MIL-HDBK-1164
F2 = measured flow rate (gpm or L/min)
Note: If the error is greater than 3 percent, make the necessary
adjustments.
(3)
Twice a year, check the pressure pipelines to the float
chamber and clean and remove encrustation to allow for free flow.
(4)
Once a year, clean the float and check the mercury for
replacement. If necessary, paint the interior and the exterior of the float chamber and
other parts to protect against corrosion.
11.5.5.9 Piping and Valves. Each month, check for leaks at the joints. Also check the
pipe hangers and replace any that have deteriorated. Paint piping, valves, and
hangers if necessary to prevent corrosion. Maintenance procedures for valves appear
in Section 8.
11.5.5.10 Maintenance Schedule. The maintenance operation frequency and
schedule of inspections for filtration are presented in Table 36.
11.5.6
Pressure Filters. Pressure filters need the same care and attention as
gravity filters. Open these filters regularly and inspect them carefully. The following
maintenance procedures apply:
a)
Inspect piping and valves for leaks each week. Lubricate and
repack valves if necessary.
b)
Open the pressure shell and inspect the filter bed surface each
month. Follow procedures described in (1) through (6).
(1)
Use a garden rake or probe during backwashing (while the
manhole is open) to test for mud balls in the lower part of the filter bed and for
evenness of the gravel layer surface.
(2)
Determine whether the sand bed level has changed since
the last inspection by comparing the bed surface elevation with some reference point.
(3)
If the filter does not have a surface wash system and shows
evidence of mud balls, backwash it at the highest rate possible while jetting the surface
with a stream of water from a high-pressure hose. Install a permanent surface wash
system.
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