MTS Water Quality Guide - Manual (Page 18)

Heat Exchanger Care and Water Quality Guide 18 Heat Exchanger Care
Tube and shell heat
exchangers
1. Clean all filters and screens.
2. Begin with an external inspection of the heat exchanger. Visually inspect
for:
• Dents or bulges in the shell
• Extruded or damaged gaskets
• Corrosion
• Damaged flanges on the bonnets and hub or tube sheets
• Stress marks in the shell
• Signs of a previous repair
• Leakage
3. After you have completed the external inspection, continue with an internal
inspection of the heat exchanger:
A. Completely drain and inspect the tubing and internal parts to determine
the extent of cleaning necessary. If severe fouling or corrosion of the
tubes and/or bonnets of the tube and shell heat exchanger is found, then
disassembly of the heat exchanger may be necessary.
B. If disassembly of the heat exchanger is required, discard the old gaskets
and replace them with new ones. Visually inspect for the following:
• Damage to the tube ends due to corrosion or erosion
• Wearing of the zinc anodes (copper-nickel tubing units)
• Damage to the nozzle threads on the tube and shell side
• Erosion of the tubes under the shell side nozzle
Signs of any of the above conditions may indicate high flow rate with
particle entrainment in the fluid, or the presence of a corrosive
environment. Depending on the degree of degradation of the unit, it
may need replacement.
C. Inspect all zinc anodes and replace them if a marked corrosion is
visible. If they are coated with scale, remove the scale.
D. Unscrew and remove the bonnets, carefully inspect the tubes for
corrosion, erosion and any foreign materials and clean as required.
Note Protect the baffle plates and tubes from damage. Bent baffle plates will
cause in the hydraulic fluid to bypass the tube surface, resulting in a
decrease in heat transfer rate.
Be careful when you remove or handle the tube bundle of a removable
tube bundle exchanger.