Gas meters

90.28 - Gas, liquid or electricity supply or production meters, including calibrating meters therefor. 9028.10 9028.20 9028.30 9028.90 - Gas meters - Liquid meters - Electricity meters - Parts and accessories These meters are generally fitted with a device driven at a speed proportional to the rate of fluid flow or to the electrical quantity being measured. They are often fitted in a bypass or shunt off the main or connected to measurin transformers, so that only part of the flow passes through them, but are calibrated so as to hficate the total quantity passlng through the service pipes or through the main. Gas, liquid or electrici sup ly or production meters fall in this head in^ whether or not fitted with a clockwork recor g evice, or with a simple mechanical or electrical device for bringing controlling, signalling, etc., appliances into action. &$ (I) GAS OR LIQUID SUPPLY OR PRODUCTION METERS These meters are used to measure in volumetric units the amount of fluid passing through a pipe. Flowmeters, which measure rate of flow are excluded (heading 90.26). This heading includes household sup ly meters, plant production or supply meters, and standard meters for checkin the accuracy o ordinary meters). In addition to simple meters, the heading also inc udes specia meters such as maximum, prepayment, price-calculating, etc., meters. Y P Sup ly or production meters consist essential1 of the measuring device turbine, piston, diap agm, etc.), the mechanism for regulating J e admission of flud (general y slide valves) the transmission (endless screw, camshaft, gears or other systems), and a recorder or indicator (pointer or drum type) or both. R \ (A) Gas supply or production meters. (1) Wet meters. The measuring device generally consists of a drum or wheel partitioned into compartments; this revolves in a cylindrical casing rather more than half filled with a liquld (water, oil, etc.). The drum is rotated by the gas which on enterin the meter, fills the submerged compartments and thus raises them above the level o the water. The revolutions of the drum are indicated on a counting mechanism. P e of meter (nutating bell meter), consists of a bell in which the as passes in and out o a succession of chambers; the bell, which is centrally guided, is t us made to nutate around an inclined axis which engages a cranked arm attached to the driving spindle of the counting mechanism. 'F % (2) Dry meters. These are of several types. The measuring device may consist of pistons, diaphragms or of a fan wheel, driven by the pressure of the gas, and connected to a counter mechanism. The usual meter consists of a box hvided in two compartments by a partition. Each compartment is itself divided by a central diaphragm; the gas passes successively in and out of these four compartments. The alternating motion of the diaphragm operates the counting mechanism. (B) Li uid sup ly or production meters (cold or hot water, mineral oil, alcohol, beer, wine, mi&, etc.), put not including pumps for liquids (even if fitted with measuring devices) of heading 84.13. These meters include : (I) Impeller or fan wheel meters. These are also called inferential meters since the volume of li uid is inferred fiom its speed. The measuring device consists of a fan wheel or impel er which revolves at a speed proportional to the flow of the liquid. These revolutions operate a counting mechanism. (2) Diaphragm meters. These are similar to the dry gas meters described above. A cast iron cylinder is divided into two compartments by a flexible diaphragm which extends or retracts when the com artments are alternately filled or emptied. This motion operates the counter mec anism. R (3) Reciprocating piston meters. These meters may consist of one or more pistons which perform a reci rocating movement inside the cylinders. As in a steam engine, a system of sli e valves alternately directs the liquid under measure to the top and bottom sides of the piston and opens or closes the plug cocks. The motion of the pistons is geared to the counter mechanism. f (4) Disc-piston meters. In these meters the piston is replaced by a revolvin disc which divides a spherical i led and emptied. The resulting chamber into two equal compartments alternately f? 'oscillating motion of the disc is geared to the counter mechanism. (5) Rotary piston meters. One type of these meters consists of a cylindrical working chamber fitted with a radial partit~onwhich pro'ects artially across the chamber. The measuring device is a c lindrical piston, t e wa 1 of which is split, and which fits over the partition. The dling and emptying of the compartment imparts an oscillating (semi-rotary) motion to the cylinder and this motion is geared to the counter mechanism. A f In another type of meter there is no artition in the working chamber, and a true rotary motion of an elliptical piston is o tained. In some cases, the meter consists of a nutating cone in a partitioned spherical chamber. \ The meters referred to in items (2) to (5) above are known as positive displacement type. (11) ELECTRICITY SUPPLY OR PRODUCTION METERS These meters measure the amount of electricity consumed (in ampere-hours or multiples (quantity meters), or the amount of energy consumed (in watt-hours or multi les thereo (energy meters). When the voltage is constant, quantity meters may be calibrate in watt-hours (or In multiples of watt-hours). Some meters are devised for use with direct current, others for alternating current. thereo8 !i The heading excludes a paratus such as voltmeters, ammeters, wattmeters, etc., which simply measure electrical uantities !anc are not designed for registering the total amount of electricity or energy consumed ?heeding 90.30). This heading includes the following main types of electricity supply meters : (A) Motor meters. These meters consist essentially of one or more inductors, a revolving element (armature whose speed of revolution is proportional to the amount of electricity or ener consumed a counting mechanism and a pointer or dnun indicator (or a combination of bo ). % Motor meters are usually fitted with an eddy current brake, a metal brake-disc in which eddy currents are generated as it revolves between the poles of one or more permanent magnets. (B) Static meters. These meters consist essentially of electronic static sub-assemblies, such as multipliers or quantifiers equip ed with an indicating device. They produce an electrical current or resistance direct y proportional to the amount of electrical ener consumed. The indicator) or indicating device may be mechanical (fitted with a pointer or electronic. P k These include : (1) Prepayment meters. (2) Multiple-rate meters (calculating the electrical energy supplied at two ox more different rates). (3) Maximum meters (indicating the maximum value of the average load during a given period). (4) Peak meters (indicating the consumption above a certain peak value). (5) Excess meters (similar to peak meters but also indicating the total energy used). (6) Impulsing meters (fitted with a pulse transmitter). (7) Reactive meters, (8) Demonstration meters. (9) Direct current meters (volt-hour (Vh) meters, ampere-hour (Ah) meters, watt-hour (Wh) meters). (10) Meters with pulse input for connection to impulsing meters, fitted with a consumption register and a totalling device or a maximum device (indicating or recording) or an excess device, etc. (11) Standard meters for checking and calibrating other meters. PARTS AND ACCESSORIES Subject to the provisions of Notes 1 and 2 to this Chapter (see the General Explanatory Note), separately presented parts and accessories of meters of this heading remain classxfied here.