The basis of protection in the case of intrinsically safe systems is the limitation of energy into the hazardous area. A document detailing permissible energy levels in the system is an essential requirement. It enables you in the first instance to prove the protection method, and in the event of modifications is a reminder of the safety restrictions.
An Intrinsically Safe Descriptive System Document demonstrates compliance by proving that the energy limiting device, the barrier, is compatible with the field device in terms of power, capacitance and inductance values.
These are documents that are often hard to come by, particularly in older establishments. In keeping with their importance it is necessary at times for us to rewrite them using information gathered from the installation itself.