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Cable Fall Arrest / Mansafe Systems

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Cable safety lines – horizontal and vertical

There are many different products on the market, with widely differing merits in terms of quality and application.

When considering a cable system it is important to have a basic understanding of the following facts:

  • The loading on the end posts/ supports can be up to 30kN

  • Each support must be considered for a 6kN direct fall

  • If the supports are not fitted back to the structure in exact compliance with the manufacturers specifications structural calculations must be provided by the installer.

  • Resin and mechanical concrete, masonry and timber fixings must be structurally  calculated and verified with the design engineer. No company without this expertise will be able to provide sound proposals in this situation( without employing external structural consultants)

  • The manufacturer must provide a calculable and proven method to  accurately predict the loads placed upon the structure in the event of a fall

  • Shock absorption methods must have proven reliability to  limit the loads to the structure and to the user.

  • Top fix systems to roof sheets. ply and other thin materials must act to apply the fall arrest load in shear only – eg they must be proven to collapse in a controlled manner and horizontal to the affixed structure

  • All products and systems fully tested and compliant to industry best standards, which in the UK are required exceed EN795:2012.

Case studies: MacIntosh Mill Uboat Burnley LIFT

 

 

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Newsletter March 2012 – Bacup Medical Centre – Highwire’s recent success story

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Bacup Medical Centre -Highwire’s recent success story

Installation Details

Background:

East Lancashire NHS Partnership appointed Eric Wright Construction to build a new Health centre in Bacup as part of the East Lancashire LIFT program established as public–private partnership to provide bespoke tailor-made medical facilities.

Challenge:

Highwire Safety Engineers designed the fall protection to enable the access to all areas of the roof. This large medical centre comprises of several blocks with a combination of flat and pitched roofs with different roof coverings. The main challenge was to provide high standard but economical design that ensured safe, protected access to all the roof areas in need of maintenance.

Solution:

Our design utilised a combination of height safety products to provide cost effective solution for the provision of safe access to all levels of the roof.

Our engineers have proposed a layout combining the following systems:

 – Soll safety ladder 
 – Evowalk Stepped Walkway with a curved step
 – Latchways Mansafe Constant Force to slate roof
 – Latchways Mansafe Constant Force to flat roof

 

Top Trumps – The greatest Engineers of all time.

We really like this idea from Glen Cooper at Avatar Engineering. It’s fun, educational and a great way to promote the skills required to create the built environment. Take a look for a chance to vote on the Engineers included or your own personalised pack.

www.crowdfunder.co.uk/investment/top-trumps-the-greatest-engineers-of-all-time-636

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Newsletter February 2012 – An Independent Expert

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An Independent Expert

Established for over 15 years Highwire Safety Engineers pride ourselves on being a truly independent height safety provider:

  • No limitation on geographic location
  • Adaptability
  • Flexibility
 
We work hard to promote the products of Latchways PLC, as we believe that they can offer the best quality currently available on the UK market. Their products are tested to a standard higher than any other, as well as being approved by all the major roofing manufacturers. However they do not provide an exhaustive range of height safety products.

Meanwhile at HIGHWIRE, we continue to search the market for the latest innovations available, enabling us to offer tailored solutions that best suit your requirements.  

Cable systems are just one aspect of a large portfolio of products we utilize. We use our professional engineering expertise to select the products that best suit your access requirements and the structural limitation of the fix available. We analyse each and every product we recommend to ensure that, in our engineering judgement, it is fit for purpose.

Whilst valuing the association with the market leader, being an approved and certified installer of a certain product does not mean we are a part of the same corporation.

Being an independent company it is easier for us to adapt to new trends within our industry and provide solutions that incorporate the latest cutting edge engineering.  
Within our business everything is kept in-house, where our highly trained professionals strive to offer an outstanding customer service – hard to come by in construction.  At HIGHWIRE the safety of the end user always comes first.We would not propose anything we would not trust our own lives to.  

Our expertise lies within: 

Bespoke Structural fixings 
Design and installation of traditional post 
Abseiling & Fall Arrest Tracks
Abseiling Anchor Points 
Pushlocks & Eyebolts 
Specialist Safety Ladders 
Guardrails
Walkways

 Always here to answer any of your questions!

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Just the weight of a man?

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Summary

  • Yes the load is  significant structurally; as it is a product of the mans’ weight and the speed he is falling at; if we get it wrong the man will fall to the ground and the structure may fail posing a significant risk to others.

  • The speed is determined by gravity and the possible free fall distance.

  •   The potential free fall distance is dependant on the building layout, PPE used and the location of the safety system.

  • With a wire system the distance between supports (or post centres) has a significant effect- The greater the post centres, the greater the wire deflection, the greater the fall distance and potential speed.

  • Due to the number of variables the design  load should be taken as the limiting load for the PPE, 6kN per man/user.

  • Finally the shock absorbing qualities of all components must be taken seriously and be quantifiable, the legislation stipulates that selection of the equipment must best limit injury to the user.

 

The “British Standard” man weighs 15 stone 8 pounds, 100kg on metric measurements. This does not seem a significant load in construction terms.

No one would consider a ball bearing heavy, however very few people would willingly drop one on their toe. Because we all instinctively know that when objects fall they gather speed and momentum, so the further something falls the more force is required to stop it.

 

Given that basic principle of physics let’s put ourselves in the position of a man standing on a roof.

To introduce the basic concept of the loads associated with a fall, I will assume that I have carefully put on my harness and attached this to a basic anchor point using a standard 1.75m lanyard, which will extend by an additional 1.25m once deployed. So the worst case is that I can fall 3m.

  • At 1 m due to gravity I am travelling at 9.81m/s or 22 mph
  • At 1.75m when my lanyard should start to deploy I am travelling at 39mph – the impact load to my body of coming to a sudden halt is already a very uncomfortable thought.
  • Just prior to my fall being arrested after 3m I could be travelling at 66mph.

Now let’s consider I have attached myself to a wire or cable system, I now have the potential to fall a greater distance due to the deflection of the wire. If I assume that the wire supports are no greater than 10m apart I now have a maximum possible free fall height of between 5 and 6 m, with a potential impact speed of 100mph.

Clearly, if the wire is fixed at greater centres the deflection of the wire and  free-fall distance will be greater.

Simplistically

Impact force is a function of  speed and mass

So after falling 5-6 m a 100kg man will exert an impact force of around 5kN equivalent to 500kg or a large motor bike.

Anyone with experience of the construction and maintenance industries would accept that whilst 15 stone 8lb is a reasonable ‘median’ weight, a significant proportion of users are likely to weigh over 16 stone.

Most systems are designed for 2 users and the possibility of a rescue situation must be accounted for.

Lanyards generally start to deploy at just over 4kN and exert no more that 6kN at the point of their connection.

For this reason the  fall load must always be taken as min 6kN per user.

 

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Cable systems the simple facts

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Two men would have no problem at all picking up crate of beer. But if the beer was suspended in the centre of a rope, and they could only pick it up by pulling each end of the rope, this would be far more difficult: and become more and more difficult as the rope length increased.

Exactly the same principle applies with fall arrest.

This basic post is more than adequate to hold the weight of this small worker high above this famous city.However when he is suspended from a string between two posts, it can be seen that exactly the same weight exerts more force on the posts and that this effect increases as the posts are placed further apart.

In this basic desk top example, we are only considering supporting the Lego character, not arresting his fall.

In real life the fall arrest force exerted by a man falling is  6kN as discussed in technical paper 1.

The force required at each end (or reaction) if the wire  is to resist this fall, can be worked out by resolution of forces.

 

It can be seen that reactions, are a tan function of the 6kN force which gives a very narrow range of angles which will be practical.

The angle is dependant on the distance between the posts, the pretension in the wire, the deflection of the wire and lengthening of the wire under load.

 

The distance between the posts has an exponential effect on the force applied as it increases.

Basically  if proper consideration is not given to all the following :

• The post centres
• The cable tension
• The deflection of the cable
• The extension of the cable at impact
• The load absorption of the cable and shock absorbers

The load applied to the structure the system is fitted to can increase exponentially.
For a system with posts at 10 m apart and no shock absorption, and incorrectly tensioned wire, a force  up to and over 30kN – equivalent  to the weight of two 4 wheel drive vehicles will be exerted on the posts.

 

The only way to absorb energy and reduce the load is through calculable and proven energy absorption.

A system with controlled energy absorption and correctly tensioned wire can reduce the load on the post to around 10kN.

Wire systems the facts

STOP !  A cable  system is NOT  class A anchors to EN795 with a wire connecting them!

  • Cable systems are covered under clause 4.3.3 Class C Anchor devices employing horizontal flexible anchor lines. According to the standard the manufacturer must be able to calculate the loads their system will induce, and prove the accuracy of their calculations by testing.
  • All component parts of the system should be CE marked.
  • Never use a manufacturer who is unable to provide  calculations to prove their products, or who states that post centres do not matter.

There are some systems being sold, that quite simply do not work and have not been correctly tested.

 

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Newsletter August 2010 – Summer Special

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Summer Special

It’s that time of year again… the weather has perked up (sort of) the kids are off school again (joy) so it’s about time that much needed maintenance works on the roof is carried out.

However with the never ending list of regulations in place it’s difficult to know how to keep yourself and your staff safe from both falls AND prosecution.

It’s all about preventative measures; you wouldn’t enter the sun without sun cream so why endanger lives by not using the appropriate fall protection equipment.

Keep reading for Highwire Ltd’s guide to staying safe this summer:

Why do I need to have any fall prevention in place?

The Regulation that govern safe works at height are:

The Work at Height Regulations 2005
and  The Construction (Design and Maintenance) Regulations 2007

These are in place not to make our life difficult but to keep ourselves and our work force safe. Recent figures published by Riddor show that these Regulations are working as the number of deaths in construction has fallen by 15%.

When working at height what are the best products to prevent falls?

There are two products Highwire Ltd supplies to prevent fall from height on roofs, these are:

Latchways VersiRail – guardrail is perfect for group protection. The Latchways VersiRail product comes in a variety of finishes such as curved or aluminium.

Latchways Mansafe Systems – the Latchways Mansafe Systems are ideal for one or two man jobs such as routine roof maintenance works. The Latchways Constant Force technology is a market leader within the height safety sector.

We believe these are the best products on the market for not only best limiting the damage to the building but also best limiting the injury to the end user in the event of a fall.

What are the Latchways Mansafe Systems used for?

Flat roof edges – accessing gutters, lights, waterproofing, lightening conductors, cleaning and inspection.

Flat roofs – access to other roofs, aerials, air conditioning, ventilation shafts, access to cradles, falls through sky lights.

Pitches roofs – maintenance, repair, gutters, equipment inspection, and snow clearance.

What are the benefits of choosing a Latchways Mansafe System?

 

  •  EC Declaration of Conformity
  •  CE Marked
  •  Roofing System Manufacturer Approved
  •  Product Marking
  •  Product Testing
  •  Fall Arrest or Fall Restraint
  •  Registered Installers
  •  Insurances and Guarantees

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Fall Arrest – Track systems

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Fall arrest track systems (class D EN795)

Fall arrest track systems can be used as an alternative to cable systems, however they are not suitable for afixing direct to the roof structure.

Appropriate  applications include, walkways , gantries and unguarded balconies.

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Guardrail

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Guardrail

Highwire can provide, free standing,  fixed  or collapsible guardrail to suit  any situation where collective fall protection is required.

 

 

We  can provide a range of styles to suit aesthetic and budget requirements, whilst ensuring your height safety responsibilities are fully met.

Our experienced teams work quickly and effectively to  provide a high quality install with minimum disruption.

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Walkway

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Walkway

Walkway

Walkway provides a level, anti slip  route for tasks such as rooflight cleaning and plant inspection. Both safeguarding the worker and the delicate surface of the roof.

Highwire can provide a range of walkway and gantries to suit a wide variety of applications and budgets.

Case Studies: Bacup

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Eye bolts & Push locks

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Eye bolts (class a/A1 EN795)

Latchways, d-ring, eye bolt, window cleaning, height safety, highwireSingle point anchorage  work positioning device mainly used for window cleaning applications.

Eye bolts can be fitted  to a wide variety of differing buildings and structures, including  retrofit.

 

Our in house structural expertise enable us to verify the affixed structure for the appropriate applied loads.

 

Push lock, latchways, highwire, window cleaning, height safetyPush locks (class A1 795) is essentially a demountable eye bolt  providing a flush finish, generally for internal applications.

 

Both are available in a variety of different finishes.

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