Safety PLC

I was thinking this would be a good place to get some opinions on Safety PLCs. I have been given the task of implementing a safety system around 2 machines and the conveyors that feed them product as well as conveyors that finish the product after it is processed. The feeding conveyors need to operate independently (ie...product setup) as well as under control of 1 of the machines with the safety systems seperated accordingly. The conveyors and equipment that finishes the product can be controlled by either machine with their safety systems interlocked with the feeding machine only. I am thinking to prevent a Estop cicuit nightmare a Safety PLC is the best method to accomplish this task. Any advice on ease of use, expandability, and reliability would be greatly appreciated.

Thank You,
Chad

If you go with a safety PLC be ready to shell out some bucks. As an alternative though you might want to check this out. It is a programmable safety relay and it is expandable depending on your system size. I have used a few of them and they work pretty well. A little expensive but it cuts down on wiring and all your E-Stop functions can be controlled through it.

I agree that the Pilz relay is a good choice. However on my last job we guarded macheinery and conveyors. Our circuit was connected to the e-stop circuit external of the PLC. Our guard doors were keyed so a door couldn't be moved and used elswhere.

The only two manufacturers of safety PLCs I've seen on the market so far are Pilz and Siemens.
I have evaluated both, and they both seem to be able to do the job.
I also did a cost benifit analysis for my company, and found that a safety PLC hardware generally costs much less than the equivelent hardware system on larger, more extensive, safety systems.
The system I did the study on had around 3 light curtains, 12 safety gates 5 E-stops and 3 overlapping zones.

Smaller, single zone systems, we found that ASi safety relays were as good.

A really small plant with 1 E-stop, a safety access gate and a couple of light curtains can still be easily setup with hardware relays.

One major benifit of the safety PLC is when you have overlapping safety zones. Hardware for this is a nightmare (this is from personal experience).

Hope this helps

Doug

Omron have a type 4 safety relay card to suit the C200 Alpha/CS1 PLCs. The PLC cannot control the safety relay but can only read it. An added benefit is that the card has extra inputs as well. It has 2 safety circuit inputs and contols and monitors 2 contactors. Full type 4.

It is also quite inexpensive. I am using it on crane controls at thec present time. Worth a look.

I have looked at the Allen Bradley GaurdPlc as well as Siemens offerings. I am leaning towards the AB due to it uses eternet to communicate to remote I/O Modules, they have built in switches for communicating, and the fact that I am already neck deep in AB hardware.

The system once complete will have over 30 E-stops 15 gates and 3 light curtains all spread out over 500' of production line with 2 S7-400s and 3 AB SLC 5/03s controlling the process.

Thanks to all that replied it is appreciated,
Chad

In Australia E/stops, light guards etc (safety devices) MUST be hard wired. This is not negotiable. These are either wired into a hard wired shut down chain or into a safety relay. I do not think I would trust these things to Ethernet.

BobB,

Australia, like America, has different states with different rules.
Western Australia, where I live and work, allows these devices.

NSW and Victoria also seem to allow it.

I do not know about the other states.

The policy in Western Australia is that safety functions are to be achived by devices built for the purpose. Ordinary PLCs are not built for the purpose. Safety PLCs are.

I have to agree with you on ethernet. I have not heard that an ethernet standard for safety functions had been implemented. Although I have heard that there are studies being done on safety ethernet.

If you want to use a bus system for safety, I think the only ones available are SafetyBus-P, Profisafe(Profibus) and ASi Safety Bus (ASi). I know examples of all three bus systems being used for safety functions in Australia.

Doug

hi Dear
try Siemens S-7F or H Safety PLC u would be spelbound by this control animal response its a very very relybel PLC in Safety regared area v r using and experienceing the large amount of benefit from this PLC in very very hazrdous area in our Refinery and oil movement and storage area and v firmly conclude that there is no match with Siemens S-7F or H safety PLC aroud u.
try this
ur sincere


Muhammad Faisal Qureshi.
SCADA Engineer
Pak Arab Refinery Limited
Karachi
Pakistan.

6ES7315-6FF01-0AB0 1
SIMATIC S7-300, CPU 315F CENTRAL UNIT FOR S7-300F 192 KB WORKING MEM., 40MM WIDE 384 BYTES PAE/384 BYTES PAA 2 INTERFACES: 1 MPI/DP UND 1 DP INTEGRATED 24V DC POWER SUPPLY MICRO MEMORY CARD REQUIRED prize in Finland: 1484 €

For design of a fail-safe automation system for plants with increased safety requirements
·Based on the SIMATIC CPU 315-2 DP
·With 2 interfaces (1x MPI, 1x DP/MPI)
·Complies with safety requirements up to SIL 3 according to IEC 61508, AK6 according to DIN V 19250 and Cat. 4 according to EN 954-1
·Without additional wiring of safety-relevant I/O
·Safety-relevant communication via PROFIBUS DP with PROFIsafe profile with distributed I/O stations
·Distributed connection of fail-safe I/O modules of the ET200S PROFIsafe possible;
central and distributed connection of fail-safe I/O modules of the ET200M possible
·Central and distributed use of standard modules for non-safety-relevant application