The installation of mechanical and electrical equipment cannot be judged by the completion of construction. The commissioning, testing, trial operation and acceptance of the equipment all fall under the important processes in the project management of mechanical and electrical equipment installation. Especially in engineering, many small and medium-sized mechanical and electrical equipment are often applied. Although they are small in size and relatively simple to install and debug, the involved supporting components and corresponding standards will be more. The installation and commissioning of large-scale mechanical and electrical equipment involve more coordinated management of individual aspects such as personnel, machinery, materials and energy, all of which bring objective difficulties to the installation and commissioning of mechanical and electrical equipment.
Common technical problems in the installation of mechanical and electrical equipment
With the improvement of the standardization and modernization of production equipment, especially the application of automated equipment, the installation and commissioning processes of mechanical and electrical equipment have become increasingly complex. Professional division of labor has been refined, and the equipment installation profession has gradually tilted towards a technology-intensive direction. This has caused considerable obstacles to the construction period of mechanical and electrical equipment installation projects. This requires that the installation schedule plan for mechanical and electrical equipment must carefully consider the time prediction of each process, taking into account the needs of project commissioning and technical debugging. Generally speaking, common problems in mechanical and electrical installation mainly include the following points
1) Bolt connection issues. Bolt connection is the most fundamental assembly in mechanical and electrical installation. However, if the operation is improper, such as when the connection is too tight, the bolts may experience metal fatigue due to the long-term action of electromagnetic force and mechanical force, which may lead to phenomena such as shearing and thread slithering during component assembly, thus posing potential accident hazards. Especially for bolt connections used in electrical engineering for conducting current, it is even more necessary to properly handle the mechanical and electric heating effects between bolts and nuts. They should be compacted and tightened to avoid an increase in contact resistance due to loose crimping, which can trigger a series of chain reactions such as heating, oxidation of the contact surface, and increased resistance, ultimately leading to overheating and melting at the connection point, resulting in grounding short circuits and disconnection accidents.
2) Vibration issues. The causes of vibration problems usually include three aspects: ① Pumps, mainly due to the influence of factors such as large bearing clearance, poor concentricity between the rotor and the casing, or excessive friction between the rotor and the stator. ② For motors, the causes include large bearing clearance, unbalanced rotor or uneven air gap between the rotor and the stator. ③ Installation and operation: If the process operation parameters deviate too much from the rated parameters, it is very likely to cause an imbalance in the stability of the pump operation, such as vibration caused by unstable flow control of the outlet valve. This requires that the equipment installation process should be operated as close as possible to the rated parameters.
3) Overcurrent problem. There could be three reasons for this situation: the pump bearing is damaged or there are foreign objects inside the equipment; The motor overload current setting is too low, and the line resistance is too high, etc. The medium used in the process operation has a high density or viscosity, which exceeds the design capacity of the pump.
4) Electrical equipment issues. Improper installation and operation of the disconnector led to insufficient contact pressure and contact area between the moving and static contacts, resulting in thermal oxidation and increased resistance on the contact surface. Eventually, the contacts were burned out, causing an accident. If the arc contact finger and contact assembly of the circuit breaker are incorrect, and the insertion stroke, contact pressure, synchronization, and opening and closing speed do not meet the requirements, it will cause the contact to overheat, prolong the arc extinction time, lead to the decomposition of the insulating medium, cause a sudden increase in pressure, and result in an explosion of the circuit breaker. ③ If there are errors in the assembly of the pressure regulating device or foreign objects fall in during assembly and jam the mechanism, and if not dealt with in time, safety accidents of varying degrees will also occur. ④ The insulation of the main transformer is damaged or broken down. When installing the hoisting core of the main transformer and the high-voltage pipe, if foreign objects such as nuts fall in, or if the sealing device is installed incorrectly, it will directly affect the change in the insulation strength of the main transformer. It is highly likely to cause local insulation damage or breakdown, resulting in a serious accident. ⑤ If the primary winding of a current transformer is open-circuited due to improper installation or maintenance, it will generate a very high overvoltage, posing a threat to personal and equipment safety.
2. Organization and management of installation and commissioning personnel
The common technical problems in the installation of mechanical and electrical equipment mentioned above are sufficient to prove that details are the key to the success or failure of equipment installation and commissioning. The first and foremost thing is to do a good job in personnel organization and technical training.
For large-scale mechanical and electrical equipment, during the initial installation and commissioning, the supplier should be required to dispatch technical personnel to be specifically responsible. The design of small and medium-sized mechanical and electrical equipment is relatively simple, and most of the equipment has been installed and debugged before leaving the factory. However, some highly precise and expensive equipment must be installed and debugged by the factory's technical personnel. When the purchasing unit is responsible for selecting and matching members of the commissioning coordination team, it should pay attention to implementing the following issues: First, the selection of auxiliary installation personnel. The selected personnel should meet the basic quality requirements such as proficiency in business, flexibility in response, and strong sense of responsibility. According to the differences of large and medium-sized machinery, technicians should be selected from different trades such as hydraulic, mechanical and fitter, and mechanical worker to serve as machine operators. Second, organize the training work before installation and commissioning well. On the basis of selecting and matching operators, carry out job division and on-site technical training.
3. Process management of mechanical and electrical equipment installation
The installation process of mechanical and electrical equipment usually consists of three steps: formulating an installation preparation plan, preparation, and installation.
Before the formal installation, the equipment installation personnel should draw up a plan based on their previous practical experience, make detailed plans for the site selection of mechanical and electrical equipment installation, equipment entry, and organizational arrangements, reasonably predict the possible difficulties that may be encountered during the installation process, and propose emergency plans.
2) Preparations before installation. The main task is to check whether the required materials, accessories, etc. are complete and whether the quality meets the standards. Such as whether the power layout at the equipment installation site is reasonable and whether there is any loosening of the equipment nuts, etc.
3) Installation. During the equipment installation process, ensuring the personal safety of personnel is the top priority. Safety helmets, insulated handbags, anti-glare mirrors and other equipment must be fully equipped. Secondly, a thorough inspection of the appearance quality of the equipment components and accessories should be carried out. Installation should be carried out in accordance with the proposed plan, with division of labor and collaboration, as well as designated positions and responsibilities. After completing the task, conduct a preliminary check on the integrity and safety of the equipment.
4. Commissioning of electromechanical equipment
After the mechanical and electrical equipment is installed, the subsequent work is to put the equipment into production as soon as possible. To achieve this goal, debugging is an inevitable process. Thorough and meticulous equipment assembly inspection is the foundation and prerequisite for the smooth completion of equipment commissioning work. Before commissioning, it is necessary to conduct another inspection of the integrity, safety and installation conditions of the equipment assembly. The main contents of equipment debugging include: equipment performance, working quality and whether the operation is normal, etc. During the commissioning process, the corresponding mechanical technicians and auxiliary personnel must be in place on time and in full. They should further familiarize themselves with the operation essentials, basic procedures and various functional control methods of the equipment during the commissioning process.
During the debugging process, there should be dedicated personnel to record each step of the equipment debugging. Through a systematic summary of the equipment installation experience, the basic operating status and characteristics of the equipment can be objectively summarized. It can also provide first-hand data for solving various technical problems that may occur during the future operation of the equipment, and play a positive auxiliary role in the upgrading and transformation of the equipment.
During the equipment commissioning process, two fundamental principles must be followed: First, the "Five Firsts and Five Postings" principle, that is, single machine commissioning first and then joint commissioning; First on-site, then remote control. Jog first and then link. No-load first, then load; Manual first, then automatic. Secondly, "safety first" is the fundamental principle. Personal safety and equipment safety must be given top priority. We cannot rush into production or neglect the importance of safety commissioning due to carelessness.
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