Emerson XDF Expansion Tanks, Fluid Relief Valves and Other Devices, Corrosion Protection

Piping Considerations—Water/Glycol Models Only

5.2.1Expansion Tanks, Fluid Relief Valves and Other Devices

An expansion tank must be provided for expansion and contraction of the fluid due to temperature change in this closed system. Vents are required at system high points to vent trapped air when fill- ing the system. A relief valve is also necessary.

Depending on the complexity of the system, various other devices may be specified. Pressure gauges, flow switches, automatic air separator, tempering valves, standby pumps, sensors for electrical con- trols and flow switches are just a few of these devices.

Manual shutoff valves should be installed on the supply and return lines. In addition, multiple pump packages require a check valve at the discharge of each pump to prevent back-flow through the standby pump(s). These check valves permit isolating units for routine maintenance or in an emer- gency.

Liebert also recommends installing these items in the system:

•cleanable, 60 mesh filters—These filters will trap the particles in the coolant supply line and extend the service life of the water cooled condenser.

•floor drains with wet traps or a leak-detection system, such as Liebert’s Liqui-tect

•hose bibs at the lowest point of the system to facilitate filling

•relief valve—to protect against burst water pipes

5.2.2Corrosion Protection

Read and follow individual unit installation instructions for precautions regarding fluid system design, material selection and use of field-provided devices. Liebert systems contain iron and copper alloys that require appropriate corrosion protection.

Contact a local water consultant regarding water quality, corrosion and freeze protection require- ments. Water chemistry varies greatly by location, as do the required additives, called inhibitors that reduce the corrosive effect of the fluids on the piping systems and components. The chemistry of the water used must be considered because water may contain corrosive elements that reduce the effec- tiveness of the inhibited formulation.

Surface waters that are classified as soft and are low in chloride and sulfate ion content (less than 100 parts per million each) should be used. Proper inhibitor maintenance must be performed to prevent corrosion of the system. Consult glycol manufacturer for testing and maintenance of inhibitors.

Commercial ethylene glycol, when pure, is generally less corrosive to the common metals of construc- tion than water itself. It will, however, assume the corrosivity of the water from which it is prepared and may become increasingly corrosive with use if not properly mixed with corrosion inhibitors. For further details on corrosion prevention, see 5.3.1 - Glycol Solutions.

Idle fluid allows the collection of sediment and that prevents the formation of a protective oxide layer on the inside of tubes. Keep the unit switched On and the system pump operating.

5.2.3Freeze Protection—Coolant Type and Insulation

Glycol solutions should be considered for use as a coolant to protect the coil against freezing and cor- rosion from water.

! CAUTION

Risk of frozen fluid. Can cause piping rupture and equipment damage.

When the field piping or unit can be exposed to freezing temperatures, charge the system with the proper percentage of glycol and water for the coldest design ambient to prevent freezing.

! CAUTION

Risk of frozen fluid. Can cause piping rupture and equipment damage.

Immediately after using water for leak testing or system cleaning, charge the tested system with the proper percentage of glycol and water for your coldest design ambient. Complete system drain-down cannot be ensured and damage to the system could result from freezing of residual water.

The minimum coolant temperature to be supplied to the XDF will determine whether the supply and return lines require insulation to prevent condensation.

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