Comprehensive Guidelines for Controlling Leaks of Flammable and Explosive Materials in the Fine Chemical Industry (Including the “Work Permit for Opening Pipeline Equipment”)

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In the production of fine chemicals, flammable, explosive, toxic, and corrosive materials such as methanol, toluene, and synthetic intermediates are widely used. Compared to sudden explosions, leaks that are difficult to detect and occur frequently pose a far more serious safety threat. A single leak at a flange, a loose valve, or a detached hose can all lead to fires and explosions, poisoning of people, environmental accidents, and production disruptions. By taking into account the characteristics of fine chemical production, this article identifies the root causes of leaks, implements comprehensive control measures, and strengthens the safety safeguards. I. Awareness of leaks: A deadly hazard in chemical production. Chemical synthesis workshops, raw material storage areas, as well as solvent transportation and intermediate transfer processes are areas where leaks occur frequently. The vast majority of leaks are not due to sudden equipment failure, but rather to repetitive hazards resulting from operational mistakes and inadequate inspections; the consequences of such leaks amplify exponentially, leading to fires and explosions, injuries to people, environmental violations, and production disruptions. Core principle: Flammable and explosive materials must be securely contained within equipment, pipelines, and storage tanks. In the context of fine chemical production, the most common types of leaks and their underlying causes include failed gaskets/seals, improper installation of pipeline flanges, lack of proper inspections before starting up operations, tank overfilling, leaks in jacket systems, improper handling of transfer containers, and corrosion of equipment and pipelines. All of these are minor hazards that can be prevented and controlled. II. Two-dimensional and three-dimensional control system: An integrated approach of engineering measures, behavioral protocols, and institutional frameworks. Given the intermittent nature of production in fine chemicals, the variety of solvents used, and the high corrosivity of certain substances, a three-in-one control system is established to prevent leakage risks at the source. (1) Engineering controls: Hardware-based preventive measures against leaks. 1. Strictly enforce a 100% blind flange installation policy; the ends of solvent pipelines and sampling points must not be sealed solely with valves, and sampling of highly toxic solvents must be carried out using sealed samplers ； 2. Flange assembly follows the four-step process of \"cleaning—aligning—matching—tightening\", using corrosion-resistant gaskets suitable for the material environment ； 3. The solvent storage tank is equipped with dual protection mechanisms: a high liquid level alarm and an interlock shutdown function at extremely high liquid levels, to prevent control based on only one liquid level indicator ； 4. The delivery hoses are of a pressure-resistant and corrosion-resistant type; pressure tests are conducted annually, and the sealing rings are replaced regularly ； 5. Release pressure before opening the filter cover; the transfer tank is sealed, stacking should not exceed 2 meters, and a secondary liquid collection tray should be provided. (II) Code of Conduct: Adhering to Standard Operating Procedures 1. For material transfer, follow the five-step verification method of \"checking pipelines, valves, lids, capacity, and hoses\" ； 2. During material transfer operations, adhere to the three \"no’s\" and two \"musts\": no reliance on interlocks, no leaving the post without permission, no illegal material transfer; it is necessary to inspect the pipelines and confirm the transfer process ； 3. After maintenance, adhere to the “Four Musts and Four Don’ts”; the system must not be put into use without double verification. Serial Number | Required Content | Core Requirements | Safety Significance
1 | Mandatory comprehensive inspection | The quality of equipment maintenance must meet design standards; key parameters must be within specified limits, and individual or combined tests must pass. This prevents the equipment from operating with defects and avoids accidents caused by mechanical failures.
2 | Restoration of safety facilities | All temporarily removed protective covers, guards, interlocks, safety valves, etc., must be reinstalled and verified to restore intrinsic safety, thereby preventing injuries to personnel and process control losses.
3 | Site cleanup and inventory check | The work area must be thoroughly cleaned; tools, parts, and waste materials must be removed completely, leaving no residues. This prevents foreign objects from entering the equipment and causing jams or blockages, as well as eliminating fire hazards.
4 | Closure of work permits and documentation | All maintenance work permits, hot work permits, etc., must be formally closed with complete signatures, and maintenance records must be properly archived. This creates a safety closure loop that facilitates tracking and responsibility determination.

Serial Number | Prohibited Actions | Risk Consequences
1 | Starting the equipment prematurely | Starting the equipment without inspection or safety verification may lead to serious accidents such as leaks, explosions, or mechanical injuries.
2 | Failing to maintain isolation measures | Failure to remove blind flanges, reset valves, or restore power supply can result in system disruptions, abnormal pressures, and impaired equipment operation.
3 | Ignoring leak checks | Failure to conduct airtightness tests or leak inspections on equipment, pipes, flanges, and other connections can lead to leaks of flammable/toxic substances, causing fires, explosions, or poisoning.
4 | Omitting personnel training | Failure to inform operators about the equipment’s condition after maintenance and the key operating procedures can lead to misoperations that cause equipment damage or casualties.

(III) Institutional safeguards: Strict rules to eliminate reliance on luck. Maintain records of sealing integrity, with item-by-item signature confirmation prior to solvent addition ； Include pipeline pressure testing, hose inspection, and flange inspections within the process safety management system to establish a regular inspection record-keeping system. III. Red Lines for Operations and Self-Inspection Checklist (1) Red lines for pipeline disconnection operations: A work permit for installing or removing blind flanges must be obtained when disconnecting pipelines, and a HAZOP risk analysis must be carried out. It is assumed that the pipelines contain hazardous materials; therefore, the end of the pipeline farthest from human beings should be opened first. It is strictly prohibited to disassemble or assemble the pipelines without authorization. (II) Rapid self-check checklist: Compliance standards for inspection items, common vulnerabilities. Blind flanges installed at the ends of pipes; sufficient bolts, but sealing relies solely on valves. Flange gaskets are properly matched and tightened diagonally; gaskets are aged or bolts are missing. Transport hoses must be pressure-resistant and corrosion-proof, with annual test records; ordinary hoses are used as substitutes. Solvent storage tanks should have dual-level interlocks to automatically stop feed flow; control is based on a single level only. Emergency supplies and leak-sealing tools should be readily available; shortages or expired items exist. In cases of leaks in fine chemical industries, the root cause lies in carelessness and operational negligence.