Mercury Systems are Operational
A long overdue update…
All of the little issues have finally been resolved and both Mercury Freedom Systems are working. We have the mercuric chloride generators and nitrogen generators on order and expect to receive them in the next few weeks.
We encountered a number of difficulties during the commissioning of the systems. Our original plan to commission the systems in two weeks turned into a two month project. To their credit, Thermo stuck to the job and eventually resolved all of the issues. We have been very happy with their dedication and tenacity in getting the systems to work. I think that it is pretty amazing that whenever we needed a new part they were able to ship it to us the next day. At this point in the game I would have expected shortages in parts but they have apparently done a very good job on the manufacturing end and it shows.
It is becoming apparent that everyone at Thermo has a lot on their plate and I expect that the plates will only be piled higher as more systems are installed. If you got in the game early then you were smart. If you are just getting started I would say that you will probably have to be patient. I remember many days in 1994 sitting on the phone trying to get support as we installed new CEMS. Everyone was overloaded with the impending 1/1/95 deadline and it sometimes took a long time just to get to the right person to fix the problem. I know that everyone is gearing up for the rush but there will be so many people installing systems that I think that we can realistically expect everyone to be a little more shorthanded than they would prefer. This is just the nature of the beast and in my opinion an avoidable consequence of the EPA not taking a more phased approach to implementing these systems. I think that it is very hard to run a business when you have to gear up to meet this huge rush knowing that things are likely to settle down again after the deadlines pass. That is what happened in ’95 after all of the CEMS were installed. Everyone hired like mad heading into the deadline and then turned around and laid off afterwards. That may not happen this time because overall the regulatory pressures are more intense and the systems are even more complex and will likely require more support. We’ll have to wait and see how it plays out.
I guess I should provide a summary of some of the problems that we encountered during the install. We ordered the first productions 82X (dubbed the “X Box”) systems. These systems take the probe controller components and place them on the stack. This design allows the heaters and thermocouples in the umbilical to terminate on the stack and not in the shelter which eliminates the likelihood that lightning will cause problems in the shelter. This is generally considered to be a good design decision in Florida which is the lightning capital of the US.
The approach that Thermo took with the X Box was to basically turn the umbilical upside down. The regular probe controller components were taken out of the blue rack mount box and placed in a NEMA 4X enclosure. All of the terminations that are regularly made in the shelter are made on the stack and the umbilical terminates at the probe with a short piece of umbilical running from the probe controller to the probe. The RS-485 signals from the analyzer in the shelter pass through a fiber converter and travel through fiber optic cable to another converter in the X Box NEMA enclosure which then plugs into one of the probe controller circuit boards as an RS-485 connection again.
I’ve heard several people make a big deal about the fiber like it is some exotic new technology. I’m not sure why this is as converting serial signals and Ethernet to fiber and back again is a no brainer these days. I do it all the time and never run into any problems. We had zero trouble with this aspect of the design except for the fact that some of the DIP switches on the converter were not set properly from the factory. A quick Google search for the product literature and a few switch changes and we were up and running.
The first problem that we identified with the X Box was the result of improper wiring. We originally planned two 30A 220V circuits to the cabinet to run the umbilical heaters and one 20A 120V circuit. This is what we were told would be required but when the box arrived they had modified the design so that it only required the 220V feeds. A converter in the box supplied the 120V where it was needed. This is a good thing except that it wasn’t wired correctly internally and because this was the first system out the door, the wiring diagrams had not been completed. It took some time to figure everything out and get it working. The I&C techs and GE field service guys were not really happy about this. The bad thing about the box being on the stack is that it is usually around 108 degrees up there in the summer. It really isn’t fun trying to troubleshoot electrical wiring while you are soaked in sweat.
We quickly ran into another problem on the stack. The solenoid valves on the probe were not operating properly. We did a lot of head scratching before we finally checked continuity on the wiring in the umbilical piece running between the probe controller and the probe. We discovered that one end of the wire wasn’t really connected to the other end. We ordered another short umbilical piece and it had the same problem. The third time was the charm. It is my understanding that Technical Heaters supplies these parts and they really shouldn’t have shipped these parts without QA’ing them better.
We also ran into some problems with the signals between the probe controller and the probe. I think that most of those were caused by grounding and shielding issues in the cabling. I got married in July and was wine tasting in Napa or hanging out around Monterey Bay around the time that they guys were on the 108 degree stack working this one out.
There is one aspect of the design of the probe controller that leaves a lot to be desired. The probe controller can control a maximum of two umbilical heater zones. Each umbilical heater zone can run 200-250ft so a number of users will have more than two zones. You aren’t going to be able to control them with the probe controller. You are going to have to go to a Watlow and wire it to your PLC for indication. You are better doing that even if you only have two zones as we do. Each heater zone has its own thermocouple but the probe controller has no place to connect the second thermocouple. It controls both zones from one thermocouple. I guess in theory this shouldn’t present a problem but it is the kind of thing that drive the guys in the field nuts and makes them question the intelligence of the guys in the lab. If you aren’t measuring your second zone, how would you know if it failed? I would think that a better design would have used off the shelf temperature controllers and provided plenty of 4-20mA inputs on the probe controller to provide indication. As it is I would recommend using Watlows and feeding the signal into your PLC or system controller and not use the Thermo probe controller for this function.
While we are talking about the issue of umbilical temperature I guess there are a few items to discuss. First off Thermo suspects that you really don’t need to keep the umbilical heated but they don’t have enough field data to prove it so they figure it is better to be safe than sorry. I think this is one of the reasons that they aren’t too concerned about monitoring that second heater zone. If it does go out, they suspect that it might not cause a problem. We don’t know that for sure. We are going to program the PLC to put the system in purge mode if we lose temperature indications just to be safe. At some point in time we will have to decide what we want to do long term. Luckily when we installed the NOx/SOx CEMS upgrade we put an Allen Bradley Micrologix 1100 DIN rail mounted PLC on the stack. This means that we have the capability of sending down the extra temperature signal. Having the Micrologix on the stack has given us the flexibility to respond to these types of issues and I am glad that we included it in the upgrades.
In addition to measuring the second umbilical zone we also chose to add a thermocouple to the stinger heater. This will also be connected to the Micrologix. Without this, there is no way to know if you stinger heater has failed. We also plan to add a probe enclosure temperature indication. During the many incursions into the probe during troubleshooting the temperature sensor in the converter wasn’t seated properly and we overheated the probe enough to begin to melt the Teflon tubing. This is bad business so we figure that adding that indication would have keyed us to the fact that we had a problem. Without it we thought that the converter heater wasn’t working properly when in fact it was cooking everything.
The system integration issues on the stack caused a number of problems which resulted in probe pluggage and other issues that all had to be fixed. This ate up extra time.
At this point the systems have been running for a while and the probes seem fine. We have a number of issues to address in the near future. The first item will be running a linearity. GE has had a number of questions to Thermo about how to do this and I don’t think that the systems have been acting entirely as expected. I believe that GE has this part figured out and we should be able to get it working around the beginning of November.
We are awaiting a firmware update from Thermo that will add the code to handle the Mercuric Chloride Generators. This has been delayed but we are hoping to get it in the next couple of weeks. Right now we are planning to install the MCG’s around Nov 12th.