Describe the best practices for safe commissioning of a new gas-handling system, including essential tests and validations that should be performed before placing the system into operation.

The safe commissioning of a new gas-handling system is a critical process that involves a series of well-defined steps and meticulous validation procedures to ensure the system operates safely and reliably before it is put into service. These best practices cover the entire commissioning phase, from initial checks to final operational tests, focusing on safety, functionality, and adherence to regulatory standards.

First, a thorough review of all design documents and specifications is essential. This step involves verifying that the system's design meets the required standards and codes, and that all equipment is specified correctly for its intended purpose. This includes reviewing the process flow diagrams (PFDs), piping and instrumentation diagrams (P&IDs), equipment specifications, and material safety data sheets (MSDS) for all gases involved. For example, before commissioning a new hydrogen gas storage system, the piping design must be reviewed against all relevant codes for hydrogen gas handling, verifying material compatibility and ensuring the system is appropriate for the working pressure and temperatures.

Next, a detailed pre-commissioning checklist should be completed, ensuring that all components have been correctly installed and are in proper working condition. This checklist should cover all aspects of the system, such as verifying the proper installation and orientation of valves, regulators, pressure gauges, and other instruments, ensuring correct wiring and connection of electrical components and control systems, and confirming the availability of all required safety devices, such as gas detectors and emergency shut-off valves. This stage ensures that all the equipment is ready to start the commissioning. For instance, for a new oxygen pipeline in a hospital, the pre-commissioning checklist would include confirming the correct identification and installation of all pipeline segments, the correct assembly of fittings, and the proper functioning of regulators and flow control devices.

Following the pre-commissioning checks, a pressure testing procedure should be performed to ensure the integrity of the piping system. This test is typically done with an inert gas, such as nitrogen, to prevent the formation of a flammable mixture. The piping system is pressurized to a level exceeding its intended operating pressure, and the pressure is held for a set duration. Any pressure drop would indicate a leak which must be addressed and fixed. After a fix, the system must be retested. For instance, in commissioning a new liquefied petroleum gas (LPG) distribution system, the piping is pressurized with nitrogen to a level higher than the working pressure to detect leaks or mechanical failures before introducing the gas itself. This test must be documented as part of the commissioning record.

Once the piping integrity is confirmed, the next step involves purging the system to remove any air or other contaminants. This procedure replaces the air in the system with an inert gas, such as nitrogen, to prevent the formation of a flammable mixture when the flammable gas is introduced. Purging must be done carefully following all safety protocols. For example, when commissioning a new ammonia storage tank and its associated piping, a purge using nitrogen will remove any air in the system, preventing a flammable condition when the ammonia is introduced.

After purging, the gas is introduced to the system in a controlled and gradual manner. The entire system should be monitored during this phase to detect any leaks or unusual behavior. This includes continuously monitoring pressure, temperature, and gas concentrations using calibrated instruments. Localized leak testing is used to check all connections and fittings after the gas is introduced. For instance, during the initial introduction of natural gas into a distribution pipeline, pressure is slowly increased while checking the system and all connections for any indications of leaks or abnormal operation using hand held gas leak detectors.

Finally, operational performance tests must be conducted to verify that the system functions correctly under normal operating conditions. This includes verifying the correct functioning of all control systems, alarm systems, and safety devices, and that it performs at the designed capacity and meets the performance requirements. This is done before the system is brought online. For instance, after commissioning a new biogas processing plant, the system is tested under typical operating conditions to verify that the gas flow rate, pressure regulation, and flare system are all performing as designed and meeting regulatory standards.

Documentation is a critical aspect of the commissioning process. Records should be maintained for each step of the procedure, including the design review, pre-commissioning checklist, pressure testing, purging, gas introduction, and operational performance tests. This documentation will be needed for future maintenance and compliance purposes. All checklists and tests should be signed and approved by qualified personnel. Furthermore, all personnel must be fully trained on the safe operations of the new gas handling system before it is brought online.

In summary, the safe commissioning of a new gas handling system demands a comprehensive, methodical approach that emphasizes thorough design reviews, detailed inspections, rigorous testing, and robust documentation. By adhering to these best practices, facilities can ensure the system is safe, efficient, and reliable before putting it into service.