4 Reasons Why Your Hose Assemblies Fail

Posted on March 26, 2020 by Kurz Industrial Solutions

Written by Dan Frantz (see contact info below)

When I first started working in Wind, I had assumed gearbox hose assemblies were an afterthought for wind site managers.  With multi-million-dollar machines and many high dollar components, why would a site manager pay close attention to hose assemblies?

My assumption could not be farther from the truth.

Technicians and site managers across the country were frustrated with sourcing quality hose assemblies, on-time, that alleviated common failure modes for multiple gearbox types.  Compounded with hefty cleanup costs and oil-ridden nacelles, sites were pleading for a better solution.

As a team, we decided to travel across the country and visit hundreds of wind farms to climb towers, inspect gearbox hose assemblies, and document hose failure modes.

What problems did we ultimately see needed to be solved?

1. Fluid and Hose Material Compatibility.
2. Excess Systematic Heat.
3. Improper Routing and Minimum Bend Radius.
4. Inconsistent Manufacturing Processes.

Oil Compatibility and Material Quality.

Wind turbine gearbox oils (Castrol, Amsoil, Exxon Mobil) contain additives that help lubricate the complex gearing system in the gearbox.  The entire hose assembly, including the fittings and seals, are susceptible to premature failure if it’s not compatible with the gearbox fluid.

Unfortunately, most hose assemblies installed on your wind turbine gearboxes are made with a

synthetic rubber sourced from multiple manufacturers across the globe.  It is next to impossible to ensure oil compatibility when your rubber matrix cannot be identified or traced to its original source.

You’ll start to see your hoses break down, swell and ‘sweat’ if your oil is incompatible to your hose assemblies.  Visibly, do you see your assemblies expanding? If you run your finger down the outside of the hose, are you seeing a thin layer of oil?

If you’ve answered yes, oil has already started to work its way out of the hose.  These hoses need to be replaced.

Systemic Heat Can Accelerate Aging

Certain synthetic materials in your hoses are susceptible to excess heat.  This can be compounded if your turbines are operating in a hot climate like Texas or Oklahoma.

Do you see your hoses cracking or hardening? Most likely, your hoses are not rated to handle the heat demands of a wind turbine gearbox. According to our data, oil compatibility and overheating oil are a recipe for leaks and costly oil clean-ups.

You should also take into consideration the efficacy of your heat exchanger.  Heat exchangers, or coolers, are meant to keep temperatures at optimal operating temperature ranges.  Outside of a high-temperature hose, you may want to examine your heat exchanger.

There are a few questions to ask if you believe heat is an issue:

• Why is my system overheating?
  • Hose material? Under-sized heat exchanger?
• What is the temperature rating of my hoses?
• Are my coolers starting to foul or become gummed up with particulates?
• Am I servicing my coolers enough?

Evaluate all the variables in your system, including the quality and service cycles of your hose and coolers, and it should give you a solid snapshot of how we can fix hose failures.

For cooler questions, you can always get in touch with us and we can help identify areas of improvement.

Minimum Bend Radius

To start: A hose’s minimum bend radius the maximum amount of bend you can apply to a hose without affecting its overall performance and wear.

In layman’s terms: Don’t overbend your hose and compromise its structural integrity.

As a team, we’ve seen gearbox designs that require extreme bends and routing of hoses from outlet to inlet.  This can push your hoses outside of their allowable minimum bend radius and place unnecessary strain on your assemblies.

As an example, see Picture 1 above. You’ve exceeded your minimum bend radius and caused a volatile kink in the system where oil will start to wear the hose inner tube.  Oil likes to take the path of least resistance. To make sure you don’t experience failures due to bending radius, make sure your hoses are sized and oriented appropriately for your system. We recommend you start with our article on How to Measure Hoses.

Wind Turbine Gearbox Hoses – Proper Assembly and Crimping

Wind requires non-standard hose and fittings that are not like your traditional industries such as Industrial and Construction.  This non-standard hose and fittings must be properly sized, assembled, and crimped to spec to ensure longevity and performance.

Here are the most common hose assembly manufacturing mistakes:

• Overtightening the hose assembly causing the O-ring to fail.
• Interlocking sockets don’t match up with the crimp specs.
• Hoses are not pressure tested at 4x working pressure to ensure quality and performance.

You must consistently manufacture quality hose and fittings that are crimped to spec with proper length and orientation.  Otherwise, your hose assemblies will fail prematurely. We recommend working with a company that has decades of hose manufacturing experience and deep insight into the Wind industry.

Dan Frantz
Outside Sales – Wind Division
15755 Rogers Drive
New Berlin, WI 53151
Mobile: 920-851-5066
Email: Dfrantz@kurz.com

Categorised in: Latest Wind Power Industry News - Kurz Wind Division

This post was written by Aaron Rood