(Please read the SPE-Xpress white-paper before reading the Smart Bottle Rack paper)
EPA 1664 is a frequently used test standard in the Environmental Testing industry. This process, though simple, requires constant technician involvement over a period of time ranging from thirty minutes to an hour. Fortunately this problem has been solved by Orbis’s SPE-Express, a piece of bench-top lab equipment specifically designed to automate the performance of EPA 1664. However, the ability to simultaneously run as many as six 1L samples through the SPE-Express means that considerable volumes of reagents will be consumed and considerable waste fluid space will be used.
Performing EPA 1664 requires the use of Methanol, DI Water, and n-Hexane. These three fluids, used in technician variable quantities, are supplied to the SPE-Express from standard GL38 threaded glass bottles. The bottles are pressurized with Nitrogen, forcing the fluid through tubes leading to the SPE-Express for use.
On the waste side of the system there are two containers. The first is a glass bottle used to store Hexane Waste and any contaminants that are carried along with it. The second is a large plastic carboy that stores all Water Soluble Waste. The waste is drawn to these two containers via a vacuum connection that pulls the fluid through the lines.
Because of the adjustable rates of reagent use and the large amount of waste water that is drawn from the system (at least 1L of fluid for each sample), simply relying on the technician to monitor fluid levels could lead to aborted sample processing and over flows of fluid in the waste containers.
The improper testing of a sample because of a lack of reagent is of great concern for two reasons. First, it is not uncommon for a lab to only have one sample from a customer. Therefor the loss of the sample would make it impossible to deliver results to the customer. Second, unknowingly performing a complete test without enough reagent would produce incorrect results.
There is also risk involved with overfilling one of the waste containers. Because the waste is brought to the containers by a vacuum pulling them through, if they were to over-fill to the level of the vacuum outlet, the waste liquids could get sucked into the vacuum pump. This could result in erratic pressures for other systems tied to the vacuum as well as potentially damage the vacuum pump itself. It is very important that the waste containers never overfill.
It is not acceptable to simply notice during a test that there is a lack of reagent or that the waste containers are full. The test contains too many steps that are time dependent, the lines in the system are long enough that they have to be bled of air, once a line has gone dry it is very likely that a critical step has been missed, and taking the cap off of a waste container would eliminate the vacuum in the entire system. It is absolutely necessary that all reagent bottles contain enough reagent and that all waste containers have enough spare volume for the test(s) being run before they are started.
Because of the criticality in ensuring that reagent bottles and waste containers are at acceptable levels, a system that can monitor fluid levels and alert the user to inadequate volumes is needed for the automated performance of EPA 1664.
The nature of the system presents some challenges to the design of a level monitoring solution. Several of the reagents are highly volatile and flammable. This means that electronics must be kept outside of the containers. In addition, special purpose containers should be avoided so that technicians are not required to pour reagents from their shipping containers into a product specific one; they should be able to place the reagent into the system as shipped. Finally, the solution must be compact as bench space is at a premium in a laboratory.
In order to create a compact, lightweight system that will monitor levels without coming in contact with the fluids, capacitive sensors present the best solution. Capacitive level sensors have a small footprint, don’t require large amounts of power, and are capable of detecting a fluid’s presence from outside of the fluid’s container.
There are two challenges with a capacitance based system. First, the fluids are contained in both glass bottles and a large plastic carboy. These very different containers have very different capacitances. Secondly, the system has to detect DI Water, Methanol, and n-Hexane. These substances have very different dielectric constants, making measuring them all with a single sensor type very difficult.
Orbis has developed the Smart Bottle Rack to make fluid monitoring an automated process for environmental testing labs using the SPE-Express. The Smart Bottle Rack provides proper tubing for both pressure and vacuum systems, holds the standard sized supply bottles, and has mounts for capacitive sensors at the exact heights required to allow for 6 tests to be started simultaneously without running out of reagents or overfilling waste containers. In addition, the system interfaces directly with the SPE-Express software to alert the user if a threshold has been reached.
The Smart Bottle Rack utilizes two different types of capacitive sensor made by IMF Effector. The KI5086 is tuned to sense water and the KI5082 is tuned to sense low dielectric constant fluids such as Methanol and Hexane. In addition, these sensors can be calibrated in the field by technicians if necessary, making the system extremely robust. Both sensors are meant to detect fluid levels through the side of the bottle, meaning that no electronics have to be present inside of the source bottle.
Each sensor is placed at a height so that when the sensor trips, the user knows that there is now either not enough reagent or not enough free space to perform analysis on six samples. The Smart Bottle Rack plugs directly into the SPE-Express using a serial cable. The SPE-Express monitors the signals coming from the capacitive sensors, and if the user attempts to start a sample while one of the sensors is tripped, the software alerts the user as to which bottle needs attention.
The Smart Bottle Rack provides environmental testing laboratories with a compact system to monitor the levels of reagents and waste fluids for the performance of EPA 1664. With the Smart Bottle Rack interfacing with the SPE-Express, laboratory technicians no longer have to be concerned with monitoring fluid levels themselves, ensuring that samples won’t be aborted mid-test and that the vacuum pump won’t inadvertently pull fluid through itself.
If you have any questions, please do not hesitate to contact us. We would be happy to discuss the particular needs of your automation application.