Oerlikon Leybold Vacuum obtained and ATEX Certificate for Steel Degassing Vacuum Systems, June 30, 2014.
Today, standard mechanical vacuum pumps fulfill high requirement for safety. Nevertheless, in case there are uncertainties regarding the flammability of gas mixtures which need to be handled by the pump sets, the user will have to conduct a risk analysis of the various plant parts to define the relevant explosion protection zones. The result will most probably be the definition of an explosion Zone 1 for the inner part of the vacuum system. For this assessment, components with an ATEX-certificate Category 2 (inside) for gases can be the easy solution. Thus way the user can reach the highest safety standard for his employees with relatively low investment expenditure.
The same considerations are also valid for all vacuum process with forced decarburization like VD-OB and RH-OB, or for processes with natural decarburization like VCD as well as for the VD-degassing of fully killed steel grades in presence of a reactive slag, especially in connection with higher leak rates. The off-gas composition and the moment of appearance of flammable mixture are very different in these processes.
ATEX vacuum solutions from Oerlikon Leybold Vacuum consist of pumps and components that meet the specification of ATEX Cat 2 (i) G IIC T2. This equipment can be combined into ATEX certified vacuum systems. To meet the requirements, an additional gas cooling and temperature control between the pumps is provided to prevent gas temperatures from exceeding the defined limits. Furthermore, all pumps are controlled and monitored by a specially programmed frequency converter.
Potential ignition sources
Regarding the vacuum pump set, potential ignition sources such as overheating or electrostatic charging must be considered, which will be achieved with the usual attention during design and manufacturing of ATEX-certified pumps. In particular, the pumps must be protected efficiently against overload by too high pressure differences in order to avoid excessive temperatures.
This is valid for all possible operating point starting with high suction pressures, passing to medium operating pressures, that are to be hold over a longer time as for example during delayed pump down in the VD-process or during the oxygen blow phase in the VOD-process, down to lowest end pressures with its high compression ratios.
Capable products alone do not guarantee trouble-free operation of the degasser. User errors can be made with an insufficient system design. The vacuum pump supplier must be able to combine the single products into a smart turnkey solution to ensure a satisfied user. The modern and highly performant vacuum solutions of Oerlikon Leybold Vacuum consist of two different standard pump models only, combined into three-stage vacuum systems. Such three stage designs allow highest suction speed combined with lowest power consumption.