In China, electric devices and electric actuators for valves belong to different industries. Electric devices belong to the general machinery industry. Since the 1950s and 1960s, electric devices have been introduced in the form of complete sets of equipment and technology and gradually applied to various industrial fields in China. At the end of the 20th century, valves with intelligent electric devices began to be used in large numbers. At present, a production pattern with electric devices as the main manufacturing base in many regions has been formed. There are many manufacturing companies, but they are not well known internationally. A lot of national standards for electric devices have been successively formulated in China, which has provided the basis and guidelines for common compliance with the production and technological progress of domestic enterprises.
There are certain differences between the electric device and electric actuator for valves in terms of implementation standards, structural design, matching motors, functions, etc. The electric device is mainly positioned in the terminal control (the switch type), while the electric actuator is positioned in the process control (the regulating type). The two kinds are called electric devices generally for better understanding.
The applications of electric devices
Among the national standards for electric devices in China, GB/T24923-2010 mainly stipulates the technical requirements for ordinary multi-turn and part-turn on-off electric devices of valves. GB/T28270-2012 mainly stipulates the technical requirements for intelligent multi-turn and part-turn on-off or regulating electric devices of valves. GB/T26155.1-2010 mainly stipulates the related requirements for intelligent multi-turn, part-turn and straight travel on-off and regulating electric devices for valves used for industrial process measurement and control systems.
The electric device standard ISA96.02.01-2007 formulated by the American Instrument and Association mainly specifies the general requirements for multi-turn, part-turn and straight travel electric devices. The European standard EN15714-2:2009 is a standard established by the CEN/TC69 Technical Committee of the European Committee. This standard mainly stipulates part-turn and multi-turn, straight travel on-off and regulating electric devices of valves, among which the regulating type includes the micro or slow action type, adjustment and continuous adjustment type. From the analysis of the scope of use, the contents of the domestic and foreign standards for electric devices are different, and the EU standards are more detailed.
Working environment conditions of electric devices
GB/T24923-2010, GB/T28270-2012, GB/T26155.1-2010 and EN15714-2: 2009 stipulate that the electric device is used at an altitude not higher than 1 km. Considering that the low air density in high altitude areas affects dissipation of heat inside the motor of an electric device, the altitude is specified. In addition, the characteristics and conditions of some seals and lubricants may also change under different pressures. The standard ISA96.02.01-2007 has no clear provisions in this regard.
Operating temperature and relative humidity of electric devices
(1) Operating temperatures
GB/T24923-2010, GB/T28270-2012 and EN15714-2:2009 stipulate that the operating temperature of electric devices is -20 to 60℃. GB/T26155.1-2010 stipulates that the operating temperature of electric devices is -25 to 70℃. ISA96.02.01-2007 stipulates that the operating temperature of electric devices is -30 to 70℃.
(2) Relative humidity
GB/T24923-2010 and GB/T28270-2012 stipulate that the relative humidity used by electric devices is below 90% (25°C). The relative humidity specified in GB/T26155.1-2010 is below 95%, and there is no condensation. The relative humidity specified in EN15714-2:2009 is below 80%. The relative humidity specified by ISA96.02.01-2007 is 0 to 95%. The relative humidity at different temperatures will vary. At this point, the technical indicators stipulated by the Chinese standards are relatively reasonable.
Protection levels
The protection level is one of the important technical indicators for the application of electric devices. The protection level of electric devices specified in GB/T24923-2010 and EN15714-2:2009 shall not be lower than IP65, and that of electric devices specified in GB/T28270-2012 shall not be lower than IP67. GB/T26155.1-2010 stipulates that the protection level of electric devices should meet the requirements of GB/T4208 according to the requirements for the manufacturer. It is not specified in ISA96.02.01-2007. There are many applications for electric devices, and there are many protection levels specified in GB/T4208. The reasonable protection level specified in the standard has important guiding significance for the manufacture of electric devices.
Surface anticorrosion
GB/T24923-2010, GB/T28270-2012 and ISA96.02.01-2007 all qualitatively stipulate requirements for the surface anti-corrosion of electric devices. EN15714-2:2009 stipulates different anti-corrosion grades under different environmental conditions according to requirements of ISO. GB/T26155.1-2010 does not specify the requirements for surface anti-corrosion of electric devices.
Connection of electric devices
The connection of the electric device mainly refers to the part connected to the valve, and the provisions of the relevant standards are based on the ISO standards. GB/T24923-2010 and GB/T28270-2012 stipulate that the connection of part-turn and multi-turn electric devices should be in accordance with the requirements of GB/T12222 and GB/T12223. There are no requirements on the connection of drive devices in GB/T26155.1-2010 Standard. ISA96.02.01-2007 and EN15714-2:2009 stipulate the connection requirements for part-turn and multi-turn electric devices, respectively in accordance with ISO5211 and ISO5210. At the same time, European and American standards stipulate the requirements for the connection of straight travel electric devices, which are more comprehensive than those stipulated in Chinese standards. At present, the latest editions of ISO521 and ISO5211 are the 2017 edition, and the new edition of the international standard has added the technical content of the connection of the straight travel actuating device. This part of the content can be considered in the follow-up adoption for Chinese standards.
Electrical connections
There are corresponding provisions for electrical connection GB/T24923-2010, GB/T28270-2012, EN15714-2:2009 and ISA96.02.01-2007 standards. GB/T26155.1-2010 does not specify the electrical connection of electric devices. As for the requirements for an electrical connection involving electrical requirements, there are no detailed regulations in the standards. The reason may be related to the different laws and regulations on electrical connections in various countries.
The service life test
GB/T24923-2010 and GB/T28270-2012 stipulate that the service life test of electric devices shall be no less than 8000 times of continuous operation. ISA96.02.01-2007 stipulates that the service life test of electric devices shall be no less than 10,000 times of continuous operation. EN15714-2:2009 stipulates different times of the service life according to the different rated torque or rated thrust of part-turn, multi-turn and straight travel electric devices, and some of them need to be negotiated with the user. According to the composition mechanism of the electric device, for the electric device with great output torque, for example, hundreds of thousands of Nm, the standard service life is too many due to the limitation of the transmission mechanism. Because of the wear of the mechanical transmission part, after the service life test of the whole electric device, it may cause problems with some performance indicators. For example, the repeat accuracy of the position is great. The EU standards are more reasonable in this regard.
