A Brief Discussion on Instrument Installation

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A Brief Discussion on Instrument Installation Author: Dong Gaofeng, Quzhou, Zhejiang 324004 Abstract: This article discusses the importance of instruments in chemical production, the various stages of instrument installation during the construction process, the key tasks at each stage, as well as the specific construction methods. Keywords: instruments, installation, phase, method. 0 Introduction: In modern industrial production, the level of automation is increasing steadily, and as a result, the use of automated instruments is also on the rise. For the entire system to operate stably over the long term, it is essential that the instruments function stably as well; therefore, their proper use and maintenance are of great importance. Moreover, the quality of the initial installation of the instruments has a direct impact on the subsequent operation and maintenance of the entire system. Next, I will share my experience regarding the installation of instruments for everyone’s reference. Instrument installation refers to the process of combining various individual components, such as the instrument itself, pipelines, cables, and auxiliary equipment, into circuits or systems as required by the design, in order to carry out detection or control functions. In other words, instrument installation is carried out in accordance with design requirements, to establish various connections between instruments, between instruments and process equipment, between instruments and process pipelines, as well as between field instruments and the central control room, and between field control rooms. Such connections can be made using pipes (such as measurement pipes, pneumatic pipes, heat tracing pipes, etc.), or via cables (including wires and compensation wires); usually, a combination of both types of connections is used. The installation of instruments can generally be divided into three stages: the construction preparation stage, the construction stage, and the commissioning and handover stage. 1 The construction preparation phase, which refers to the preparatory work done before the project begins, is actually the most important stage. If the work at this stage is done well and thoroughly, future tasks will naturally proceed smoothly. Our factory does well in this regard. First and foremost, the management attaches great importance to it; each project is organized and coordinated by the management, with project management teams established. Dedicated personnel are responsible for preparing various documents and handling material supply, etc. The installation workers are organized to study the blueprints, receive technical training, and undergo safety education. In addition, the tools and equipment used for installation are also well maintained on a regular basis to ensure they can perform effectively during construction. Some standard calibration instruments and instrument calibration benches should also be prepared before installation. The specific tasks during the construction preparation phase include: 1.1 Preparation of documents. The installation documents consist of construction drawings, commonly used standard drawings, manuals for automatic control installation, the \"Code for Construction and Acceptance of Industrial Automation Instrumentation Projects\" GBJ93-86, as well as quality inspection standards and various related handbooks and technical requirements for construction. The construction contractor obtains the construction drawings from the project owner, and uses them as a basis to prepare a budget as well as various submission forms and record sheets, including construction forms and quality record forms. 1.2 Technical preparation: The installation of instruments requires participation in the preparation of the overall project construction organization plan, as well as the development of a separate construction plan specific to the automation control field. The most important parts of a construction plan are the construction methods and procedures, which need to be described in detail so that workers can follow the steps outlined in the plan to carry out their work, address technical issues, and ensure quality. Quality assurance measures are the foundation of the construction plan; only by ensuring quality can progress in construction be considered. Safety technical measures are also a key aspect of the plan; safety must be given top priority throughout the entire installation process. The technical preparation phase also includes a joint review of the design drawings. In this review, the automation team focuses on identifying any issues that other departments might pose to the installation of instrumentation; such issues must be detected and raised promptly, with the design department organizing coordination among all relevant departments to resolve them before actual construction begins. Three types of briefings: First, the construction entity organizes the construction company to attend, with the design entity providing design-related briefings; each specialty is responsible for giving its own briefings. Next, there are the construction technical briefings organized by the construction company, during which the person in charge of the project team provides instructions to the technical staff on site. Finally, there are the technical briefings given by the technical staff to the workers. This process should continue throughout the entire construction period; for now, we can consider it part of the construction preparation phase. 1.3 Material Preparation: The instrument installation team shall obtain all the instrument equipment and materials as specified in the construction drawings. In addition, consumables that are not mentioned in the drawings, such as electrical tape, heat-shrink tubing, welding electrodes, and various clamps and screws/nuts used for fixing brackets, should also be prepared. In the preparation of materials, it is also necessary to ensure proper storage in the warehouse; all kinds of equipment and materials must be kept safely to prevent damage, so as to guarantee the progress and quality of construction. After all equipment and materials pass the self-inspection, the certificates of conformity and warranty documents are compiled, and a submission form is filled out to be submitted to the supervisor for review; installation can proceed only after the supervisor gives approval. 1.4 Preparation of construction tools and standard instruments. Common tools used for instrument installation include electric threaders, hydraulic pipe benders, cutters, hole-making machines, electric hammers, electric drills, and welding machines; in addition, small tools such as hammers, wrenches, and saws should also be prepared. Standard instruments mainly refer to calibration instruments, including pressure gauge calibration benches and field standard signal generators. All the aforementioned common construction machinery and standard instruments must be prepared in advance before the construction phase begins. 2 Construction phase: The installation period for instruments is relatively long, spanning from the start of civil work all the way to the completion of the actual commissioning tests. Therefore, the labor arrangement for instrument installation should be planned well in advance. During the civil engineering phase, only a small number of workers are required to carry out all the necessary embedding work in accordance with the construction drawings. During the installation of pipeline systems in equipment, a small number of additional workers should be assigned to keep an eye on their progress. For instruments such as control valves and flow meters that are installed directly on the pipelines, it is necessary to work in coordination with the pipeline installers – the instruments should be installed at the same locations as the pipelines, so as to ensure that the installation of these instruments proceeds smoothly without affecting the progress of other tasks. The peak phase of instrument installation should occur when 70% of the work related to the installation of the equipment’s process pipelines has been completed; at this point, all personnel responsible for instrument installation should be on site and begin the installation work in full force. Specific tasks during the instrument installation phase: 2.1 Installation of cable trays. Instrument cable trays mainly include fiberglass-reinforced plastic trays and galvanized steel trays. Installation shall be carried out in accordance with the cable layout plan shown in the construction drawings; the overall requirement is that the cables should be arranged neatly and horizontally, with sufficient space between them and the building. When the cable tray is connected by welding, it is necessary to ensure that the welds are strong and that the tray does not deform. When the tray is connected and fixed using bolts, half-round head bolts should be used with nuts placed on the outside, so as to prevent the cables from being scratched or caught inside the tray. 2.2 Installation of on-site instruments (including the calibration of various instruments)：Based on the process flow diagram with control points, locate the positions of each instrument; make openings in the equipment pipelines or use flange bolts for connection, and install the instruments and their accessories one by one. Once the instruments are in place, various instrument pipelines can be installed, including pressure transfer pipes, air supply pipes, and cable conduits. The field control box, junction box, and instrument protection box can also be installed simultaneously along with the piping. All of these shall be installed in accordance with the construction drawings, and must meet the requirements of the \"Code for Construction and Acceptance of Automation Instrumentation Installation Projects\". While installing on-site, keep proper records, including calibration records for various instruments, installation records, and various quality control forms. 2.3 Installation of the control room dashboard: First, prepare a base for the dashboard according to the construction drawings; channel steel is generally used for this purpose, and after anti-corrosion treatment it is installed in the control room and fixed horizontally. Once that is done, the dashboard can be installed on top. Oxyacetylene welding must be strictly avoided during installation to prevent deformation of the dashboard and damage to its surface paint. 2.4 Cable laying and wiring adjustment At this stage, the field instruments, cable trays, various pipelines, and instrument panels have all been installed in place; it is now possible to start laying the cables and adjusting the wiring, thereby completing the cable connections between the instruments and the control room as well as the field control boxes. Cable laying generally requires no intermediate joints; if this cannot be avoided, the connections should be made within junction boxes or conduit boxes. After the cables are laid, their conductivity and insulation resistance should be checked; once they meet the requirements, they can be marked and connected according to the diagram. A cable label should be attached at the control room end. 2.5 Pressure testing and purging of instrument pipelines: Once the on-site instruments and pipelines have been installed, the instrument installers should carry out purging and pressure testing in conjunction with the process pipelines. Instruments mounted on these pipelines, such as control valves and orifice plates, must be removed and replaced with temporary short pipes; they can then be reinstalled after the purging is complete. When purging the instrument pipelines, care must be taken to avoid damaging the instruments. The air supply pipe for control valves should not be connected to those valves; instead, purging should be carried out by venting. For transmitters, the pressure lead pipes should have their drain valves opened, while the valves leading to the transmitters should be closed. Pressure testing shall be carried out in accordance with the regulations: the hydraulic test pressure is 1.5 times the design pressure, while the pneumatic test uses 1.15 times the design pressure. Soap water can be used to detect leaks during the pneumatic test. If a leak is detected during the pressure test and the pressure cannot be maintained, the leak location must be identified; after it has been repaired, the pressure test should be attempted again until it passes. 2.6 Secondary Calibration (System Commissioning) Secondary calibration refers to the process in which each instrument has been individually calibrated and found to be satisfactory during the construction phase; these instruments are then connected together via cables to form circuits. For each circuit, we carry out calibration of the analog signals. Various corresponding signals are sent into the detection circuits using standard signal generators on-site, and the status of each circuit is checked on the instrument panels in the control room or on the DCS system, with errors being calculated accordingly. The error of the loop display value is required to be no greater than the square root of the sum of the squares of the basic errors of each instrument in the loop. For the control loop, control signals are sent from the control room to the actuators via controllers, and on-site it is checked whether the direction of operation and the stroke of the actuators comply with the design specifications. For the alarm system, tests must be carried out as required by the design to check whether the alarm lights, sounds, and the operation of the output relays are satisfactory. The entire system debugging should be carried out in conjunction with the project owner and the design agency; after the debugging is completed, all relevant records must be kept, and signatures of Party A and the supervisor are required for approval. 3 Commissioning phase: With the above work completed, the instrument installation is largely finished, and testing can now begin. Single-unit testing mainly involves individual devices, transmission systems, power systems, etc., with the instruments requiring only simple coordination. During the joint commissioning, all instruments must be activated, and all display instruments should be able to accurately indicate the signals being measured. Various control systems are generally operated manually at first, and only after the system is running stably is automatic control engaged. The commissioning testing should be led by the construction unit, with the installation unit playing a supporting role. After 72 hours of normal operation during the commissioning testing, the entire system along with its instruments are handed over to the construction unit, which will then carry out trials using chemical feedstocks. During this process, the instrument installation personnel must keep various records; together with the various forms filled out earlier, these records are used to conduct quality assessments, and forms such as sub-project quality inspection reports and quality assessment sheets for individual items are completed. In this way, only by handing over the hardware of the entire instrumentation system along with the detailed as-built drawings and other technical documents can the installation of the instrumentation for this project be considered truly complete. 4 Conclusion The above briefly introduces the various stages of instrument installation and the specific tasks for each stage. In actual installation work, various problems arise, and it is impossible to cover them all here. As long as we carry out the construction strictly in accordance with the plans, adhere to various standards and specifications, maintain timely communication with the client, the design unit, and the supervisor, and address all issues that arise during the installation process, we can ensure the successful completion of the instrument installation project. References: Le Jiaqian, Editor, Handbook for Instrument Operators, Chemical Industry Press, April 1998. Wang Shaochun, Editor, Automatic Detection Technology (2nd Edition), Beijing: Metallurgical Industry Press, 1995. Gao Kuiming, Editor, Thermal Measurement Instruments (Revised Edition), Beijing: Metallurgical Industry Press, 1993