Restriction Orifice in Lube oil rundown tank filling line

Dear all,
In run down tank of lube oil system of compressors there are two restriction orifices as you can see in drawing attached. Problem ( in our particular situation ) is in start up condition when filling time of run down tank when HV1303 is fully open, time duration of filling tank is 40 minutes as this time does not satisfy operators and they need to decrease it so they can start compressor immediately after power loss when tank gets empty after coast down time. my question is if we can increase bore diameter of FO1303 to decrease time by filling tank quickly as possible? what are constraints regarding this matter? Is there any calculations that are required to calculate this timing based on our needs? what is purpose of FO 1303 while there is another one FO1302, I mean does not it enough to have only FO1302 and why we need to have FO 1303 after gate valve? Any answer would be appreciated. Thanks to all.