Warren Controls PICV Series - Manual (Page 14)

14
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VALVE PACKING LEAKS
The service life of valve stems and packing is dependent on
maintaining non-damaging fluid conditions. Inadequate treatment
or filtration, not in accordance with the recommendations of this
guide, or a qualified treatment specialist, can result in corrosion,
scaling, or abrasive particle formation. Scale and particles migrating
from pipe walls to control valves, will result in scratching the valve
stem, which will prevent the packing from sealing. This problem can
be avoided by the use of proper cleaning, treatment chemicals, and
storage procedures. Water must be treated and soft. Trace leaks of
hard water result in hard calcium carbonate particles on the outside
of the valve, which will scratch the sealing members creating a
packing leak. To avoid a damaging condition, the system should be
cleaned prior to start-up. Filtration equipment and strainers should
be employed as required and a regularly scheduled program of
water condition monitoring and treatment should be followed. Side
stream water filtration may be needed in closed systems, if there is
no regular blow down of the system.
Control valve ‘hunting’ will cause excessive stroking of the valve
stem and result in premature failure of the valve packing seal. The
system must be stabilized to ensure reasonable packing life and
optimal control performance.
Over sizing of a control valve will result in an un-stable condition,
can result in, noise, vibration, premature trim and packing seal
failure. The use of the Warren Controls ValveWorks sizing program
Will facilitate the selection of the optimum valve.
COMMISSIONING
Thorough flushing of the system is necessary before start-up as new
systems, or old systems that have been shut down for an extended
period of time, will usually contain dirt, Weld slag, solder flux, and
pipe scale.
Water hardness should be less than 100 ppm of hard water ions (Ca++, Mg++), where 17.1 ppm = 1 Grain Hardness. Additionally, levels of
chloride and sulfate should remain less than 25 ppm. When water hardness is at unacceptable levels, a water softener expert should be
consulted.
ANTIFREEZE SOLUTIONS-GLYCOLS
The commonly used heat transfer glycol fluids are, either ethylene glycol or propylene glycol. Glycol concentrations of <25% often do not
provide sufficient corrosion inhibiting properties and at levels <20% can actually provide a food source for bacteria. As bacteria consume
the food and die off, a highly acidic condition can result. The recommended concentration for popular glycol based solutions is 25% to 60%.
WATER QUALITY RECOMMENDED PARAMETERS
Chilled Water, Closed Loops, and Hot Water Systems up to 212°F (100° C).
8.0
< pH < 10.3
Conductivity < 3000 MMHS
Iron < 0.5 ppm
Copper < 0.5 ppm
100 ppm < Molybdenum < 150 ppm
(Mild Steel Corrosion Inhibitor)
200 ppm < Molybdenum < 250 ppm
(Mild Steel Corrosion Inhibitor)
400 ppm < Nitrite < 1000 ppm
(Mild Steel Corrosion Inhibitor)
Azole > 5 ppm free and available
(Yellow Metal Inhibitor)
Bacteria < 1000 cells/ml
(when system is cool)
Chilled Systems
Hot Systems
!
CAUTION
The use of hydrazine can
result in the formation of
ammonia and must be con-
trolled to prevent stress cor-
rosion and embrittlement,
which can lead to fracture
of some brass alloys.
STORAGE
Systems that are stored wet should be completely filled with
properly treated water and isolated to avoid slow leaks, which can
cause serious corrosion problems.
Drained system should be air dried, sealed, and treated with a
desiccant to prevent “atmospheric corrosion” of pipes, which is a
major source of pipe scale.