Your Underestimated Life-Line…… - Breathe Safety · Breathing air hoses are probably the simplest component in any airline breathing apparatus system, yet they are one of the

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Copyright © Breathe Safety Ltd 2017

Your Underestimated Life-Line……

The Importance of Breathing Air Hose or Compressed Air Supply Tube (CAST)

Construction, Assembly, Inspection and Working

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Contents

Introduction

Investigating incidents with breathing apparatus failure.

EN Standards for breathing hose and CE Marking

Critical elements in a breathing hose construction

Typical Failures in Manufacturing

Where breathing air hoses fail in use

How to avoid failure of breathing air hose

Summary – what are the loses?

Further Information

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Introduction

Breathing air hoses are probably the simplest component in any airline breathing apparatus

system, yet they are one of the most under-rated in terms of importance. When you don an

airline breathing apparatus set, a long duration supply of compressed air feeds you either

from a compressor or high-pressure cylinder bank, the functionality of the whole system

depends on the integrity of the airline that connects the wearer’s breathing apparatus to the

compressed air source, and yet it is the most neglected part of the system in terms of

manufacturing quality control, and ongoing maintenance. Airline breathing apparatus sets

are checked meticulously, cylinders are tested, compressors are serviced and air quality

tested, but what about the humble airline that everyone expects to just ‘work’, and yet the

statistics show that more than half the serious failure incidents with airline systems are with

the airline!

Compressor / Cylinders Breathing Airline Airline set

In advanced breathing air systems and diving applications the air supply hose is not

surprisingly called the ‘umbilical’, bringing the essentials for maintaining life in the most

hazardous of environments, it remains one of the most critical parts of the system.

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Investigating incidents with breathing apparatus failure.

Any incident involving breathing air hose is generally high profile in terms of safety, because

typically they are used in atmospheres which are not respirable or I.D.L.H. (Immediately

Dangerous to Life and Health) There has been many incidents, which as a hirer we have

had to investigate with hire fleet hose failures. Establishing the root cause of failure has

always been the emphasis of our investigation, and learning how we as a manufacturer and

hirer of breathing air hose can improve the following in view of there being no repeat

incidents:

• Our hose, couplings, and specification of the product

• Our processes in hire and manufacturing inspection

• The client’s working processes

The successful strategy of refining the cause of failure, means that repeat incidents have

been almost eliminated.

EN Standards for breathing hose and CE Marking

The standards which cover breathing hose are EN14593 and EN14594, and these cover not

only the hose but the integrity and type of coupling. Some of the type approval tests are

quite challenging to pass. Tests cover tensile (pull) testing to 1000 Newtons, kink resistance,

crush resistance, flexibility, heat resistance and antistatic properties. The hose should

generate no significantly noticeable odour, and be resistant to the environment in which it is

used. It should withstand over pressure of up to 30 bar.

The standards state that couplings should not be affected by hose twisting, with at least one

swivelling coupling fitted adjacent to the wearer. The couplings should be designed such that

they prevent unintentional interruption of the air supply, typically this means that they require

at least 2 intentional actions to un-couple.

Hoses should be marked with appropriate standard conformity and any special conformity

such as antistatic.

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Critical elements in a breathing hose construction

A breathing air hose is not a lot different to other compressed air hoses, other than the

requirements of the standards. The construction is the same typically with an inner layer,

outer layer, and braided reinforcement in between. Materials used will depend on the

application but typically are PVC, nitrile rubber or Polyurethane.

Hose terminations are critical – quick release couplings must comply with the EN standard

which requires 2 deliberate actions to uncouple. Major manufacturers who have breathing air

specific couplings are CEJN, Rectus and Stabil. The greases used in these couplings are

also breathing air safe.

Hose terminations will be made from nickel plated brass, brass, or stainless. Corrosion is

minimised with these materials. Stainless is preferable as its corrosion resistance is better

and the material is harder and tougher. Brass although acceptable will tend to crack if its

thickness is inadequate.

Apart from the quick release couplings themselves, the success of a hose termination

consists of 3 elements, very much like the fire triangle, if one is removed then it will result in

failure of the hose assembly:

Hose

Hose tail Ferule

Outer layer

Braided reinforcement

Inner layer

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Typical Failures in Manufacturing

The following shows typical hose damage/ failure and its cause:

• Hose bore restricted by overcrimping, or improper hosetail/ ferule specification,

where hose ferule is longer than the tail.

• Hosetail pulls out easily – improper hosetail/ferule specification

• Hosetail specification and design inadequate – hose retention will be affected by

number of barbs , length of tail, and barb shape.

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• Ferule design -length, material, how much it is swaged.

• Hose tail fitting cracked either through overtightening or impact in use

• This cross section shows where the hose is not pushed up tightly to the end of the

ferule. Although not serious in this case it can be pushed off further and inadequate

barbs on the hose tail grip the hose.

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Where breathing air hoses fail in use

The environments where breathing apparatus is used are typically harsh, and the brunt of

this is taken by the hose. The airline set is on the wearer and who usually has respect to his

safety, the air source is outside the work environment, but the hose is dragged, dropped,

and snagged in the worst conditions, and exposed to the worst chemicals and

contamination. In some ways, the failures are no surprise. The following are typical failures

in use:

• Steam or hot pipework damage to hose – weakening its wall

• Hose tail pulls out of hose – hose tail inadequate, or ferule not correctly swaged on to

the hose

• Coupling comes apart – dirt ingress prevents swivelling of male and female

couplings, and unscrews the female coupling itself, or can unscrew the coupling from

the hose tail.

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• Hose rupture caused by hose tail digging into hose and creating weakness when

sharply bent.

How to avoid failure of breathing air hose

1. Ensure the hose is approved

Hoses must be either CE of NIOSH Approved, and should be marked accordingly.

2. Ensure the hose is correctly specified for the environment it will be used in.

There are many hoses that will meet the requirements of breathing air standards, that

will not necessarily hold up to the work environment they are used in. light duty will

fail in heavy industrial environments, while other seemingly adequate hoses may not

offer proper chemical resistance.

3. Ensure the hose is assembled by a company who:

• Batch tests their assembled hoses at a suitable regularity.

• Has proper hose assembly design and validation before product launch

• Has assembly quality control in place.

• Inspects and tests hoses adequately before supply or hire.

4. Ensure the hose is inspected in line with manufacturer’s requirements

5. Ensure the hose is inspected before and after use, bearing in mind the severity of the

usage. Maintenance is critical – no hose will last forever. Some hoses are used for 5

years and look like new – others will barely last for weeks in very harsh environment.

Inspection and testing needs to be appropriate for the application.

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Summary – what are the loses?

The ultimate price of breathing air hose failure is loss of life.

Although less serious, but still very disruptive, any incident creates other losses. Crews of

workers are stood down while incidents are investigated, machinery lies idle, and work is

delayed. One such case where we investigated an airline incident, it cost a tank cleaning

contractor with 10 operatives and associated machinery over £6000.00 per day!

Learning from the past is key in ensuring that there are no incidents and an airline BA user

can go to work confident that his hose will not fail.

Report Prepared by Nick Aris, Breathe Safety Ltd, 6 June 2017

Further Information

Breathe Safety and its sister company, Luno Systems, specialise in the manufacture of airline breathing

apparatus, and have a range of equipment for hire and sale. Other support services offered are consultancy,

product development, training, and equipment servicing. Having the ability to manufacture equipment compliant

to CE and NIOSH Regulations, and conduct type approval testing in our ISO17025 UKAS Accredited laboratory

means we can offer a full support service to any client in this sector of safety.

This whitepaper is copyright © Breathe Safety 2017. No part of this document may be

copied without prior consent from Breathe Safety Ltd

Your Underestimated Life-Line…… - Breathe Safety · Breathing air hoses are probably the simplest component in any airline breathing apparatus system, yet they are one of the

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