The city may issue blanket purchase orders to provide a means for capturing total requirements of budgeted for noncapital items for a period of time not to exceed 12 months. Any blanket purchase orders, purchases from which are expected to exceed $20,000.00, shall be entered into using the procedures described in section 2-218. Other blanket purchase orders, purchases from which are expected to exceed $1,000.00, shall be entered into utilizing open-market procedures. Each purchase requisition issued against the blanket purchase order may be issued by the city purchasing agent without further approval. No blanket purchase order issued by the city shall confer upon any person the exclusive right to furnish the city's requirements for the supplies, services or construction called for by the blanket purchase order.