If the insulation and sheath of the bus duct are in a"hidden crack"state,they are not easily detected during acceptance.However,over time or when the casing is in a damp state or even flooded,the insulation and sheath are more susceptible to damage.When the sheath and insulation layer age,if they do not meet the standard requirements,it will cause leakage and even spark in the wire,causing major accidents.

　　3.1 Quality Inspection Plan Work

　　The main contents of the quality inspection plan include:designing a flowchart;Select the inspection method;Analyze and supplement technical specifications;Carefully classify quality characteristic defects;Develop a quality characteristic analysis table and establish inspection procedures.

　　3.1.1 Selection of Inspection Methods:In the past,the wire and cable industry used full inspection or percentage inspection,and there was no unified regulation on the implementation of statistical sampling standards in GB2828 and GB2829.Manufacturers generally need to comply with relevant standards.Over the past three years,we have conducted some explorations,combining product export inspection,superior sampling inspection,and product introduction,to specifically develop and implement methods for sampling inspection of warehouse products,accumulating experience.

　　The implementation method for spot checks of stored products shall be carried out in accordance with the GB2828-81 standard.The content includes:

　　①General Provisions;

　　②Inspection items;

　　③Defect classification;

　　④The AQL requirements for qualified quality levels(temporary fatal defects 0.05 times/100 times,serious defects 1.5 times,general defects 10 times,minor defects not specified);

　　⑤Check the liquid level;

　　⑥Sampling plan type(using a one-time sampling plan);

　　⑦Strict sampling plan(according to GB28283.2.4);

　　⑧Determination of sampling methods and sample size;

　　⑨Statistical methods for non-conforming products;

　　⑩Determination of qualified and unqualified batches;Batch processing of non-conforming products,etc.

　　3.1.2 Product quality audit:In order to timely grasp the quality fluctuations of major products,especially to quickly detect the decline of product quality level to the second level,product quality audit activities must be carried out.It is important to have a national quality standard for conducting audits on the quality of enterprise products and services,and relying solely on the number of defects discovered during the product inspection process is not enough.

　　This is because the severity of different forms of defects may not be the same,and the severity of the same type of defect is also different.Defects such as size and outer diameter are not too large for most types of cables used.However,for mining cables that require sealing rings with explosion-proof devices,this defect can have consequences that endanger human life and cause serious losses.Therefore,a weighted value is usually set to reflect the severity of each defect,resulting in a better quality scale.At present,Chinese manufacturing technology enterprises have a first level market defect rating of 100 points for A level,50 points for B level,10 points for C level,and 1 point for D.

　　The average level defect score P is the product service quality and safety level evaluation scale,where DA is the number of A-level defects;DB represents the number of B-level defects,DC represents the number of C-level defects,and DD represents the number of D-level defects.N is the number of inspections.

　　Through product quality audits,early product quality can be compared with current product quality,high-quality products can be compared with current product quality,and quality level information can be fed back to design,manufacturing,and other departments as further improvement control based on product quality.In addition,further improve the foundation of product quality control.In addition,it has laid a solid foundation for the application of computers in quality management,creating conditions for sensitive,timely,and systematic collection of quality information,and scientific,accurate,and comprehensive analysis of quality performance levels.

　　Bus duct is a widely used material in building electrical engineering,but its quality is difficult to compare solely based on its appearance.Therefore,it is necessary to strengthen the inspection of its insulation material thickness,sheath thickness,conductor DC input resistance,and mechanical system performance to ensure the construction project.The quality and protection of property and personal safety are necessary.

　　According to the inspection results of over 700 sets of wire and cable products sent for testing in the Guangdong market,the pass rate is over 96%.The overall quality is good.However,it can also be found that the insulation thickness,sheath thickness,conductor resistance,and mechanical properties of some enterprise products do not meet the requirements and cannot be used for investment,otherwise it will cause information engineering security risks.Therefore,it is necessary to strengthen the management of the construction market,squeeze out unqualified products through inspection,encourage production enterprises to improve production processes,and enhance product quality.