Matters Needing Attention of Electrical Equipment Installation Engineering in Hazardous Areas. Wang Qiaoli

Transcription

1 Matters Needing Attention of Electrical Equipment Installation Engineering in Hazardous Areas Wang Qiaoli Nanyang Explosion Protected Electrical Apparatus Research Institute Keywords: hazardous areas; explosion protected electrical equipments; matters needing attention. Abstract. According to the characteristics of explosion protected electrical equipments installation in hazardous areas, and combining with the requirements of relevant explosion protection standards, some matters needing attention about qualifications of personnel, equipments and documentation, installations and completion acceptance are put forward. Introduction Mixture of flammable gas, vapour, steam, dust, fibers or flyings with air can form an explosive atmosphere which can cause an explosion when ignited. The area in which an explosive atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of equipment is called hazardous area[1]. For example petroleum, chemical industries mainly deal with flammable materials, so there are many hazardous areas. Electrical equipments design, selection and installation are different from non-hazardous area, the equipments are explosion protected electrical equipments, in addition to the realization of the function of normal use, the integrity of the explosion-proof function must be realized. The installation of explosion protected electrical equipments shall not only comply with the electrical installation standards but also the explosion protection standards, so the installation management of explosion protected electrical equipments shall also have some matters needing attention. 1 Qualifications of personnel According to the international explosion protection standard IEC [2],design of the installation, the selection of equipment and the erection covered by this standard shall be carried out only by persons whose training has included instruction on the various types of protection and installation practices, relevant rules and regulations and on the general principles of area classification. The competency of the person shall be relevant to the type of work to be undertaken. 22

2 Responsible persons who are responsible for the processes involved in the design, selection and erection of explosion protected equipment shall possess, at least, the following: (1) General understanding of relevant electrical engineering; (2) Understanding and ability to read and assess engineering drawings; (3) Practical understanding of explosion protection principles and techniques; (4) Working knowledge and understanding of relevant standards in explosion protection; (5) Basic knowledge of quality assurance, including the principles of auditing, documentation, traceability of measurement and instrument calibration. Such persons shall confine their involvement to the management of competent Operatives conducting selection and erection duties and not engage themselves directly in the work without ensuring their practical skills at least meet the requirements of Operatives. Operatives shall possess, to the extent necessary to perform their tasks, the following: (1) Understanding of the general principles of explosion protection; (2) Understanding of the general principles of types of protection and marking; (3) Understanding of those aspects of equipment design which affect the protection concept; (4) Understanding of content of certificates and relevant parts of this standard; (5) General understanding of inspection and maintenance requirements of IEC [3]; (6) Familiarity with the particular techniques to be employed in the selection and erection of equipment referred to in this standard; (7) Understanding of the additional importance of permit to work systems and safe isolation in relation to explosion protection. Responsible persons and Operatives can conduct training and assessment in accordance with national regulations or standards or user requirements to demonstrate the competency to obtain the corresponding qualification certificate. Appropriate continuing education or training shall be undertaken by personnel on a regular. The competency of Responsible persons and Operatives shall be verified and attributed at intervals. At present, this standard is being translated into Chinese national standard. 2 Equipment and Documentation 2.1 Equipment 23

3 Chinese national Explosion protection standard GB [4] specifies the design of electrical installations in explosive atmospheres. The selections of equipment are generally specified in the design documents. Procurement of equipments must be carried out in accordance with the the design documents. GB [5] specifies that the equipments shall be checked on site and shall comply with the following provisions: (1) Packing and sealing shall be in good condition; (2) Open package to check the equipment. The type, specification and explosion-proof mark shall comply with the design requirements. The accessories, accessories, spare parts shall be complete and in good condition. The classification, level, group, ambient conditions and special mark shall comply with the design requirements; (3) The technical documents of the products shall be complete; (4) The explosion protected electrical equipment nameplate shall be marked with the certificate no. issued by the state inspecton body; (5) The appearance of the equipment shall be free from damage, corrosion and moisture. 2.2 Documentation In order to install correctly, Chinese national explosion protection standard GB [6] specifies the following requirements about documentation: (1) Area classification documents; (2) Instructions for erection and connection; (3) Documents of special electrical equipments, such as equipments with certificate numbers which have the suffix X ; (4) Descriptive system document for the intrinsically safe system; (5) Manufacturer's/qualified person's declaration. 3 Installation At present, there are some Chinese explosion protection standards which specify the requirements for the installations of explosion protected electrical equipments, such as GB , GB , 12D401-3[7]and other relevant industry standards, the installation work should strictly comply with the relevant standards. The following questions are most common in the installation of explosion protected electrical equipments, and should pay special attention to. 24

4 (1) Cable inlet; (2) Plugging of unused cable inlets; (4) Installation of fastening bolts; (3) Connection of earth wires. 4 Completion acceptance Explosion protected electrical equipments shall be inspected and the relevant documents shall be provided in the completion acceptance. GB specifies a number of inspection projects that shall be carried out in the completion acceptance, such as: (1) The explosion-proof certificate no. shall be marked in the nameplate of the explosion protected electrical equipments. The equipment with U or X after the explosion-proof certificate shall comply with the requirements of the technical documentation. (2) The type, classification, level and group shall be in accordance with the design requirements and shall be in accordance with the level of hazardous areas. (3) The enclosure of explosion protected electrical equipments shall be free of cracks and damage. The cover of the junction box shall be fastened, and the fixing bolt and the loose-proof device shall be complete. (4) The unused cable inlets shall be sealed correctly. (5) The installation of sealing devices in electrical wiring systems shall comply with the provisions. (6) The grounding and anti-static grounding wires of the electrical equipments shall comply with the design requirements, grounding should be firm and reliable. At the completion acceptance, GB requires the provision of relevant documents and information, such as: (1) Design change document; (2) Documents provided by the manufacturers, such as the product instructions, test records, certificates and installation drawings; (3) Records of equipment installation and debugging; (4) Records of Pressurized Enclosures "P", such as adjustment records of wind pressure and gas pressure relay protection devices, the highest enclosures temperature record in the test run and the anti-static grounding resistance test record. 25

5 5 Conclusion The installation quality of explosion protected electrical equipments is critical for the safety of hazardous areas, so more attention should be paid on the installation management. Matters needing attention in this paper are derived from the relevant standards and are only a little part, therefore these standards shall be carefully studied and strictly implemented. References [1] GB , Explosive atmospheres Part 1: Equipment General requirements [S]. [2] IEC :2007, Explosive atmospheres Part 14: Electrical installations design, selection and erection [S]. [3] IEC :2007, Explosive atmospheres Part 14: Electrical installations inspection maintenance [S]. [4] GB , Code for design of electrical installations in explosive atmospheres[s]. [5] GB , Code for construction and acceptance of electrical equipment on fire and explosion hazard electrical equipment installation engineering [S]. [6] GB , Electrical apparatus for explosive gas atmospheres Part 15: Electrical installations in hazardous (other than mines) [S]. [7] 12D401 3, Electrical wiring and electrical equipment installation in explosion hazardous area[s]. 26