Technic all y speaking 20 Mining Constru C tion 1 2013 By T omas Otterberg Product Manager Underground V entilation Systems F e w people think about v entilation as the y go about their dail y li v es in o u r m o d e r n s o c i e t y T h e f a c t t h a t our offces depar tment stores schools museums cinemas and so on are all w ell v entilated is something w e tak e for g ranted Belo w g round ho w e v er it s a completel y dif fer ent stor y H ere v enti la tion is c riti cal and can ne v er be tak en for g ranted W ithout proper v entilation human beings c an no t s ur vi v e be lo w t he ea r th s su rf a c e and e xca v ation w ork of an y kind is simpl y impossib le Compared to most industrial applica tions the v entilation systems required for under g round acti vities such as tunneling or mining present a range of dif ferent and often comple x challenges There are tw o main obstacles that ha v e to be o v ercome F irstl y substances that are hazardous to health such as diesel fumes from equipment and g ases from e xplosi v es must be pre v ented from contaminating the f r e s h a i r t h a t h u m a n s b r e a t h e S e c o n d l y toda y s under g round en vironment is in a per manent state of e v olution as our tun nels and mines continuousl y e xpand and this requires solutions that not onl y pro vide a good en vironment for w ork ers b ut that also suppl y constant v entilation for tunnel ing and mining areas as costef fecti v el y as possib le F or simple tunnel projects the economics of constr ucting the most suitab le v entilation system can be di vided into three par ts the in v estment required for a f an station the in v estment for ducting and the total operat ing cost and it is interesting to see that a higher in v estment will not al w a ys lo w er the operating cost The right combination of in v estment and r unning cost will contrib ute to reducing the o v erall cost for a project In order to optimize both the in v estment and the r unning cost it is essential to choose the right equipment combination This is most impor tant w hen choosing the size of the ducting A lar ger duct reduces the risk of pressure loss w hich in tur n lo w ers the f an in v estment as w ell as the r unning cost But it s not that simple Ho w can a lar ge diameter duct be installed in a h ydropo w er tunnel for e xample if all of the a v ailab le space is tak en up b y other installations or w here the size of the tunnel cross section is so limited that a lar ge duct will obstr uct m ac h i ne r y a n d d is t u rb t h e e x ca v a t io n sequence The solution is to be ab le to select from a range of f an stations and ducting not onl y in ter ms of diameters b ut also in ter ms of the amount of pressure r equired In addi tion it should be possib le to install one or more ducts in parallel t he s wedV ent solution In this respect the Sw edV ent under g round v entilation solution is w or th e xamining This system w hich w as introduced at the MINExpo sho w in September last y ear fea tures high pressure f ans w hich deli v er air along e xtensi v e lengths of tunneling with a capacity of 25 175 m 3 sec The system also includes fe xib le ducting and control systems and is equipped with effcient noise reduction Ho w e v er the biggest adv antage of the system is that it of fers a range of dif ferent diameters as w ell as v ariab le angles of the impeller b lades that can be set up in series T o gether these features enab le the air fo w to be optimized for each indi vidual application and the required po w er can be adjusted simpl y b y changing the motor size Pitch and balance This leads us to the allimpor tant pitch setting of the impeller b lade angle W ith a n o n a d j u s t a b l e i m p e l l e r w e w o u l d n e e d as man y impellers as there are motors for each gi v en diameter T o solv e this prob lem Atlas Copco has equipped the impellers with adjustab le b lades and also car ries out s t a t i c a n d d y n a m i c b a l a nc i n g of e a c h i m p e l ler before use By balancing the required pressure and airfo w the system will al w a ys pro vide the optimal solution There are cur rentl y nine dif ferent diameters and a total of 19 motor alter nati v es in the Sw edV ent range and the r e q u i re d p r e s s u r e c a n b e o b t a i n e d b y s e t t in g up three to fv e f ans in a multif an system F or these units high pressure means up to 4 200 P a for one impeller This is achie v ed due to small tolerances in a rob ust design F or e xample the distance betw een the tip of the b lade and the inside of the housing must be betw een 1 and 3 mm That ma y seem wide b ut considering the lar gest diameter for a f an housing is 2 240 mm it t he smar t way to ventilate s imple solutions to complex challenges V entilation systems for underground applications are mainly intended to provide human beings with a good working environment However to supply the right amount of fresh air to the right place at the right time and at the lowest possible cost is easier said than done