Flush alleys

Alleys can also be cleaned by flushing. Grade is critical and can vary between 1.25 and 5 percent. It may change for long flush alleys. The alley should be level perpendicular to the centerline. The amount of water used for flushing is also critical. An initial flow depth of 3 inches for underslat gutters and 4 to 6 inches for open alleys is necessary.

The length and width of the flush alley are also factors. Most flush alleys should be less than 200 feet long. The width generally varies from 3 to 10 feet depending on animal type. For underslat gutters and alleys, channel width should not exceed 4 feet. The width of open flush alleys for cattle is frequently 8 to 10 feet.

Table 10-1 Recommended total daily flush volumes ^^^^ (MWPS 1985)

Flush alleys and gutters should be cleaned at least twice per day. For pump flushing, each flushing event should have a minimum duration of 3 to 5 minutes.

Tables 10-1 and 10-2 indicate general recommendations for the amount of flush volume. Table 10-3 gives the minimum slope required for flush alleys and gutters. Figures 10-4 and 10-5 illustrate flush alleys.

Several mechanisms are used for flushing alleys. The most common rapidly empties large tanks of water or use high-volume pumps. Several kinds of flush tanks are used (fig. 10-6). One known as a tipping tank pivots on a shaft as the water level increases. At a certain design volume, the tank tips, emptying the entire amount in a few seconds, which causes a wave that runs the length of the alley.

Table lO-2 Flush tank volumes and discharge rates (MWPS 1985)

Initial flow depth, in.

Tank volume, gal/ft of gutter width

Tank discharge rate, gpm/ft of gutter width

Pump discharge, gpm/ft of gutter width

1.5

30

112

55

2.0

40

150

75

2.5

45

195

95

3.0

55

255

110

4.0

75

615

150

5.0

100

985

175

6.0

120

1,440

200

Table 10-3 Minimum slope for flush alleys (MWPS 1985)

Animal type gal/head

Swine Sow and litter Prenursery pig Nursery pig Growing pig Finishing pig Gestating sow

Dairy cow

Beef feeder

Table 10-3 Minimum slope for flush alleys (MWPS 1985)

Underslat Open Alley Open Alley alley narrow width wide width

Underslat Open Alley Open Alley alley narrow width wide width

Initial flow

3.0

1.5

2.0

2.5

4.0

5.0

6.0

depth, in.

Slope, %

1.25

2.0

1.5

1.25

5.0

4.0

3.0

Some flush tanks have manually opened gates. These tanks are emptied by opening either a valve, a stand-pipe, a pipe plug, or a flush gate. Float switches can be used to control flushing devices.

Another kind of flush tank uses the principle of a siphon. In this tank the water level increases to a given point where the head pressure of the liquid overcomes the pressure of the air trapped in the siphon mechanism. At this point the tank rapidly empties, causing the desired flushing effect.

pumps. If struvite formation is anticipated, recycle systems should be designed for periodic clean out of pumps and pipe. A mild acid, such as dilute hydrochloric acid (1 part 20 mole hydrochloric acid to 12 parts water), can be used. A separate pipe may be needed to accomplish acid recycling. The acid solution should be circulated throughout the pumping system until normal flow rates are restored. The acid solution should then be removed. Caution should be exercised when disposing of the spent acid solution to prevent ground or surface water pollution.

Most flush systems use pumps to recharge the flush tanks or to supply the necessary flow if the pump flush technique is used. Centrifugal pumps typically are used. The pumps should be designed for the work that they will be doing. Low volume pumps (10 to 150 gpm) may be used for flush tanks, but high volume pumps (200 to 1,000 gpm) are needed for alley flushing. Pumps should be the proper size to produce the desired flow rate. Flush systems may rely on recycled lagoon water for the flushing liquid.

In some parts of the country where wastewater is recycled from lagoons for flush water, salt crystals (struvite) may form inside pipes and pumps and cause decreased flow. Use of plastic pipe and fittings and pumps that have plastic impellers can reduce the frequency between cleaning or replacing pipes and

Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment