Working for an EPC firm myself, my experience is that such a situation might arise from a number of reasons, in order of common-ness:
(1) The Package Engineer has simply attached a standard specification or data sheet that has not been completely reviewed and modified to suit the site-specific situation.
(2) The client has a specification that he does not want to deviate from.
(3) The skid may be going into a facility with a "life after life" expectation that, at some point in future, it may be relocated and, as such, it might in future require hazardous area classification.
(4) There may be impacts associated with start-up and maintenance spares if general purpose devices are on a skid in a facility that otherwise would not stock them.
Not sure where you are at in the BEA (or post BEA) process but a summary of the cost and delivery credits available to the customer if the area classification is downgraded is typically what is needed and welcomed by clients and their consultants in order for them to make an informed decision.
Regards,
SNORGY.
