Layout and Spacing of Exchangers & Air Cooled Exchangers | Plant Layout Levels

This article is about technical requirement as per international codes and standards for Layout and Spacing of Exchangers & Air Cooled Exchangers in power plants.

Layout and Spacing of Exchangers & Air Cooled Exchangers

Exchangers Spacing Requirements

The following general points should be noted:

1. Maintenance of exchangers involves blinding nozzles and testing; removing channel, shell, and floating head covers; cleaning tubes; and removing tube bundles or removing tubes from fixed tube sheet bundles or completely removing fixed tube sheet exchangers.
2. Facilities for bundle cleaning should be provided. Locate these facilities to avoid creating a housekeeping problem. Drains from this facility must connect to the oily water sewer system.
3. All exchangers with removable bundles shall have clearance equal to the bundle length or bundle extractor plus 5 m and extending 6 m on at least one side. Clearance at the back of the exchangers should be about 3 m for exchangers with removable shell covers. (See L-004, 13.3)
4. Exchangers in rows shall have a minimum clearance of 1 m between shell flanges and shall have their shell covers in line. This clearance should be increased for hot exchangers requiring onstream cleaning.

Stacking exchangers conserves plot space. Exchangers 1.2 meter in diameter and smaller may be stacked three high. Exchangers 1.5 m in diameter may be stacked two high. Exchangers over 1.8 m in diameter, or those with tube bundles weighing over 19 MT, should not be stacked.

Equipment should not be located above heat exchangers containing flammable or combustible liquids over 260 °C.

Trolley beams may be required above heavy exchangers for removing covers and tube bundles where mobile equipment is not available. If bundle extractors are not used, anchor columns or beams are required for pulling heavy tube bundles. Overhead condensers and barometric condensers in a structure shall be provided with platforms for maintenance. Adequate area shall be provided for onstream cleaning.

Facilities for chemically cleaning exchangers in situ shall be provided where specified.

Air Cooled Exchangers Spacing Requirements

1. Air-cooled exchangers are usually mounted over pipe racks when elevated air coolers are required. When elevation is not required, sufficient plot space is available, and only a few exchangers are required, these exchangers may be located at grade level.
2. Vessels and/or pumps containing flammable or combustible liquids shall not be located beneath air coolers. Air coolers should be spaced 15 m from positive ignition sources such as fired heaters. Heat exchangers containing hydrocarbons over 260 °C shall not be located beneath air coolers.
3. Pumps containing flammable or combustible liquids may be located adjacent to (but not beneath) air coolers provided they are protected by fire intensity control water sprays. However, pumps containing flammable liquids over 3450 kPa, gage discharge pressure or hot oils over 260 °C should be located a minimum of 3 m horizontally from air coolers if fixed water spray protection is provided or 4.5 m if fixed water spray protection is not provided. (See Figure 1)
4. An extensive platforming system is required in front of exchanger header boxes.
5. Platforms are required below the air cooled exchangers for maintenance access to exchanger motors and fan drives. These platforms must allow access without scaffolding. When air coolers are located on top of the piperack and a significant number of bays are required, a rolling platform should be considered instead of fixed platforms. The selection should be based upon economic evaluation.
6. Material handling and drop areas must be provided.
7. When the air cooler is located over a process unit pipe rack, the clearance between the lowest portion of an air cooler and the uppermost pipe or cable tray should be 2.4 m minimum. To the greatest extent possible, critical cable trays should be routed underground or, at a minimum, away from high fire potential process equipment, such as air coolers. Flanges and valves in hydrocarbon pipelines should be minimized beneath an air cooler. Multiple flanges and valves such as in control stations should not be located under air coolers.

Read Main Aritcle of: Safety Considerations for Plant Layout Levels