5 Arrangement for Common Equipment
5.1 Arrangement for Towers and Vertical Vessels
5.1.1 Tower and its associated equipment，such as feed furnaces，non-fired reboilers，overhead condensers，reflux drums and bottom draw-off pumps，should be located near to the towers as per P&ID.
5.1.2 Arrangement for towers and vertical vessels shall comply with the following requirements：
1 Towers and vertical vessels arranged in single row should have their centerlines or tangent lines aligned；
2 Towers and vertical vessels with small diameter and large height may be arranged in double rows or in triangle form；
3 Towers and vertical vessels with diameter equal to or less than 1m should be arranged in structures or on one side of the structures.
5.1.3 Towers and vertical vessels should be arranged on both sides of the piperacks，in case no equipment is arranged above piperacks.Maintenance areas or accesses shall be reserved on one side of piperacks，in case equipment is arranged above piperacks.
5.1.4 Maintenance areas or accesses should be provided on one side of the towers and vertical vessels，and manholes should be faced towards maintenance side.
5.1.5 The spacing between tower（large vertical vessels）and piperack shall comply with the following requirements：
1 In case pumps are installed between tower and piperack，the spacing between tower and piperack shall allow for pump operation，maintenance and piping arrangement；
2 In case no pumps are installed between tower and piperack，the distance from the exterior surface of the tower to the centerline of piperack column should not be less than 3m.
5.1.6 In addition to satisfying the arrangement and installation requirements for piping，platforms，instruments and small equipment，the spacing between towers or between tower and adjacent equipment shall also meet the operation and maintenance requirements.The clearance between two towers should not be less than 2.5m.
5.1.7 Elevation of towers and vertical vessels shall comply with the following requirements：
1 In case the fluid is delivered to other equipment or piping by internal pressure or gravity flow，the elevation of towers and vertical vessels shall be determined according to the internal pressure of the towers and vertical vessels，the operating pressure and elevation of the equipment or piping to which the fluid is delivered，and the pressure drop of the transfer piping；
2 In case towers and vertical vessels are designed with draw-off pumps，their elevation shall be greater than the net positive suction head required for the pumps（NPSH）r；
3 In case of towers with non-fired reboilers，their elevation shall be determined according to the relative location of towers and reboilers，and the operation requirements；
4 The elevation of towers shall provide a minimum overhead clearance required for installation and operation of the piping of the towers bottom，and the elevation of the tower foundation shall be at least more than 200mm above the ground；
5 If combined platforms are designed for grouped towers，the heights of towers may be properly adjusted to have the platforms at the same elevation.
5.1.8 When the sectional towers are arranged in the structures，the permanent overhaul and hoisting facilities shall be provided in the structures if mobile hoist is unavailable.