WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
90.32 - Automatic regulating or controlling instruments and apparatus. 9032.10 9032.20 - Thermostats - Manostats - 9032.8 1 9032.89 9032.90 Other instruments and apparatus : - - Hydraulic or pneumatic - - Other - Parts and accessories In accordance with Note 7 to this Chapter, this heading covers : (A) Instruments and a paratus for automatically controlling the flow, level, pressure or other variables of liqui s or gases, or for automatically controlling temperature, whether or not their operation depends on an electrical phenomenon which varies according to the factor to be automatically controlled, which are designed to bring this factor to, and maintain it at, a desired value, stabilised against disturbances, by constantly or periodically measuring its actual value; and it' (B) Automatic regulators of electrical quantities, and instruments or apparatus for automatically controlling non-electrical quantities, the o eration of which depends on an electrical phenomenon varying according to the factor to e controlled, which are designed to bring this factor to, and rnalntaln it at, a desired value, stabilised against d~sturbances,by constantly or periodically measuring its actual value. YI (I) INSTRUMENTS AND APPARATUS FOR AUTOMATICALLY CONTROLLING THE FLOW, LEVEL, PRESSURE OR OTHER VARIABLES OF LIQUIDS OR GASES, OR FOR AUTOMATICALLY CONTROLLING TEMPERATW Automatic control apparatus for li uids or gases and apparatus for automaticey complete automat~ccontrol systems and cons~st controlling temperature form part essentially of the following devices : (A) A device for measuring the variable to be controlled (pressure or level in a tank, tem erature in a room, etc.); in some cases, a sim le device which is sensitive to changes in!t e variable metal or bi-metal rod, chamber or ellows containing an expanding liquid, float, etc.) may e used instead of a measuring device. % (B) A control device which com ares the measured value with the desired value and actuates the device described in (C) be ow accordngly. P (C) A starting, stopping or operating device. Apparatus for automatically controlling liquids or gases or temperature, within the meaning of Note 7 (a) to this Chapter, consists of these three devices forming a single entity or in accordance with Note 3 to this Chapter, a functional unit. Some instruments and ap aratus do not incorporate devices which compare the measured value with the desired value. %hey are directly activated by means of a switch, e.g., when the predetermined value is reached. Instruments and apparatus for automatically controllin the flow, level, pressure and other variables of li uids or gases or for automatically contro ling temperature are connected to an appliance whic carries out the orders (pump, compressor, valve, h a c e burner, etc.) which restores the variable (e.g., liquid measured in a tank or temperature measured in a room) to the prescribed value, or which, in the case of a safety system, for instance, stops the operation of the machine or apparatus controlled. This appliance, generally remote controlled by a mechanical, hydraulic, pneumatic or electric control, 1s to be classified in its own appro riate heading (pump or compressor : heading 84.13 or 84.14; valve : heading 84.81, etc.). If t e automatic control apparatus is combined with the appliance which carries out the orders, the classification of the whole is to be determined under either Interpretative Rule 1 or Inte retative Rule 3 (b) (see Part (III) of the General Explanatory Note to Section XVI and 'g t e Explanatory Note to heading 84.8 1). B a R This group includes : (A) Pressure controllers or regulators, also called manostats. These consist essentially of a pressure sensitive device, a controlling device which compares (e.g., by means of an adjustable sprin the pressure to be controlled with the prescribed pressure, and an electric contact or a sma!I{ valve operating a servo-circuit. This apparatus may be used, for instance, to control a motor pump or compressor which supplies a pressure tank, or to o erate pneumatic valve posttioners, or wtth a valve to regulate the flow, pressure, etc., o liquids or gases. ? r These pressure re lators differ from the ressure reducing valves of heading 84.81 (somettmes also ca led " pressure regulators 'y. (B) Level regulators or controllers for the automatic control of a level. In the float-type level controller, the float acts on a diaphragm or a magnetic or other device which operates an electric switch; this in turn switches on or off a pump, a valve, etc. In the electrode system the liquid is connected to earth and forms past of the circuit. One pole of the transformer is also earthed. When the surface of the liquid comes into contact with the electrode, the circuit is closed and a relay comes into operation. (C) Humidity regulators, sometimes also called humidistats, are instruments for automatically controlling humidity in steaming cabinets, furnaces, workshops, warehouses, etc. The operation depends on variations in the length of a bundle of hair or some other element sensibve to hurmdity and they generalIy operate a si alling device or control an a paratus which can modify the degree of hurmdity foun (steam input valve, humi xfier ar de-humidifier, fan, etc.). r S (D) Thermostats are used for automatically controlling temperature. The main components of a thermostat are : (1) An element sensitive to changes in temperature whose action may depend on : (a) The change in shape of a bi-metal strip (straight, U or spiral-shaped, etc.); (b) The vapour pressure of a liquid; (c) The expansion of a liquid or of a metal rod; (d) An electrical resistor or a thermocouple. In bi-metal strip thermostats, the strip is fixed inside a plunger tube or in a case. In metal rod thermostats, the rod fits in a plun er tube. In vapour pressure or liquid types, enclosing a fluid, or of a the sensitive element may consist of a fo ded diaphra system incorporating a diaphragm, a capillary tube and a ulb or elbow. f ?? (2) A drum, disc or other device for pre-setting the desired temperature. (3) A triggering or operating device which consists mainly, de ending on the type of tratlsrmssion used (mechanical, servo-fluid, electrical), of a ever assembly, springs, etc., a valve, or an electrical switch. This device operates a signal or an appliance (generally remote) such as a steam or hot water intake valve, boiler burner, air conditioning unit, fan, etc., which regulates the temperature. P Thermostats are used, in particular, for buildings, in ovens, cookers, boilers, flues, s t e m n g apparatus or cabinets, and in houses or other (E) Temperature regulators for setting and maintaining pre-set temperatures on electrical heating a pliances (cookers, grills, percolators, etc.) consist essentially of a bi-metal strip which, w en deflected by the heat from a shunt resistor on the power circuit, operates a switch to make and break the ower circuit, the" On" and" Off" eriods (and consequently the tem erature of the eating elements) being determined by t% e posjtion.of a manual control dia ; the " Full " position renders the bi-metal assembly inoperatrve and thus, particularly in the initial stages of heating, permits continuous operation of the heating element. R P i This heading excludes : (a) Thermostatic " or " thermostat " steamers, cabinets, etc., @ which the !em era$re is kept !eadlngs. constant by means of a thermostat, which are to be classdied m thelr respectweI (b) Thermostatically controlled valves (heading 84.81). (F) Oven-draught regulators are used, for example, in central heating or air conditioning plants, to control automatically the air intake by reference to the temperature, pressure, etc. (11) AUTOMATIC REGULATORS OF ELECTRICAL QUANTITIES,AND INSTRUMENTS OR APPARATUS FOR AUTOMATICALLY CONTROLLING NON-ELECTRICAL QUANTITIES Tl!E OPERATION OF WHICH DEPENDS ON AN ELECTRICAL PHENOMENON VARYING ACCORDING TO THE FACTOR TO BE CONTROLLED The automatic regulators of this heading are intended for use in complete automatic control systems which are designed to bring a quantity, electrical or non-electrical, to, and maintain it at, a desired value, stabilised against any disturbances, by constantly or periodically measuring its actual value. They consist essentially of the following devices : (A) A measuring device (sensing device, converter, resistance probe, thermocouple, etc.) which determines the actual value of the variable to be controlled and converts it into a proportional electrical signal. (B) An electrical control device which corn ares the measured value with the desired value and gives a signal (generally in the form o a modulated current). F (C) A starting, sto ping or operating device (generally contacts, switches or circuit breakers, reversing switc es or, sometimes, relay switches) which supplies current to an actuator in accordance with the signal received fiom the control device. f An automatic re lator within the meanin of Note 7 (b to this Chapter consists of the devices described in (B) and (C) above, w8,ether assem led together as a single entity or in accordance with Note 3 to thls Chapter, a functional unit. b (~k;l If they do not conform to the definitions outlined above, these devices are to be classified as follows : (1) Electrical measwing devices generally fall in heading 90.25,90.26 or 90.30. (2) Electrical control devices are to be classified in this heading as incomplete automatically controlling instruments or apparatus. (3) Starting, sto ping or operating devices are generally to be classified in heading 85.36 (switches, re ays, etc.). P Automatic regulators are connected to an electrical, pneumatic or hydraulic actuator, which brings the controlled variable back to the desired value. This actuator may be the clamps which adjust the gap between the electrodes of an arc furnace, the motorised valve which controls the intake of water or steam in a boiler, a fiunace, a pulping machine, etc. The actuators are to be classified in their own appropriate headings (adjustable clamp : heading 84.25; motorised or solenoid valve : headrng 84.81; electro-magnetic positioner : heading 85.05; etc.). If the automatic regulator is combined with the actuator, the classification of the whole is to be determined under either Interpretative Rule 1 or Inte retative Rule 3 (b) (see Part I11 of the General Explanatory Note to Section XVI and the xplanatory Note to heading 8 .8 ). 3' Electronic regulators function on a strictly electrical principle, and not electro-mechanically. Their characteristic features are semiconductors (transistors) or integrated circuits. These regulators are used not only for electrical quantities, such as voltage, amperage, frequenc and power, but also for other quantities such as revolutions per minute, torque, traction orce, level, pressure, flow or temperature. r This heading also excludes (a) Cut-outs combined, in a single housing, with a voltage regulator or a current regulator, for use in conjunction with internal combustion piston engines (heading 85.11). (b) " Programmable controllers " of heading 85.37. PARTS AND ACCESSORIES Subject to the provisions of Notes 1 and 2 to this Cha ter (see the General Ex lanatory Note), parts and accessories of apparatus or appliances of this eading remain classifie here. R B -
1.- This Chapter does not cover : (a) Articles of a kind used in machines, appliances or for other technical uses, of vulcanised rubber other than hard rubber (heading 40.16), of leather or of composition leather (heading 42.05) or of textile material (heading 59.11); (b) Supporting belts or other support articles of textile material, whose intended effect on the organ to be supported or held derives solely from their elasticity (for example, maternity belts, thoracic support bandages, abdominal support bandages, supports for joints or muscles) (Section XI); (c) Refractory goods of heading 69.03; ceramic wares for laboratory, chemical or other technical uses, of heading 69.09; (d) Glass mirrors, not optically worked, of heading 70.09, or mirrors of base metal or of precious metal, not being optical elements (heading 83.06 or Chapter 71); (e) Goods of heading 70.07, 70.08, 70.11, 70.14, 70.15 or 70.17; (f) Parts of general use, as defined in Note 2 to Section XV, of base metal (Section XV) or similar goods of plastics (Chapter 39); however, articles specially designed for use exclusively in implants in medical, surgical, dental or veterinary sciences are to be classified in heading 90.21; (g) Pumps incorporating measuring devices, of heading 84.13; weight-operated counting or checking machinery, or separately presented weights for balances (heading 84.23); lifting or handling machinery (headings 84.25 to 84.28); paper or paperboard cutting machines of all kinds (heading 84.41); fittings for adjusting work or tools on machine-tools or water-jet cutting machines, of heading 84.66, including fittings with optical devices for reading the scale (for example, “optical” dividing heads) but not those which are in themselves essentially optical instruments (for example, alignment telescopes); calculating machines (heading 84.70); valves or other appliances of heading 84.81; machines and apparatus (including apparatus for the projection or drawing of circuit patterns on sensitised semiconductor materials) of heading 84.86; (h) Searchlights or spotlights of a kind used for cycles or motor vehicles (heading 85.12); portable electric lamps of heading 85.13; cinematographic sound recording, reproducing or re-recording apparatus (heading 85.19); sound-heads (heading 85.22); television cameras, digital cameras and video camera recorders (heading 85.25); radar apparatus, radio navigational aid apparatus or radio remote control apparatus (heading 85.26); connectors for optical fibres, optical fibre bundles or cables (heading 85.36); numerical control apparatus of heading 85.37; sealed beam lamp units of heading 85.39; optical fibre cables of heading 85.44; (ij) Searchlights or spotlights of heading 94.05; (k) Articles of Chapter 95; (l) Monopods, bipods, tripods and similar articles, of heading 96.20; (m) Capacity measures, which are to be classified according to their constituent material; or (n) Spools, reels or similar supports (which are to be classified according to their constituent material, for example, in heading 39.23 or Section XV).