Custom hoses for the process industry: El-traced, double-jacket and grounded

Chocolate can set halfway through the hose, and a sensitive product may risk losing its purity before it even reaches its destination. It's the consequences if the hose's properties cannot keep pace with the process requirements. 

A standard industrial hose is, amongst other things, suitable for transporting beer or yoghurt at normal temperatures. But what do you do if you have specific process requirements? It may be that your product needs to be kept in a liquid state at a constant temperature, remain within a specific temperature range, or be transported without the risk of sparks. In such cases, some hoses will be unsuitable. 

Under these conditions, it is not just a matter of moving a liquid from A to B, but of protecting the condition and purity of the medium throughout the entire process – and that is precisely where custom hoses can make a difference.  

We’ll look at three different types of hose and highlight how, in their own ways, they solve specific challenges across the process industry. 

Read on and find the solution that meets your needs! 

Before we match the hoses to specific media and application scenarios, we’ll first give you a short overview of the hoses’ basic principles and constructions. 

The el-traced hose comes with a built-in heating cable, which enables it to maintain the medium at a constant temperature throughout its length. The cable continuously compensates for the heat loss that would otherwise cause the temperature to drop towards the end of the hose, ensuring that the medium entering at one end is at the same temperature when it exits at the other. This makes it the natural choice for applications where even a slight drop in temperature along the way can cause problems. 

What do you do when the medium not only needs to be heated, but also kept within a very specific temperature range? This is where the double-jacket hose comes into the picture, as the temperature is controlled from the outside. Water or steam typically circulates in the outer jacket, either heating or cooling the medium during transport. This makes the hose suitable when the product needs to be kept warm enough not to solidify, yet cool enough not to be damaged. 

If you choose the grounded hose, it is not about temperature, but about safety. When a non-conductive medium flows through the hose, friction can build up static electricity, and in potentially explosive atmospheres, this charge can develop into a spark. With a grounded hose, you divert the charge away before it has a chance to build up, whilst the medium continues to flow freely. 

Choosing a custom hose is not simply a matter of selecting from standard sizes. It's the medium’s chemical structure, viscosity and the specific conditions in your production environment that determine the final choice. 

To make the choice clearer, we’ve outlined three classic challenges from everyday production that our custom hoses can handle. Perhaps you’ll recognise several of these challenges from your own process? 

“The syrup sets or crystallises during transport” 

Chocolate, honey, syrup, sauce and glue share a small but costly property: they set as soon as the temperature drops even slightly. If the hose loses a few degrees along the way, the medium forms a film on the inside, the flow becomes sluggish, and before you know it, a blockage has formed in the middle of a run. It's precisely this situation that the el-traced hose is designed to address. It maintains the medium at a constant temperature from the tank to the dispensing point, ensuring that the glue flows just as freely at the box sealing stage as it did when it left the tank.

“Gelatine has a tendency to overheat” 

Other products are far more sensitive. This applies, for example, to liquid gelatine and temperature-sensitive chemicals, which operate within a narrow window: they solidify and block the system if they get too cold, and break down if they get too hot. Raw materials with such a narrow tolerance require you to be able to control the process in both directions – not just heating up, but also slowing it down in time. It's precisely where the double-jacket hose comes into its own, because with water or steam in the outer jacket, you can achieve the correct temperature, keep it stable and avoid both a solidified plug and an overheated product in a single solution. 

“The solvent is flammable and static electricity can pose an ignition risk” 

Do you work with flammable and explosive solvents such as ethanol or acetone? If so, there is a significant risk from static electricity. A grounded hose is the right starting point here, but it's worth remembering that the hose is only part of the solution. The charge must be able to be conducted all the way to earth, which is why the correct earth connection at couplings and joints is an integral part of the system. If you choose the right hose and connection from the outset, you’ll manage the risk before it has a chance to arise. 

How do you move from technical principles on the drawing board to a working solution in practice? 

One of Denmark’s leading ingredients companies faced a challenge that many in the process industry will likely recognise. The company needed to transport a food-grade oil at very high temperatures whilst simultaneously keeping it warm using steam. The challenge was further compounded by the fact that the connection points were difficult to access and space was extremely limited. 

A standard hose was short because the task presented requirements on several fronts simultaneously: the medium needed to maintain a stable temperature, the assembly had to fit at precise angles, and the installation required a hose that fitted exactly. 

The solution was custom-made in our assembly workshop as a specially designed, double-jacket hose measuring 1.5 metres. 

• Inner hose: A corrugated FoodForce C teflon hose ensured maximum chemical resistance, minimal friction and full food-grade approval for the hot oil. 
• Outer jacket: A flexible, stainless steel bellow hose that could easily withstand the constant vapour pressure. 
• Geometry: To ensure the hose would fit into the compact system without kinking or straining the couplings, we welded on specially designed 90° elbows and rotated them 180° relative to one another.    

In such a confined process environment, it's practically impossible to achieve the correct bend radius and flexibility with an off-the-shelf standard product. This requires the hose's geometry to be incorporated into the initial design. 

A special-purpose hose is only as strong as the specification on which it is based. The most common and costly errors occur when the actual operating conditions are overlooked. When preparing your specification for our engineers, you should therefore always have answers to the following: 

• Pressure and vacuum: Remember not only the operating pressure, but also any vacuum. If the hose needs to withstand negative pressure during parts of the process, this fundamentally changes the construction. 
• Operating and storage temperatures: It's important to know both the temperature of the medium during operation and the temperature the hose is exposed to from its surroundings. A hose that cools down at night or heats up in a drying chamber is subjected to different stresses than those indicated by the operating conditions alone. 
• Approvals: When selecting a hose, you must take into account regulatory requirements, such as FDA approval or the EC 1935/2004 Regulation for food contact. These requirements have a direct impact on the hose’s construction and choice of materials, so they should be considered from the outset. 
• Heating principle: If you already have water or steam in your system, you can often utilise this existing resource. This choice affects both the type of hose and the connections it needs to fit with. If you are unsure which solution is right for your application, you are always welcome to get in touch. 

If you already have a drawing, we’ll use that as our starting point. If not, we’ll of course help you finalise the specifications before anything goes into production.  

Once the hose has been manufactured, the documentation is always provided. Together with the relevant approvals, we ensure the hose’s traceability, declarations and pressure test certificates, so that the material can be traced all the way from raw material to installation. 

When choosing a custom hose, it's important to focus on the medium and the operating conditions rather than on the hose itself. If the medium needs to be kept warm, regulated up and down, or protected against sparks, the requirement almost automatically points to an electrically heated, double-jacket or grounded hose. The rest is about getting the specifications right from the start. And that usually begins with the very first conversation. 

If you’re looking for a custom hose, we always begin with an initial discussion about your specific requirements. Call us on +45 7020 0422 or email inquiry@alfotech.eu, and we’ll advise you, find the right solution and see it through to completion together with you. 

You should choose an el-traced hose when your primary aim is to maintain a viscous medium at a constant, stable temperature over a long distance without the need for cooling. The double-jacket hose is the right choice if your process requires active temperature control. 

The maximum temperature depends on the materials chosen for the inner hose and the specific heating cable. Typically, our el-traced hose can be configured to maintain and withstand temperatures in excess of +200°C, but the exact limit is always determined based on the chemical composition of your medium and the hose’s pressure rating.

Yes, we can design custom hoses that withstand full vacuum. This requires the hose to have a heavy-duty stainless steel spiral or a specially reinforced weave in the hose wall construction. The spiral prevents the hose from collapsing internally when negative pressure occurs during either transfer, system drainage or intensive cleaning cycles.

Virtually all our hose types can be manufactured with a ground wire. This applies, for example, to solutions where the hose is used for antistatic purposes, and where the materials and construction support a secure earth connection. The specific solution depends on the choice of hose, the material and the application for which the hose is to be used, so we always recommend that you contact us if you are in any doubt.