hi friends,
I need your help . Please send me if you have some information on " Effect of Mobile phone usage on DCS in running plant." We are planning to ban the operation of mobile in control room. I am looking for write up for same. If you have some information pl pass on.

Regards,
Shailesh C Patel
FDC - Control Systems And Instrumentation

 

I have worked in a smaller refinery as DCS Maintenance Manager for more than 20 years, and while I have no documents to cite, I provide the following anecdotal information.

If by Mobile phone you are referring to Walkie Talkie devices, I can say that I have never seen a loss of control from our Honeywell TDC-2000 and TDC-3000 systems and Foxboro I/A at our locations that can be traced to hand-held radios in the control room. In fact, the board operators on the Honeywell Universal Stations and the Foxboro operator stations constantly use hand-held radios for communication purposes. The units produce 2 to 6 watts of power in the FM format, often within 1 meter of the operator station.

If you are referring to cellular telephones, you must realize that the power from modern mobile telephones is 600 mw or less and is tyically a digital format. We are currently using cellular phones throughout the control room without adverse effects.

John Beck
Control System Specialist, Retired

 

thank you John Beck

Thanks for putting efforts on it. I am facing this problem that's why I am worrying about it. Whenever some one uses mobile in control room. Some appear on alarm list. In actual these alarms does not persist at all in the field. please anyone have clue please inform me.

 

The effects of RFI (radio frequency interference) are well known and well documented. You have only to board an aircraft to know that cell phones or any other transmitting device, walkie talkies, some electronic devices, etc., are all capable of causing interference. There is a perception that if we do not actively talk on the cell phone, that we are not causing interference. WRONG! As long as the phone is powered up, it is communicating with the local cell. If there is no cell available in the area, the phone switches the transmitter to high power and tries to find one! The end effect that
this will have is very unpredictable, depending on many factors. If you have a critical control system that cannot afford to go out of control, even for a couple of seconds, then you should make sure that RF transmitting devices are not allowed in the area.

Gerald Beaudoin

 

While the RF from VHF/UHF handhelds and cell phones typically won't cause detriment6al effects to operating HMIs, I wouldn't recommend using the same (especially the handheld VHF/UHF radios) near an open DCS processor an/or I/O rack. And not only DCS equipment can be affected. Microprocessor -based power monitoring and relaying, solid state motor controllers, VFDs, and other like equipment can suffer from RF interference, particularly if their enclosure doors are open.

 

As John said, above - We cell phones constantly. They have zero impact on plant controllers and workstations. We have had problems with walkie-talkies when used close to older VFDs, but even then only with the equipment door open.

What is causing you to consider the ban?

Randall

 

If you are getting false alarms caused by radio interference, it's more likely an issue near the controller cabinets. We don't allow radio use at all in our control equipment rooms. We have a TDC3000 system with a mix of APMs and LMs.

In the control room we have had problems with radio interference. The Universal Stations beep when a radio is keyed within a couple of feet, radios with longer antennas are worse. It can also cause the cursor to move around the screen and initiate target actions. We had an incident where a motor was stopped when the operator touched a target and keyed his radio, which selected the 'execute' instruction (we use two touch for all stop/start actions).

We have had at least 2 keyboard failures caused by an operator keying the radio when it was laying directly on a US keyboard. We have had no problems with cellular phones.

- John Flanagan

 

You may want to consider a ban on cell phones for other reasons:

1) If you have explosive atmospheres such as a refinery. Many people leave their cell phones on in the plant when walking around (outside of the control room), and cell phones are NOT rated for explosive atmospheres.

2) Security. Cell phones now have very good cameras built into them. We had an issue with an operator taking pictures of the graphics (not sure if he actually did anything with them) in an overseas plant.