IBM 7014 T00, Руководство пользователя

Страница: 175 / 196

Avoiding water-related problems
The following best practices can be used to avoid water-related problems:
• Design clean - Restrict the water-wetted metallurgies to copper alloys and stainless steels. Avoid the
use of plain-carbon steel hardware that can rust and foul the water cooling loop.
• Build clean - Ensure that the cooling loop components are clean and free of bacteria and fungi. The
cooling loop assembly must be free of soldering, brazing fluxes, or both. Clean water must be used in
the assembly operations. Any residual water must be blown out of the assembly. The finished assembly
must be clean and dry.
• Ship clean - Any residual water from the assembly, testing operations, or both must be blown out from
the cooling loop before any shipping to avoid corrosion and microbiological growth. As a final step, use
nitrogen gas to dry the system. Plug ends and ship the system with the cooling loop pressurized with
nitrogen gas.
• Install clean - The cooling loop must be kept clean during the installation step. Brazing is preferred over
soldering. Problem with soldering is porous joints that keep leaching out flux residue. All flux residues
must be cleaned off. Fill the system with clean water and, if possible, include a secondary step to
deionize the water in the cooling loop before the addition of biocide and corrosion inhibitors.
• Maintain clean - Monitor and maintain the pH, water conductivity, bacteria count, and the corrosion
inhibitor concentration.
Water quality requirements
Use the following requirements to plan for the water quality in your system:
• The water that is required to initially fill the system side cooling loop must be reasonably clean,
bacteria-free water (less than 100 CFU/ml), such as demineralized water, reverse osmosis water,
deionized water, or distilled water.
• The water must be filtered with an in-line 50 μm filter.
• If reasonably clean water is not available, the following guidelines are recommended. It is especially
useful for large cooling loops: In this method, the water is deionized before any of the racks are
connected to the water loop.
– It is important to ensure that the system water is cleaned before any chemicals are added to the
water. This can be accomplished by deionizing the water by using deionizing cartridges that are
installed in the cooling loop. Even if deionized water is used to fill the system, a deionizing step is
prudent for two reasons: the first is to ensure that the starting water is deionized and the second is to
remove any ions that might leach off the walls of the cooling loop.
– When the water needs to be deionized, the valves V2 and V3 can be opened and valve V1 partially
closed to bypass some of the water through the deionizing canister.
– During this deionizing step, the cooling loop and the computers can keep operating normally.
– When the deionization is complete, the V2 and V3 valves must be closed and V1 fully opened.
– The deionization step raises the resistivity of the water greater than 1 MΩ.cm.
– Under normal operation, the V2 and V3 valves are closed and V1 valve is fully open.
Racks and rack features 161