The Spreader and Sprayer Calibration Log SOP

Purpose

Guarantee that every spreader and sprayer that leaves the yard puts down what the work order says, per 1,000 square feet of measured turf, and that anyone can prove it later from a written line. Without this, a machine drifts after a repair or a product change and nobody notices until the stripes show, the bags run out a day early, or a customer's lawn takes twice the nitrogen the program called for. A dial setting is a starting point, not a calibration; the only accepted calibration in this shop is weight or volume over a measured area.

Scope

Covers when a machine must be calibrated, tagging out a machine that is not, running and recording the output check, the retest limit, and the office review of the log. Applies to rotary spreaders (push, walk-behind and ride-on) and to hose-reel spray guns and boom or wand sprayers on skid and tank units.

Does not cover the test methods themselves, which belong to How to Calibrate a Rotary Spreader by Weight Over a Measured Area, How to Check a Rotary Spreader Pattern With Collection Pans and How to Calibrate a Hose Reel Spray Gun for a Lawn. Does not cover product rates or mixing; the fertilizer rate comes from How to Calculate Fertilizer Product From the Bag Analysis, and any pesticide rate comes from the label, never from this log. Does not cover the per-property application record, which belongs to Fertilizer Application and Record Keeping.

Roles and responsibilities

Procedure

1. Decide whether the machine is due before it is loaded. A machine is due at the first use of the season, at every product change (a different bag, even of the same analysis, from a different manufacturer or with a different particle size), after any repair or part replacement on the metering or delivery path (impeller, gate, agitator, hopper, pump, regulator, hose, gun, tip), and whenever the office flags it. Acceptance: the truck log shows a passing line for this unit, this product and this configuration dated after the last trigger. Wrong looks like a passing line for last month's product on a machine now loaded with a new one; stop rule: no passing line for the current product means the machine goes to step 2 and is not used on a property. Hazard: none at this step; it is a check of the log made at the tailgate.

2. Tag out any machine that is due. Hang a red tag on the handle or the reel reading "NOT CALIBRATED - DO NOT USE", with unit number, date and your initials. Acceptance: tag on the machine where an operator's hand goes first, and the unit is not loaded with product for a route. Wrong looks like a tag in the cab or on the trailer gate, where the next person never sees it; stop rule: a machine found in use with no passing line is pulled off the route at once and the applications it made that day are listed for the office. Hazard: none at this step; a tag is paperwork.

3. Set up the machine and the course. Clean the machine, confirm the part named on any repair tag is fitted, set tire pressure on a spreader and the hose and tip on a sprayer to the configuration the route will use. Lay out the measured course per the method card, on turf that is due that product, or over a tarp so the product can be returned to the hopper, never on hardscape. Acceptance: course measured with a tape, area written down, machine in route configuration. Wrong looks like a course paced off by eye; stop rule: an unmeasured course is re-measured before any product goes down. Hazard: fertilizer dust and granules irritate eyes and skin, so wear the eye protection and gloves the product label lists; a spreader test over a slab near a storm drain puts product where an ordinance forbids it, so the course is never on pavement.

4. Run the output check by weight or volume. Spreaders by weight of product used over the course; sprayers by volume of clean water used over the course, never with a pesticide mix in the tank. Compute the result per 1,000 square feet and compare it with the target from the work order. Acceptance: within 5 percent of the target, the shop default; a spreader passes on one such run, and a sprayer always runs twice and needs both inside the band and within 5 percent of each other, because walking pace varies from lap to lap. Wrong looks like anything outside 5 percent; stop rule: go to step 5. Hazard: a sprayer is pressurized, so before you open the gun to a measuring container or change a tip, shut the pump off and bleed pressure at the gun with it pointed into the container, and wear eye protection against spray-back; a running spreader impeller throws granules hard at shin and eye height, so nobody stands in front of the discharge.

5. Adjust and retest, at most three runs total. Change one thing per run (spreader gate setting; sprayer pace or tip) and repeat step 4, counting step 4's runs toward the three. Acceptance: one run inside 5 percent of target for a spreader; two consecutive runs inside 5 percent of target and of each other for a sprayer. Wrong looks like results that will not settle, or a setting at the end of its range; stop rule: three runs without a pass means a mechanical fault, not a setting, and the machine stays tagged and goes to the shop with all three results on the tag. Hazard: repeat step 4's pressure-bleed before every tip change and every container swap; fatigue on a third lap is when people stop doing it.

6. Run a pattern check when the trigger was a spreader repair or a new product. After impeller, gate or agitator work, or a product with a different particle size, run the collection-pan test from the pattern card. Acceptance: pan catches roughly symmetric left and right of center, and an effective swath measured from the pans and written on the log line. Wrong looks like one side catching clearly more than the other, which a weight check cannot see because it only measures the total; stop rule: a lopsided pattern keeps the machine tagged and sends it to the shop. Hazard: collection pans laid across the swath put the tech on foot in the throw zone, so the spreader is stopped and its impeller still before anyone walks out to read or move the pans.

7. Write the log line and send it the same day. In the truck log: unit, machine type, product, setting, each run's result, target, percent difference, date, initials, and the effective swath where step 6 ran. Photograph the page and send it to the office before leaving the yard. Acceptance: one line per run, every column filled, the office has the photo the same day. Wrong looks like only the passing run written down, which hides how far off the machine was; stop rule: an incomplete line is completed before the machine is used. Hazard: none at this step; paperwork done at the tailgate, out of traffic.

8. Release the tag, and review weekly. The applicator removes the red tag only after a passing line is written. Each week the office compares, per machine, product used against measured area treated at the work-order rate. Acceptance: product used within 10 percent of rate times area. Wrong looks like a machine using notably more or less product than its area accounts for; stop rule: the office flags it back to step 1 as due. Hazard: none at this step; it is a desk review.

The record this produces

• The truck calibration log, one line per run per machine, kept in the truck with the machine. Read by the applicator at step 1 every day and by an inspector or auditor who asks how the shop knows its rates.
• The master log in the office, built from the daily photos. Read at the weekly review and when a customer complaint (stripes, burn, a lawn that never greened) needs to be traced back to a machine and a date.
• Repair tags, kept with the machine's equipment record. A unit that keeps failing step 5 after the same repair is a unit to retire, and the tags are what show it.

One pass through this procedure

Monday of a product change on Truck 7, applicator DM, two machines.

 CALIBRATION LOG - TRUCK 7
 UNIT   PRODUCT  SET  RESULT    TARGET    DIFF    DATE BY
 S-04   25-0-5   12   2.55 lb   3.00 lb  -15.0%  4/14 DM
 S-04   25-0-5   14   3.08 lb   3.00 lb   +2.7%  4/14 DM
        swath 10 ft (pans, step 6)
 SP-02  water    T1   2.30 gal  2.00 gal +15.0%  4/14 DM
 SP-02  water    T1   1.85 gal  2.00 gal  -7.5%  4/14 DM
 SP-02  water    T1   2.20 gal  2.00 gal +10.0%  4/14 DM
        3 runs, no pass. TAGGED, to shop.         4/14 DM

S-04, rotary walk-behind, new product. Step 1: the log's last line is for the old bag, so S-04 is due, and step 2 tags it. The work order calls for 0.75 lb of nitrogen per 1,000 sq ft from a 25-0-5, which is 0.75 divided by 0.25, 3.00 lb of product per 1,000 sq ft. Step 3: course 100 ft long at the card's 10 ft spacing, 1,000 sq ft, on a lawn due this feeding. Step 4 fails on run 1: 2.55 lb used, 2.55 divided by 3.00 is 85 percent, 15 percent under, outside the 5 percent band. The stop rule sends it to step 5: gate from 12 to 14, run 2 uses 3.08 lb, 3.08 minus 3.00 is 0.08, which is 2.7 percent over. Pass. A new product triggers step 6: pans symmetric, effective swath 10 ft, matching the spacing used. Step 7 lines written; step 8 tag off.

SP-02, skid sprayer after a pump repair. Step 1: repair tag means due. Target carrier volume from the program, 2.00 gal per 1,000 sq ft, water only. Run 1: 2.30 gal, 0.30 over, 15 percent. Run 2, pace slowed: 1.85 gal, 0.15 under, 7.5 percent. Run 3, tip checked and pace held: 2.20 gal, 10 percent over, and runs 2 and 3 differ by 0.35 gal, about 19 percent of 1.85. DM notices the pump pressure gauge swinging during each run. Step 5's three-run stop rule triggers: SP-02 stays tagged with all three results written on the tag. The shop finds an air leak on the pump inlet fitting from the repair; after the fix, Tuesday's recalibration passes on two runs of 2.04 and 1.98 gal.

And one step that failed outright. DM photographed the log at the end of the route, not before leaving the yard, so the office received it Tuesday morning. That is a missed acceptance on step 7, not a triggered stop rule, and it goes on DM's weekly review. It mattered: without the photo, the office route board still showed SP-02 assigned to Tuesday's weed-control route until DM called in.

References

• See related: How to Calibrate a Rotary Spreader by Weight Over a Measured Area; How to Check a Rotary Spreader Pattern With Collection Pans; How to Calibrate a Hose Reel Spray Gun for a Lawn.
• See related: How to Calculate Fertilizer Product From the Bag Analysis; Fertilizer Application and Record Keeping.
• See related: Pesticide Label Reading and Compliance, for label PPE and application limits that this log never sets.
• Manufacturer manuals for each spreader and sprayer, for settings, pressure relief and the parts on the metering path.