Aggressive media in the process industry: How to choose the right hose

The industrial hose has been running without any problems for months. Then comes a routine night of CIP cleaning, and the next day production comes to a standstill due to a leak that nobody saw coming. Or take the chemical production line, where the solvent gradually softens the hose day by day, until one morning it gives way right at the coupling.

Aggressive media represent one of the classic hazards in a process environment, on a par with hot surfaces and explosive atmospheres. They affect the hose in various hidden ways and break it down from the inside, long before the damage reaches the surface. 

This time, we’re taking a deep dive into the world of aggressive media and having a look at the practical challenge we often encounter with our customers: how to match the chemistry to the right industrial hose. But let’s start by looking at what ‘aggressive’ actually means.

Aggressiveness is a combination of chemical reactivity, concentration and temperature. The higher the levels of these three factors, the greater the strain on the hose. An acid that's harmless at 10 per cent and room temperature can behave completely differently at 65 per cent and 80°C.

Four factors increase the strain:

• Concentration – 10 per cent acid behaves differently to 65 per cent.
• Temperature – a hose that withstands the acid at 20°C may fail at 80°C.
• Duration of exposure – constant contact places a greater strain than short exposures.
• The type of medium – acids, bases, solvents and alcohols exert different levels of stress.

The point is that ‘mild’ and ‘aggressive’ aren’t absolute categories. The same medium can be both, depending on concentration and operating temperature. It’s precisely why it’s worth taking a closer look at which families of media you encounter in your process environment.

In the process industry, which encompasses the production of food, medicines and chemicals, there're countless media involved in a wide variety of processes and applications. When it comes to more demanding media, we generally divide them into three main categories.

Light liquids and flammable media
Oil and petrochemical media, petrol, gases and other hydrocarbons. These are found in refineries, the petrochemical industry and the fuel sector. The chemical load's usually moderate, whilst the fire hazard and static electricity can be significant. This forms part of the wider discussion on explosive atmospheres.

Concentrated acids and bases
Sulphuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide. Typically found in the chemical process industry, surface treatment and the metal industry, but also has application in cleaning processes within food and pharmaceutical production. Here, the actual chemical exposure's greatest, and the choice of materials is most critical.

Alcohols and alcohol-containing media
Everything from ethanol and isopropanol to beer, wine and spirits. Alcohol isn't particularly aggressive at low concentrations, and beer itself is a mildly acidic, low-alcohol liquid that places few demands on the hose. However, breweries and distilleries are nonetheless demanding environments: CIP cleaning uses concentrated acids and bases, and higher alcohol percentages later in the process chain can significantly alter the load. Hoses for beer, wine and spirits production therefore cover a wide range, from versatile solutions for low-alcohol media to UPE-liner hoses capable of handling up to 98 per cent spirits.

The three categories have different requirements, and it's the material of the industrial hose that determines whether these requirements can be met.

The choice of material determines chemical resistance. Five groups cover most of the process industry’s requirements, from light CIP tasks to the transport of the most aggressive concentrated media.

• PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene) and PFA (perfluoroalkoxy) are the most chemically resistant materials and can withstand both aggressive media and a wide range of temperatures. PTFE withstands the highest temperatures, FEP is more flexible and typically transparent, and PFA combines PTFE’s chemical and thermal strength with a flexibility closer to that of FEP. It's worth understanding the practical differences between FEP, PTFE and silicone for anyone needing to choose between them.
• UPE (ultra-high-molecular-weight polyethylene) offers good wear resistance and is resistant to many acids and bases. It's therefore often used as an inner liner in chemical hoses.
• EPDM (ethylene-propylene-diene rubber) is resistant to acids, alkalis and alcohols. It's frequently used in industrial hoses for CIP cleaning and the transport of beer and beverages. Unlike NBR, the material isn't suitable for oil and grease.
• NBR (nitrile rubber) derives its strength from its resistance to oils and fats, not from its resistance to acids. It's primarily used for the transport of oil- and fatty media, as well as dry powders with high friction.
• Silicone offers good flexibility and a wide temperature tolerance, and it's the material of choice in many hygienic environments, particularly within the pharmaceutical sector. It withstands milder chemicals well, but not strong solvents or media containing oil and fatty substances.

A summary of the materials and media is as follows:

The entries in the table are a starting point, not a definitive list. Concentration, temperature and operating cycle can easily affect the material’s compatibility. If you have a specific compatibility query, we’ll look into it with you.

A classic problem in the process industry is the industrial hose, which copes well with transporting the day-to-day process medium but fails far too early due to the regular cleaning cycle. In food and pharmaceutical production, there're two methods in particular that put a strain on the hose in their own ways.

CIP (Clean-in-Place) exposes the hose to aggressive chemicals. Take a dairy or a brewery as an example. The daily process medium – milk or beer – is mild, but during CIP, hot lye (sodium hydroxide) and acid, typically nitric or phosphoric acid, circulate through the system to break down fat, protein and mineral deposits, often at 80°C or higher. The overall strain's often greater than that caused by the process medium itself, and materials that cope well with the daily flow may deteriorate or lose their pressure resistance over time.

SIP (Sterilise-in-Place) places a different kind of strain on the system. Here, it's not the chemicals but the steam and heat that put pressure on the hose, typically saturated steam at well over 100°C. This places specific demands on temperature and pressure ratings – but it's a thermal challenge, not a chemical one. In some places, many are now replacing SIP with hot-water cleaning via plate heat exchangers, whilst steam-based SIP remains widespread in many European markets. Regardless of the method, it's the same point: the hose must be able to withstand the heat generated by the cleaning process.

It's important to take the cleaning regime into account from the outset when specifying the hose. Both the day-to-day medium and the cleaning chemicals must be matched if the hose is to last cycle after cycle.

The more precisely you can describe the environment, the better we can identify the right hose first time. Five pieces of information do most of the work:

1. Which medium – or media – is the hose intended to carry? The choice of material starts here, as it's the medium that determines whether the hose must withstand acid, alkali, solvent or a combination thereof. Also bear in mind the cleaning chemicals: a hose selected solely for the daily medium may fail the first time the CIP system runs lye and acid through it.
2. How high is the concentration? The same acid behaves very differently at 10 per cent and 65 per cent. A material that handles a diluted solution without any problems may deteriorate rapidly at high concentrations. Without knowing the concentration, a material recommendation's effectively just a guess.
3. What's the temperature – during operation and cleaning? Temperature shifts the limits of what a material can withstand. A hose that withstands the medium at 20°C may fail at 80°C, and it's often during CIP and SIP that the temperature peaks. Therefore, specify both the normal operating conditions and the highest peaks the hose will encounter.
4. What's the pressure, and is it constant or variable? The pressure determines the hose’s construction and reinforcement, not just its material. A constant suction task places a different load on the hose than a pulsating flow, where the hose repeatedly expands and contracts. The mechanical stress interacts with the chemical stress and can accelerate degradation.
5. How often is the cleaning cycle run, and with which chemicals? A hose cleaned daily with aggressive chemicals wears out faster than one cleaned weekly. And there's a big difference between leaving the hose filled with chemicals between runs and flushing it through with water afterwards. A hose left standing with concentrated chemicals for hours is subjected to far greater stress than one that's emptied and flushed. Please tell us how you handle the hose between runs – this often changes the recommendation.
6. How often is the cleaning cycle run, and with which chemicals? A hose cleaned daily with aggressive chemicals wears out faster than one cleaned weekly. The frequency determines the cumulative chemical load over time. Together with the cleaning chemicals, this provides a realistic picture of the hose’s actual service life.

With these five factors in mind, the choice is rarely difficult. Without them, you'll risk ending up with a hose that looks suitable on paper but isn’t in practice.

These material groups are relevant across a range of industrial hoses. Three archetypes from our range cover the spectrum from light CIP tasks to the harshest concentrated chemicals:

• ChemForce ATEX is a corrugated PTFE hose with a stainless steel braid and excellent resistance to pressure, temperature and chemicals. It's also antistatic and ATEX-approved. An obvious first choice when the chemicals are harsh and the environment is also potentially explosive.
• Prochim SPL/10-UPE is a hard-wearing chemical hose with an internal UPE liner and an EPDM outer layer. It's suitable for both suction and pressure applications involving varying chemicals, and it's antistatic and ATEX-approved.
• Alichem/SPL is a chemical hose with an EPDM inner lining and a built-in steel spiral. It's suitable for light chemical liquids and CIP cleaning, but not for highly concentrated acids.

The choice between them is based on the five questions from the previous section. If the standard range isn't sufficient, our assembly workshop can tailor a bespoke solution to ensure a precise match.

Aggressive media work unseen, but choosing an industrial hose needn’t be a guessing game. The three media families, the five material groups and the five key factors together provide a solid basis for making the right decision – without needing to be a chemist to get there.

Are you unsure about what your chemical process requires? Our sales team advises on precisely these kinds of choices every day. Call us on +45 7020 0422 or send an email to inquiry@alfotech.eu, and we’ll look at your production line together.