At Hinkley Point C , this operation will be carried out by a huge circular crane located inside the reactor building , a so called a polar crane . Used once or twice a year , the crane is designed to have a lifting capacity of 300 tons . To ensure the crane stops with the maximum reliability and redundancy , the crane OEM selected Stromag to provide the service brakes and emergency brakes for the design .
SERVICE AND EMERGENCY BRAKES
“ The crane in the reactor building requires two braking systems ,” explains Jonathan Balland , Area Sales Manager at Stromag . “ Service brakes carry out the normal braking operations for the crane when it is in use . These units are usually mounted on the high speed shaft . Emergency brakes are mounted on the drum and offer highly responsive stopping performance if the load falls for any reason .”
For service braking , Stromag specified its C range of electromagnetic disc brakes . Rated for over four million cycles in normal operating conditions , the electromagnetic design eliminates any risk of hydraulic fluid leakage , maximising reliability . The brake only opens when power is applied , staying closed otherwise . Once powered , only a small current is required to keep the brake open , which ensures low energy consumption in operation .
Hydraulic brakes are preferred for emergency braking applications due to the higher torque figure this configuration can achieve . While the world ’ s largest electromagnetic brakes can reach up to 10 tons clamping force , there is almost no
Stromag provided brakes , couplings , limit switches , hydraulic power units ( HPUs ) and monitoring systems .
limit to what hydraulic brakes can achieve , with some in mining applications reaching up to 100 tons of force . This exceptional performance is critical for the polar crane at Hinkley Point C , ensuring that the heavy radioactive fuel rods can be stopped dead . To meet these application requirements , Stromag specified SH hydraulic disc brakes .
“ The key with the emergency brakes is to stop the load in the shortest distance possible . Our SH32 brake offers a 32-ton clamping force , but critically , with a closing time of less than 0.3 seconds . This ensures we can offer a reduced minimum distance of travel for the load if it begins to fall . For example , the braking systems may be required to stop 300 tons of load within 50 centimetres of travel .”
“ For an application as critical at the polar crane at Hinkley Point C , we also had to offer extra clamping force to ensure the required redundancy , which we achieved by specifying multiple units . If a brake fails for whatever reason , another unit can provide the necessary performance to halt the load .” Jonathan adds .
In addition to the brakes , Stromag also supplied couplings , limit switches , hydraulic power units ( HPUs ) and monitoring systems .
EXACTING STANDARDS
Stromag ensures the suitability of its braking systems for all customer applications thanks to rigorous testing and modelling . However , providing braking systems for the nuclear industry requires achieving the highest possible standards .
Michel says : “ As a specialist in nuclear applications , we are accredited to the highest quality specifications . EDF has certified our applicable products as C3 , which denotes suitability for use in all buildings at a nuclear power plant . We undertake customer surveys , independent consultations and assessments to define our critical steps and certify that all aspects of engineering work are carried out correctly . Typically , the quality documents we supply for products used on critical cranes in nuclear power stations can reach up to 1000 pages long .”
“ We carry out all engineering work in-house at our facility in France , while offering our crane OEM customers technical support at their production facilities too . We are among a handful of companies worldwide who can provide these braking systems for critical nuclear applications .”
Stromag braking technologies are proven in nuclear facilities across Europe and Asia . ( Photo : Adobe stock – 22340770 )
For further information , please visit www . stromag . com
Issue 55 PECM 21