Pulse Confirmation Signal
Having good information is critical to running a successful operation. PULSAIR builds pulse signal devices into most of the systems that can be operated remotely. The goal is to provide process efficiencies by keeping personnel apprised of what the PULSAIR system is or is not doing.
The pulse confirmation signal was designed for systems like the PPC, PRSC and DCS systems. The signal is generated by taking a reading that is down stream of the injection valve. This is slightly different from the pulse signal report, which is taken up stream of the injection valve. It is possible to get a positive pulse signal reading even though the injection valve may be jammed shut. However, it is not possible to receive a pulse confirmation signal unless the injection valve actually opens.
PULSAIR developed the pulse confirmation signal because John Butler, Exxon Chemical's instrument engineer, needed to know that the valve was actually opening and closing. In most scenarios the closer the sensor is to the device being monitored, the better the situation. For instance, if you wanted to know a pumps output, it would be better to measure the flow from a pump than to sense the rotation of the electric motor driving the pump. With this in mind we decided to monitor the airflow downstream from the injection valve. A measurement of the air at this point confirms that the injection valve has opened and that compressed air is flowing to the accumulator plates.
The pulse confirmation signal is generated by tapping the pipe down stream of the injection valve and connecting a tube whose other end is attached to an air actuated micro switch inside the controller. When the injection valve is opened, the ensuing pulse pressurizes the tube, which actuates the micro switch that generates the electrical signal. It was a bit trickier than we thought at first, but we were able to configure the Exxon EPI to accept a downstream air signal from the system. We had to add another valve to bleed the system once the contacts had been closed. Additionally, John wanted to monitor both the center and radial pulses so the one extra valve turned into two. But the system is now installed and performing as promised.