The silencer depicted apears to be one intended to reduce noise. This type is not good at separating out water from steam. Usually these silencers are design to operate at 1/2 psi differential from the inlet to outlet at design flow. If you flow rate is higher first the mufflers become nosier than the specification states. If the DP gets large enough sometimes the baffles get damaged. The drain is intended for draining water out of the silencer, as if you do not drain the silencer the resulting water hammer can destroy it.
If you has a separator vent, those have baffles that spin the flow, it will sort liquid from steam, but for the situation you describe the drain probably needs to be close to the steam inlet size. This inquiry form lists the parameters needed for design
Disclaimer - while I have installed some exhaust hoods (one incorrectly) - I have never worked for Wright Auston, there are other suppliers, and it is possible to do this with a knockout drum.
Here are the startup procedure we used to solve this problem.
Open the system drains - ALL of them, including all of the trap strainers.
Open the end of line vent valves wide open.
Warm the boiler plant up with the distribution stop valves closed. Once the boiler plant is operating stably, if the distribution stop valves have warmup bypasses open them. Not too fast, as the goal now is to heat the distribution pipe slowly, measured by freely flowing steam at the system drains, and steam trap strainers. We found we needed to add bypasses as the original design did not size the bypasses to pass an appropriate steam flow for system warmup.
You or the responsible engineer needs to figure our the appropriate sequence to close the valves down. Too slow, delays warmup. Too fast creates water hammer. This part of the sequence is site specific, be aware that water hammer on startup can create enormous shock load forces. 500 lb water slugs flying down the pipe at near sonic velocities is capable of rupturing most piping, often anchors get damaged.
