New contact block design for Emergency Stop devices from Siemens

This entry is part 9 of 14 in the series Emer­gency Stop

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, and in cases where the e-stop sys­tem is 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 though I’d share it with you!

Emer­gency stop con­tact block with mount­ing mon­it­or­ing

Siemens E-Stop Contact Block 3SB34
Siemens 3SB34 E-Stop Con­tact Block

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 not just the con­nec­tion to the actu­at­or but also the cor­rect mount­ing on the EMERGENCY STOP. The mon­itored con­tact blocks are nor­mally closed con­tact blocks with pos­it­ive open­ing oper­a­tion. 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.

For fur­ther inform­a­tion, click here.

Since I don’t sell any kind of con­trol products, you’ll have to talk to 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!

Series Nav­ig­a­tionUpdates to Pop­u­lar Art­iclesEmer­gency stop devices: the risks of installer liab­il­ity

Author: Doug Nix

Doug Nix is Managing Director and Principal Consultant at Compliance InSight Consulting, Inc. ( in Kitchener, Ontario, and is Lead Author and Senior Editor of the Machinery Safety 101 blog. Doug's work includes teaching machinery risk assessment techniques privately and through Conestoga College Institute of Technology and Advanced Learning in Kitchener, Ontario, as well as providing technical services and training programs to clients related to risk assessment, industrial machinery safety, safety-related control system integration and reliability, laser safety and regulatory conformity. For more see Doug's LinkedIn profile.