Updated publication for calibrations of stationary and traveling systems

Amanda Hatcher- Livestock Agent Duplin County, Publication courtesy of NCSU, AG-553-09

North Carolina State University has released an updated version of “Calibration and Uniformity Assessment for Animal Wastewater Application Equipment” to give updated information on hard hose travelers and solid set systems. Irrigation systems wear and develop buildup, which affects their performance, both from an irrigation quality standpoint and from an economic standpoint. Calibrations are required once every two years for swine facilities in North Carolina with a state general permit and required once a year for swine facilities with an NPDES permit.

Here is a summary and how it will affect the calibrations you do:

· Before starting the calibration, you’ll need a manufacturer’s chart for your system’s sprinkler and nozzle combination, your irrigation design or wetted acreage determination.

· Perform calibrations during periods of no to very light wind (less than 5 mph)

· Check wetted diameter and flow under periods of normal pressure

For hard-hose travelers and stationary systems (solid sets), the following steps are needed:

1) Measure the nozzle size of traveler guns

2) Measure pressure at the nozzle or sprinkler

3) Measure the wetted diameter of the nozzle or sprinkler

4) Measure the flow rate, and

5) Compare the measured pressure, wetted diameter, and flow rate against the manufacturer’s chart, irrigation design documents, and/or the wetted acreage determination.

Equipment needed to complete a calibration:

1) Pressure gauge, either a mounted gauge or a hand-held with pitot tube

2) Flow meter with in-line adapters IF field-measured nozzle pressure and manufacturer’s charts will not be used to obtain flow rate

3) Measuring tape or wheel (need about 200-300 feet of tape)

4) Flags for checking wetted diameter

5) Caliper for measuring nozzle size, and

6) Calibration forms for recording measurements

Although the rain gauge method that was once needed every three years is not required now to determine uniformity, sprinkler spacing (or lane spacing for travelers) must be within design specifications and pressure must be within the ranges provided by manufacturer (Liu, 2009; 9^th SB 1217 Guidance Document, North Carolina 1217 Interagency Group, 2009). To check uniformity:

1) Compare field-measured wetted diameter and pressure to manufacturer’s charts, and

2) Calculate the sprinkler or lane spacing as a percentage of field-measured wetted diameter to determine if spacing falls in the recommended range.

Field data sheets at the end of the publication help calibrations to go more smoothly. If you have questions about calibrations, contact your county Extension Agent.