Rationes Decidendi:

An arbitration clause suspends the otherwise general jurisdiction of courts.
Arbitration is characteristic, inter alia, for the expeditious hearing of a case. However, the parties must not be deprived of certain fundamental rights, which litigation would otherwise guarantee. The mechanism of observance of these fundamental rights is represented by the posibility of the annulment of an arbitral award by a court.
Statutory grounds for the annulment of the arbitral award are the subject of public policy, and the parties cannot suspend or exclude these grounds or the possibility of the annulment of the arbitral award.
Post-hearing petitions and statements of fact, incorporated only in the final briefs of the parties, cannot be considered duly heard. Such petitions are procedurally null and void (non-existent).
The partial annulment of an arbitral award (annulment of only one or more, not all, of the orders pronounced by the arbitral award) is not possible. An arbitral award may only be set aside as a whole. Grounds for the annulment of an arbitral award only applicable to one of the orders are also applicable to the other paragraphs of the order.
The motion for the annulment of an arbitral award is not a regular remedial measure. It is a revision mechanism sui generis used in order to guarantee fundamental procedural rights. Consequently, the grounds for the annulment of an arbitral award have effects with respect to the entire decision on the merits; as opposed to a regular remedial measure applicable in litigation, it is not possible to set aside only one or more, not all, of the orders pronounced by the arbitral award.
When the court rules on a motion for the annulment of an arbitral award based on the allegation that the arbitrators decided ultra petita, the court must first establish the scope of the duly made and heard petition (statement of claim) on which the arbitration was based. Only after the scope of the petition (statement of claim) is established may the court decide whether or not the arbitral award is ultra petita.