It comes down to the type of explosion or fire and which units/equipment is damaged. Some long lead equipment takes years to procure. If a typically reliable equipment got blown up, there might not be a spare in a warehouse, since it's not expected to break. If it was just some piping and small valves, those can be replaced fairly quickly.
Well, as a starter, a typical heavy refinery eqipment is as strong as the sidearmour of a main battle tank.
Additionally, all refinfery has few hundred, or thousand count maintanance team, whom has decades worth of experience about the equipment.
They have spares, and usually the equipment accross internal plants similar or same.
Means, if you destroy the pumps of the main fractional distillation column third time, and they haven't got more spare then they will switch off a less important plant , and raid the pumps and valves of it.
Worst case they can't make the proper diesel : Petrol : kertosene ratio,and has to store excess heavy for bit longer time.
There are engineers in the plant, and if needed they will re-design the equipment to continue the process.
So, to cause real harm you need to drop lot of bombs, periodically, and destroy lot of equipment .
And of course, in half year time the new spares manufactured, so this process needs to repeated continously, and with increased speed.
Bescause they are not stupid, so the supliers will start to make more equipment epxecting repeated strikes.