One issue that frequently comes up when inspecting machinery is the contact blocks used on emergency stop devices. Until now, e-stop devices were normally fitted with the same contact blocks used on other operator devices. In cases where the e-stop system is a single channel, you could lose the contact block off the back of the operator device and not be able to detect it. Since the latching detent device on the button is part of the button and not part of the contact block, the button would appear to latch down normally, but the machine would keep running!
I got a newsletter in my email today from Siemens that included the following snip on their new 3SB34 emergency stop contact block, and I thought I’d share it with you!
Emergency stop contact block with mounting monitoring
It is common practice to equip actuators such as EMERGENCY STOP with standard contact blocks. Now the new 3SB34 contact block with mounting monitoring from the SIRIUS family offers increased safety — automatically monitoring the connection to the actuator and the correct mounting on the EMERGENCY STOP device. The monitored contact blocks are normally closed contact blocks with positive opening operations. If the mounting is defective or should it fall off the actuator, the innovative contact block triggers an automatic shutdown of the machine or plant (safe state). As long as the plant is operating, you can be sure that all the necessary contacts are functioning perfectly.
The advantages are obvious:
- Increased safety thanks to the test required for initial commissioning
- Higher plant availability thanks to automatic monitoring of the mounting status during operation (according to the Machinery Directive)
- Space-saving thanks to a compact design and small installation depth (max. 63 mm)
- Free slots for further contact blocks due to integrated mounting monitoring
The contact block is available in two versions — with screw connection 3SB3400-0M or with spring-loaded connection 3SB3403-0M. (Note: these products are now obsolete.)
Note that the 3SU1400-1AA10-1HA0 has replaced the 3SB34 discussed in this post.
Since I don’t sell control products, you’ll have to contact your local Siemens representative to get pricing and availability.
If anyone has any experiences with these products that they would like to share, please leave a comment!
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