53 Pa. Stat. § 22722
The Department of Supplies shall have the direction, control, and administration of the purchase and supply of all personal property required in the conduct of the business of the city. All other departments shall obtain such personal property by requisition upon the Department of Supplies, and not by purchase direct. The manner and form of such requisition may be prescribed by ordinance, or, in default thereof, by standing rule of the Department of Supplies. All appropriations of money for the purchase and supply of such personal property shall be made to, and be expended by, the Department of Supplies; and all contracts for the purchase of such personal property shall be made and entered into by and with the mayor and Director of the Department of Supplies, in the manner now required by law.
53 P.S. § 22722