Measuring Stripwound Hose: Compressed, Relaxed, and Extended

Measuring Stripwound Hose: Compressed, Relaxed, & Extended State

By: Cam LaRocco | On: April 1, 2024

If you’ve ever found yourself puzzled over stripwound hoses and how to accurately measure them, you’re not alone. Whether you’re safeguarding cables or transferring dry bulk materials, understanding the unique characteristics and proper measurement techniques of stripwound hose is crucial. In this blog, we’ll discuss the different types of stripwound hose and their applications, the importance of measuring them correctly, and share some valuable tips to ensure you get the most out of your hose assembly. Let’s jump right in and get you well-equipped to make an informed decision.

Defining Stripwound Hose

Stripwound metal hose is a rugged product made from a strip of steel that is profiled and continuously wound around a mandrel to form a hose. Stripwound metal hose, although not gas tight, is rugged, making it excellent for use as a guard, an open-ended exhaust hose, and for the transfer of dry bulk materials.

Importance of Measuring Overall Length in Stripwound Hose

Every application is different, so you must ensure each assembly is designed specifically for your purpose and operating conditions. A hose must be of the correct length in order to serve its purpose. A hose that is too short – or too long – could result in reduced hose life, product damage, and/or safety concerns.

Properly measuring the overall length (OAL) is important to ensure the hose will perform properly in the intended application. The overall length (OAL) of a hose assembly is defined as the total length of the hose including the fittings, and must be measured carefully since stripwound hose can compress and extend to various states of length.

Types of Stripwound Hose

There are two main types of stripwound helical profiles: interlocked and squarelocked. Interlocked profiles can be further identified as roughbore (made using a single strip) or smoothbore (adding a second strip to the hose interior). Stripwound hose can also be offered as a Floppy product, and can be made using either a fully interlocked profile or a squarelocked profile.

Floppy metal hose is primarily used as a protective covering for wires, fiber optic cables, and other hoses to prevent abrasion and overbending. The balanced design allows for maximum flexibility of a stripwound metal hose, whether it be interlocked or squarelocked.

Roughbore metal hose is considered a general-purpose flexible hose that is ideally suited for conveying dry bulk materials, gas exhaust, or used as a protective cover. Smoothbore metal hose is essentially a roughbore hose with another metal strip added to the profile, providing a smoother interior surface to prevent media damage or buildup inside the hose. Smoothbore hose is used for dry bulk conveying where the media being transferred is finely milled, easily damaged, and/or abrasive.

(Roughbore interlocked profile)

(Smoothbore interlocked profile)

(Floppy interlocked profile)

(Squarelocked profile)

Various States of Length of Stripwound Hose

There are generally three states of length regarding any type of stripwound metal hose: compressed, extended, or relaxed.

A stripwound hose is in its compressed state when all the convolutions are completely closed and against one another. This is the shortest possible length the hose can achieve and also the least common. Additionally, when an interlocked hose is bent as far as it can go, the inside surface is in the compressed state.

On the other hand, when fully bent, the outside surface of the hose is in the extended state. A stripwound hose is at its extended length when it is stretched as far as it can reach, and its convolutions are at max separation. This is the longest possible length the hose can achieve.

All stripwound hose assemblies are measured in the relaxed state. For bulk hose, consult the catalog to verify in which state the hose is sold. To measure a hose, it must first be returned to the relaxed state. To do this, coil the hose tightly, then gently lay it out straight without pulling on the assembly. The Relaxed Length (R – Figure 2) is defined as the average between the Extended Length (E – Figure 3) and the Compressed Length (C) of the hose (Figure 1)

The difference in length between extended and relaxed is referred to by Hose Master as the “relaxation factor” and is typically around fifteen percent, which is a significant change in the length of the hose.

(Various states of length)

Tips and Tools for Measuring Stripwound Hose

There are some basic tools you want to have on-hand before you measure the length of a stripwound hose. Including a tape measure and possibly an extra set of hands—depending on the size and length of the assembly. When it comes to getting interlocked hoses into their fully extended state, it is best to use heavy-duty pliers or clamps to securely latch on to each end of the hose.

Roughbore & Smoothbore Interlocked Assemblies: First, take the assembly and roll it into a tight coil. Then, gently lay the hose out flat and straight. This will put the assembly into its “relaxed” length, which can then be measured.
Roughbore & Smoothbore Interlocked BULK: All of these bulk products are sold in the relaxed state except for unpacked bulk roughbore, which is sold in the extended state. Bulk unpacked roughbore should be ordered in lengths approximately 15% longer than the required relaxed length.

Floppy Interlock and Squarelock: These products are typically sold in their neutral or resting state, which is often near the fully extended state. Other measurement methods (relaxed, compressed) can be used upon customer request.

In the world of stripwound hoses, comprehending the nuances between compressed, relaxed, and extended states is necessary to make an informed purchase decision. At Hose Master, we pride ourselves on our commitment to continuous improvement, ensuring that each hose we manufacture adheres to the most stringent standards of durability, flexibility, and performance. Our team is always here to assist you in ensuring you measure your hose assemblies properly, helping you make the right choice for your needs. Our crafted stripwound metal hoses are designed to cater to a diverse range of industry requirements, setting the benchmark for quality and reliability.

We invite you to experience the Hose Master difference firsthand. Reach out to us directly or connect with one of our authorized distributors today to discover the unparalleled quality and expertise we bring to the table.