How to Choose the Right CIP Chemicals

Cleaning in place (CIP) is a process that employs chemicals to clean the inside of pipes, tubing, and equipment. The CIP process can be used on all types of piping systems, including; open-ended pipe, closed pipe loop, run-around loops, or other configurations. The cleaning solution travels through the system at high pressure and velocity, which helps remove any deposits from the tubes and internal surfaces of the pipeline. Cleaning-in-Place is typically applied when no fluid is pumping through your system for some time, such as during shutdowns or off-hours.

Maintaining a clean facility improves efficiency and reduces unnecessary wear on equipment due to corrosion caused by hard water minerals left behind from use without proper chemical treatment.

The use of chemicals during CIP cleaning is crucial, and it is essential to select the proper chemical for your process. The chemical selection must be based on:

• Application: Some products may not be appropriate for all types of heat exchangers or piping systems due to the number of tube passes or different construction materials, such as carbon steel, stainless steel, copper, or aluminum.
• Heat Resistance: Some chemicals can withstand high temperatures while others cannot. When performing CIP, the temperature of the fluid applied to the system will range from 70°C to 85°C. You must choose a chemical that meets your cleaning needs at this elevated temperature.
• Materials compatibility: It is vital to select a chemical that will not attack or corrode other metals in your systems, such as carbon steel, stainless steel, and many alloys used for heat exchanger tubing and pipe construction.

Once it is time to reestablish product flow through your system, be sure to flush using clean H₂O or use another chemical that will not damage any rubber seals or polymer gaskets that may have been used during shutdown.

Chemicals commonly used in CIP operations

Hydrochloric Acid (Muriatic acid)

Some of the functions of hydrochloric acid are to remove rust, scale, and corrosion from the surface, which are left behind by water. The temperature of hydrochloric acid is not too high or too low, which allows for more effective cleaning.

Hydrochloric Acid also has some downsides, which can be lessened by using it properly. Hydrochloric Acid is corrosive to copper alloys which means that surfaces containing these alloys will need to be coated before being exposed to acid. This corrosion can also extend into tubing downstream of the heat exchanger surface. Using a surfactant with the acid will lower its corrosivity, but this will not prevent corrosion.

Hydrogen Peroxide

Hydrogen peroxide can be used in CIP operations on industrial heat exchangers. During these operations, it is often used in conjunction with other chemicals, such as citric acid or bleach. Hydrogen peroxide can effectively reduce the contact time between the cleaning chemical and the metal surface of the heat exchanger, which limits corrosion and thermal shock.

Furthermore, hydrogen peroxide can help break down organic deposits on the metal surface, making it easier for other chemicals to reach and dissolve them. Hydrogen peroxide is highly effective at reaching deep deposits and often requires a shorter contact time with the metal surface than other chemicals. It is also effective at preventing the deposition of new sediments and protects against corrosion during idle periods.

Hydrogen peroxide is not an ideal chemical for CIP chemical operations where organic growths are not a concern because it will also oxidize metal surfaces, leading to increased corrosion rates. To prevent this, pH is used to control the oxidation rate of hydrogen peroxide. This means that it is necessary to set the pH of the solution created with hydrogen peroxide at less than 12.5 to not corrode metal surfaces.

Phosphoric Acid

Phosphoric acid is a weak mineral acid that produced by combining phosphorous and oxygen atoms. It has many uses, including in the production of food products, the manufacture of fertilizers, and as a cleaning agent for metal surfaces.

Its ability to break down deposits on metal surfaces is what makes it an ideal choice for use in CIP operations. Its slightly acidic hydrogen ions make it an effective agent to clean minerals out of CIP systems. The acid works by breaking down carbon and mineral deposits and converting them into soluble compounds, which can be easily washed away with the cleaning solution itself.

When used as a cleaning agent in industrial heat exchangers, phosphoric acid is applied by spraying the liquid solution onto the heat exchanger surfaces. The heat of the surface causes some of the liquid to evaporate, which immediately starts breaking down any carbon or mineral deposits on the metal surface.

Phosphoric acid cleaning is usually performed during periods when no other chemicals are used to avoid chemical reactions with other process chemicals that might result in less effective cleaning.

Citric Acid

Citric acid is a versatile organic acid that can be produced by fermenting sugar or starchy material with certain strains of bacteria, usually found in the genus Acetobacter. For commercial production, it is usually manufactured through chemical synthesis, but this consumes large amounts of fossil fuels and leaves behind a potentially hazardous by-product. As such, citric acid is usually produced using the biological route, making it one of the few organic acids that can actually be made completely from scratch.

Citric acid has many uses in industrial applications, one of them being its use in cleaning processes. Citric acid is an effective agent against many types of organic materials, and due to its low toxicity, it is used as a cleaning agent for heat exchangers. Citric acid is applied as an aqueous solution onto the heat exchanger surface, where it immediately starts breaking down any deposits on the metal surfaces.

In addition to this, citric acid significantly increases the surface energy of carbon deposits, which helps in their removal. This means that citric acid is effective even when used alone without any additional chemicals.

Sodium Hydroxide

When used in industrial settings, sodium hydroxide is usually made by adding caustic soda (sodium carbonate) to water and then adding slaked lime (calcium hydroxide) to the solution. The result is a strong alkaline cleaning agent that can be used in the removal of carbon and mineral deposits from heat exchangers.

When applied as an aqueous solution, sodium hydroxide immediately starts breaking down any carbon or mineral deposits on metal surfaces because it dissolves these materials by altering their chemical structures in the same way that acids do.

Sodium hydroxide is less corrosive than phosphoric acid, but it still poses some challenges when used in industrial heat exchanger cleaning. Firstly, its high pH value means that if sodium hydroxide comes into contact with another chemical during CIP operations, a chemical reaction could reduce its effectiveness. Sodium hydroxide is usually used alongside other cleaning agents, not as a standalone one.

Another challenge is sodium hydroxide solutions’ high pH value, which can cause equipment corrosion if left standing for long periods after application, especially inside metal pipes and tubes where there might be no flow present to flush out the solution. As such, it is essential to flush out sodium hydroxide with high-pressure hot water immediately after application.

Nitric Acid

Nitric acid can be used in cleaning-in-place operations. It is primarily used to remove corrosion from the outside of the exchanger. Nitric acid can dissolve many other types of contamination, including grease, fatty acids, and oils.

Nitric acid is one of the most common chemicals that can be used in a variety of situations. For example, remove several different materials, including rust and carbon deposits, from the tubes inside the heat exchanger. Nitric acid is pretty safe to use as long as it’s handled carefully. In addition, this chemical has low toxicity, which means that it can be safely washed away with water after it’s used. It is one of the most commonly available chemicals for Clean-in-Place operations

Sulfamic acid

In the CIP process, sulfamic acid is used to remove deposits from heat exchangers. The effectiveness of this chemical depends on the pH level and temperature of the solution.

The higher the pH level, or a lower temperature solution, will make it more difficult for sulfamic acid to work effectively during CIP operations on industrial heat exchangers.

For sulfamic acid to be effective when cleaning an industrial heat exchanger in a low-pH or high-temperature solution, you would need a stronger concentration of sulfamic acid than what is typically recommended by most manufacturers – 10% instead of 8%. In these cases where there are not enough chemicals present in the fluid being circulated through your system’s pipes and tubes, adding an alkaline chemical such as sodium hydroxide, caustic soda or trisodium phosphate (TSP) can also help make sulfamic acid more effective.

Another option to increase the effectiveness of sulfamic acid is to circulate the solutions through your system for a longer period – typically 10 minutes instead of 7 minutes.

Sodium Hydroxide (caustic soda)

The use of caustic soda to remove scale buildup has been increasingly used where the equipment surface can tolerate it, but it is also known that there are three serious drawbacks to using caustic soda for CIP cleaning.

• The difficulty in rinsing out the chemical once treatment time has elapsed due to the extremely small amounts of water required because caustic soda can irritate if it comes into contact with eyes or skin. Furthermore, it can burn the skin and damage clothing if allowed to remain in contact for a prolonged period of time.
• The difficulty in neutralizing the chemical once treatment time has elapsed, as it must be done with an acid rinse if other substances are going to be used after that. Because caustic soda is not a strong enough base, a weak acid rinse is required after elapsed treatment time.
• The corrosive nature of caustic soda itself, as the chemical can damage equipment or cause corrosion if used on its own.

A typical use for caustic soda would be at 12% concentration with an acid rinse after exposure time has elapsed; this will help remove any residuals left behind by caustic soda while also removing scale buildup.

Maleic Acid

Maleic acid is a strong organic acid that can be used to remove deposits from the surfaces of metal pipes. It does not attack hard metals such as steel but removes carbonaceous deposits from copper, brass, aluminium, and other soft metals. The maleic acid solution may contain heavy-duty detergent to help remove the deposits. This cleaning process uses saturated steam with or without pressure injection at about 60°C (140°F).

The most common use for maleic acids in CIP cleaning operations is in removing scaling caused by hard water when using sodium hypochlorite in the scrubbing stage. Scaling can be removed at temperatures between 60°C (140°F) – 80°C (176°F).

Things to consider when using the right CIP chemicals

Fluid/chemistry compatibility

• Some chemicals may not be appropriate for all types of heat exchangers due to the number of tube passes or different construction materials (carbon steel, stainless steel, copper, or aluminium).
• Heat Resistance: Some chemicals can withstand high temperatures while others cannot.
• Corrosion/erosion: Some chemicals may corrode certain metals, while others are more forgiving.
• Rinsability: Chemicals should be easily rinsed away with water or minimal wastewater generation.
• Rinse cycle time: Not all chemical cleaners require the same amount of rinsing (i.e., time, labor, and equipment).
• Dirty Solution recycling: Some chemicals are not suited for recycling dirty solutions (i.e. turn black in color, cloud up).

Application Compatibility

Some products may not be appropriate for all types of heat exchangers due to the number of tube passes or different construction materials (carbon steel, stainless steel, copper or aluminium).

Chemical concentrations

Concentrations should not exceed 4% w/w. A 2% concentration is ideal for heat exchangers.

Temperature

The fluid temperature should be maintained at 70°C to 85°C.

Duration of exposure

The fluid should not remain on the heat exchanger for more than 30 minutes.

Cleaning of push-on fittings

Care must be taken to ensure that cleaning fluids do not get behind the gasket and contaminate the fluid system or damage internal components by corroding them from within.

Protective gear

When utilizing acid cleaners, it is important to use proper personal protective equipment (PPE) such as gloves, safety goggles, face shields and aprons.

Neutralizing acids

When using acids or bleach, it is essential to neutralize them through the use of an alkaline detergent immediately after they are used to avoid the acid contaminating downstream equipment.

A Chemistry Compatibility Guide can provide information about whether chemicals can be used on certain materials and at what concentrations, as well as recommendations on the best product to use.