Tag Archives: flexible metal hose

Interlocked Hose: Combating Common Failures

picture of metal hoseAs Albert Einstein once said, “The only source of knowledge is experience.” When it comes to interlocked hose, Hose Master has had a fair share of experience.  While other product lines have been added and developed over the years, Hose Master has been manufacturing and continuously refining interlocked hose since the company opened its doors in 1982.  During that time, they’ve seen hoses both excel in the field, as well as fail from a variety of factors. However, in their decades of experience, the majority of interlocked hose failures can be attributed to one of three failure modes: torque, abrasion, and over-bending.

Torque Failures

If an interlocked hose is torqued, it can cause the profile to come unlocked from itself.

Torque is arguably the greatest enemy of interlocked hoses. In any piping installation, torque can wreak havoc on the components in the system, but this is especially true for interlocked hose given its construction. Interlocked hose is made using a single strip of stainless steel. The shaping process performed on this strip makes it able to interlock onto itself and is what gives an interlocked hose its ability to flex. When an interlocked hose is torqued it begins to ‘unwind,’ which loosens the interlocked profile, increases leakage and creates a possible unraveling of the hose. Torquing the hose is a common problem because it is often a direct result of mishandling the hose in its application, but can be prevented with proper handling. However, if a hose has been known to fail from torque consistently or will see excessive handling, manufacturers often offer varying options on interlocked hoses to help combat torque and make the hose more resilient.

Abrasion Failures

Abrasion is another common killer of interlocked metal hose. Interlocked hoses are often used in pneumatic transfer applications and the conveyed media is usually some sort of particulate. For example, powders, pellets, granules, and aggregate materials are all commonly transferred media in interlocked metal hoses. One issue with these media types is that they are known to be abrasive. While the degree of abrasiveness depends both on the media type and the speed at which the media is traveling through the hose, this abrasiveness can cause a problem. Metal hoses have a relatively smooth, hard interior which allows the material to move through it at a higher speed than other hose materials. In the case of finer media, this can result in a “sandblasting” effect, which can rapidly wear through the walls of the hose. The best way to avoid excessive abrasion is to make sure that there are no extreme bends in the hose and the hose construction is compatible with the media type. Adding a liner or using a heavier gauge of material are both good options for making the hose more robust.

Over-bending Failures

The interlocked guard on this assembly has been over-bent, causing it to pull away from the fitting.

Over-bending is the third most common failure mode seen with interlocked hoses. While interlocked hose can be quite rugged, once it becomes over bent it is much less forgiving than other hose types. Because the hose’s ability to flex comes from its interlocked profile, the flexing ability is mechanical (i.e. the metal strips sliding against each other) as opposed to the material stretching like with rubber or plastic hoses. If a hose is forced to bend beyond its capabilities, the metal profile becomes distorted and will not return to its original shape. This will negatively affect the hose’s ability to flex and transfer media, and can potentially lead to a loss of interlock. Luckily, because of the hose’s mechanical construction, you don’t have to guess where it’s bending limits are.  If the hose is being flexed to a point where it stops and the ridges are touching each other, do not continue to push as the hose has reached its bending limit.

Getting the Most from Interlocked Hose

Knowing these sources of interlocked hose failure can help prevent them in an application and, if identified early on, can be addressed in the hose’s construction before it ever sees service.


The original article was written by Abby Svitana, Market Analyst,  can be found on Hose Master’s website here.

For more information about metal hose applications, or how Gallagher Fluid Seals can help with your MRO and OEM applications, contact our engineering department.

How to Handle Corrosion in Your Mill

Avoiding as Much Unplanned Downtime as Possible

Steel mill operators don’t like to have downtime problems, in fact they can’t afford to.  They want to run as much as possible, and as efficiently as possible.  Production equals dollars.  As problems pop up that cause unplanned downtime or upset production (and subsequently get addressed) over the years, they’ve driven the industry to continue to change and evolve as a whole.  So the mills of today don’t have the same issues that mills did in the past.  You can’t as easily say “Hey, we saw this exact same problem up the street on their furnace!” the way you may have been able to 50 years ago.

That doesn’t mean that mills still don’t run into issues, they just tend to be a bit more personalized. And when you have a unique issue, you tend to get a unique solution.  A mill will do its best to solve its own problems, yet each mill has their own idiosyncrasies.  When these “little” problems pop up, the mill has to find a way to deal with it.  When it comes to problem-solving in mills, there are two main schools of thought: get to the real core of the problem and fix it as completely as possible for a lasting solution, or stabilize the issue and control it through regular coordinated maintenance.  Both strategies have the same end goal: avoid as much unplanned downtime as possible by solving the problem.  But which strategy is correct?

A Lasting Solution vs Regular Coordinated Maintenance

This is seen all the time with hoses and expansion joints.  To illustrate this issue, let’s use two real-life examples: Mill A and Mill B were both using Hose Master’s Annuflex hose assemblies to transfer cooling water on the caster and experiencing similar hose failures due to corrosion from an unknown source. Both Mills had seen unplanned downtime due to the failure of these hoses, but each had a different philosophy on how to solve to the problem.

picture of steel mill“Mill A” takes the long-term calculated approach.  They analyze it, looking at everything regarding the application to isolate the underlying issue.  Surrounding piping, surrounding equipment, the hose construction, the media inside the hose…and discover that the mold powder being used during the casting is mixing with cooling water spray, and floating down onto the outside of the hoses, causing them to corrode.  In the short term, they made piping adjustments and redesigned their Annuflex hose assemblies to be made out of ChemKing which uses a nobler alloy (Hastelloy C276) to resist the corrosion, and add an external guard to help prevent particulate from coming into contact with the hose in the first place.  They then plan to install a metal shield around the casting segment where the mold powder is originating to prevent it from escaping and damaging the surrounding equipment in the future.  This solution is more time consuming and more expensive, but the issue is solved for good and removes the need for regular maintenance!

“Mill B” sees the same problem for what it is at face value: just a hose failure.  Because the hoses have been allowed to stay in service for an extended period of time, they seek to remedy the maintenance issue of hoses failing unexpectedly. Because the mill has a planned maintenance outage every 6 months, scheduling the hoses to be replaced regularly at this time will remove the issue of unplanned failures.  In order to increase the service life and guarantee performance in-between the planned maintenance outages, they make the lateral switch from Annuflex to Masterflex.  The added flexibility ensures that all the assemblies they use on the caster will be flexible enough regardless of the slight differences in piping configuration,  and that the hoses will not fail due to fatigue. The standard alloy construction can withstand the corrosion long enough to survive between outages, so by replacing them all at once they now have taken control of the service life issue.  Because of the more economical construction, they can easily afford to replace the hoses at their planned intervals and avoid any further lost production!

So, Which Solution is Right?

Well – both are right. Each mill found a way to keep their production up-and-running that makes sense to them. The hose issue plays a very small part in the overall production flow of the mill, and how they strategize and organize their overall approach to maximizing production and uptime takes into account a huge number of variables.  When helping to solve these problems, manufacturers like Hose Master have to take these differences into account.  There’s more than one way to skin a cat; and what may work for one mill, may be an unacceptable solution in another.


The original article was written by Erik Kane and can be found on Hosemaster’s website.

Gallagher Fluid Seals is a preferred distributor of HoseMaster. To learn more about how we can help with your MRO solutions, contact Gallagher today.