Valves are responsible for the flow and control of all gases and liquids. In many instances, you also want to control the pressure behind and in front of valves, but it is hard to do that without gauging the pressure. If the pressure is not sufficiently monitored, it could affect the efficacy of the valves in use. Here is how you can manage all of the above.
Incorporate Pressure Meters into the Line
Pressure meters for pipelines are easy enough to incorporate. Place one meter just slightly ahead of the valve, and one just behind the valve. By monitoring both gauges, you can tell how the pressure is acting in the line leading up to the valve, and how the pressure is acting when the valve is opened to release gas or fluid. If you need to check the pressure each time because it has to register in a safe zone, mark the gauges with a permanent dry-erase marker in the areas where the pressure would be safe and unsafe, or purchase gauges that are already marked for you (if you can find them).
If there are deviations in pressure, the valve may be working improperly. It may be failing, or it may not be tightened or closed all the way. Fiddle with the valve a bit to see if the deviations in pressure go away. If the deviations remain, you may have a faulty valve that needs replacing. If you replace the valve with the exact same type of valve, and you still have these issues, consider replacing the valve again with a different type of valve that may give you more control over the pressure, flow, and rate of what runs through it.
Consulting with an Engineer
If you are particularly worried about what a valve is or is not doing, consult with an engineer on the matter. He or she can take a look at the line, the valve, and the gauges you had installed to see if there is not something else that can be done. The engineer might have some alternative ideas on how to handle the situation, or improve on what is already present. The type of engineer you need is typically a mechanical engineer, although you could also tap a structural engineer in regards to the construction of the pipeline, its functionality, and its expected work load. The engineer might also have some ideas in regards to what valves would work best.