The seven stages of chemical technology from concept to industrialization (Issue 55/100) -- HSE and analytical testing

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This post was last edited by xiouxingzhe on 2026-7-2 at 14:45. The seven stages of chemical technology from concept to industrialization (Issue 55/100) —— Technology refinement: HSE and analytical testing. Dear friends: Hello everyone! In the previous issue, we discussed equipment layout and boundary conditions, thereby establishing the overall spatial arrangement of the installation. In this episode, we’ll discuss a topic that is often overlooked by technical professionals during the preparation of process packages, yet is extremely important in subsequent reviews—namely, HSE (Health, Safety, and Environment) as well as analysis and testing. Engineers working on process design often devote most of their effort to core tasks such as process simulation, equipment selection, and piping layout. However, at the project approval stage, specialized reviews such as safety assessments, environmental impact assessments, and occupational health assessments rely to a large extent on the HSE baseline data provided in the process package. If HSE work is not properly carried out during the process package phase, subsequent reviews will either result in the submission of additional materials or force additional investment to make corrections during the detailed design phase – in either case, it is much more troublesome than doing everything properly right from the process package stage. This issue will be discussed in two parts: the HSE part and the analysis and testing part. I. MSDS compilation and occupational health protection: The starting point for HSE efforts is to compile all the Material Safety Data Sheets for chemicals, based on the material property sheets, that is, the MSDS. The material property sheet was completed in issue 36—the basic physical properties, safety data, and toxicity data for each component have all been compiled. The role of the HSE team is to systematically organize and present these data. For each material, it is necessary to clearly define where its handling station is within the facility, how operators might come into contact with it, what the exposure limits are, and what level of protective equipment is required—these details must be specified one by one. The core logic of occupational health protection is “control at the source”. The priority order is as follows: The top priority is process improvement—whether it’s possible to replace toxic materials with non-toxic or low-toxicity materials. The second priority is engineering controls – whether it is possible to operate in a sealed environment, to improve ventilation, and to set up isolated work areas. The third priority is management measures—rotating shifts, limiting exposure time, and regular health checks. Last are the personal protective equipment – gas masks, protective clothing, and gloves. The design during the package engineering phase should address problems at the source, rather than waiting until the plant is built to provide operators with gas masks. For toxic, harmful, or corrosive materials, specific procedures for dealing with leaks, first-aid measures, and requirements for regular monitoring must be established. The leak handling procedure cannot simply state “handle it promptly”; instead, it should specify what to do in the first step and second step after a leak occurs, as well as what emergency supplies are needed. A practical approach is to prepare an emergency response card for each major hazard source, so that operators know exactly what to do when they receive it. II. Hazard identification: Systematically analyze all potential hazards within the equipment, including fire, explosion, poisoning, asphyxiation, chemical burns, falls from heights, electric shock, and mechanical injuries. Identifying hazard factors cannot be done by simply creating a list; instead, it is necessary to inquire individually about the triggering conditions and consequences of each hazard. Which materials are flammable and explosive, and what are their flash points and explosion limits under operating conditions? Which equipment or operating points pose a leakage risk, and whether the leakage results in a flammable vapor cloud or the dispersion of toxic gases? Which devices may experience overpressure under abnormal operating conditions. Which areas contain confined spaces, and what level of protective measures is required to enter them. Based on the results of hazard factor identification, basic safety measures such as fire and explosion protection requirements, the zoning boundaries of hazardous areas, and fire separation distances are determined. The explosion hazard zone classification diagram serves as the basis for subsequent electrical design – it determines which areas require explosion-proof motors, which areas need explosion-proof lighting fixtures, and which areas require cables equipped with explosion-proof sealing connectors; everything is decided based on the classification of the hazard zones. The zoning was incorrect; non-explosion-proof equipment may have been used in areas prone to explosions, which represents a serious safety hazard. Another aspect of hazard identification that is easily overlooked is the synergistic effect between different hazards. For example, in a given area where there are both flammable liquids and high-temperature steam pipes, if a leak occurs and the liquid comes into contact with the high-temperature pipes, it may vaporize instantly, resulting in a larger-scale cloud of flammable vapor. Such scenarios with multiple factors overlapping require special attention when identifying hazards. III. Design Principles for Safety Facilities: Based on the results of hazard identification, the basic design principles for safety facilities are determined during the process package stage. The detailed design of specific safety facilities will be carried out during the basic design phase, but the process package must provide clear design inputs. The function of a flame arrester is to prevent external flames from entering equipment pipes containing flammable and explosive gases, or to stop flames from spreading between such pipes. During the process package phase, it is necessary to determine which locations require flame arrestors and what type to use – whether it should be pipeline flame arrestors or flame arrestors built into breather valves, as well as whether they should be of a fire-resistant type or a standard type. The selection of the installation location for flame arresters directly affects the safety of the equipment in case of a fire. Breather valves are used in atmospheric storage tanks to balance the pressure difference between the inside and outside of the tank, preventing overpressure or vacuum from occurring due to material transfer or temperature changes. A flame arrester is typically integrated into the breather valve to prevent external flames from entering the tank through the breather opening. During the package engineering phase, it is necessary to determine the breathing volume and set pressure of the breather valve. The setting pressure and discharge capacity of the safety valve have been covered in Issue 53; this issue provides additional explanations regarding the material selection and interfacing principles for safety valves. The material of the safety valve’s body, seat, and spring must be selected based on the corrosivity and temperature of the medium to be discharged. The inlet and outlet flange grades and pipe connection sizes of the safety valve must correspond to those specified in the pipe connection table. IV. List of waste emissions. Environmental protection is of top priority in the approval process for chemical projects today. In the HSE efforts during the package phase, the list of emissions of three types of waste is a key deliverable. Starting from the material balance data on the PFD, identify all the emission points for waste gas, wastewater, waste liquid, and solid waste one by one. For each emission point, it is necessary to determine: which device or operational step is the source of the emissions, what the amount of emissions is, what their composition is, the emission temperature and pressure, and whether the emissions occur continuously or intermittently. Current environmental impact assessment requirements are very strict; not only must the overall quality be balanced, but the key elements as well must be balanced. A clear explanation must be provided for the final fate of each type of material that enters the facility, as well as of each key element—sulfur, chlorine, nitrogen, phosphorus. Which materials does sulfur get into, where does it ultimately end up, how much of it goes into wastewater, how much is released into exhaust gases, and how much remains in the products—these are all matters that must be clearly addressed in the preparation of an environmental impact assessment report. If these data are not organized properly during the process package phase, and questions are raised during the environmental impact assessment, one will have to guess and fill in the gaps, which carries a high risk. For the three types of waste discharged from process units, if they can be discharged directly, the discharge standards and monitoring requirements must be specified. If discharge is possible only after treatment, recommended treatment methods and the expected treatment outcomes must be provided. In special cases, if the three types of waste are reused in the process units after treatment – for example, treated wastewater is reused as make-up water for cooling – then the process package needs to specify clear requirements regarding the quality of the treated water, as this directly affects the operation of the process units themselves. V. List of analyses and tests: Analyses and tests are the “eyes” of process control. All the design work done earlier—such as material balance calculations, determination of operating conditions, and setting up interlock protections—ultimately depends on analytical and test data to verify whether these design intentions have been realized and whether the plant is operating in a safe and efficient manner. However, for many process packages, in terms of analysis and testing, there is merely a list of analysis items – what tests to perform, what methods to use, and how often to conduct them. It doesn’t clarify how to determine the sampling points, which samplers to use, or how to design the sampling system. By the time of the detailed design phase, the piping team did not know where to locate the sampling points, and the instrumentation team did not know how to install on-line analysis instruments. After construction was completed, it was found that the locations of the sampling points were inappropriate and that the operators could not reach them – all these problems stemmed from insufficient attention paid to analysis and testing during the process package stage. A complete list of analytical tests should include the following: sample point number, description of the sampling location, analysis items, normal control parameters and allowable ranges, analysis methods, analysis frequency, type of sampler, and any additional notes. The determination of the analysis frequency needs to be based on the purpose of the analysis. For safety interlocks, continuous monitoring is required. Online analyzers must be used, and their analysis frequency must meet the requirements regarding the interlock response time—the total delay from sampling to signal output must be significantly less than the specified interlock response time. Used for process control, the frequency is usually once every one to four hours, depending on the dynamic characteristics of the process and the frequency of product changes. Used for quality inspection, usually once per shift or per day. VI. Sampling System Design The design of the sampling system is an aspect that requires detailed attention during the process package phase, as the location of the sampling points has a direct impact on the operability and safety of the facility. There are several basic principles for setting sampling points. Representativeness principle – The sampling point must be at a location where the material has been thoroughly mixed and where the composition no longer changes. For example, in the reflux line of a distillation column, the composition of the material at the outlet of the condenser is uniform, so it can be used as a reference ； However, sampling from the vapor line at the top of the tower may be affected by condensate on the pipe wall, compromising representativeness. Principle of timeliness — For parameters requiring closed-loop control, online analyzers should be given priority. For parameters that only require trend monitoring, offline sampling is sufficient. Operational principle – Sampling points must be located in positions that are easily accessible to operators and where safe operation is possible. The height of the sampling valve should be between 1.0 and 1.3 meters; sufficient space should be provided below the sampling valve for placing the sampling container. Safety principle — For sampling at high temperatures, high pressures, or with toxic and harmful media, a dedicated cooling, depressurization, or sealed sampling system must be designed. The selection of sampler type depends on the medium’s temperature, pressure, phase state, and hazards. Conventional liquid samplers are suitable for liquid media at normal or low pressure that are non-toxic and harmless; all that is needed is to install a sampling valve and a sampling tube on the pipeline, with a needle valve being chosen for the sampling valve to enable precise control of flow rate. A cooling sampler is used for sampling high-temperature liquids; a small cooler is placed in front of the sampling valve to cool the material to a safe temperature before sampling. A closed sampling system is used for toxic, hazardous, flammable, and explosive media; during sampling, it is not allowed for the sample to come into contact with the atmosphere, and nitrogen purging as well as discharge and collection facilities are required. Gas sampling systems are used for gaseous media; the shorter the sampling pipeline, the better. Heat tracing is required when necessary to prevent condensation. A solid-containing medium sampler requires a full-bore ball valve or mud sampling valve, with a sampling port large enough to prevent clogging. All sampling points must be clearly specified on the PID, indicating the sampling point number, sampler type, sampling valve configuration, and requirements for utility connections. If the sampler requires cooling water or nitrogen purging, these utility connections must be indicated on the PID; it is not acceptable to discover that no such connections have been provided until the construction phase begins. The final destination of the analytical test data also needs to be specified in the process package. Normal operation data is used for process control and quality management, and is directly entered into the DCS trend records. Safety interlock data is input into the SIS, independent of the DCS. Environmental monitoring data needs to be integrated into the online environmental monitoring system and connected to the regulatory platform of environmental protection agencies. Quality inspection data is stored on a long-term basis as part of the product quality archive. Data for different purposes have varying storage periods and access rights—basic requirements for these should be specified in the analysis and testing section of the process package. Preview for the next issue: Issue 56 – Integration of process flow descriptions and the general specification. HSE and analytical testing have been completed, and almost all of the technical documents related to the process package have been prepared. What needs to be done next is to integrate these documents into a complete deliverable that is logically consistent and has consistent data – this involves drafting the process description, integrating the overall manual, and verifying data consistency. To be continued in the next issue.