In the world of natural gas liquification, turbine trip valves play a major role. There may be no piece of equipment that is more important to the safety of the plant and its personnel than a turbine trip valve. These valves are designed to completely cut off the flow if the turbo compressor encounters a challenge and stops for whatever reason. This automatic shutoff prevents the turbine from over-revving and potentially damaging the equipment.
These turbine trip valves, however, need to be specified correctly in order to properly function. There are many factors that ultimately affect this exercise. The first thing to determine is the maximum flow rate the valve must deal with. This flowrate will determine the size of the valve required. For many systems, a butterfly valve is the best option.
After determining flowrate, you need to look at the temperatures at play. How low will the temperature get in the process? With some operating at -100°C or colder, there can often be a need for thick piping insulation and valves need long stem extensions to keep critical components out of the cold zone.
Next, we look at torque. By analyzing required torque and cycle speed, we can calculate the maximum rotational force that the long stem extension will need to withstand. With this information, the proper actuator can be selected that can provide the required torque.
Once the valve and actuator are settled on, control components are the next piece of the puzzle. The pneumatic system must be modeled to allow the selection of solenoid valves and quick exhaust devices to vent the air from the actuator quickly enough to meet the trip requirements.
Then, the all-important tests. Each trip valve assembly must be tested and timed to verify it meets the trip speed requirement.
There is much more that goes into specifying a trip valve for LNG than initially meets the eye. In fact, I fleshed out this topic even more in an article I penned for
Gas Processing and LNG Magazine. If you haven’t already, check it out and give us a call for your next trip valve assembly.
Printer-friendly version