Interesting predictions about the growth in the CEMS market can be found here.

It is pretty likely that as the EPA imposes restrictions and taxes on CO2 emissions that the need to maintain reliable and accurate CEMS will become even more important.

It will also be interesting to see how the Hg CEMS market progresses. As the article mentions, many plants have Hg CEMS that have been moth balled. I have already seen instances where state agencies are starting to arm twist to get data from these systems. They may not be required by the EPA but the states definitely want this data and they are pressuring utilities to provide it. I predict new regulations and even where new regulations are not enacted I suspect that states will start negotiating to add this data to reporting requirements when operating permits are renewed.

Thermo recently released a press release saying that they had 25 systems that have passed all of the required regulatory testing (I’m sure that they mean as far as they can given the state of the regulations and standards at this point). Hopefully we will soon be able to add a couple more to the list.

Here is a link to the release:

Thermo Scientific Mercury Freedom System Demonstrating Complianc.

The installation of the MCG’s has been going a little rough. At this time we have one of the units installed but not completely tested.

We have the first production “X Box” systems and the design has been updated and standardized since we installed ours. As a result there are a few standard parts that didn’t fit in our box the way they were indented to so some field modifications had to be made. We also had the types of problems that you always seem to have when you have a system that has been operating for months. When you turn it off, it doesn’t always like to come back up. We had to replace one of the regulators.

The nitrogen generator has also been installed on that one unit. It took a little while to get the analyzer tuned back in after that. The PMT voltage had to be adjusted quite a bit. I’ll try to put together a few before and after plots to show how the data has been effected.

We did run into a problem with one of the systems just prior to the MCG install. It started to fail span cals. A couple of split nylon fittings were found. They were parts that were to be removed as part of the MCG install anyway.

We have also added some new thermocouple readings to the system. Our choice to install a PLC on the stack has started to pay dividends as it was relatively easy to add new signals to the system. We added a thermocouple to the stinger heater so that we can monitor its operation. We also added the second umbilical heater zone temperature.

We will have a RATA team in tomorrow to start performing EPA Method 30B tests to prove out the systems and satisfy the contract requirements. Thermo is recommending that you check the output of your calibrator during the RATA. The plan is to run a couple of traps off of the analyzer and have them analyzed to insure that the calibration gas generator is operating properly.

If things go reasonable well tomorrow I should have a chance to post about the RATA and the first few calibrations with the MCG installed.

We are working on the last few steps to complete the project.

Thermo sent us a mercuric choloride generator for a game cube probe but we have the modified inertial probe installed so we had to wait a couple of months for the right kit. We are scheduled to have it installed the week of the 14^th. If all goes well that will be the last piece of hardware to install.

We have tentatively scheduled a 30A RATA test for the last week of January. This will of course not be for official certification but GE is obligated to perform the test in order to prove out the system.

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 12^th.

Quite a bit of progress has been made. Unit 1 is up and running. Thermo was installing the lamp upgrade in the analyzer and the calibration gas hydrator today. Below is a picture of the hydrator.

It is mounted on the outside of the cabinet with a growing number of components. I will take another picture of the cabinet and post later. I’ll also let you know how it works.

Most of the problems that we were having stemmed from some wiring mistakes that were made when the “X box” cabinet was assembled. The “X box” is basically the components from the standard blue box probe controller that have been mounted in a NEMA enclosure suitable for the stack environment. Once the wiring problems were identified they were not that difficult to fix.

Unit 2 was still experiencing a few problems that are probably due to a leak in the probe tubing. Hopefully that won’t be too hard to fix.

Hopefully by the end of this week both systems will be running and have the hydrator and lamp upgrade installed. We will hopefully be receiving the nitrogen generators and the mercuric chloride generators soon.

I’ll post some more details as soon as I can.

We have been working on the Thermo Fisher Scientific Mercury Freedom installation for 3 weeks and have hit a series of snags. We are the first production installation (there is 1 R&D unit running) of the probe controller on the stack using the 82X configuration dubbed the “X Box”. Basically we did not want to run copper lines down the stack because here in Flordia we call that a lightning rod. We instead opted to install the probe controller on the stack and use fiber converters to connect the analyzer and the probe controller which normally sit in the rack together and use RS-485 over copper. The communication via fiber seems to work well and I must say that the analyzer and calibrator with their i-Series displays and menu system are very easy to use. The analyzer coordinates the actions of the calibrator and the probe controller. Thermo excels at this sort of thing and those components are impressive.

The 82X design basically takes the guts out of the standard Thermo blue box and puts them in a NEMA enslosure that is mounted on the stack. Fiber converters carry the RS-485 signals but other than that it is supposed to be identical to the regular probe controller.The long umbilical runs from the analyzer and calibrator up the stack and into the probe enclosure. The long umbilical going up the stack contains only tubing, thermocouples, and heat trace (the thermocouples and heat trace are terminated on the stack inside the X Box). Another short umbilical connects the probe controller box and the probe. This short umbilical contains tubing and a series of wires which allow the probe controller to read the thermocouples, power the heat traces, and control all of the probe components such as solenoid valves, the large ball valve, and heaters for the probe, stringer, and converter. This short umbilical has caused many of the problems. We discovered that the first set (1 for each unit we are installing) contained some bad wires meaning that there was no continuity from one end to the other. We were sent replacements which I am told have the same problem. For now we are using outside wires to carry these signals.

We have discovered some problems with the umbilical heater circuits. This has been a confusing issue from the beginning because Thermo states that you need a heater zone for each 200ft of umbilical. Our lines are in the 500+ ft range so I originally planned on 3 zones but the probe controller will only support one or two zones so we have 2 zones of about 250+ ft each. Right now we cannot get the probe controller to properly read the two zones and there are some problems with the control circuitry so we cannot maintain the proper temperature. We received upgraded controller boards since they have been tweaked since our unit shipped but this did not correct all of the problems. This could be a grounding or shielding issue and we have some work to do to get to the bottom of it. At this point we have shut the systems down with a purge to keep everything clean and we are working with Thermo to determine the next step.

It is expected to have some hiccups at this early stage. I am told that Thermo has about 100 systems shipped so far and I’m sure that most of those have not yet been installed. I’m pretty confident that we will get past these problems.

On another note, I received confirmation that your calibration gas hydrators, a firmware upgrade, and a lamp controller update for the analyzer were all shipped and should arrive next week.

I’ll post again next week with more details. I imagine that it will take a few weeks to get everything straight.

We are in the early stages of commissioning two new Thermo Fisher Scientific Mercury Freedom Systems at St Johns River Power Park in Jacksonville, FL. It is nice to have a customer who has decided to be an early adopter of this technology. There are still a lot of unanswered questions and uncertainty but I think that it is ultimately wise to jump in and get the system installed, get hands on experience, and develop your in house expertise as early as possible.

The mercury systems were added to an existing project to replace the NOx/SOx CEMS that were installed in 1994. We spent a considerable amount of time specifying the NOx/SOx systems but did not have much time to add the mercury systems to the specifications. After looking at the available options, the plant decided that the best option was to go with Thermo. I got up to speed on the mercury regulations and technologies as quickly as possible and added the equipment to the specification.  

We decided to use the Thermo supplied rack. In hind sight we should have chosen to purchase the components and install them in Hoffman racks to match the other systems. We specified the NOx/SOx dilution air train to be able to supply the 3cfm required for the mercury systems. I decided to let Thermo supply their air cleanup train so that if we had any problems with the system they could not point to the dilution air system as a cause. The plan was to commission the system and then switch to using the common dilution air train and retire the Thermo supplied components. We have hit a snag in that plan. We are going to add a nitrogen generator and use nitrogen as the dilution gas in the mercury system and this requires 6cfm so it looks like the dilution air train supplied with the NOx/SOx will not be able to supply both systems. I am looking for the easiest way to resolve the problem.

We were a little disappointed in the layout and design of the cabinet. Some of the dilution air components are installed on the outside of the cabinet. We have removed the beige panels from the front of the rack so that we will not have to unscrew them when we need to get into the cabinet.

The back of the cabinet is pretty cramped. In this picture the umbilical has not been terminated so it is just hanging in the cabinet.

Some of the air cleanup train is mounted to a pull out shelf in the middle of the cabinet.

The vacuum pump appears to be high quality. It probably should have been mounted on a pull out shelf as well to make it easier to get to.

We only have the analyzer and calibrator in the cabinet. The probe controller has been mounted on the stack. All power terminations are made on the stack and the analyzer communicates to the probe controller via a fiber optic line and RS-422 converter. This design variation is known as the 82X probe controller and is recommended for sites that are prone to lightning as this installation in Florida, the lightning capital of the US.

We are using the 83i probe for now. We have an agreement with Thermo that will allow us to switch to the GC probe if we desire. The 83i was delivered with the system and a GC was not available prior to commissioning so we went with what we had.

Here is the probe with the stinger and return tube installed. The stinger and “tea cup” at the end are hastelloy. The return tube is Teflon. The support tube is Restek coated stainless. I would have preferred hastelloy and I predict that we will need to replace this item in 2–3 years.

One of the things that we liked about the 83i probe is that it has more room and should be easier to work on than the GC. I’m not entirely sure that this is the case after seeing the GC in person and working on the i. The above picture shows the probe after mounting it to the stack. It looks nice and roomy but notice that the umbilical has not been landed.

With the umbilical landed things start to look more crowded. There is a design tweak that needs to happen here. If you look a the picture below you will see that there is one bulkhead available for three of the lines. Many of the lines however terminate deeper inside the probe and there are a lot of Teflon tubes and fittings in there. You have to be careful routing all of these lines to avoid melting them to the clam shell that heats the probe. This differs from the NOx/SOx probes which typically run stainless lines back to a bulkhead where all of the umbilical terminations are made in one location. This helps to reduce the opportunity for leaks, eliminates the possibility of melting tubing, and makes the probe easier to work on at 2am when you’ve been called out because of a problem.

The 82X probe controller is shown below. As you can see they pretty much took the probe controller guts out of the blue box and mounted them in a NEMA enclosure. This is also a little bit of a rough design. I would recommend specifying a bigger enclosure and scrutinizing the layout a little more. I don’t know if Thermo will be super responsive to your requests so you may have to talk nice to your integrator. We currently have one of these units powered up and have found that the temperature control for the heat trace is a little erratic. We found that there is an upgrade to the responsible component and we should have it on Monday.

We still have a lot of work ahead of us. We will have the base systems installed next week and should be performing daily calibrations. Thermo will be sending us a lamp upgrade for the analyzer as well as a calibration gas hydrator that are now part of the base systems. We have also ordered the mercuric chloride calibrator to perform the weekly system integrity checks and nitrogen generators. These will all need to be installed and tested.

Overall I would say that Thermo has done an excellent job in choosing shier approach to the problem of reliably measuring mercury. The things that I have complained about are minor tweaks and when it comes to the major design decisions that affect the overall performance of the system I don’t think that anyone else can beat them.

I will post more as time allows after we have the systems running. I will also post some details of the system integration with the CEMS PLC and the DAHS.

We have recently completed upgrading two NOx/SOx CEMS systems at St Johns River Power Park in Jacksonville, FL. This project was started during the summer of 2006 when I started a series of meetings with the plant staff to review their existing systems piece by piece and ultimately developed a very detailed specification for the upgraded hardware and software. This was an important step in successfully completing the project.

The plant has environmental personnel who are responsible for the reporting and I&C staff who are responsible for maintaining the hardware. During the course of several meetings we discussed many design issues that they wanted to correct with the new design. We also specified in detail the equipment that we wanted to use and the standards that we wanted to follow. The time that we invested at this early stage has paid dividends in the final product. As with all new systems, we have had to track down some annoying bugs and work out a few unexpected issues but the upgrade went about as smoothly as can be expected.

Few things are as intimidating as ripping out a vital power plant system that has been running for about 13 years and committing to installing its replacement. We had a ten day outage for the installation of Unit 1. The goal was to use the lessons learned during the first installation to allow us to upgrade Unit 2 in 3 days. It was not easy but we were able to accomplish this goal.

The guys from Williams Industrial Services stand over the carcass of their recently defeated foe, the old CEMS cabinets. These things were built to last forever and did not give in easily.

Buzzards started to circle the stack about mid way through the outage. No one can remember that happening before. Despite the bad omen we pressed on and were ultimately successful.

A separate crew installed the new cabinets on the duct.

The new cabinets were staged outside the shelter so that they could be installed as soon as the old cabinets were removed.

The new cabinets were put in place.

We swapped the duct and stack analyzer racks after the factory acceptance test so that the new layout matched the old cabinet layout. This ended up requiring a great deal of re-wiring and re-tubing on site. For Unit 1 each cabinet was brought in separately and they were bolted together on site. This required the factory to disconnect all of the wiring between the cabinets. It took much longer than expected to reconnect everything. For Unit 2 we brought the air cleanup train, the duct analyzer cabinet, the stack analyzer cabinet, and the PLC cabinet into the shelter as a complete unit, rolling the cabinets along a few pieces of conduit. This proved to be a much better plan.

This picture shows the new Unit 1 cabinets on the right and the old Unit 2 cabinets on the left. 14 or so years of development makes a huge difference and the I&C techs love the new analyzers. They previously had pre-C series Thermo analyzers. I like to joke that the old analyzers actually had a little bird with a chemistry set who would then tweak a potentiometer to adjust the 4�20mA output like an old Fred Flintstone cartoon. The new i Series analyzers really pay off when you are prepping for linearities. The techs look so much more relaxed as they confidently flow the gas knowing that the analyzers will read as they should. They definitely don�t miss the drama of the old system.

One of our many design improvements was to mount the Teledyne Ultraflow 150 TIE components in a larger NEMA 4 box. This allows more room to work and the cables fold up neatly in the bottom. We don�t expect to have much trouble with the instrument but when they do it will definitely be easier to work on. Another tweak was to add a slow instrument air purge to the cabinet so that it always has clean dry air inside instead of stack gas.

The calibration gas cabinet to the new system has a couple of new tweaks. The CGA bottles have two solenoids in series to insure that a leak in a single solenoid will not cause them to fail a test.

One thing that we did miss in our spec and didn�t catch during the FAT was that the solenoid arrangement in the cabinet does not allow the solenoids to be easily removed. This was one of the few items in the new system that we were not completely happy with. I�m pretty sure that as soon as we wrap up the project the techs will be in here reworking this cabinet.

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We upgraded the calibration gas racks. The old system had the regulators mounted to the bottle with Teflon tubing going to the cal gas solenoids. We installed a bulkhead and mounted all of the regulators in fixed positions with SS tubing to the solenoids. A braided SS hose attaches the regulator to the bottle. This makes everything easier to read and the bottles easier to change out. One problem during installation is that we did not have an experienced tube bender available so it ended up looking like an Escher drawing of impossible angles. This still needs to be cleaned up and is a remaining punch list item.

One major improvement in the design of this system was to install accumulator tanks near the probes for blowback. The old system performed blowback through a 1/4� line with the solenoid actuated down in the shelter. The new system uses the accumulator tank mounted at the probe and 3/8� lines. The accumulator pressure is monitored and the solenoid is actuated small PLC�s mounted on the stack and duct. The blowback is much more forceful than the old system�s and the time to perform a blowback was cut to a third of the old time. This means that the blowbacks are more effective and disrupt the system for less time.

We call this the multiplexer box and we have one on the stack and one on the duct. The top left corner has a little AB Micrologix PLC which acts as a MODBUS slave to the PLC in the shelter. The PLC controls the blowbacks and multiplexes other measurements onto a single fiber cable going down to the shelter. The PLC also measures the temperature of the cabinet so that we know how hot the equipment gets during the day. The PLC will easily allow expansion of the system if we need to add anything to the duct or stack in the future and was relatively inexpensive. We also used a larger box to allow for expansion. The box is also purged with instrument air. The old system used a fixed multiplexer that allowed a couple of 4�20mA and a couple of digital signals to be passed. The two blue boxes on the top right corner control the probe and stinger heaters on the new M&C probe.

The new M&C probe on the stack and duct replaced EPM out of stack probes. The M&C has a superior design for the coarse filter that allows it to be easily changed. The coarse filter also has a much larger surface area than the M&C so we expect fewer problems. The probe sits at an angle because the welder who originally installed this flange 20 years ago did not pay attention to the bolt pattern when he attached it to the stack.

This picture shows the Teledyne UF 150 TIE enclosure on the left, the M&C probe in the middle, and the blowback accumulator box on the right.

It seems that as the original Part 75 CEMS systems start to reach the 12�13 year old mark it makes sense to replace them. Old PLC�s, analyzers, and other instruments are much harder to maintain than the newest generation of equipment. Spare parts are becoming harder to locate. Availability suffers and your technicians spend too much time baby sitting temperamental equipment. It ultimately becomes justifiable to replace everything. Many utilities are also realizing as they prepare for new Mercury CEMS that it is a good time to revisit their NOx/SOx CEMS as well. Your techs will have their hands full with these complex new system so upgrading the old systems to free up their time is a good strategy. It is important to do the preliminary legwork and specifiy a system that will fix any problems or design flaws in your old system and insure that your new system will perform reliably.

Everyone struggles to comply with the assortment of environmental restraints that are the result of federal, state, local, and permit requirements. It is important to present information to your operators in an unambiguous manner that lets them know immediately if they are on target. I recently put together a little solution for a customer who was having problems. They could produce reports from their DAHS but it was cumbersome and the unit operators do not have time to login to the DAHS, select the report and set the dates, and then print it up. Furthermore the DAHS reports did not give them an adequate presentation of their progress toward the limit.

They use the GE NetDAHS software. Most people do not know it but there is a Minute Data ODBC driver that will allow you to access any of the data channels configured on the DAHS. I was able to build a web page that queries the minute data and calculates the hourly averages along with a running total of their emissions and present the status as shown in the screen shot below. As you can see it shows them how much they have emitted that day, the projected total based on their current operation and tells them whether they should be concerned. 

I was also able to add a trend of their emission rate and a graph of their accumulating total compared to the emission limit. This allows the operators to quickly glance at the page and get a feel for where they stand.

If you are having problems tracking your compliance, you should evaluate the way that you report and present the data to your operators. You may be able to eliminate compliance lapses by organizing and presenting your data in real time allowing your operators to quickly see where they stand and make more informed decisions.

From the geek standpoint I pulled a few tricks out of my sleeve to make sure that the application would run smoothly. I used ASP.NET and C# to code the web pages. I made use of the ASP.NET caching features to cache the dataset when a query is made. If another user requests the page within one minute, the cached dataset is used. This insures that no more than one request is made to the ODBC driver per minute so that the NetDAHS server will not get bogged down if a bunch of users start requesting the page all at once. It also means that once the dataset has been queried, additional requests are returned to the user much more quickly.