Case Study: Egg Wash Spray Bar Retrofit on a Packing Line
An egg wash sprayer retrofit cut wash water an hour by 62 percent and sanitizer use a shift by 75 percent on a conveyorized egg packing wash line.
A wash tunnel that runs wet pays for it twice. Eggs leave the grader stained or dry where the spray never reached, get pulled as seconds, and the once-through water that should have rinsed them goes to drain with the sanitizer still active in it. A regional egg grading and packing operation in the US Midwest measured both losses on one line.
The work below is an egg wash sprayer rebuild on a conveyorized wash tunnel. Every figure is a working value for this class of line, built from published washing guidance and nozzle arithmetic. The client stays anonymous, so no company name appears.
Case Snapshot
The figures below are the generic shape of this class of wash tunnel retrofit, not a record from one plant.
| Item | Reference configuration |
|---|---|
| Egg throughput | about 100,000 eggs an hour, about 278 cases an hour |
| Conveyor | 1.2 m belt at 0.08 m/s, 4.0 m wash tunnel |
| Original setup | flood wash header, once-through rinse, hand dosed sanitizer bath |
| After | five spray bars, three nozzles each, fifteen spray bar nozzles |
| Wash nozzle | 110 degree flat fan, 2.5 mm equivalent orifice |
| Wash pressure | 2.0 to 3.0 bar, 29 to 43.5 psi |
| Belt coverage | 83 percent before, 100 percent after at 12 percent overlap |
| Wash water an hour | 13.2 cubic metres before, 4.98 after |
| Sanitizer | peracetic acid at 200 ppm, 9.6 L/h before and 2.4 after at 5 percent |
The Challenge
The line ran a flood wash header of eight nozzles over a 1.2 m belt, then a once-through rinse manifold of ten nozzles, then a sanitizer bath dosed by hand each shift.
Water was the visible loss. Every litre that entered left it, 13.2 cubic metres an hour across two shifts on a 16 hour day and a 250 day year.
Coverage was uneven. The header spanned 1.0 m of the 1.2 m belt, so the outer 100 mm at each side saw splash, and stained shells came off that band.
Sanitizer was uncontrolled. A fall from 200 to 100 ppm halves the active dose on the shell while the water volume stays the same. Temperature was the quiet one, because a header on one unregulated supply made the published rule, wash water warmer than the egg, a guess rather than a set point.
Why Egg Washing Is a Temperature and Chemistry Problem
Shell egg washing is regulated, and the regulation logic sets the nozzle spec before any arithmetic starts. Published guidance describes a wash step with a detergent at a controlled temperature, a potable rinse, and a final sanitising rinse inside a permitted concentration band. Approved sanitizer categories for that step include chlorine based products, peracetic acid and other oxidisers cleared for food contact surfaces.
Temperature is the part a nozzle must respect. Commonly published guidance places wash water between 90 and 120 °F, or about 32 to 49 °C, and holds it warmer than the egg, often at least 11 °F above the internal egg temperature. An egg washed in water cooler than itself contracts as it cools, the contents pull away from the shell membranes, and the pressure drop draws wash water through the pores by reverse suction.
Contact time and concentration set the kill. Published sanitizer practice for a shell rinse sits in a 100 to 200 ppm band for the common oxidisers, with a contact window of roughly 20 to 60 seconds depending on the product and the validation the plant runs. Temperature, concentration, contact time and coverage are the whole brief, and a flood satisfies the water volume while losing the last one.
The Old Wash Line and Where It Lost Water
Break the 13.2 cubic metres an hour into parts. The wash header passed 80 L/min, the rinse manifold 70 L/min, the sanitizer rinse 40 L/min, sump make-up 25 L/min, and the hand hose averaged 5 L/min.
| Element | Flow, L/min | Share | Why it ran that way |
|---|---|---|---|
| Flood wash header | 80 | 36 percent | Volume, not coverage, was the design rule |
| Rinse manifold | 70 | 32 percent | Once-through potable rinse, no recovery |
| Sanitizer rinse | 40 | 18 percent | Hand dosed bath on a continuous manifold |
| Sump make-up and overflow | 25 | 11 percent | Constant overflow to control solids |
| Hand hose-down | 5 | 3 percent | Manual wash at both ends of the tunnel |
| Total | 220 | 100 percent | 13.2 cubic metres an hour |
At 100,000 eggs an hour the old line used about 1.58 litres per dozen and none of it returned. The coverage number decided the retrofit: 83 percent of belt width saw a directed spray, and the outer bands ran on splash alone.
Spray Bar Coverage on a Conveyorized Wash Tunnel
One piece of trigonometry fixes every bar. A flat fan of total angle theta at standoff d paints a band of width w, where w = 2 x d x tan(theta / 2).
Work it for the chosen nozzle. The fan angle is 110 degrees, so half the angle is 55 degrees and its tangent is 1.428. At a 200 mm standoff above the belt, w = 2 x 0.200 x 1.428 = 0.571 m. One spray bar nozzle wets a 571 mm band.
Overlap sets the pitch. Published practice for an even band is 10 to 15 percent. Take 12 percent, so the pitch is 0.571 x 0.88 = 0.503 m, rounded to 0.50 m.
Two nozzles wet 1.074 m, short of the 1.2 m belt, so they leave a dry edge. Three nozzles span 1.00 m and wet 1.571 m, which clears the belt with 185 mm of overhang at each side.
| Geometry step | Working figure | How it was set |
|---|---|---|
| Fan angle | 110 degrees | Chosen for a short standoff band |
| Standoff above the belt | 200 mm | Clears the egg height with margin |
| Band width | 0.571 m | 2 x 0.200 x tan(55 degrees) |
| Overlap | 12 percent | Middle of the 10 to 15 percent band |
| Pitch | 0.50 m | 0.571 x 0.88, rounded |
| Nozzles per bar | 3 | 1.2 m belt at a 0.50 m pitch |
| Wetted width | 1.571 m | 1.00 m span plus one full band |
A 65 degree fan at the same standoff paints only 0.255 m, so covering 1.2 m would take five nozzles per bar. The spray angle guide tabulates that trade, and the flat fan header layout guide covers the overlap rule across a manifold.
Nozzle Sizing at the Bar
Flow through a fixed orifice follows the standard hydraulic relation. For water in L/min, with the orifice d in mm and gauge pressure P in bar, Q is about 0.65 x d squared x the square root of P.
Pick the wash orifice at 2.5 mm and 3.0 bar. The square root of 3.0 is 1.732, so Q = 0.65 x 6.25 x 1.732 = 7.04 L/min. At 2.0 bar the same nozzle passes 0.65 x 6.25 x 1.414 = 5.75 L/min.
| Bar | Duty | Nozzles | Orifice | Pressure | Per nozzle | Per bar |
|---|---|---|---|---|---|---|
| A | Pre-wet | 3 | 2.5 mm | 2.0 bar | 5.75 L/min | 17.24 L/min |
| B | Detergent wash | 3 | 2.5 mm | 3.0 bar | 7.04 L/min | 21.11 L/min |
| C | Detergent wash | 3 | 2.5 mm | 3.0 bar | 7.04 L/min | 21.11 L/min |
| D | Potable rinse | 3 | 2.0 mm | 3.0 bar | 4.50 L/min | 13.51 L/min |
| E | Sanitizer rinse | 3 | 1.8 mm | 2.5 bar | 3.33 L/min | 9.99 L/min |
| Total | Five bars | 15 | mixed | 2.0 to 3.0 bar | average 5.53 L/min | 82.95 L/min |
The rinse bar steps down to a 2.0 mm orifice at 3.0 bar, where Q = 0.65 x 4.0 x 1.732 = 4.50 L/min, and the sanitizer bar runs a 1.8 mm orifice at 2.5 bar to hold the dose down without narrowing the pattern.
Fifteen nozzles move 82.95 L/min, which is 4.98 cubic metres an hour, a 62 percent cut against the old 13.2.
The Solution
The retrofit put five spray bars in the tunnel and a metered dosing loop behind them, with the once-through rinse closed into a controlled loop.
The egg wash sprayer here is a fixed pressure system. Nozzle pressure holds at a set point per bar by a regulator, so flow depends only on orifice size and not on pump wear or draw from another station.
A peracetic acid concentrate at 5 percent is drawn by a metering pump into the sanitizer line at a fixed ratio, and an in-line probe reads the residual every few minutes. The set point is 200 ppm, the top of the published band, chosen because the contact window here is short at about 25 seconds.
| Retrofit element | Specification | Why |
|---|---|---|
| Spray bars | five, three spray bar nozzles each | Replace one flood header and three manifolds |
| Pre-wet stage | bar A at 2.0 bar | Soften the film before detergent |
| Wash stage | bars B and C at 3.0 bar | Detergent contact on a moving shell |
| Rinse stage | bar D at 3.0 bar, potable water | Clear detergent before sanitizing |
| Sanitizer stage | bar E at 2.5 bar, 200 ppm | Final rinse inside the permitted band |
| Dosing | metering pump, in-line residual probe | Hold concentration instead of guessing |
| Cleaning | CIP on the same headers | No strip down for the tunnel internals |
The flat fan nozzle range carries the wash and rinse bar tips, and the pattern logic is set out in the spray patterns explained guide.
Sanitation Gun Stations and Hot Water
The tunnel does not clean the packer heads, the grader rollers or the floor around the wash area. That duty belongs to a hand station, and it is a different design problem from the tunnel bars.
The plant kept two stations, one at each end. Each carries a sanitation gun on a 10 m hose, rated 3.0 gpm, which is 11.36 L/min, at 5.0 bar, or 72.5 psi. Hot water is a requirement, not a preference, and published washdown practice for food equipment sits at 140 °F or about 60 °C.
Size the station pump on two guns, since one operator can open both. Two guns at 11.36 L/min is 22.71 L/min, or 6.0 gpm. Hydraulic power is kW = Q x P / 612, so 22.71 x 5.0 / 612 = 0.186 kW. At 0.6 pump efficiency the shaft load is 0.186 / 0.6 = 0.31 kW, so a 0.75 kW motor covers the duty.
Hand held sanitation sprayers that atomise are the wrong tool for a caked surface, and two sanitation spray guns at a fixed 5 bar beat one high volume hose. The spray gun nozzle range and the spray gun nozzle guide cover the tip options. A poultry house washer faces the same hot water demand on a larger footprint, with boom mounted washdown spray nozzles, but it tolerates a colder rinse and is not the right reference for a shell egg line.
Line Washing Systems and CIP
The tunnel bars, the manifold and the sanitizer loop all have to be cleaned without a strip down, and that is what separates a metered system from a set of headers.
Published CIP practice for food contact equipment runs a caustic wash at 1 to 2 percent sodium hydroxide at 140 to 160 °F, a potable rinse, an acid rinse to strip mineral scale, and a final sanitizer step. The tunnel headers run that cycle on the same manifold the bars use in production.
| CIP step | Fluid | Temperature | Purpose on this line |
|---|---|---|---|
| Caustic wash | 1 to 2 percent NaOH | 140 to 160 °F | Lift detergent and protein film |
| Potable rinse | water | ambient | Carry the caustic away |
| Acid rinse | dilute acid | 120 to 140 °F | Strip mineral scale from tips |
| Sanitizer | 200 ppm peracetic acid | ambient | Final step before production |
The CIP tank washing systems guide covers the same loop for closed vessels, and the dairy CIP tank cleaning case shows how the sequence scales from a tunnel to a tank. The tank cleaning nozzle range covers the rotary heads used where the wetted path is long and closed.
Nozzle Material for Chlorinated Sanitizer Duty
Published materials guidance on chlorinated service puts 316 stainless ahead of 304, because the molybdenum in 316 resists chloride pitting that 304 accepts at higher ppm and warmer temperatures.
Plastics split the same way. Published guidance rates PTFE, PVDF and polypropylene well against hypochlorite and keeps acetal, nylon and polycarbonate out of the wetted path on oxidiser duty. Peracetic acid attacks nitrile and degrades FKM, so seals in that loop run PTFE or EPDM.
| Wetted material | Chlorinated rinse | Peracetic acid | Note |
|---|---|---|---|
| 316L stainless | Good | Good | Default for the body and tip |
| 304 stainless | Fair | Good | Pitting risk rises with ppm and heat |
| PTFE | Good | Good | Seals and inserts |
| PVDF | Good | Good | Manifold blocks and caps |
| Polypropylene | Good | Good | Bodies on low pressure bars |
| Acetal, nylon, polycarbonate | Poor | Poor | Keep out of the wetted path |
| Nitrile | Fair | Poor | Not for peracetic acid |
The stainless versus brass nozzle guide covers the metal side and the plastic nozzle overview the polymer side. One rule then covers the whole tunnel: 316L bodies with PTFE seals, whatever the sanitizer.
Engineering Notes and Worked Arithmetic
Orifice flow. For water, Q (L/min) is about 0.65 x d (mm) squared x the square root of P (bar). At 3.0 bar a 2.5 mm orifice passes 0.65 x 6.25 x 1.732 = 7.04 L/min, and a 1.8 mm orifice at 2.5 bar passes 0.65 x 3.24 x 1.581 = 3.33 L/min.
Ideal flow check. A 2.5 mm orifice has an area of 0.7854 x 6.25 = 4.909 square mm, or 4.909e-6 square metres, and exit velocity at 3.0 bar is the square root of 2 x 300,000 / 1,000 = 24.5 m/s. That gives 4.909e-6 x 24.5 x 60,000 = 7.21 L/min against 7.04 L/min from the coefficient.
Pump duty. Hydraulic power is kW = Q (L/min) x P (bar) / 612. The tunnel moves 82.95 L/min, and with 0.5 bar of header loss the pump discharge is 3.5 bar. Hydraulic power is 82.95 x 3.5 / 612 = 0.474 kW. At 0.65 pump efficiency the shaft load is 0.474 / 0.65 = 0.73 kW, so a 1.5 kW motor covers the duty.
Wear against flow. Flow scales with the square of orifice diameter, so a wear of x percent on the diameter raises flow by (1 + x/100) squared minus 1. A 5 percent diameter wear is 1.05 squared, or about a 10 percent flow rise with no extra impact on the shell. A 2.5 mm tip at that wear passes 7.04 x 1.1025 = 7.76 L/min, and 5 percent is the change-out trigger.
Unit discipline. One bar is 14.5 psi, so 2.0 bar is 29.0 psi and 3.0 bar is 43.5 psi. One gpm is 3.785 L/min, so the 82.95 L/min tunnel flow is 21.9 gpm and the two gun station is 6.0 gpm. Holding both sets on the setting sheet avoids the common error of quoting one unit for flow and another for pressure.
| Quantity | Substitution | Result |
|---|---|---|
| Wash nozzle flow | 0.65 x 6.25 x 1.732 | 7.04 L/min |
| Sanitizer nozzle flow | 0.65 x 3.24 x 1.581 | 3.33 L/min |
| Ideal flow, 2.5 mm at 3.0 bar | 4.909e-6 x 24.5 x 60,000 | 7.21 L/min |
| Tunnel system flow | 82.95 L/min | 21.9 gpm |
| Pump hydraulic power | 82.95 x 3.5 / 612 | 0.474 kW |
| Shaft power at 0.65 efficiency | 0.474 / 0.65 | 0.73 kW |
| Gun station flow, two guns | 2 x 11.36 | 22.71 L/min |
| Gun station hydraulic power | 22.71 x 5.0 / 612 | 0.186 kW |
The Results
No plant audit figures appear below. These are working outcomes for this class of retrofit, held inside published bands.
| Metric | Before | After | Basis |
|---|---|---|---|
| Wash water an hour | 13.2 m3 | 4.98 m3 | Once-through against five metered bars |
| Wash water a day, 16 h | 211 m3 | 79.6 m3 | Same duty cycle both sides |
| Water per dozen eggs | 1.58 L | 0.60 L | At 100,000 eggs an hour |
| Active sanitizer an hour | 480 g | 120 g | 200 ppm held on a smaller rinse volume |
| Sanitizer product an hour, 5 percent | 9.6 L | 2.4 L | Dosed from concentrate at a fixed ratio |
| Belt coverage | 83 percent | 100 percent | 1.0 m header against a 1.571 m band |
| Pattern overlap | about 5 percent | 12 percent | Middle of the 10 to 15 percent band |
| Wash rejects per 10,000 eggs | direction high | direction low | Stained shells pulled after the tunnel |
| Breakage per 10,000 eggs | direction high | direction low | Regulated wash water temperature |
| Manual wash labour | 45 min a shift | 15 min a shift | Inspection and gun station top-up |
| Nozzles replaced a year | not applicable | 6 to 10 of 15 | 5 percent flow rise trigger |
The water cut is 62 percent, from 13.2 to 4.98 cubic metres an hour. The active sanitizer cut is 75 percent, from 480 to 120 grams an hour, because the rinse volume fell and the concentration is now held instead of guessed.
At 0.60 litres per dozen against the old 1.58 litres, the egg wash sprayer does the shell with about 38 percent of the water the flood used, and a 1.571 m wetted band over a 1.2 m belt leaves no dry edge.
Reading the Numbers Against Published Ranges
The comparison below is the check a maintenance planner should run. Nothing here is presented as measured fact.
| Figure in this case | Published class range | Verdict |
|---|---|---|
| Sanitizer at 200 ppm on the final rinse | 100 to 200 ppm, published band | Top of the band, short contact |
| Wash water at 90 to 120 °F | Commonly published guidance | Inside the band |
| Wash water warmer than the egg | Commonly published guidance | The rule the regulator checks |
| Sanitizer contact about 25 s | 20 to 60 s, published windows | Inside the band |
| Overlap at 12 percent | 10 to 15 percent, published practice | Middle of the band |
| Pump efficiency at 0.65 | Typical for this class of duty | Conservative |
| Nozzle change at 5 percent flow rise | 5 to 10 percent trigger | Conservative end |
| 316L on chlorinated duty | Published materials guidance | Consistent |
Two of these need a caveat. The temperature differential is commonly described as at least 11 °F above the egg, and a plant with colder incoming eggs needs a warmer supply. The sanitizer band also depends on the category, because a chlorinated rinse and a peracetic acid rinse carry different published limits and contact windows.
The bottle filler disinfection case shows the same logic on a dry disinfection duty, where contact time rather than water volume is the asset. The industrial water spray nozzle reference covers the material and pattern guidance behind the bar layout.
Why This Matters
A wash tunnel is a coverage problem dressed as a volume problem. The flood design moves water fast and lands it unevenly, so the plant pays once for the water and again for the seconds it fails to clean.
Sizing follows the surface, not the tank. Work the band width from the standoff and the fan angle, set the pitch from a 10 to 15 percent overlap, and let the belt width decide the nozzle count.
Flow follows the orifice and the pressure, and pressure is a weak lever, because going from 2.0 to 3.0 bar buys 22.5 percent more water rather than 50 percent.
Three thresholds carry into any egg line. Keep the wash water warmer than the egg, keep the sanitizer inside its published band, keep the pattern overlap between 10 and 15 percent. Miss the temperature rule and the shell draws water in, and miss the band and the validation fails.
A five bar tunnel with a dosing loop and a gun station is a template for a plant weighing a new egg wash sprayer. A plant running line washing systems across several tunnels can copy the bar layout stage for stage, because a metered egg sprayer keeps the same coverage math and the same pressure rule at any capacity.
The Final Call
BoreJet supplies spray bars and does the sizing arithmetic behind them: orifice flow, band geometry, overlap, pump duty, and the water and chemical ledger under it. The bars used here sit in the flat fan nozzle range, the hand station in the spray gun nozzle range, and the CIP loop follows the CIP tank washing systems guide.
Send the belt width, the belt speed, the eggs an hour, the wash water temperature and the sanitizer category to the contact page. The reply comes back with the bar count, the orifice sizes, the pressure per bar, the pump duty and the water ledger your duty needs.
Your Duty May Differ
Send the Vessel Drawing and the Pump Curve.
We size the head class, the count and the operating point for your tank, not a catalogue guess. A coverage test on the actual vessel beats any estimate.