What is the current product standard for mobile towers?
EN 1004-1:2020 is the latest European standard for mobile access and working towers made from prefabricated elements. It was released in 2020 and replaces the withdrawn EN 1004:2004 (published in the UK as BS EN 1004:2004). The latest EN 1004 Standard now covers all standard mobile towers, even those under 2.5m. Maximum heights remain at 8m externally and 12m internally.
BS1139 Part 6 Metal Scaffolding, is the British standard which covers mobile access towers outside of the scope of EN 1004 but which use the same components. Examples are high level towers greater than 12m for internal use and 8m for external use, towers with cantilever platforms, towers less than 2.5m in height commonly referred to as room scaffolds, linked towers and high clearance towers.
What is the 3T method and what is Advance Guardrail (AGR)?
3T stands for Through the Trap and it is one of two processes used for fall protection on mobile towers recommended by PASMA and the HSE. The other process is the use of Advance Guardrail (AGR) systems. If you don’t know what the 3T method is or how Advance Guardrail (AGR) systems work and you are involved in the building of mobile towers or you have responsibilities for the use of mobile towers, then you need to get PASMA trained.
Do I need the manufacturer’s instruction manual to assemble a tower?
Quite simply – if you don’t have a copy of the manufacturer’s instructions, you cannot assemble the tower.
If you hire a tower you should be issued a copy by the hire company. When you are assembling, altering or dismantling a mobile tower:
- You must have a copy of the correct instructions with you.
- You must note all of the safety information, the schedule of components and follow the step by step instructions every time and you must do this, even if you are a PASMA trained operative.
- Remember your PASMA training – no instruction manual means you cannot assemble the tower!
When should mobile towers be inspected?
Towers must be inspected as often as is necessary to ensure safety.
PASMA recommends that towers where it is possible to fall 2m or more you should carry out inspections after assembly or significant alteration, before use and following any event likely to have affected the towers stability or structural integrity. You should complete and issue the inspection report in accordance with the requirements of the work at Height Regulations. Re-inspect the tower as often as is necessary to ensure safety and at a minimum of every 7 days. A new report should be issued at each inspection.
You do not need to re-inspect the tower if it is moved unless it was necessary to significantly alter it to make that movement or if anything happens when moving it that may have affected its safety.
A tower from which it is possible to fall a distance of less than 2m has different inspection requirements. It must be inspected after assembly, and before use; after any event likely to have affected its stability or structural integrity and at suitable intervals depending on frequency and conditions of use.
PASMA recommends the use of the PASMA Tower Inspection Record which not only gives a visual indicator of the tower’s inspection status but also, when affixed to the tower and retained on completion, satisfies the inspection requirements of the Work at Height Regulations. PASMA have produced a pocket card and posters explaining the inspection requirements for mobile towers. The Inspection Records, pocket card and poster may be purchased online through their Online Shop.
If the tower is not high enough to complete the task is it acceptable to increase the height using the adjustable legs?
Never use the adjustable legs on a mobile tower to gain extra height. The only purpose of the adjustable legs is to level the tower on uneven or sloping surfaces. At least one adjustable leg should always be on minimum extension.
Is it acceptable to assemble a mobile tower on a slope?
That depends on various factors, it is therefore not possible to give an absolute answer. Conditions on site can vary so much and only your risk assessment can determine if it is safe to assemble a tower on a slope.
It is safer to assemble a tower on a slope on base plates instead of castors. Even if the tower is on base plates you may still need to tie the tower to a supporting structure or ground anchors to prevent movement. If the slope is steep then you may need to consider digging it out locally to accommodate the base plates on a flat area.
Check if the ground surface is suitable. Loose, soft or otherwise unstable sloping ground surfaces can be particularly dangerous. Where levelling is required beyond the adjustment available from the adjustable legs, consideration should be given to offsetting or using different end frames.
What are the guidelines for using a mobile access tower in bad weather?
The general guidance given by PASMA and many manufacturers is that mobile access towers (tower scaffolds) certified as conforming to the product standard EN1004 should be stable in a freestanding condition in wind speeds up to 27mph (Beaufort 6).
If the wind speed should exceed 17 mph you must STOP any work on the mobile access tower. The wind speed on the mobile access tower during work may be monitored using hand held anemometers which are readily available.
If the wind speed is likely to reach 25 mph then the mobile access tower must be properly tied to a suitable adjacent rigid supporting structure, capable of supporting the additional loads imposed by the mobile access tower. The connections (ties) between the tower and the supporting structure must be rigid in compression and tension i.e. you should NOT use rope, webbing, wire etc. You could use an arrangement of suitable aluminum or steel tubes and couplers.
As the tower must be tied if the wind speed is likely to reach 25mph, you will need to consider this point and take appropriate measures in your planning for the task. Potential wind speed may be established by reference to weather forecasts for the duration of the time that the mobile access tower will be standing and also by reference to meteorological data for the geographical area where it will be located.
If the wind speed is likely to reach 40mph, then the mobile access tower must be dismantled. Again, you will need to consider this point and take appropriate measures in your planning for the task.
The location of the site and the surrounding terrain will affect potential wind speeds e.g. on the top of a slope, hill, escarpment or cliff, close to the sea or estuaries, near woodland, in open country or near buildings. All of these terrains have an effect on wind speed.
If the mobile access tower is to be placed on a high structure where it will be exposed to wind (e.g. on a tall building) then wind speeds at the top of that structure may be considerably higher compared to those experienced at ground level. Therefore you must consider wind speed data which takes this point into account.
Do I need to fit stabilisers on mobile towers at 2.5m height or less?
It depends on the manufacturer’s instructions for the tower height you are building. The old 3:1 rule for the ratio of tower height to base dimension no longer works for determining the stability of a mobile tower. The base dimensions are now determined by a complex calculation in EN1004 which takes into account numerous factors. The only way you can determine if the stabilisers are required and which size of stabilisers to use, is to refer to the manufacturer’s instructions schedule of components. Remember that you must fit stabilisers at the first opportunity in the build sequence and remove them at the end when dismantling.
Can I mix and match tower components from different manufacturers with BoSS components to form a tower?
No. We strongly advise against mixing product components because of the potential risks for users, and their inability to rely upon the manufacturers Product Liability Insurance in the event of an accident occurring as a result of mixing components from different manufacturers.
When you combine components from different manufacturers, a new structure has been created that has not been tested to latest European Standard EN 1004:2020 for Mobile Access and Working Towers. Concerns are being raised in the industry that this practice is becoming more common and often users are unaware of the safety risks.
Although it may appear that all access towers look the same, and components may be similar to each other, the actual characteristics and performance of the components can be very different. It is important to remember that in EN 1004:2020 it is not the components that are approved it is the overall tower structure. In the event of mixing tower components from different manufacturers with BoSS components to form a tower, then the EN 1004 tower standard approval will be invalid.
It is not common practice for manufacturers to share performance and strength data. That means rigorous testing, calculations and manufacturer assessments would need to be carried out in order to determine the safety and reliability of every conceivable component mix. Not only is this impractical it is not something BoSS carries out, meaning liability will lie with those who authorise the build of the towers if a fault was to occur in a scheme where a mix of components from different manufacturers was used.
It is always recommended that mobile access towers conform to EN 1004:2020, which is the European Standard ensuring meet minimum safety requirements. All BoSS towers must be accompanied by an approved BoSS instruction manual. This manual lists the components permitted to be used on a particular tower build.
Should you require any further clarification or information on this matter please do not hesitate to contact us.