Sandia National Laboratories (SNL) awarded Raytheon Ktech a contract to fabricate a Filter Test Bed System
(Figure 1) that would evaluate the efficiency of filter materials used to capture aerosols in a variety of field test and airborne applications. The system had to operate at flow velocities of between 1,000 and 5,000 ft/min and at air temperatures of 70º, 0º, and -40º F. The challenge was that SNL had limited funds and needed the system fabricated, assembled, and delivered by September 12, 2008, in order to use FY2008 funds. Raytheon Ktech revised the Process and Instrumentation Diagram (P&ID) layout and specified and ordered all the materials, instrumentation, and hardware. We worked with Fluid Technologies in Colorado who provided the heat exchange to reach -40ºF, and the 10 horsepower rotary vane vacuum pump to produce the flow rates required. To cool the air, we incorporated liquid nitrogen (LN2) with a cryogenic solenoid valve controlled by a programmable temperature controller and thermocouple located just up stream of the filter holder to maintain the test temperature of the air. This saved SNL approximately $160K, the cost of a refrigeration system to achieve the sub-ambient temperatures. The Filter Test Bed System used a sharp edge orifice coupled with a differential pressure transducer to measure the flow of air through the system. Filter material is tested by injecting well-characterized aerosols into the flow just upstream of the filter holder using an Aerosol Generator/Classifier. An aerosol sample extractor periodically takes aerosol samples and transfers the sample to a Condensation Particle Counter for analyzing concentration.
Figure 1.
Filter Test Bed System with 10 hp
vacuum pump installed at SNL
(Cryogenic heat exchanger not shown).
Figure 2.
Solenoid valve control and instrument chassis.
The system is designed so that aerosol samples can be taken both up stream and down stream of the filter to verify efficiency. A differential pressure transducer measures pressure across the filter to indicate relative loading during experiments. Air flow is controlled using two 2” diameter diaphragm valves. Aerosol samples are taken by manually operating a series of solenoid valves. To assist the experimenters in determining what valves to operate during experiments, the front panel of the solenoid valve control and instrument chassis
(Figure 2) contains a screen print of the sample extraction flow circuit.
Collaboration with engineers designers, and technicians from Raytheon Ktech, Applied Physics and Testing, Engineering Development and Pulsed Power Technologies contributed to the final assembly and check out of the system. We delivered the system to SNL on time and within their budget. The Filter Test Bed System demonstrates Raytheon Ktech’s adaptability to matrix across departments and companies to acquire the skilled personnel needed to meet a critical deadline for a client.
