Report on Roof Anchor Safety
Report on Roof Anchor Safety (Word Doc)
Contents
1.0 INTRODUCTION 4
2.0 SCALE OF THE ISSUE 4
3.0 NATIONAL STANDARDS 5
4.0 ANCHOR DESIGN AND TESTING 6
5.0 ANCHOR MATERIAL 7
6.0 ANCHOR ATTACHMENT 8
7.0 SUBSTRATE STRENGTH 8
8.0 INSTALLATION 8
9.0 INSPECTION AND MAINTENANCE 9
10.0 RECOMMENDATIONS 9
11.0 CONCLUSION 10
APPENDIX A 11
APPENDIX B 12
APPENDIX C 13
1.0 Introduction
1.1This report is tendered in response to the unfolding crisis in Wellington regarding the safety of roof anchors.1.2 It is presented to the Chief Executive of Standards New Zealand, Department of Labour, ACC, Height Safety Organisation of New Zealand and all interested bodies or companies.
1.3This report is intended to show that the anchor crisis in Wellington is not a unique situation, but a systemic problem across Australia and New Zealand, with potentially catastrophic consequences.
1.4 Further this report intends to highlight the areas of weakness within the current ASNZ Standards and recommend amendments to ensure quality and safety within the industry.
2.0 Scale of the Issue
2.1 According to reports 60 buildings in Wellington are being assessed for possible failing anchors.
2.2 Forty-two anchors tested at St Peters Apartments in Willis Street have been condemned.
2.3 Three other buildings in Wellington have been found to have faulty anchors.
2.4 Anecdotal evidence suggests that a survey of roof anchors throughout New Zealand will follow the wellington trend, compromising structures, anchors and safety.
3.0 National Standards
3.1 ASNZ1891.4(2009) states:
1.2 Objectives and principals ….’The objective of the standard is to provide the users of fall-arrest devices and systems with requirements and recommendations relating to their selection, use and maintenance.’
3.1.2 Single point anchorages suitable for direct connection or personal fall-arrest equipment
(a) ‘The anchorage and structure to which it is attached shall be capable of sustaining an ultimate load equal to that shown in table 3.1’ (15KN for 1 person, 21KM for 2 people).
Paragraph 3 ’The building or structure and anchorage point shall be assessed by an engineer, unless it is clear to a height safety supervisor that anchorage system is structurally adequate.’
(f) Possible deterioration of anchorages or substrate damage e.g. that caused by chemical attack, corrosion or atmospheric conditions, should be considered in the anchor material and design.
3.2 While the objective of the standard is clear there is no clarity over how the objectives should be met.
3.3 The lack of direction and clarity in the standard has lead to the systemic anchor crisis the industry is now facing.
3.4 New anchors and rivets are tested to the loading rate required by the standard and accepted as suitable.
3.5 No testing is required on the attachment point.
3.5 This is totally inadequate.
3.6 For the fall arrest system to operate safety over the lifetime of the system the following areas must be addressed:
1 Anchor design and testing
2 Anchor material
3 Anchor attachment
4 Substrate strength
5 Installation
6 Inspections and maintenance
3.7 The fall arrest system is only as strong as the weakest link in the system.
3.8 All aspects of the system must be legislated and regulated to ensure safety.
4.0 Anchor design and Testing
4.1 The anchor design must:
1 Withstand the loading (including safety factor) specified in
ASNZS1891.4(2009)
2 Be manufactured from material compatible with the environment, in
particular the effects of:
1 Cold temperatures
2 Hydrogen sulphate
3 Salt
4 Moisture
5 Humidity
3 Be compatible with other roofing products and materials
4.2 Anchor testing must be undertaken under the following conditions:
1 Destructive testing
2 Load testing
3 Age tested
4 Simulated in situ Tested
4.3 Destructive testing should be carried out to demonstrate the anchor can withstand the appropriate stresses established in ASNZS1891.4(2009), in both the strongest and weakest directions.
4.4 Load testing should be carried out to demonstrate the anchor can withstand the appropriate loads established in ASNZS1891.4(2009), in both the strongest and weakest directions.
4.5 Age Testing should be carried out to demonstrate that the anchor is capable of performing above ASNZS standards throughout the duration of its life in the harsh environments of New Zealand and Australia.
4.6 Simulated in situ testing should be carried out to demonstrate that the anchor, fixing attachments and substrate together provide performance above ASNZS1891.4(2009) both when new and by age testing over the duration of the system.
4.7 All testing should be undertaken by an independent testing facility on calibrated machinery.
4.8 The anchors should have a Producer Statement (PS1) issued by an engineer.
5.0 Anchor Material
5.1 Traditionally anchors are manufactured from stainless steel.
5.2 However stainless steel is not appropriate in all situations, particularly in acidic environments or for use with certain roofing materials.
5.3 The finish on stainless steel must be of high quality to ensure durability of the product.
5.4 Polishing or pickling creates a smooth finish which significantly reduces surface area and increases resistance to corrosion.
5.5 However stainless steel anchors with a rough finish are acceptable within current standards despite their tendency to produce long term safety concerns.
5.6 Mild steel has been shown to provide a better anchor material than other grades of steel, this is because it deforms slowly under stress rather than fracture or snap. (See appendix A)
5.7 Galvanised material tests show that load bearing capacity is reduced by up to fifty per cent. (See appendix B)
5.8 New materials are becoming available all the time, it is essential that all materials or treatments are thoroughly tested and certified in the tests indicated in 4.2 before being used in the field.
5.9 New material and systems are being introduced without appropriate safety buffers, or tested to European Standards not ASNZS1891.4(2009)
5.10 Conditions in Europe are different to those in Australia and New Zealand and it is not appropriate or safe to use European Standards.
5.11 Systems with inbuilt shock absorption are available reducing theoretical stress on the anchor to 3.1KN.
5.12 These systems are then installed with attachments and on substrates designed or rated at 3.1 KN.
5.12 The shock absorption systems should still have a times two built in safety factor.
5.13 Hollow steel anchors are acceptable under the standard; however there is no way of inspecting these for internal corrosion or rust.
5.14 New Zealand has an average humidity of ninety per cent (world wide the average is seventy per cent), this combined with night sky radiation makes any hollow anchors dangerous in our environment.
6.0 Anchor Attachment
6.1 Having anchors that surpass ASNZS1891.4(2009) is insufficient if the anchor attachment and or the substrate is not capable of handling the required load. (See appendix C)
6.2 The anchor attachment requirements are different for different anchor designs and for different substrate materials and designs.
6.3 Anchor attachments must be physically tested to demonstrate they are capable of absorbing the appropriate stress and load.
6.4 Testing should be mandatory for each situation, post production and age tested to ensure standards can be met over the lifetime of the system.
7.0 Substrate Strength
7.1 It is essential that a structural engineer or the structural component manufacturer provides a certificate of appropriate substrate strength before anchors can be mounted.
7.2 This is particularly important on older buildings where anchors are introduced or replaced.
8.0 Installation
8.1 Correct installation of anchors is vital to ensuring safe operation of the system.
8.2 Installation of anchor systems should only be permitted by fully trained, experienced and certified installers.
8.3 Certified installers ensure products are installed by professionals who understand and comply with manufacturer’s instructions, building codes and regulations and all relevant ASNZ Standards.
9.0 Inspection and Maintenance
9.1 All systems must be inspected in line with ASNZS1891.4(2009).
9.2 Inspection and testing should only be carried out by fully trained, experienced and certified personnel.
9.4 A national certificate should be introduced covering installation and inspection of roof anchors.
10.0 Recommendations
10.1 ASNZS1891.4(2009) be expanded to include detailed descriptions of how its objectives should be met; or an ancillary document created to provide this information.
10.2 All existing anchors and attachments must be inspected and certified prior to use.
10.3 A full independent report into the extent of the crisis and ways of preventing future safety problems is commissioned.
10.4 A suite of standards be introduced covering:
1 Anchor design and testing
2 Anchor material
3 Anchor attachment
4 Substrate strength
5 Installation
6 Inspections and maintenance
10.5 All installers of roof anchors must be registered and certified.
10.6 Inspection and testing should only be carried out by fully trained, experienced and certified personnel.
11.0 Conclusion
11.1 There is a systemic failure in the industrial fall-arrest systems and devices industry.11.2 ASNZS1819.4(2009) is not working to provide sufficient guidance and legislation in the industry.
11.3 Urgent action to mitigate the current failure of systems and put systems in place to remedy the situation is required to prevent serious harm and fatalities from occurring due to systemic failures.
11.4 The recommendations 10.1 to 10.6 can end the crisis and lead to dramatic improvements in height safety.
Appendix A
SAFETOR ANCHORS;
1. Are manufactured from mild steel.
2. Will deform gradually when loads are imposed on them.
3. Have ease of adjustment for installation to different size structural members.
4. Provide for immediate visual signs of having had a load imposed on them.
We at Collins Corporation Ltd believe that these features are very important aspects for consideration when choosing which type of Anchor Device to install in any building or structure. We engaged the services of a Telarc registered Material Testing Laboratory during our design process to ensure that these features were optimized, and that compliance with the Australian and New Zealand Standards was achieved.
MILD STEEL has been used because this grade of steel bends gradually as loads are imposed on the Anchor. We noted during the testing process that other grades of steel had a tendency to fracture and snap at lower loading capacities. The other tensile steels would bend under loading but not deform. We believe it is important that strain from falls sufficient to bend the Anchor should leave a visible sign that the Anchor has withstood those loads. This feature is similar to other fall safety equipment items which have in-built signs of shock loading.
TENSILE STEEL was not selected for the anchors for two reasons.
1. Although tensile steel does have some elasticity in the steel it can snap without warning. This showed in our tests when we loaded the anchor to 15kN then backed it off and reloaded it again. Only 8kN was achieved on the second test. This was to simulate a two person fall.
2. The second reason was temperature. After a discussion with MTL and a number of engineer’s low temperature of around -10 degree can effect the tensile steel by causing it to become brittle and the possibility of failure could increase.
BENDING due to significant loading is a safety feature that will alert any prospective user that the Anchor has been damaged and should be replaced before anybody attempts to use it. Bending may occur if the Anchor is used for some purpose other than fall prevention or fall arrest. It is amazing what Anchors have been used for in some situations.
Note: The anchor that has just had an impact placed on it by a 1 or 2 person fall may be required in the rescue or recovery of the person/persons. That is why the anchor point and attachment needs to be of such a significant strength.
Appendix B
WHY NOT GALVANISING? is a question we are often asked. We tested our product with galvanizing as the protective system. The results were alarming. The load bearing capacity was reduced to less than half of that for the zinc plated product. The galvanizing process alters the tensile properties of steel, which in our case causes a fracturing and breaking of the Anchor stem at a load less than we were happy with as a safety margin. Galvanizing does not provide the durability protection required in the Building Code for coastal and harsh environs.
The coating systems we use on all Safetor products comply to the durability clause of the Building Code for all environments.
Appendix C
Topfix Anchors
A large number of fall-arrest anchors are being attached to roofing products and testing is inconclusive on the attachment point of the anchor to the roofing products.
The prime function of roofing is exclude water from the structure.
There are a large number of variables that have to be considered before attaching
Fall-arrest anchor devices/systems to any roofing products, these include: age of the roofing, Profile, structures, stress factor on the roofing, type of environment, unwashed areas, thickness of the roofing and expansion and contraction of the roofing.
Roofing manufactures have changed coating systems a number of times over the years, this is to keep up with the changing environment.
Reports of a number of roofs around the country have failed after only 8 years in use and some sooner, this is due to the type of harsh environments we have in this country.
Corrosion categories identified in AS/NZS 2728 are:
C1 Mild Far inland
C2 Moderate Inland other than far inland
C3-4 Industrial Around major industrial complexes
C3 Marine 300-1000m but can be 30km from coast
C4 Severe Marine 100m-1000m from coast
C5 Very Severe Marine 0-400m from surf and offshore
C5 Geothermal Rotorua District.
Corrosion is one of the biggest factors that should be looked at before installing any roof anchor points that could possibly end up taking a force loading.
This email was sent to me from Stuart Thomson technical adviser for the Roofing Association NZ (RANZ). Stewart also wrote the Best Code of Practice for RANZ
Hi Nick,
The roofing Industry would not endorse any anchor fixing system only fixed to metal roof cladding simply because the qualification of the cladding is not possible.
The thickness, profile, material and purlin spacing all have a bearing on any performance claimed and therefore could not comply with the required safety loads.
The weather tightness issue and also the unwashed area would probably negate the manufacturer’s warranty. The workmanship warranty would also be voided as it is given on the existing roof as installed, not on subsequent work by others.
Cheers,
Stuart.