Ray Howarth,long term engineer at the Runcorn plant explains the ongoing success and improved levels of safety with the introduction of the company's Arc Flash Mitigation Programme
InterGen is a global power generation company with plants in the UK,Netherlands,Mexico,Philippines and Australia,collectively generating 8,146MW of electricity.As a corporation,InterGen is committed to a healthy and injury free workplace and to the safety of its employees,contractors,visitors and the communities in which it operates.The organisation claims that safety is its most important performance metric and is fundamental to its overall operational and managerial excellence.
This claim is certainly borne out at InterGen's Runcorn plant,Rocksavage Power Station,one of the three plants based in the UK.This plant is not only one of the cleanest and environmentally efficient facilities in the UK,but it has an excellent safety record,operating more than one million safe man-hours without a lost time incident during the last five years.
Ray Howarth explains"To maintain the consistent generation of electricity it is essential the plant operates effectively and is commercially viable all the time.This level of operation results in ongoing maintenance work and it is this activity that potentially exposes our workers to higher risks and one that InterGen wants to mitigate as much as possible.The rule,throughout the organisation,is never to work on anything above 1000V live.'Live Working'procedures are in place for lower voltages and when essential maintenance work must take place,a physical isolation or'air gap'is required to maintain safety from the system.It is this particular procedure that poses an increased risk and one where a major hazard such as an electric arc flash could occur".
Electrical flashover or'arc flash'is one of the most deadly and least understood hazards of electricity.Each year around 1,000 electrical accidents at work are reported and as many as 25 people die from their injuries.It is widely recognised the higher the voltage of an electrical power system,the greater the risk for people working on or near energised conductors and equipment.However,arc flash can still cause devastating,injuries even at low voltages.
An arc flash is usually caused by inadvertent contact between an energised conductor such as a bus bar or wire with another conductor or an earthed surface.When this occurs,the resulting short circuit current will melt the conductors,ionise the air and create a conducting plasma fireball with temperatures in the core of the arc that can reach upwards of 20,000 degrees centigrade.The risk of injury can extend beyond the immediate area.
Arc flash injury can include external burns to the skin,internal burns from inhaling hot gases and vaporised metal,hearing damage,eye damage such as blindness from the ultraviolet light of the flash as well as many others.Depending on the severity of the arc flash,an explosive force known as an arc blast may also occur which can result in pressures of over 100 kilopascal(kpa),launching debris as shrapnel at speeds up to 300 metres per second(a high speed train travels,on average,85 metres per second).
Following'Arc flash'incidents at a number of locations,InterGen senior management launched their Arc Flash Mitigation programme across their facilities.The programme is designed to identify the potential risk to personnel from all items of LV and HV apparatus and more importantly,to provide instruction and training to all staff on the impact of electric arc flash.
Ray who is leading the European regional branch of the programme explains"The risk behind the arc flash hazard is really being understood in this organisation now but the approach to managing the risk varies from country to country.For example in the US the approach is to provide protective clothing from the beginning whereas in the UK supply of protective clothing is usually the last line of defence.It is these different approaches that are being reviewed,although it is collectively understood that exposing our workers to the risk should be the last resort and this will help mitigate it.The programme has been divided into two phases–phase one is to carry out thorough technical risk assessments of all equipment and provide an engineering solution wherever possible.Phase two is to provide adequate protection and training if and when needed.After comprehensive full Arc Flash studies are completed there will calculated details of the incident energy release at each point of work and this can reduced or engineered out to reduce risk even further.Existing Arc Flash personal protective equipment(PPE)will then be supplied to match the incident energy release identified from the study.
Due to the complexities of this hazard,InterGen called in local manufacturer and distributor J&K Ross who has developed,in conjunction with leading safety expert DuPont,ARCBAN,a range of arc flash protection clothing incorporating Nomex.The clothing is teamed with specialist gloves and head protection to provide the complete protection package.The approach recommended by J&K Ross is to'layer'garments as opposed to using heavy,bulky single layers to achieve the level of protection required.Combining varying layers of clothing will achieve increased levels of protection and can be added to or reduced depending on the level of protection required.However,whatever layering is chosen,it is important that clothing selected to work together has been tested to work together and that it is also worn over flame resistant undergarments.But sophisticated protection such as this can only be successful if a full risk assessment has been done and this is the work being carried out during phase one of the Arc Flash Mitigation Programme.
Ray explains"During phase one we have provided the highest level of personal protection until we have thoroughly analysed the risk and J&K Ross has supplied its 40cal/cm²suit including hood and gloves.It has taken time and education for our workers to comprehend the potential severity of the arc flash hazard but now they are keen to be provided with the correct clothing."
It has been a very successful partnership so far and InterGen has been reassured with the knowledge and support that the organisation has received from JK Ross.The workers are also very willing to wear the specialist clothing because it is comfortable and surprisingly doesn't restrict movement too much.Team that with the education they have received from the manufacturer and their understanding of the risk of an electric arc flash has reiterated the importance of wearing suitable protective clothing."The range of clothing supplied is of a very high quality",Ray confirms"and it is exceptionally good value for money.Once our assessments are complete it may be appropriate to provide slightly different clothing-the layering approach as they recommend,that has minimum restriction for the worker but still provides adequate protection against the hazard."
There is still much work to be done to complete this thorough review programme but the results from it will ensure that,not only are the maintenance workers with InterGen going to be some of the most protected workers in this type of industry,but they will have an increased respect for the dangers of working with electricity too.
