorbed by appropriate chemical substances, or burnt. These include : (i) Orsat's apparatus consisting mainly of an aspirating bottle, one or more absorption bulbs and a measuring burette. (ii) Combustion or explosion ap combustion or explosion pipette tube, with induction sparlung, This is e uipped, in addition, with a capillary tu e, platinum or palladium wire B These various types of apparatus may also be used in combination. Other models work on the basis of density, or by fractional condensation and distillation (cracking), or on the following principles : (i) Heat conductivity of a gas. (ii) Heating effect of combustible gases on an electrode, (e.g., carbon monoxide and hydrogen in flue gases). (iii) Selective absorption of ultra-violet, visible, infia-red or microwave radiations by the gas. (iv) Difference in the magnetic permeability of gases. (v) Chemiluminescent reactions of the gas with a suitable auxiliary gas component. (vi) Flame ionisation of hydrocarbons in a hydrogen flame. (vii) Difference in the conductivity of a suitable liquid reagent before and after reaction with the gas. (viii) Electrochemical reaction in cells with solid (especially zirconium oxide for oxygen analysis) or liquid electrolytes. It should be noted that the heading includes as or smoke analysis apparatus for use in industrial processes (i.e., directly connected to &rn aces, gas generators, etc.). But apparatus consisting merely of laboratory glassware falls in heading 70.17. (9) Electronic smoke detectors, used in furnaces, ovens, etc., for example, in which a beam of light (or infia-red) rays is directed on to a photoelectric cell. Accordmg to the density of the smoke, the passage of this beam through the smoke causes variations in the current in the photoelectric cell circuit, thus operating a graduated indicator or a recording system and, in certain cases, a regulating valve. These apparatus may be fitted with an alarm device. EIectronic smoke detectors equipped solely with an alarm fall in heading 85.31. (10) Fire damp detectors and other detectors (e-g., for carbon dioxide). These include portable apparatus for gas detection in mines or tunnels, for detecting leaks in mains, etc. (11) Apparatus for dust analysis in gases. These operate b passing a iven quantity of as category inch es through a filter disc, and weighing the filter before and a er the test. Tyndallometers used for measuring the amount of dust in the air and for testing dust masks, filters, etc. They consist of a dust chamber covered with black glass, a light source, a photometric head with a prismatic measuring device and a graduated circular scale for measuring the angles of rotation. l (12) Oxygen meters for the determination of dissolved oxygen in li uids b use of a olarometric cell or by using the chemical reaction of thallium wit dlsso ved oxygen measurement of the change in electrolytic conductivity). 1 - l" P (13) Polarographic analysers for the determination of the components of liquids, e.g., traces of chssolved metals in water, by measuring and evaluating the current/resistance relationship of electrodes immersed in the solution. (14) Wet-chemical analysers for the determination of inor anic or organic components of li uids, e-g., traces of metals, phosphates, nitrates, chlori es or integral parameters such as "%bemica1 Oxygen Demand " (COD) and " Total Organic Carbons " (TOC). The analyser consists of a sample preparation device, an analysing unit with, e.g., ion-sensitive electrodes, photometers or polarographs and, in automatic analysers, a control unit. d (15) Viscometers and the like, used to determine viscosity (i.e., the internal friction of a liquid). They may be based on : (i) The princi le of the capillary tube, that is the measurement of the time re uired by the liquid to ow through the tube under constant pressure (e.g., Ostwald, ngler, etc., viscometers). fl' b' (ii) The effect of friction between a solid and a liquid. or (iii) The time taken by a ball to fall through the liquid. I (16) Polarisco es (strain viewers). These measure internal strains in glass e.g., strains resulting I! om toughening, annealing, soldering, etc., which might cause the g ass to break easily). They cons~stessentially of a chamber containing an electric lamp, a ltght diffusion device, a polariser and a polarising telescope. Stresses in the glass are shown as bright iridescences. (17) Expansion meters. These measure the expansion or contraction on change of temperature of steel, metal alloys, coke, etc. Most of these instruments are of the record~ngtype (mechanical recording on a graph or photographic recording). (18) Apparatus for the determination of porosity or permeability (to water, air or other gases, etc.) known as porosimeters or perrneameters (not to be confused with pemeameters for measuring magnetic permeability of substances). They are used for paper, textile fibres, fabrics, plastics, leather, sand, etc. (19) Instruments for measuring the surface or interfacial tension of liquids (e.g., torsion balances). The surface or interfacial tension of li uids is usually determined by one of the three following factors : the weight of a drop fa ing from a given capillary tube (or the number of drops having a known volume) (dro -weight method); the hei ht of free rise of a liquid in a capillary tube of known diameter $qillary rise method); or t e force required to detach a ring ikom the surface of a liquid. B a (20) Apparatus for measuring osmotic pressure (osmometers), i.e., the pressure which occurs when two miscible liquids are separated by a membrane which is partially but unequally permeable to the two liquids. (21) A paratus for testing mineral oils and their derivatives (e.g., tar, bitumen, asphalt). T ese include apparatus for determining the flash oint, setting point, flow point, drop point, etc., of rmneral oils, melting polnt of para wax, water content, dlrt content, sulphur content, consistency of greases and tars, cloud point, cold point, etc. !i & (22) pH meters and rH (redoxpotential) meters. pH meters are used to measure the factor expressing the acidity or alkalinity of a solution or mixture (pure water being the neutral standard). rH meters are used to measure the oxidising or reducing power of a solution. These instruments operate on a number of different rinciples; the most common type em loys the electrometric system, in which electro!des are used to set up a potential dizerence which is pro ortional to the pH or rH of the solution. In addition to measuring, these instruments may a so be used for automatic control. ? (23) Electrophoresis instruments. These are based on the change in concentration occurring when a direct current is passed throu h a solution. The electrically charged particles migrate at &fferent speeds according to t e nature of the product. TI These instruments usually incorporate a photometric device consisting of a photoelectric cell and a milliammeter graduated drectly in units of optical density. They are used for analysing various solutions (proteins, amino-acids, etc.), for examining substances such as plasma, hormones, enzymes, viruses, etc., and for studying polymerisatlon phenomena. r -, liquid-, ion- or thin-layer chromato (24) Chromatographs (such as determination of gas or liqui components. The gas or li uid to be through columns or thin layers of absorbent material and t en detector. The characteristics of the gases or liquids under analysis are indicated by the time taken for them to pass through the columns or thin la ers of absorbent material, while the quantity of the different components to be analyse is indicated by the strength of the output signal from the detector. % 6' (25) Electronic titration instruments using measuring electrodes to titrate water, silver salts, halogens, etc. (26) AnalyticaI instruments -sometimes called "moisture meters for solids" - based on the dielectric constant, electrical conductivity, absorption of electromagnetic energy or infrared radiation of substances. (27) Conductivity meters to determine the electrolytic conductivity or the concentration of salts, acids or bases dissolved in a liquid. (28) Photoelectric cell densitometers and microdensitometers used to measure the density of s ectrogra hic photographs, and for analysing any phenomenon which is recorded on a p otograp ic emulsion. ! fv (29) Photometers. Instruments for measuring the intensity of light. The light to be measured and the standard source of light are placed so that they illuminate a given surface with equal intensity. If instead of comparing two light intensities, corn arison is made of their respective spectra, the instrument then used is known as a spectrop otometer. \ Photometers are widely used for various o tical processes and analyses (for determining, for example, degree of concentration, &gree of brilliance or transparenc of sohd substances; degree of exposure of hotographic plates or films (densitometersT; depth of colour of transparent or opaque soli substances or solutions). $ Certain photometers used in photography or cinemato aphy are known as exposure meters, and are used for measuring exposure times or for etermining lens apertures. f (30) Luxmeters (used for determining the intensity, in " lux " units, of a source of light). (3 1) Calorimeters. These measure the amounts of heat absorbed or given off by a solid, a liquid or a gas. The main categories are : (A)Ice calorimeters (Bunsen's) based on variations in volume produced by meltin ice. The consist of a test-tube surrounded by ice, dipped into a tank of water, an of a gra ' ! c uated tube containing mercury. d (B) Heatin calorimeters (Berthelot) based on the princi le of the transfer of quantities of heat. T ey consist basically of a calorimetric jar fil ed with water inside a vat also containing water; they are e uipped with stirrers and thermometers. Two current types of calorimeter are based on t?iis same principle, i.e. : R f' ecific heat of gases or of liquid through a compartment where a in the temperature of the water at (ii) Bomb calorimeters. These are used for determinin the heats of combustion of materials. Basicall they consist of a steel vessel bomb), containing a h o w n amount of the soli or fluid to be tested and also oxygen under pressure. By means of a suitable device the specimen is ignited in the oxygen and the amount of heat generated is determined by placing the bomb in a water calorimeter. This heading also includes calorimeters for industrial use; these are mounted on generators producing gas with a given calorific power. However, if they are connected to regulating apparatus in order to maintain the mixed gases at the required level of calorific power, they are excluded (generally heading 90.32). (32) Cryoscopes and ebullioscopes other than those having the character of laboratory glassware (heading 70.17). This heading also includes microtomes, instruments used in microscope work to cut very thin sections of a known thickness from substances to be examined. Microtomes may be of various types, e.g., hand type (a kind of straight razor), revolving type, sliding carriage type (horizontal or inclined plane). PARTS AND ACCESSORIES Sub'ect to the provisions of Notes 1 and 2 to this Cha ter (see the General Explanatory Note), the eading also covers parts and accessories identifia le as being solely or pnncipally for use with the above-mentioned instruments and apparatus. ! The heading also excludes : (a) Laboratory equipment of refractory materials (retorts, jars, crucibles, cups, baths and the like) (heading 69.03), and similar articles of other ceramic materials (heading 69.09). (b) Laboratory glassware (heading 70.17). (For firher details, see below.) (c) Microscopes (heading 90.11 or 90.12). (d) Precision balances (heading 90.16). (e) X-ray, etc., apparatus (heading 90.22). (f) Demonstrational apparatus of heading 90.23. (g) Machines and appliances for carrying out tests on certain materials (heading 90.24). (h) Hydrometers, thermometers, hygrometers and similar instruments of heading 90.25, whether or not for use in laboratories. (ij) The apparatus of heading 90.26. Classification of oods which are potentially within the scope both of this heading and of heading 70.17 (la oratory glassware). b In these cases, classification is governed by the following considerations : (1) If an article has the essential character of glassware (whether or not aduated or calibrated, and whether or not with subsidiary stop ers, connections, etc., of ru ber, etc.), it is not to be classified in this heading even 1 it is normally known as a particular instrument or apparatus. W P (2) In general, instruments normally cease to have the essential character of glassware when they consist partly of glass but are mainly of other materials, or if they consist of glass parts incorporated or permanently fixed m fiames, mounts, cases or the like. (3) The combination of glass parts with measurin instruments (e.g., ressure gauges, thermometers) may, in practice, provide groun s for considering suc instruments as proper to this headng. R d Accordingly, the following instruments in the form of simple calibrated glassware fall in heading 70.17 Butvrometers. lactobutvrometers and similar instruments for testing dairv moducts: albuminometers and ureimeters; eudiometirs; volumenometers; nitrometers, Ki ps Gr ~j6ldahl apparatus and the like; calcirneters; cryoscopes and ebulliosmpes for determining rno~cularwelghts, etc. This heading also excludes machines or a paratus (whether or not electric) of the type classified in Section XW, whether or not, in view of %eir low output, small sire and general structure, they an obviously intended for use in laboratories (e.g., for preparing or treating s ecimens). The headin therefore excludes ovens, autoclaves, drylug or stearmng ovens or cabinets; esiccators; crushers an mixers; centrifuges; stills, presses; filters and filter presses; stirrers; etc. s a Similarly, heating apparatus (Bunsen burners, steam-heating baths, etc.), tools, laboratory fiuniture (e.g., laboratory benches, microscope benches, fume cu boards) and brushes are classified in their own appropriate headings (Section XV, Chapter 94 or 94.