Sanjib Banerjee, J.

The award is challenged on two main grounds, but it may not be necessary to conclusively decide on the legal issue involved in the first ground since the second ground appears to be good enough.

The agreement between the parties pertained to the development of a property at Wood Street. Disputes and differences arose between the parties, whereupon the respondents issued a letter on October 21, 2009 indicating their nominee as the arbitrator. The person named by the respondents understood the nomination to be the appointment and addressed a letter to the petitioners herein on December 1, 2009, though the letter erroneously records the date as November 1, 2009.

3. The arbitration agreement between the parties is short and simple and requires disputes and differences between the parties to the agreement to "be referred to arbitration in terms of provisions of the Arbitration and Conciliation Act, 1996." There is no procedure for constitution of the arbitral tribunal that is agreed to between the parties and recorded in the arbitration agreement. Ordinarily, when the arbitration agreement between the parties does not provide for the manner of constitution of the arbitral tribunal, it is open to the parties to subsequently agree on a procedure therefore, or it is open to one party to name an arbitrator or an arbitral tribunal and require the other party or parties to agree thereto. In the present case, the respondents took it upon themselves to nominate an arbitrator despite the agreement not reserving such right unto the respondents. Surprisingly, the petitioners did not raise any objection to the appointment either upon receiving the respondents' letter of October 21, 2009 or upon receiving the arbitrator's letter of December 1, 2009. Indeed, there were six sittings before the arbitrator till or about April, 2010 in which the petitioners herein participated. The reference may not have progressed much but directions were obtained for filing pleadings and the statement of claim was filed and extensions were granted for the counter-statement to be lodged.

4. It was only in course of the seventh sitting in the reference, in May, 2010, that the petitioners lodged an application questioning the arbitrator's authority to take up the reference. The challenge was fashioned under Section 16 of the 1996 Act, though the challenge was to the personnel of the arbitrator since the petitioners had not expressly agreed to the respondent's nominee to adjudicate upon the disputes covered by the arbitration agreement.

5. The petitioners' objection should, ideally, have been under Section 13 of the 1996 Act which permits a fortnight's time from the date of the challenger being aware of the appointment to question such appointment; but notwithstanding the nomenclature, the application had to be regarded as one under Section 13 of the Act. The petitioners did not avail of the opportunity afforded by the statute, acceded to the nomination made by the respondents, attended proceedings before the arbitrator and the appointment was, thus, perfected. Though Section 16 of the 1996 Act permits the arbitrator to adjudicate upon his own jurisdiction, including the existence and validity of an arbitration agreement, the nature of the objection that was carried by the petitioners herein ought to have been made under Section 13 of the 1996 Act, rather than Section 16 thereof. In such circumstances, it does not appear that the subsequent challenge to the appointment of the arbitrator after the petitioners had accepted the appointment could have been maintained under Section 16 of the 1996 Act, particularly, as there appears to be a distinction between the two provisions on the basis of the nature of the challenge. However, as aforesaid, a conclusive finding need not be rendered on such aspect since the award is otherwise vulnerable and liable to be set aside as it does not disclose any reason in support thereof.

6. Section 31 of the 1996 Act