Your title ask for help on saddle design, but your post ask for help on designing tanks for explosion. What is really your question?
The only explosion related experience I have to share with you is the reactor section from a sulphur reactor. The heat transfer section of a sulphur plant reactor has to be designed to handle the case of an explosion from the furnace section, which is also attached to the heat exchanger shell. The sulphur plant licenser stated the shell shall also be designed for an high upper end temperature in case of an explosion. I don't recall what that temp is but I think it is in the 700°C range. "Additional" pressure was not a factor in the design as you would have a device called a PSV which is set at MAWP+10%. Of course, allowable stress is directly related to the "design temperature". So, draw your conclusion from this information. Hope this helped.
Perhaps the issue is what happens in the design of saddles when you have horizontal forces acting on the tank. To my knowledge, this is not covered in normal PV references. I think the more critical application would be seismic loading.
If the horizontal forces are fairly small relative to gravitational forces, you find the resultant force and treat the saddle as though the saddle angle were smaller by that amount (IE, 150 degree saddle with resultant 10 degrees off vertical, design as 130 degree saddle).
It is similar to wind design for a vessel on a platform. This force is usually much higher than the wind force. I don't understand what the blast force is. Hurricane? waves?
You mentioned "vessel on a platform". I'm assuming you're referring to an offshore platform. Refer to the link below and see if you can get something out of it...
Maybe lsthill meant for people to Google "Claus Reactor" or "Claus Process" the most main gas desulfurizing process used.
Re Saddle design for external forces: You can either use a pressure vessel software and use either the wind loading or seismic design to artifically increase the horizonal loadings to match the forces that you want to apply.
As an alternative, there are basic FEA programs (I use one from Paulin) that will analyze saddle supports under any imposed loading conditions.
