When a facility is looking at adding a processing unit or increasing the throughput of a unit, oftentimes there are Safe Operating Limits or PSM limits due to the flare capacity. The flare system will need to be reviewed and extra capacity found or designed into the system in order to meet the business objectives. This is not a mere academic issue as in the US (per the EIA) there were ~200 operating refineries in 1985 with only 137 thirty years later; BUT the total US throughput has increased 25% over that same 30 years (or significantly more depending on how you quantify the increase in complexity).
Oftentimes the standard solution for this problem is to propose expensive solutions to the problem (instrumentation or dynamic simulations) prior to exhausting the simpler and more cost effective solutions
Our Engineers have solved this exact problem dozens of times in the past. We first perform a quick review of the design basis for the flare. More often than not we find "conservative" assumptions that when rooted out eliminate the need for the costlier studies. If these actions don't result in the needed capacity, we perform the more detailed (and costly) studies. The time spent in this step is not wasted as the baseline for the more complex studies is always more favorable (due to the elimination of conservative assumptions).
Need a little extra flare capacity, give our engineers a call. Oftentimes in a few hours of focused review, we can determine if more analysis will yield reduced demands and extra flare capacity or cost savings.