A case study into the effects of wind

loading on pushing and pulling manual

handling operations

James McCann

2015

A study into the use and operations of manually operated gates from a shop floor perspective

.

Intr oduction .

A Manager when asked, what the safe wind speed would be for safe operations of manually operated gates, did

not know! Nor did the manager know how much force was required to put the gate into motion even without the

effects of wind. As it would only require the wind to exert a force greater than that needed to set the gate in

motion and if uncontrolled to accelerate possibly to a dangerous extent, this should be or ought to be regarded as

a significant finding in a risk assessment. The Risk Assessments that were carried out indeed mention 'windy

conditions' however failed to further amplify what was meant by windy conditions, In any manual handling

operation it is the responsibility of those carrying out the work to carry out a Risk Assessment prior to

commencement of the work. This begs the question as to how the operators can carry out a dynammic risk

assessment prior to the operating of a manually operated gate, in windy conditions, that is 'adequate and

sufficient' if they do not have the information or tools needed to make the assessment? Or indeed what the safe

parameters are after the assessment. One suggestion that was made, was for the operators to 'test' whether or not

they can operate the gate safely! This would be akin to testing whether a gun was loaded by pulling the trigger.

Operators have complained of aches and pains after prolonged use, there have also been a number of accidents

and near miss reports involving 'windy conditions' as being a contributory factor that have not been taken into

consideration

The HSE guidance regarding Risk Factors to be considered TILE;- TASK, INDIVIDUAL, LOAD &

ENVIRONMENT appears to underplay the influence of wind as a significant hazard to manual handling

operations seemingly sending the wrong measage regarding communication of risk. Manual handling injuries

reportedly contribute to one third of all 3 day absence, one wonders to what extent wind played as a factor in

these manual handling injuries?

A further suggestion that if in doubt, another person will be asked to help. None of the gates examined in this

study were found to be suited for 'team' operating and it is doubtful that the HSE guidance of "2/3 the combined

capacity" would be appropriate for any gate operations as the positioning of adequate handles would

undoubtedly make coordination difficult and increase the risk of serious injury. None of the gates looked at have

extra handles for 'team operation' and in some cases are not been fitted with any handles!

It has been observed that gates are frequently used as convenient places to place site information notices, this

practice increases the effect of wind loading on the gate by increasing the effective surface area exposed to the

wind.

Accidents; In simple terms, when the wind acts on a gate, the gate acts like a sail. The magnitude of the wind

pressure will be at its greatest when acting perpendicularly to the gate and will decrease proportionally as the

gate opens or closes, to use a sailing analogy 'luffing' or depowering of a sail. If the initial impetus from the sum

of the wind and human force is greater than the force required to keep the gate in motion then the gate will

accelerate and require an equal and opposite force to stop the momentum. If this force is greater than can be

controlled by the operator they will either be dragged or will let go and the gate will swing out of control until it

reaches a solid object that will absorb or disperse the kinetic energy . The greater the mass of the gate the

greater the kinetic energy and the greater the crash. When the wind strength is gusting and the area of the gate is

large enough then the force exerted by the wind maybe sudden and overwhelming for the operator, in tests a

2000 kg gate reqired an impetus of 9kgf and a continuous force of 5kgf to maintain a walking pace of 3mph

however a gust of wind recorded an increase to 21.5kgf requiring the operator to exert an equal and opposite

force (pulling) to bring the gate safely to a halt, simmilarly when closing the gate the operator experienced an

increase in effort to the same magnitude increasing to 21.5kgf (pushing) over a distance of 7m in this case the

greatest magnitude was at the end of the travel distance and the operator now had to change sidesand hold the

gate with one hand inorder to secure the retaining bolt. This operation being repeated several times in a one hour

period.. Other environmental conditions included: heavy rain, cold, poor ,lighting and night shift, dressed in full

ppe of high visability jacket and over trousers on top of a uniform.

In one reportable (over 3 days) accident which involved opening and closing a 1500kg gate 4 x 4m in a full

force eight gale to allow upto 12 pedestrians access between 0700 and 0800 unaware that the securing hook had

not engaged properly the guard moved towards a pedestrian to check their id passes and was hit from behind

and catapulted into the opposite gate leaf and trapped by the closing leaf, he sustained damage to three vertebrae

and a chipped thigh bone. The cause of this accident was investigated from an office and declared as an operator

error, on inspection of the risk assessment there was no mention of wind, although mentioned in the assessment,

the reason a pedestrian gate or automation were not put in place (although the electrical controls were fitted),

was that it was not cost effective? how this computation was made is unclear. Not cost effective is simply

another way of saying 'not reasonably practicable' The test here would be 'Edwards v. The National Coal Board'

and in Coltness Iron Co v Sharp. Lord Atkin said: "The time of non-protection is so short, and

the time, trouble and expense of any other form of protection is so disproportionate that I

think the defence is proved." This shows that in every case it is the risk that has to be weighed

against the measures necessary to eliminate the risk. The greater the risk, no doubt, the less

will be the weight to be given to the factor of cost.

There would appear to be a number of conflicting 'risk perceptions' at work here or perhaps one of the many

myths surrunding risk , Sven Ove Hanssson Philosophy Unit RIT Stockholm et al . The risk to the individual

and the risk to security. Empirical v. Intelegence

There appears to be little or no empirical data available for manual handling of large single or double leafed

gates and the effects that wind loading has on them, this is probably as a result of increased automation

C RR 248/1999. AK Weym an & CJ Kelly In their Repor t highlight the m any Risk Per ception & R isk

C omm unica tion T heor ies. One pa rticular comenta ry stood out "However, the degree of consensu s

r ega rding the precise nature of the influence of organisa tional role on per ception of r isk a ppear s to be

limited L ee et a l (1993) for exam ple, pr ovide findings which indica te tha t m anagers and supervisor s tend

to be m or e cautious in their a ppr oa ches to r isk tha n workmen. By contra st other stu dies have shown tha t

supervisor s ar e poor sour ces of risk inform ation and have a tendency to und erestima te r isk, r eportedly

they a r e 'too fa r r emoved from opera tions to m ake mea ningful a ssessment s, R osner & Ma rkowitz (1995)

or m or e exposed to pr oduct ion pr essur es tha n other sta ff, Ost ber g (1980) .

There are of course many other reasons and theories suggesting reasons for poor risk communication, perhaps

the expression ' aquila non capit muscas' may have some resonance whereby opening of gates is generally a

security function carried out by low skilled staff and health and safety is percieved to be a low priority over

security and perhaps it is only for those in the lowest levels of organisations that the cost of automation "is not

cost effective". This came into sharpe focus recently, The BBC Reported that a security officer in India was

murdered by being run over, for, "not opening a security gate fast enough" Other communication failures have

come to light whereby security officers failed to express their reasoning for having a security gate open " the

gate was too heavy" the response " no heavier than yesterday, now get it closed" the difference between the days

in question was that the previous day there was no wind on the next a gale force 8 was blowing!. From first

hand experience the higher the security risk the less health safety or welfare are considered! The less authority

within an organisation the less likely to challenge poor decission making by those with authority, this manifests

it's self in statements ' just get on with it' and ' you will have to put in a business plan' before changes can be

made. This becomes more evident when on closer inspection many of the gates were found to be below

industry standards to the point of being extremely dangerous. Fig 3, 1, 2, 3 5, 6, 7 & 8

It is regognised that gates come in different sizes, mass and drag coefficient making it difficult to give a more

accurate estimate compared with other push/ pulling manual handling operations, however it is believed that

sufficient data can be obtained that will allow guidance to be given as to the effects of wind loading to enable a

risk assessment to be made that is adequate and sufficient to reduce the risks to ALARP or indeed to justify

automation. Many of the gates looked at were installed prior to much of the regulations now inforce and only

recently brought into operation or back into operational use after many years of restricted use.. The imperative

to bring back these gates would appear to override safety issues or that the risks to security justifies the means,

this attidudinal disconect from policy which "inextricably linked H&S to security" manifest it's self in

comments by managers and supervisors to "just get on with it" neither empirical or epidemiological evidence

being considered, risk assessments apparently downplaying risk or ignoring wind as a significant hazard

Manual handling of loads, pushing and pulling, this type of operation is discused in HSE RR526 Fig 1 giving

data on frequency of pushing and pulling loads, giving guidance estimates of safe loads over distance and time/

frequency of pushing and pulling activities and is a useful start point.

The data collected and reproduced in RR526 was however obtained under laboratory conditions and were not

influenced by other contributory environmental factors or conditions such as wind loading. Although air

movement is mentioned as a contributory factor, contextually, 'draughts' only refer to an indoor environmental

condition and would not have sufficient energy to be regarded as significant to the load being pushed or pulled

but may have an effect on the operator I.e. Comfort.

There is also the problem of how to work out the math involved e.g. angular momentum/ torque the sum of the

forces, with or against the wind force, both positive or negative and measuring angles / vectors e.t.c. This is

complicated enough but becomes almost imposible where the wind force is unpradictable and variable, to

complicate matters the designs or where construction materials and dimentions differ make it unrealistic that

'generic' Risk Assessments would be sufficient Fig2 demonstrates the generic type risk/hazard identification

associated with gates.

There are two elements of risk associated with wind loading, first, the increase/decrease in load force for the

operator and second, the uncontrolled acceleration caused by wind loading. Unlike other manual handling

operations, pushing and pulling of gates or loads are often subject to sudden increase and or decrease of load

from the effects of wind . The analogy here would be pushing and pulling a load using a trolly, where, sudden

and unpredictable varying degrees of slopes appeared out of nowhere. Opening a gate or moving a load maybe

easier with the wind however converslely closing or changing direction would be subject to an increase in effort

from the effect of the wind acting against the gate or load. Gusting winds are more difficult to contend with, the

increased pressure may be sudden and overwhelming or again conversely a sudden drop in wind pressure may

be difficult to compensate for and control resulting in an increase likelyhood of serious injury.. These problems

are exacerbated by the lack of suitable handles often only one being fitted on one side of a gate or the only

handle that is available is fitted on a slide bolt, often only a short metal bar.

The HSE, through examination of reported accidents, have determined that 11% musculoskeletal injuries

resulting from manual handling operations are associated with pushing or pulling loads, however it is unclear

whether any of the reported incidents included wind loading as a contributory factor.

Wind loading is recognised in many other areas of Health and Safety I.e crane operations and also plays a major

role in structural engineering

There is little to no wind loading information available in Gate Manufacturers Data sheets e.g. Pitts Security

Gates, Barriers, Blockers and Bollards PAS 68 Range, et al. British Standards BS EN 13241-2003, BS EN

12635-2002 BS EN 12605, BS EN 13849 - 2008 Although some of these Standards reference automated gates,

many of these gates can be disconected from their power source and can be operated manually when necessary.

Swing type security barriers found in e.g. Carparks, were the subject of a HSE warning alert after a number of

accidents being reported (HSE Advice on horizontal swing carpark barriers) A number of simmilarities are

apparent, human intervention, locking mechenisms, the effects of wind and poor lighting and safety marking.

It is doubtful that mechanical dampening devices would be beneficial as they would only control sudden

changes in force however the push pull forces would remain.or indeed be increased.

OBJECTIVES The purpose of this study is to examine the effects of wind loading on manually operated gates.

Recognising that the operators would not have access to measuring devices inorder to carryout adequate or

sufficient risk assessments prior to operating the gates. To give managers and operators guidance on the safe

perameters for manually operating gates that are simple and easy to understand

Examine if wind loading increases the load above the accepted limits 20kgf for men 15 kgf for women, 10 kgf

and 7 kgf respectively for keeping the load in motion. The HSE advise " that even for a minority of fit well

trained individuals under faverable conditions, may if the operation guideline limits are exceeded by a factor of

2 or more may be at risk of serious injury"

Determine the operational loads in still air

Determine wind speeds above which wind loading would increase the likelyhood of serious injury

Devise a graphic manual handling tool that will give clearly understood inform

Determining risk factors for inclusion in the graphic manual handling tool

l Provide estimates of impact (kinetic energy) forces from the gates whilst in motion

l We will be looking at the effects of wind loading on gates as they affect the manual operation and not the

structural integrity or design of the gates themselves but concentrating on the generality of the effects that

wind loading may have and to prepare guidance on contributory risk

l For ease of calculation a number of assumptions are being made, area of the gates in question will be

regarded as solid flat surfaces this will give an absolute maximum for wind pressure acting on the gate.

Angular movement/acceleration will be regarded as non vector or torque for simplicity of calculation as

wind direction is complex and variable therefor will be calculated as perpendicular to the gate, again giving

a maximum for wind loading. It will be assumed that the greatest area of danger for the operator is at the

furthest from the hinge and refered to as the impact zone (IZ) . For the purpose of these calculations it is

not necessary for a higher degree of accuracy however if a higher degree of accuracy is required this may

be achieved by using the data and appropriate non linear formulas. The angle of wind direction relative to

the gate will be recorded for those that wish to make more accurate assessments.

l As the most important factor will be that of wind pressure acting on the gates and not the capabilities of

the opperators, it is intended to make direct measurements under a range of wind conditions and compare

them to those taken under still air conditions this will give a direct comparison of increased loading on

gates of different dimensions and construction under different environmental conditions

l Wind speed = m/s

l Acceleration =m/s^2

l Mass = kg

l Wind pressure = kg/m^2 = N/m^2

l Force, pushing or pulling required to control the gate in motion = kgf

Fig 1

Fig 1 It would be tempting for managers not to consider wind as a significant hazard. For managers,

RR526 Although "other environmental factors" have to be considered it is believed that this report missed the

significance of the effects of wind on high risk push pull operations being carried out

Figure 2

Fig 2 . For the average person, carrying out the mathmatics prior to a manual handling

operation (push pull) would be wholly unreasonable and like an Inspector "who do not

typically pocess objective force measuring equipement " RR562 Executive

Recommendations, et al, would be unrealistic

Figure 3 Typical layout for identifying risk areas on gates

Note that the forces required to operate the gate or frequency of use (push pull manual

handling) handles and fittings are absent nor is wind identified as a significant factor. The

'weight' of the gate is supported by the hinges and load bearing style however the mass of the

gate is independent of how the weight is supported.

Fig 4a Guidance to the increase in force required to control the loading

Figure 4a A suggested diagram of the extra force needed to carryout push pull opperations.

where wind is a significant factor. For simplicity and ease of use this diagram uses the same

'traffic signal' format and should be used in conjunction with the load diagram Fig 1. The

combination of wind pressure in N/m^2 and the bodily force in kgf to control the gate whilst

in motion

Fig 4b

Fig 4b Wind force conversion

Figure 5. Suggested data for inclusion

Figure 5 Data collection

Data collection

Details of the gates, construction, dimensions and approximate mass..

Number of hinges and fittings

Orientation I.e 270°-90° = East / West. 0° - 180° = North / South

Wind speed and direction (from perpendicular to the gate) 0° = perpendicular .

Defects

Environmental conditions, day, night, rain, lighting etc.