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The technical specifications for instrument electrical assembly compiled by Changhui Instruments (http://yunrun.com.cn/tech/2094.html) are suitable for technicians engaged in electrical manufacturing, instrument assembly, and related electrical assembly tasks. Since the technology and management vary from unit to unit, the instrument electrical assembly technical specifications are provided only for reference. 1. Preparations before instrument assembly and electrical assembly work: ① Working documents. Assembly work involves electrical schematic diagrams, instrument control principles, layout drawings, BOM lists, etc.; until the project is completed, it is essential to ensure that the drawings are complete and organized, as well as that process information is recorded fully. ②In assembly areas, electrical work and the assembly of control cabinets require a designated workspace. If no fixed workspace is available temporarily, the assembly team leader must create one and ensure that it is neat, organized, and in good order. ③Electrical materials: Before starting work, the electrical materials must be in place on time. If some non-essential materials are not available, work can still begin as planned, after which a material delivery request form should be filled out and submitted to the procurement department. 2. Layout arrangement ① The layout of cable trays, guide rails, components, instruments, etc. shall be carried out strictly in accordance with the layout diagrams provided in the electrical design and instrumentation design. ②All fixed connections must be designed to be fastened and loosened from the front side; they must not be secured using nuts behind the mounting plate. ③Conduit a: The conduit should be flat, without any twisting or deformation; its inner walls should be smooth and free of burrs. The connections between the conduits should be continuous with no interruptions. b. Each section of the cable tray should have no fewer than two fixing points; when the length of the cable tray is 400 mm or more, there should be no fewer than three fixing points. Fixing points must be provided at corners, branches, and ends, and they should be secured tightly to the mounting surface. The fastening screws should be M5×15 round-head electroplated bolts, fitted with large flat washers. c. The cable tray joints should be straight and tight; the tray covers should be complete, flat, and free of warping. The allowable deviation for the horizontal or vertical installation of the cable trays is 2‰ of their length, with a maximum allowable deviation over the entire length of ±2 mm. ④Guide rail a: The cut surface of the guide rail should be straight and perpendicular to the rail, with the ends chamfered free of burrs. b. When installing the guide rails, the gap between the ends and the cable tray should be 2±1 mm. Guide rails on the same straight line must not be connected at two points; each section of guide rail should have no fewer than two fixing points. When the length of the guide rail is over 300 mm, there should be no fewer than three fixing points. The fastening screws should be M5×20 hex head electroplated bolts, equipped with spring washers and flat washers. c. The allowable deviation for the horizontal or vertical installation of the guide rails is 2‰ of their length, with a maximum allowable deviation over the entire length of ±1 mm. ⑤The installation of component a and other electrical components shall comply with the provisions of the product user manual. b. The components with fasteners shall be designed to allow tightening and loosening from the front side; each electrical component should be able to be removed and replaced individually without affecting the fixation of other components or wire harnesses. The fastening screws for electrical components must comply with the specifications in the product manual, and anti-loosening devices such as spring washers and flat washers should be used. The installation inclination of the components shall not exceed 5°. c. For components mounted via guide rail brackets, the clips must fully secure the guide rail, and the position of the mounting/clipping mechanism for the component should be below the component. d. During the component installation process, the components must remain clean and undamaged, free from any oil contamination or excessive strain from wires; the components’ accessories should also be complete and in good condition. e. After the components are installed, write down their codes on the corresponding positions on the mounting board using a pencil, to prevent errors during wiring. Once wiring is complete and the slot covers are in place, attach component labels to those covers and erase the codes that were written with a pencil earlier. ⑥Instruments such as instrument a, flash alarms, and electromechanical intercommunication signal devices must be arranged in the first row of the instrument cabinet ； Instrumentation and control buttons that require frequent operation, such as manual operators, are located at the bottom of the instrument panel ； Other instruments are arranged in sequence. b. The tag number and name of each instrument must be marked on the back of the instrument panel, at the position corresponding to that instrument, using labels that will remain in place over time, so as to be useful for instrument wiring and subsequent troubleshooting. c. The wiring for each instrument must have sufficient slack, so that when replacing instruments from different manufacturers but with identical functions in the future, there will be enough length of wiring available (for example, when replacing an instrument with a greater depth measurement capability with one having a shorter depth measurement capability, the wiring length might prove to be insufficient). d. The shorting wires between the terminals of a single instrument are connected directly at the back of the instrument, without going through the terminal blocks. ⑦Terminal block A: The terminal block is fixed below the instrument cabinet, using mounting strips or plates for fixation; the straight-line distance between the terminal block and the bottom panel of the cabinet is 30 mm ； b. The terminal block of the electrical cabinet is fixed below the mounting plate; 45° guide rails are used to support the aluminum profiles, such that the angle between the terminal block mounting guide rails and both the mounting plate as well as the bottom panel of the cabinet is 45°. The straight-line distance between the terminal block and the bottom panel of the cabinet is 30 mm. c. The strong-current and weak-current terminals should be arranged separately; the straight-line distance between the power terminals and the cable tray is 30 mm, while the straight-line distance between the control terminals and the cable tray is 20 mm. d. After the terminal block is fixed, terminal numbers should be applied. 3. Wiring of instrument cabinets and electrical cabinets: ① Wires should be connected to the designated terminals in accordance with the markings on the drawings. ②The cross-sectional area of wires a and those in the main circuit is as indicated in the drawings; the cross-sectional area of wires in the electrical control circuit is 1.5 mm2, while that of wires in the electrical current circuit is 2.5 mm2 ； The cross-sectional area of the wires in the instrument circuit is 1.0 mm2; the color and cross-sectional area of the wires in the instrument’s intrinsically safe circuit are determined in accordance with the technical specifications of that instrument ； The cross-sectional area of the conductors in multi-core cables is 0.75 mm2. b. Wires of 4 mm2 and above (inclusive) are of the black RV type, while wires below 4 mm2 are of the white RV type; the color of the cable insulation is chosen to be black. The instrument intrinsically safe circuit requires the use of wires of specified colors and must be laid separately. c. Special wire stripping tools should be used to remove the insulation from the wires; the wire core must not be damaged, nor should the unstripped insulation be harmed, and the cut edges should be smooth. d. Let the length of insulation removed from the end of the wire be L. When the wire end is inserted into the terminal, L is equal to the length L1 that the wire core needs to penetrate the tubular connector sleeve, plus 1–2 mm; that is, L = L1 + (1–2). When the stripped wire is crimped to the terminal, all copper wires must pass through the terminal sleeve, and wires with a cross-sectional area of 0.75 mm2 or less must be folded before being passed through the terminal sleeve. It is best to solder the wires of the instrument circuit using terminal sleeves, one by one with tin, and then protect them with heat-shrink tubing; this ensures that no soft failures due to poor contact will occur over several years in corrosive environments. e. For wire connections that cannot use terminals, solder should be applied after the insulation has been removed. The wires must not be connected to each other at intermediate points; when connection is necessary in special cases, welding must be used, and the joint should be protected with heat-shrink tubing after welding. f. When connecting wires to components, the shortest path should be chosen; the wiring for the PLC input circuits inside the cabinet should, as much as possible, not be run in the same conduit as the control wires of the main circuits and other voltage levels. g. When the wire is connected to the panel components, and the panel has no grooves, a wrapping tube should be used for protection. The panel harness is connected to the inside of the cabinet, and it should be ensured that the harness is not subjected to friction when the cabinet door is opened and closed. h. Avoid connecting multiple wires to the same terminal; there should be no more than 2 wire connections to the same terminal on a component. When two wire connections are used at the same terminal, the contact must be flat and secure. i. When there are too many wires of the same gauge to be secured all on the terminals, multiple crimping using end terminals can be used, but this method is only suitable for control wires. j. For the welding between the wire and the connector, solder should be applied first to both the wire and the connector; the welds must be firm and reliable, and heat-shrink tubing must be used to protect the welded areas. k. The wires should be laid smoothly and loosely within the conduit; they must not be subjected to additional tension or pressure, nor should they be compressed into a clump inside the conduit. ③At terminal A and at the points where wires are connected to components, cold-press terminals must be used. Unless in special cases, the wires should not be stripped before being connected directly to the devices. b. The diameter of the wire number tube for terminals must match that of the wires, and the shape of the connection ports must fit those of the component terminals. Fork-shaped terminals can be used in control circuits, while ring-shaped terminals must be used for motor terminals, heating power supply terminals, ground terminals, and some main circuit terminals, in order to increase the contact area. Pin-shaped terminals are required for certain connectors. c. Special terminal crimping pliers must be used for terminal crimping; the crimping die used must match the terminal. After crimping, there must be good and firm contact between the wire and the terminal. d. After the wire terminals are crimped and connected to the component, they should pass through the nearest slot tooth, with an angle of 90° relative to the component’s end face; the inclination shall not exceed 5°. e. When connecting the terminal to the component terminal block, it should be inserted as far as possible into the terminal block; the contact should be flat and secure, and the torque applied when tightening the screws should be appropriate. f. All terminals must be fitted with wire number sleeves; for those in the main circuit whose terminals cannot be fitted with sleeves after crimping, heat-shrink tubing should be used for protection. ④Wire number sleeve a: The wire number sleeve serves two purposes; one is to protect the insulation of the crimped part of the bare terminal, and the other is to identify the wire’s number. b、The wire number sleeve selected must match the cross-sectional area of the wire; when printing the wire numbers, the font size chosen must be appropriate for the diameter of the sleeve. c. The length of the control circuit wire is 25 mm, while the length of the wire with a main circuit sleeve having a diameter of φ5 mm is 30 mm. d. Before crimping the terminals, it is necessary to first insert the printed wire number sleeves; these sleeves should cover the bare terminal portion by 1–1.5 mm, with the text orientation parallel to the front side of the component. e. After the terminals are tightened, the corresponding wire numbers, when viewed vertically, follow a reading order from bottom to top ； When viewed horizontally, it follows a reading flow from left to right. f. The wire numbers at both ends of each wire are unique; it is strictly prohibited for one wire to have different wire numbers. g. When the wire cross-section is too large to allow for the use of a suitable sleeve, nylon zip ties can be used to secure the sleeve to the wire; the direction of flow is indicated in the same manner, and cable labeling is carried out using the same approach. 4. External components and cable installation: ① The external components of the cabinet are electrically connected to the cabinet through terminal blocks or cable connectors. ②The fixing positions of external components should be accurate and secure, and the fixing points of connection cables should be protected from friction caused by moving mechanical parts. ③The connection of the heating element must use high-temperature wires, along with high-temperature resistant connectors. ④External components must be connected through intermediate terminal boxes, which in turn are connected to the cabinet via cables; it is strictly prohibited to connect external components directly using wires. ⑤For components with built-in wires, when the wires are short, male and female bullet terminal connections can be used. ⑥After the cable is stripped, the stripped area must be protected with a heat shrink tube; all connected wires must have terminals pressed on them and their wire numbers marked. ⑦Mechanical force. ⑧When connecting a cable to a connector, the clamping force applied by the connector’s terminal clamps must be appropriate; too loose a fit can cause the wire to pull out, while too tight a fit can break the wire. 5. Inspection work ①Check the model, specifications of the connection wires, and whether they are being used correctly. ②Check whether the models of various components, instruments, and drawings match those in the material list, and whether the setting values of the components correspond to the protection values. ③Check the quality of the wire terminal connection; it should be secure. ④Check whether the fastening screws and the terminal screws are loose. ⑤Check the correctness and completeness of the wire end markings. ⑥Check the quality of wire arrangement and bundling. ⑦When using the resistance setting of a multimeter to check the circuit, test one path at a time to prevent the formation of false circuits. ⑧When checking the circuit with a multimeter’s resistance setting, one end of the transformer terminal must be disconnected. ⑨ Check the phase connections of the main circuit, as well as the connection of the ground wire. ⑩After the task is completed, the iron shavings, wire insulation, and other debris inside the cabinet must be cleaned. Compressed air should not be used for cleaning; instead, a vacuum cleaner or magnets should be employed. ⑪At least two people must be present when powering on. When checking for the first time after power-up, do not close both circuits simultaneously. ⑫First, check the voltage of all power circuits, then check the operation of the sensors in the control circuit.