4 Factors of Open Plant Cleaning in Food Factories

Open plant cleaning (OPC) — the practice of cleaning food processing equipment and surfaces in place, without dismantling or enclosing them in a CIP system

 — succeeds or fails on four variables. Get all four right, and surfaces come clean and pass swab tests. Miss one, and the other three can't compensate. This 

article breaks down the four factors of open plant cleaning — mechanical action, chemicals, time, and temperature — and explains what "right" actually means 

for each one.

The Four Factors of Open Plant Cleaning, at a Glance

Factor	What It Does	Typical Target
Mechanical action	Physically dislodges soil from the surface	High-pressure water at 10–25 kg (roughly 10–25 bar)
Chemical action	Dissolves and lifts specific soil types	Alkaline foam for fats/oils; acid foam for scale
Time	Gives chemicals enough contact time to work	5–10 min light soil; 10-15 min heavy soil
Temperature	Speeds up chemical reactions and softens fats	Warm water, typically 40–60 °C

The four factors are interdependent — a principle sometimes called the TACT framework (Time, Action, Chemistry, Temperature). Increase mechanical energy 

and you may shorten contact time; raise temperature and you may lower chemical concentration. What you cannot do is skip one entirely.

Factor 1: Mechanical Action — Why Pressure Matters

Mechanical action is the physical energy applied to the soil. In open plant cleaning, it usually comes from high-pressure water delivered through a spray gun.

The Pressure Question: "What's the standard?"

There is no single universal number for cleaning pressure, because the right pressure depends on the surface and soil type. What matters in practice is that the

pressure is high enough to remove soil but not so high that it damages equipment or drives contaminants into crevices.

WONE's foam cleaning equipment operates at a working pressure of 20 bar, with a rated pump capability reaching 25 kg (25 bar) . WONE's chemical 

application guidance recommends rinsing with high-pressure water at 10–25 kg — a range wide enough to give operators flexibility between a gentle rinse and 

a strong dislodging pass.

For context, general food industry practice typically treats low-pressure cleaning as below about 15 bar, medium-pressure cleaning as roughly 15–25 bar, and 

cleaning above about 30 bar as high-pressure work where protection and mist control become more critical. Matching pressure to the job prevents two 

common failures: under-pressure (soil left behind) and over-pressure (water driven into electrical panels and bearings).

The Real Advantage: Foam as a Mechanical Multiplier

The most important mechanical insight in open plant cleaning is that foam and pressure work together. A foam lance throws cleaning chemistry over vertical 

surfaces where a thin liquid would simply run off. WONE's alkaline and acid foam cleaners are engineered to produce micron-scale foam with a foam expansion

ratio up to 30x, meaning the foam clings to walls and equipment, extending contact time on vertical surfaces.

Factor 2: Chemical Action — Alkaline for Fats, Acid for Scale

Chemicals are matched to soil type. Choosing the wrong chemistry means the other three factors must do work they cannot do.

Alkaline Foam: For Fats, Oils, and Protein

Food processing soil is dominated by fats, oils, proteins, and blood. These are organic soils and require alkaline chemistry. WONE's F8-25/F8-05, a liquid 

self-foaming alkaline foam cleaner, is a compound alkaline cleaner with a high pH (pH 12.0–13.0) that effectively removes lubricating oils, fats, oils, blood, and 

proteins — as well as the soils common in canning, baking, dairy, breweries, soft drinks, and aquatic product processing.

For heavier organic loads,F7-25/F7-05 is a chlorinated alkaline foam cleaner with a higher pH (13.0–14.0). Its chlorine content rapidly breaks down organic and 

protein soils, while added surfactants and chelating agents give excellent soil penetration and hard-water tolerance, and it rinses off easily.

Acid Foam: For Scale, Water Spots, and Mineral Deposits

The mineral counterpart to organic soil is scale — the hard water deposits, milk stone, and water spots that accumulate on stainless steel, kettles, and heating 

surfaces. These are alkaline themselves and require acid chemistry to dissolve.

WONE's F23-05) is an acidic compound foam cleaner designed to remove scale and rust in food, beverage, and dairy facilities. It targets water scale directly 

— the visible "water spots" and hard deposits left after washing — and its micron-scale foam clings for a long wall time, with a foam expansion ratio up to 30x 

for chemical savings.

The pairing logic is simple: you cannot remove fat with acid, and you cannot remove scale with alkali. A complete open plant cleaning program alternates both 

— alkali for the organic pass, acid for the mineral pass.

Concentration: 1–10%, Applied Consistently

WONE's application guidance recommends diluting foam cleaners to 1–10% before applying to the soiled surface, with the concentration valve setting (a 

six-stage adjustable valve on WONE machines) controlling the dilution. Getting the concentration right and applying it consistently matters more than adding 

extra chemical — over-strength chemistry wastes money and can damage surfaces, while under-strength chemistry fails to break down soil.

Factor 3: Time — The Contact Window That Does the Work

Time is the factor most often sacrificed for the sake of production schedules. Chemicals need contact time — time to wet the soil, penetrate it, dissolve it, and 

hold it in suspension so it rinses away.

Recommended Contact Times
WONE's foam cleaning guidance is specific about dwell times:

• Light soil (light oil or light scale): apply the foam and let it remain for 5–10 minutes before rinsing
• Heavy soil: extend the dwell to 15–30 minutes

This applies to both manual spray-and-brush cleaning and foam machine cleaning. The rule to remember is more soil, more time — but not infinite time. Foam 

that has fully run off its surface and dried a surface has stopped working; the foam needs to stay wet and active through the dwell.

Foam Design Extends Time "For Free"

This is where foam engineering earns its place. Because WONE's alkaline and acid foams produce a micron-scale, fine, dense foam with a high wall-cling time,

the chemistry stays in contact with vertical surfaces far longer than a liquid spray would. The foam expansion ratio up to 30x means a smaller volume of 

chemical covers a larger area and clings longer — effectively buying contact time without buying more labour.

Factor 4: Temperature — Warm Enough to Soften, Not So Hot It Fails

Temperature raises the reaction rate of the chemistry and, critically in food plants, softens and melts animal fats. Warm water cuts through congealed fat and 

grease dramatically faster than cold water.

The Working Range: 40–60 °C

WONE's application guidance recommends rinsing with warm water at 40–60 °C, noting that this performs better than cold water for fat and oil removal. In the 

WONE foam cleaning equipment range, the water source requirement is ≤60 °C — the upper limit is set by the equipment's internal components and seals.

The logic is two-sided:

Too cold: 

• Fats and heavy grease congeal and stick to surfaces. The chemistry works slowly, and mechanical action has to carry the entire load.

Too hot: 

• Above the equipment's rated limit, seals and pump components suffer; and on protein-rich soils, very hot water can "cook" proteins onto surfaces, makingthem harder to remove.

Why Fat Type Changes the Optimal Temperature

Not all animal fats behave the same way, and this is where temperature selection gets interesting for meat and poultry plants. Fats with higher melting points 

stay solid at higher temperatures, meaning they need warmer water and more mechanical dwell to lift off, while fats with lower melting points soften in cooler 

water.

Fat Source	Relative Melting Range	Cleaning Implication
Beef tallow	Highest (roughly 40–50 °C)	Needs warmer water and longer dwell; extends into the upper part of the 40–60 °C range
Pork lard	Mid (roughly 30–40 °C)	Softens in mid-range warm water; responds well around 45–55 °C
Chicken/poultry fat	Lowest (roughly 20–30 °C)	Softens readily; cooler warm water (40–50 °C), the lower end of the range, is sufficient

The practical takeaway: beef processing areas generally need hotter cleaning water than poultry areas. Using a single temperature across a plant handling 

multiple meat types either wastes energy on the poultry side or under-cleans the beef side. Setting the temperature to the hardest fat in the zone and trimming it

for lighter zones is the more efficient approach.

Bringing the Four Factors Together

No single factor is a substitute for another. A realistic open plant cleaning routine balances all four:

• Rough rinse with high-pressure water (10–25 kg / working pressure 20 bar) to remove gross soil and loose residue (mechanical action)
• Apply alkaline foam at 1–10% concentration (chemical action), covering vertical surfaces with clinging foam
• Allow 5–10 minutes dwell for light soil, 15–30 minutes for heavy soil (time)
• Rinse with warm water at 40–60 °C (temperature), adjusting up for higher-melting fats like beef tallow

Frequently Asked Questions

What are the four factors of open plant cleaning?

Mechanical action (pressure and agitation), chemical action (the right detergent for the soil), time (contact/dwell time), and temperature (warm water to soften 

fats and speed chemistry). They are interdependent — improving one can compensate for another.

What pressure should I use for open plant cleaning?

WONE equipment operates at a working pressure of 20 bar with pump capability to 25 bar, and WONE guidance recommends rinsing at 10–25 kg. Match 

pressure to the soil and surface to avoid damage.

How long should foam stay on the surface?
5–10 minutes for light soil, 15–30 minutes for heavy soil, keeping the foam wet throughout the dwell.

What water temperature is best?

40–60 °C, never exceeding the equipment's ≤60 °C water source limit. Higher-melting fats (beef tallow) need the upper end; lower-melting fats (poultry) perform

well at the lower end.

Do I need both alkaline and acid cleaners?
Yes. Alkaline foam removes fats, oils, and protein; acid foam removes scale and water spots. They are not interchangeable.

Open plant cleaning is a controlled equation, not a chore. Mechanical action, chemical action, time, and temperature each carry a share of the cleaning load — 

and the standards behind them are concrete: 10–25 kg rinsing pressure, 1–10% foam concentration, 5–30 minutes contact time depending on soil load, and 40

–60 °C water matched to the fat in your process.

The facilities that pass swab tests consistently are the ones that manage all four factors deliberately, with equipment and chemistry engineered to make each 

factor easy to control. To find out which foam cleaning system fits your plant's open cleaning routine, contact WONE at 008618028007427.

Next: Get close to WONE's 4 in 1 foam cleaning machine