Welcome to the primogenial blog post of the B&D Technologies Applications Engineering Group (AEG).
The word “primogenial” defined by Webster’s means the primitive first. We choose this word to define this post because of how our group views blogging and the world of technical information on the web. Some information is very helpful, while other information is borderline rubbish or corporate sales pitches. We will strive for honesty above all else.
Our blog posts will focus on applications that we see on a daily basis. The format will be to define the problem, describe the solution, elaborate on one specific attribute that we find challenging or elusive, then offer an opinion based on the collective 500 years of experience within our group.
There will be two similar blog streams produced by our group. This blog will focus on automation, electrical power, motor control, fluid power, PT, and material handling. Basically anything that we feel is noteworthy of discussion. The other blog will be about ABB and the high technology products that they offer and our relationship with them as the ABB Authorized Value Provider (AVP) in the Southeast.
So to get started…
Banner Safety Application Applied Correctly
The following application is from a hydraulic press where the Banner light curtains are interfaced with a Banner safety controller. The safety controllers allow for greater flexibility as well as allowing for easier integration of safety system components like e-stops and pull cords. The system also uses a Banner run-bar with a two button anti-tie down control for press operation. The system was custom designed by B&D Technologies and built by an integration partner. The customer had no previous safety on this system and wanted a starting point.
An operator uses a normal approach to a 14 mm light curtain, which is connected to a monitoring safety relay which is connected to a DC powered contactor with a diode suppressor. The safety system response time, Tr, is 10 + 15 + 90 = 115 ms. The machine stopping time, Ts+Tc, is 160 ms. A brake monitor is not used. The Dpf value is 1 inch, and the C value is zero. The calculation would be as follows:
Dpf = 3.4 (14 – 6.875) = 24.2 mm (1 in)
C = 8 (14-14) = 0
Ds = K x (Ts + Tc + Tr + Tbm) + Dpf
Ds = 63 x (0.16 + 0.115 + 0) + 1
Ds = 63 x (0.275) + 1
Ds = 17.325 + 1
Ds = 18.325 in (440 mm)
Therefore, the minimum safe distance the safety light curtain must be mounted from the hazard is 440 mm (18.325 in) for this machine to be used in North America. (Countries vary on requirements)
The equation does not seem all that hard; the issue is that most companies do not understand the proper light curtain distance. Our biggest challenge in the local market is the other companies selling safety that have no clue what they are doing. When we came into this customer, they were told that it did not matter by one distributor. After we ran the calculations, the customer asked a different distributor what their calculation was. After several days, they had an answer that was similar. We assume they had to go to the vendor to get an answer. Which is OK, but we feel that expertise needs to be local. . .IOHO. . .
Safety design is driven from a foundation of Risk Assessment. Understanding that and then learning how to apply solutions that fit the requirements derived from the assessment is the formula for safe production.
Carl Lee Tolbert – DOE