Emerson Exchange 365

Hello Rob,

Assuming your 1 meter restriction is only due to the location of the steam traps, have you considered mounting repeaters above the process infrastructure, rather than around the outside of the unit?

Additionally, I recommend that you check out the latest version of AMS Wireless SNAP-ON for planning your network.  We have added the ability to place obstructions directly the network diagram, providing more fidelity to your network plan.

Regards,

Nicholas Meyer | Product Manager | Reliability Solutions

Echoing Nick Meyer, the best approach is to use the AMS Wireless SNAP-ON application and BE CONSERVATIVE ON RANGES! The range suggestions for heavy infrastructure (refinery process blocks, for instance) is 100'/30m. If you assume a heavier infrastructure than you think you have you may use more repeater devices but you will wind up with a more reliable network for sure.

Two suggestions:

The antennas on 708s are not "aim-able" but those on devices like 702 are. If you use 702s as repeaters in the "canopy" (area above most of the infrastructure) you can mount the devices and adjust the angles of their antennas so that the maximum signal strength can be aimed to maximize coverage of the 708s at 1m elevation. Think of the maximum signal strength as a doughnut dropped over the antenna with the tangents defining the best strength.

It is always better to form a network from the gateway out and that's the way the Network Manager in the gateway builds/optimizes. If you add devices later at the periphery you can speed up incorporating the added devices by power-cycling the gateway so that the Network Manager can re-learn and re-optimize. Obviously your monitoring infrastructure has to allow the loss of data during this process but a reasonably well-formed network will be back in short order (15-25 minutes). if you do this DO NOT FORGET TO TAKE A SYSTEM BACKUP before powering down as the collected performance data will be lost as soon as the gateway loses power.

In reply to Russ Muller:

Thank you all for your suggestions.

Having repeaters at strategic locations high in the structure have been considered. But customer was not to pleased with WirelessHART devices in the plant with no measurement function. The customer rather have more acoustic transmitters deployed at other steamtraps.

This is a pilot starting with 10 critical steamtraps to proof the WirelessHART mesh concept and faulty steamtrap detection with an additional 10 acoustic transmitters to be placed as repeaters on other steam traps. After the succesful pilot additional acoustic transmitters will be acquired en improve the mesh.

From the signal strenght data gathered during a site survey we learned that strenght of radio signal varies heavily between two devices depending on the location of the devices and the holes in the heavy structure. Putting the repeaters low but at the right places should result in a good mesh.

Does someone know the direction of the antenna in the acoustic transmitter? How can i get the signal doughnut flat on?

In reply to Rob Sosef:

Hi Rob,

I would like to share our experience on one of our 708 installation which is similar to your situation.

The control room is at the middle of the plant and majority of the steam traps are on the ground level. The plant has medium to heavy obstructions.The Gateways are installed on the roof top.

We divided the network into two so we could place the Gateway antenna at the edge of the roof top of the control room to have a better LOS with the nearest 708.

We designed the mesh from inside out. After we installed the farthest 708, we took the backup file and looked for pinch points and hops. We used this to decide where it is necessary to put repeaters or in some cases just simply changed the mounting orientation.

Take note of the propagation angle of the 708 as what Jonas illustrated from his reply. Mounting orientation is very important for 708s.
I suggest that for those in clusters, mount some of them in slightly different angle so the fresnel zone can reach more areas and you will not need to worry if your gateway or the closest neighbor is way up.