Three Checks and Four Fixes for Petrochemical Plants

Thread Content

““The three inspections and four determinations” is a process undertaken in the petrochemical industry during project construction, prior to the handover of the project. This approach was formally introduced in the regulations regarding chemical plant commissioning issued by the Ministry of Chemical Industry in 1988; it serves as a mechanism for ensuring the quality of the project； Thus, it becomes an effective means to ensure the success of joint commissioning and trial operation with materials fed in. The three inspections and four determinations represent an inspection process carried out jointly by the owner and the supervisor prior to the completion of work by the construction unit; this process is a prerequisite for the long-term stable operation of the facility. “\"Three inspections and four determinations\" refer to the process in which, after the installation of a project is completed in accordance with the specifications outlined in the design documents, and after the construction unit has conducted its own inspections and the supervision unit has carried out further inspections, the project owner, together with the production preparation department, organizes relevant parties such as those responsible for design, procurement, construction contracting, and supervision to carry out thorough inspections and evaluations of the project on a unit-by-unit and system-by-system basis, as well as by specialty. “The “three inspections” refer to checking for missing items in the design, identifying potential problems with construction quality, and examining unfinished work; the “four determinations” involve setting tasks for the issues identified, specifying the units and individuals responsible for addressing them, determining the measures to be taken, and setting deadlines for making corrections. ➢In the early stages of construction, the main focus is on identifying any omissions in the design, with the construction entity and the design institute playing key roles. ➢During construction, the main focus is on identifying potential quality issues and defects, with supervision carried out primarily by the supervision company. ➢ In the later stages of testing, the focus is on unfinished works, with the construction unit taking the lead. The three-inspection process must be thorough: ➢ Each specialty should check items one by one in accordance with the design requirements, to determine whether equipment, pipelines, valves, instruments, electrical systems, civil works, etc., meet the design specifications; ➢ Whether the process is reasonable and the flow is unobstructed; ➢ Whether operation is convenient; ➢ Whether the positioning of the equipment is correct; ➢ Whether there are any defects in pipeline welding; ➢ Whether blind flanges, flanges, and gaskets meet the required standards; ➢ Whether the orientation of the valves is correct; ➢ Whether lightning protection and static electricity control devices meet the requirements; ➢ Whether the valves open and close smoothly; ➢ Whether the location and quantity of pressure gauges and thermometers meet the requirements. The principles to be followed for the three-inspection and four-fixation process include ➢ Identifying any omissions in the design. In addition to the designers, managers from the construction unit, operators, and industry experts must also attend. ➢Inspect for potential construction quality issues. It occurs in areas where operations are not carried out in accordance with regulations and standards, thereby compromising the functional and safety aspects. Construction workers, quality inspection personnel, and supervisors are all responsible for this, but the professional supervision engineer should provide leading opinions. ➢Check unfinished projects. The construction contractor bears primary responsibility; therefore, it should promptly compare the work with the design to identify any missing items. The four fixations must be accurate: the contents of the four fixations are determined based on the issues identified through the three checks.     The four determinations are generally made by the technical supervisor in charge of production preparation, in collaboration with the design and construction teams, who examine each identified issue in detail. Any item that affects the start of work, normal production, safe production, or clean production must be addressed or corrected; items that merely add extra benefits but are not essential are omitted, so as to ensure project progress and control costs. For added or modified items, especially major issues (such as equipment openings, additions or modifications to control schemes, changes in process flows, addition or removal of pipelines with a diameter exceeding 150 mm, etc.), thorough deliberation is required, and tasks must be defined precisely. Preparations for the Three Checks and Four Determinations ➢ Personnel preparation (including various technical specialists, engineers, supervisors, operators, etc.) ➢ Document preparation (PID, design drawings, construction drawings, equipment diagrams, installation documents, standard references, and manufacturer information, etc.) ➢ Preparation of personal protective equipment (PPE, safety ropes, ladders, etc.) ➢ Preparation of measuring and other tools (feelers, calipers, tape measures, levels, etc.) ➢ Training on safety and the procedures of the Three Checks and Four Determinations (training in specialized knowledge, safety precautions, and emergency response skills) ➢ Preparation for task allocation within the framework of the Three Checks and Four Determinations (assignment of tasks to individuals, division of responsibilities by area, and scheduling plans). HSE in the Three Checks and Four Determinations: Safety is of utmost importance in these procedures; therefore, when carrying out necessary inspections in unsafe conditions, it is essential to follow these steps: 1. Use a backpack to carry documents, so that the body can maintain three points of contact with the ladder while climbing it. 2. Use a safety rope when outside the railing; for example, when climbing pipes other than handrails. 3. Do not cross railings (temporary or permanent). 4. Appropriate tools for the job; the correct tools should be used for all tasks. The process team has a toolbox on site, where tools are stored along with spare parts. 5. Protective clothing must be worn when entering the site. 6. A license is required to carry out any work. 7. Entry into any container or confined space, such as tower bases and tanks, is prohibited without a permit and external supervision. How to check valves on-site? Valves are the most common types of equipment in installations; they come in two categories: control valves and on/off valves. There is also a type known as electric valve. For valves, it is necessary to check the air supply lines, power supply lines, inlet ports, manometers, nameplate markings, grounding, flange connections, gasket bolts, and the overall integrity of the valve body. During inspection, we might overlook the coupling bolts of the flanges. It is advisable to use carbon steel double-ended bolts; for them to be considered acceptable, 3–5 threads must remain exposed after installation. Some cable outlets may face upward; if it is not possible to change their orientation, those outlets must be properly sealed to prevent water from getting in. If the valve is installed outdoors, it is advisable to fit a waterproof cover on the actuator to facilitate subsequent inspection and maintenance. Level measuring instruments include differential pressure dual-flange level gauges, ultrasonic level gauges, radar level gauges, etc. The installation position of the gauge body in a differential pressure double-flange level gauge is closely related to the two flanges, and migration issues must be taken into account. During inspection, the positive and negative pressures of the double flange must not be reversed, and the capillary tube must be aligned with the H and L positions on the gauge body. The table body must be fixed to a stable instrument column, and the vertically extending capillaries also need to be supported by metal grooves for protection. Temperature instruments are divided into thermocouples and thermal resistors; some come with temperature transmitters, while others have a screen with button controls. Thermometers are relatively simple compared to other instruments. In some case, the insertable part of a thermometer isn’t fully inserted, leaving a portion of its metal body exposed. This makes it easy for other objects to bend it; extra care must be taken during inspection. There are also some that are installed on pipelines, and in such cases we consider whether the flow direction of the medium in the pipeline and its properties meet the installation requirements. Pressure instruments, pressure transmitters, and double-flange level gauges have a similar structure; the inlet port, air release and drain valves, explosion-proof plugs, position labeling, fastening joints, and the stability of the gauge body—all of these need to be checked. If necessary, it is also necessary to check whether the ranges are consistent; if not, they should be adjusted promptly. Alarms are divided into flammability alarms and toxicity alarms. Check whether the threads at the inlet are tight; pull the wire slightly to see if it is loose. Do not overlook the small explosion-proof plug on the right side; check to see if it is tightened properly. Check whether the entire table body and columns are firmly fixed, and whether the front and rear covers are tightly closed. Tag numbers and nameplates are also essential. If it is installed in an outdoor area, it is necessary to ensure proper waterproofing and to install surge protection. When the density of the gas being detected is greater than that of air, the detector should be installed at a height of 30–60 centimeters above the ground. When the density of the gas being tested is less than that of air, the detector should be installed 0.5 to 2 meters above the leak site, with the sensor facing downward. The detector should be installed in a location free from impacts, vibrations, and strong electromagnetic interference, with at least 0.3 m of clearance around it. How to check the local pressure and local temperature with on-site instruments: there are two connection types, flange and thread. During inspection, shims must be used where required, and the specifications for bolt fixation must meet the requirements. For a table of this type, bit numbers for identification are essential, along with certificates of conformity and calibration certificates. The local pressure gauges and local thermometers are relatively small and scattered, hidden quite well within the device; they require patience and careful attention to be detected. How to check non-instrument components? In addition to the three inspections and four adjustments required for instrument equipment, there are many other small details in the system that are not instruments and also need to be checked by us. For example, in the case of an intermediate junction box, if no other equipment has cables entering it at the site, the inlet plug at the bottom should be replaced with a hole-free explosion-proof plug; the box cover must be properly sealed; there should be grounding terminals on the sides; the interior should be insulated; and the internal terminals must be in place and securely fastened. There are also cable protection tubes that can be found everywhere; it’s better to replace the tubes that bend upward with tees or elbows, so that rainwater cannot enter the pipes and accumulate there on rainy days. All issues identified during on-site inspections and the information collected must be systematically compiled and recorded to ensure that subsequent corrective actions can be carried out smoothly.