Before a natural gas processing plant or similar processing facility can begin operations, the facility must go through the final stage of preparations: start-up and commissioning. The activities performed during the start-up and commissioning phase should ensure that the facility will operate safely and according to the facility’s design.
This phase is most often included in an EPC turnkey contract. During this time- and labor-intensive process, engineers, field technicians, and operations personnel will comb through every inch of the facility, checking thousands of connections, instruments, valves, and equipment. For complex facilities, it may take weeks or even several months to complete.
Some of the specific tasks involved in start-up and commissioning include:
As construction draws to a close, the start-up and commissioning manager will create a completion checklist. This list will provide the verification that every element of the facility is finished. All mechanical, electrical, piping, and auxiliary components are checked off as they are completed. All secondary components, like office space for the operators and break rooms, are also included. The clients and their EPC contractor work together to make sure that expectations for the facility are met.
Once the completion checklist is squared away, mechanical verification can begin. Engineers will thoroughly examine all the piping and instrumentation to ensure that it has been installed as indicated on the Piping and Instrument Diagrams (P&IDs) and mechanical design drawings.
Valves will be inspected to make sure they meet the pressure and temperature ratings of their piping system. Proper access to the valves and orientation/functionality of the valves are evaluated at this time as well. Pressure safety valves (PSVs) receive an extra thorough inspection process. PSVs are an important safety feature for natural gas processing plants because they prevent piping and equipment from being over pressured, which could lead to critical equipment failures or loss of containment to the surrounding environment. These valves are checked to make sure that they are installed in the correct locations and that the PSVs have the correct set point.
All the vessels, columns/towers, heat exchangers, heaters/flares, and tanks will be checked to make sure they are installed properly and that all the required connections are accounted for and connected properly. Grounding connections, heat tracing (if required), insulation (if required), and the paint will also be inspected at this time.
Additionally, the drivers for all the rotating equipment are “bump tested” to confirm that they have the proper rotation. Control valves are also inspected to confirm that the appropriate valve has been used in its designated location.
Instrumentation and Electrical Check Out
Once a mechanical system is given the green light, Instrumentation and Electrical Check Out can begin. The control system for the natural gas processing facility must be carefully tested. The general purpose of this inspection is to verify that the control system is connected properly to the components and they all function as designed.
Electrical wiring is inspected for safety and quality. All electrical systems are compared to design schematics and drawings. Electric motors connected to fans, compressors and pumps are also examined. After the inspections are completed, the functionality of each connection (Loop) is then tested by performing “Loop Checks”. The loop checks involve testing each control loop over the control system and having an operator verify in the field that the physical device is doing what the control system is telling it to do or reading the proper value, if it is a measurement device.
The control system also has a variety of alarms and safety systems. These indicate when the measured system variables, such as pressure, temperature, level, or flow, strays far enough away from the normal design point that the operator needs to be alerted about it because the equipment/plant could be in danger. These are tested by using electrical signals to confirm that the sensors are functioning, and the appropriate alarms will go off when certain conditions are met in the process or around the facility.
Throughout the inspection/testing process described above, engineers or other staff will document any changes that are made. After the work is completed, those systems will be inspected once more.
With a facility as complex as a natural gas processing plant, some troubleshooting is to be expected. However, an experienced engineering and design team and quality craftsmanship from an EPC contractor will go a long way toward a smooth inspection process.
Starting-Up Your Natural Gas Processing Facility
Once the client and contractor are satisfied with all of the inspections/tests and both parties have signed off on the facility, the start-up process can begin.
Before a product can be introduced into the system, all of the air must be purged from the equipment and piping. Typically, this is achieved with a dry, inert gas such as nitrogen, but dry natural gas or liquid hydrocarbon may be used as well for the parts of the plant where those are appropriate. Once the air has been purged out, the facility can be started systematically.
Keys to Success for Start-Up and Commissioning
When making such a large infrastructure investment, both hard and soft strengths of the firm are important. A firm’s integrity, quality, and commitment to safety are as important as the technical skills required to design and build the facility. Choosing a firm with a solid reputation in both areas will serve you in this phase of the project and throughout the life of your facility.
Whether you plan to engage an EPC contractor for a turnkey project or you prefer to manage some of the construction inhouse, attention to detail is paramount, especially as you prepare for operation. The safety of the facility will be directly impacted by the quality of the work in the start-up and commissioning process.
Start-up and Commissioning should not be brushed over in the push for operations. These checkouts and inspections serve as the final failsafe for your facility. It is no easy feat to carefully inspect thousands of components that make up a natural gas processing facility. This phase of the project must be proactively managed to stay on track and avoid delays.