For various process reasons, horizontal drums often are furnished with what appears to be small vertical drum, called a boot, attached to the underside of the vessel.
Because the boot is inaccessible to themain drum platforming, special consideration must be given to the arrangement of additional platforming for access to the instrumentation on the boot.
In certain cases, drums must slope as shown below. If the nozzles are not perpendicular to the horizontal plane, all vertical piping runs from these nozzles must be calculated because they will be offset at an angle.
The dimensions, clearances and guidelines highlighted in this book are example of what can be used for drum arrangement.
The plant layout designer should be familiar with company and client standards. However before proceeding with drum layout and should coordinate the effort with such supporting groups as vessels, systems and process and instrument engineering.