Just like dirt, dust and extreme temperatures, chemicals require special adaptations in mechanical engineering. What do you do if the machine or machine parts come into contact with acids and alkalis? And how does a pneumatic cylinder react to contact with chemicals? In this blog we will explain the problems and challenges that may arise, the options that Festo offers and which product is ultimately best suited to a particular application and is resistant to acids and alkalis.
Machine builders who build for the food & beverage sector know that these machines must be resistant to chemical agents. We distinguish between acids with a pH value <7 and alkalis with a pH value >7. If we look at acids, we encounter cleaning agents, such as phosphoric acid. But also in the processing of vegetables, fruit and fruit juice production we have to deal with natural acids. And in the processing of yoghurt, we are dealing with lactic acids. If we look at alkaline detergents, we see alkaline detergents, disinfectant detergents (for example used in the meat processing industry) and finally caustic soda. The latter is used, for example, in the sweets industry.
Challenges and problems in using chemicals
So there are a number of challenges when dealing with chemicals. But what actually happens to a pneumatic cylinder when it comes into contact with chemicals? A number of things. First of all, the material may be affected. There can also be an accumulation of chemicals, for example due to insufficient cleaning or condensation of the chemicals. In addition, the durability (life span) of the cylinder depends on the concentration, residence time and temperature of the chemicals.
Chemicals therefore certainly have an effect on the functioning of the cylinder. The seals can be damaged. Air can leak because acids and bases enter the cylinder. And because the surface of the piston rod can corrode under the influence of chemicals, it is possible that a mechanical nick will occur in the seal.
When choosing pneumatic cylinders that must be resistant to chemicals, it is very important that the cylinder material is also corrosion resistant. The cylinders with specific seals mentioned in this blog all have stainless steel piston rods and corrosion-resistant housings. The cylinders are also designed to be easy to clean. A cylinder made entirely of stainless steel offers the best protection against corrosion. These cylinder series can be recognised by the 'CR' designation (CRDSNU, CRDNG).
Festo has various solutions for pneumatic cylinders that come into contact with chemicals:
A cylinder resistant to both acids and alkalis (P5600)
Cylinder variants with P5600 sealing are specially designed for use with acids and alkalis. They are often used in the food industry, in applications where there is direct contact with water and cleaning agents (acids and alkalis) and in applications where the cylinder is in direct contact with food in the production process (food safety).
Benefits and considerations
The chemical resistant cylinder (P5600) offers several advantages. It offers high resistance to acids and bases and good resistance to water (hydrolysis). Another important advantage is that the sealing material is FDA-approved and the grease meets NSF-H1 requirements.
A point for consideration when choosing this type is the short service life if the cylinder is cleaned intensively with the piston rod extended. This causes the grease to disappear from the piston rod, causing it to run dry. It is then possible that the seal is pushed out of the cylinder nose.
Which cylinder series?
A cylinder resistant to both acids and alkalis (A3)
Cylinder variants in the A3 version, like the cylinders with P5600 seals, are specifically designed for use with acids and alkalis. They are often used in the food industry, in applications where there is direct contact with water and cleaning agents (acids and alkalis) and in applications where the cylinder has direct contact with food in the production process (food safety).
Benefits and considerations
The chemical resistant cylinder (A3) offers several advantages. It offers high resistance to acids and bases and good resistance to water (hydrolysis). Another important advantage is that the sealing material is FDA-approved and the grease meets NSF-H1 requirements. Compared to the P5600 version, the A3 version does offer a long service life in the event of piston dry running.
A consideration in choosing this type is the expensive material used and the high production costs of this cylinder. Due to the soft material of the seal, particles can cause grooves in the seal. We therefore recommend that you always consult Festo specialists to find out what substances this type of cylinder is resistant to.
Which cylinder series?
A cylinder resistant to acids (A1)
Cylinder versions in the A1 range have good resistance to moisture and acids, unlike the P5600 and A3 range, but less resistance to alkalis. This variant is used where the PUR seal is excessively affected by chemicals or coolants as used in metalworking machinery.
Benefits and considerations
The acid resistant cylinder (A1) offers several advantages. Thanks to the FKM seal, it is highly resistant to acids and water (hydrolysis). In addition, this type offers very good resistance to oils.
A point to note when choosing this type is the low protection against alkalis with a pH value >9. This type of cylinder is not suitable for temperatures below freezing and cannot withstand particles, rust and dust due to the low tear strength of the FKM material.
An additional consideration is the use at high temperatures. In this case, the S6/T1/T4 version should be considered at the same time. Here, all other seals are made of FKM and high-temperature-resistant grease is used.
Which cylinder series?
For all the above mentioned versions, the degree of protection depends to a great extent on the type of chemicals, the concentration, the exposure time and the temperature. If in doubt, always consult our Festo specialists for specific resistance to certain materials.
Did this blog give you more insight and knowledge about the use of pneumatic cylinders with chemicals, acids and alkalis? Please feel free to contact us for more advice or tips.