EPA-650/2-74-067 Hoy 1974 Environmental Protection Technology Series DESIGN, DEVELOPMENT, AND FABRICATION OF A PROTOTYPE HIGH-VOLUME PARTICULATE MASS SAMPLING TRAIN Of o p m e n t US Agency Washington, ' -60 ------- EfA-650/2-74-067 DESIGN, DEVELOPMENT, AND FABRICATION OF A PROTOTYPE HIGH-VOLUME PARTICULATE MASS SAMPLING TRAIN by W.F. Lapson and H.J. Dehne Aerotherm/Acurex Corporation 485 Clyde Avenue Mountain View, California 94042 Contract No. 68-02-1339 Program Element No. 1AB012 ROAPNo. 21 AD J-080 EPA Project Officer: D.B.Harris Control Systems Laboratory National Environmental Research Center Research Triangle Park, North Carolina 27711 Prepared for OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D . C. 20460 May 1974 ------- This report has been reviewed by the Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. 11 ------- ACKNOWLEDGEMENTS The project described in this report was conducted for the Environmental Protection Agency, Control Systems Laboratory, Research Triangle Park, North Carolina, under Contract 68-02-1339. The project was initiated by Mr. James A- Dorsey, Chief of Process Measurements Section, with Mr. Bruce Harris as Project Officer. The technical guidance of Mssrs. Dorsey and Harris is grate- fully acknowledged. The principal individuals involved at Aerotherm were Dr. W. F. Lapson, Project Manager, Mr. Hans-Joachim Dehne, Project Engineer, and Mr. Richard Beer, Designer. Appreciation is also acknowledged for those who participated in the conception of the project; Mr. Ken Lambson, Mr. Nick Davis, and Dr. Larry Anderson ------- TABLE OF CONTENTS Section Page 1 INTRODUCTION 1-1 2 REVIEW OF THE DEVELOPMENT OF A PROTOTYPE HIGH-VOLUME PARTICULATE MASS SAMPLING TRAIN 2-1 2.1 Control Unit 2-1 2.2 Oven 2-8 2.3 Probe 2-8 2.4 Impinger Train 2-14 2.5 Vacuum Pump 2-16 2.6 Umbilical Line 2-21 2.7 Traversing Stand 2-21 2.8 Comparison of Actual Sampling System to Design Objectives 2-21 3 RECOMMENDATIONS FOR FUTURE WORK 3-1 APPENDIX A A-l TECHNICAL DATA REPORT T-l iii ------- LIST OF FIGURES Figure Page 2-1 High Volume Particulate Sampling Train 2-2 2-2 Control Unit 2-3 2-3 Control Unit, Back Cover Removed 2-6 2-4 Oven with Carrying Case 2-9 2-5 Oven with Cyclone Separator and Filter in Position for Use 2-10 2-6 Details of Filter Housing and Cyclone Separator 2-11 2-7 Probe Mounting for Vertical or Horizontal Traverses 2-12 2-8 Rotation of Sampling Probe 2-13 2-9 Probe Details 2-15 2-10 Lexan Impingers with Combination Ice Bath/Carrying Case 2-17 2-11 Lexan Impinger Dimensions 2-18 2-12 Vacuum Pump Assembly 2-19 2-13 Traversing Stand Set Up for Horizontal or Vertical Traverses 2-22 3-1 Automated Particulate Sampler 3-4 IV ------- SECTION 1 INTRODUCTION Currently available particulate mass sampling systems typically sample at rates less than 1 cfm. One consequence of this low sampling rate is an exces- sively long sampling period during which plant operating conditions may vary widely. Another shortcoming of most sampling trains is that the temperature of the probe and filter oven is usually less than 300°F. This permits condensation of such vapors as sulfur trioxide which interferes with the determination of par- ticulate concentration. The Control Systems Laboratory of the EPA has been using a high volume (approximately 7 cfm) version of a Federal Register, Method 5 particulate sam- pling train for several years. This sampling train was bulky, difficult to transport, and in many respects lacked the refinement of a commercial product. The Control Systems Laboratory therefore sponsored a program for the development of a high volume sampling train having the following features: Sampling rate of 5-10 cfm Modular assembly Portability Probe and oven temperatures up to 500°F Conformance to basic requirements of Method 5, Standards of Performance for New Stationary Sources, Federal Register (December 23, 1971) , Vol- ume 36, No. 247. Aerotherm has delivered two high volume sampler trains to the EPA satisfy- ing the above requirements. The new samplers are not much larger than the common samplers operating at 1 cfm. One of the objectives of this program was to study the overall requirements of stack sampling instrumentation. The study concludes with recommendations for sampling systems which are more portable, easier to use, and effective over a wide range of sampling rates. It appears that the greatest advance in sampling trains will result from automation based on the use of a small, dedicated digital compu- ter. The flowrate adjustments for isokinetic conditions would be established by this computer. In an automated system, all of the parameters important to the ------- stack sampling procedure would exist as electrical signals and therefore can be recorded easily. By relying on electronic rather than mechanical instrumentation, many bulky components can be eliminated, thus resulting in a lighter system. One of the most important advantages of the automated sampler would be its capability for rapidly adjusting to changes in stack velocity or temperature. This is especially important when sampling at high flowrates. 1-2 ------- SECTION 2 REVIEW OF THE DEVELOPMENT OF A PROTOTYPE HIGH-VOLUME PARTICULATE MASS SAMPLING TRAIN The high volume sampling train delivered to the EPA samples at nearly ten times the rate of ordinary sampling systems while remaining nearly as compact (Figure 2-1), The system is very rugged. The principal features are summarized below: Sampling rates up to 6 cfm Oven and probe temperatures up to 500°F System breaks down into easily carried modules Fiberglass, cushioned cases for carrying and shipment of each piece of equipment Oil-less vane pump modified for low leakage Two Magnehelic gages for accurate readout over the pitot tube range of 0-4 inches of water Round probe body for ease in sealing the sampling port Probe can be rotated for sampling horizontal ducts located at same level or below the sampling train Impinger train and ice bath separable from oven All glassware eliminated to avoid breakage problems - stainless steel, Lexan, or teflon are used instead of glass Enlarged impinger bottles with demisters to prevent water carry-over at flowrates up to 8 cfm Stable uni-rail traversing stand for guiding probe in horizontal or vertical directions Circuit breakers instead of fuses Separate power lines for heaters and pump to assure obtainability of required power. In the following discussion, the sampling train will be described in greater detail with comments regarding the basis of design decisions. 2.1 CONTROL UNIT The control unit contains all of the instruments required for measuring stack velocity, sampling flowrate and cumulative flow, and temperatures at var- ious points in the sampling system (Figure 2-2). All of the controls for the sampling system are located in the control unit with the exception of the valves for controlling sample flowrate. The valves are mounted on the vacuum pump, which is placed adjacent to the control unit when using the sampling system. Thus all of the controls and measurement displays are centered about the control unit. Each of the items seen on the face of the control unit are described below. 2-1 ------- I - Figure 2-1. High Volume Particulate Sampling Train ------- - AEROTHERM ACUREX Corporation Figure 2-2. Control Unit ------- Switches There are five electrical switches with the following functions: Main power (with pilot light and circuit breaker) Probe heater (with pilot light and circuit breaker) Oven heater (with pilot light and circuit breaker) Fan power Elapsed time indicator start/stop switch Circuit breakers have been used instead of fuses to avoid the problem of running short of fuses. The oven circulation fan has been connected so that dur- ing heating the fan is in operation regardless of the position of the fan control switch. When the oven heater is "off", the fan may be turned "on" with the oven door open to hasten cooling of the oven, cyclone, and filter. Ej.apsed Time Indicator An elapsed time indicator is used to determine when to move from one traverse point to the next. The indicator has a resolution of one-hundredth of a minute. The indicator can be re-set to zero, and started or stopped with pushbuttons located near the indicator. Oven and Probe Heater Temperature Controls Power to the oven and probe heating elements is modulated with adjustable temperature controllers. These controllers use thermocouples for temperature sensing. Each controller has the following features: Actual temperature continuously displayed Maximum set-point is limited to 500°F by a mechanical stop Power "on" or "off" is indicated by red and green lights. Some sampling trains use oven and probe heater controls located at the oven. Frequently these controls are only simple adjustments to the input power and do not involve any thermostatic control. The oven and probe heater controls were located on the control unit because under some conditions the oven is inaccessible for adjustment. This occurs while sampling large stacks when the oven may be located beyond the edge of the sampling platform. Feedback control of the temperature is used because the ambient conditions under which stack sam- pling is performed are highly variable. The concern for accurate temperature control is based on the fact that many of the effluents sampled have condensible components. These components, e.g., water and sulfur trioxide, must be maintain! as vapor prior to filtering out the particulates. 2-4 ------- The actual switching of power to the heating elements in the probe and oven is done by heavy duty relays (lower right corner, Figure 2-3). This greatly increases the capacity for the system to use longer probes or hotter ovens, both requiring greater power. Temperature Display A digital temperature indicator is used together with an eight-point selector switch. The selector switch permits monitoring the temperature by means of thermocouples at each of the following locations: Stack Probe Oven Impinger train outlet Gas meter outlet Gas meter inlet Two "spare" locations. The temperature range is 0° to 2000°F with an accuracy of ± 4°F. Gas Flow The cumulative sample gas flow is measured by a Rockwell Model 415 gas meter. This is a high accuracy meter used for testing purposes. The measure- ment is displayed by a digital counter and pointer with a resolution of 0.005 ft3. Pressure Gages Three Magnehelic pressure gages can be seen on the face of the control unit. One is used for monitoring the pressure drop across the orifice meter (see discussion on orifice meter below). The other two gages are connected in parallel and indicate the pressure differential of the pitot tube used for measuring stack velocity. One of the gages has a range from 0 to 0.5 inches of water, the other, 0 to 4 inches of water. Thus the pitot tube pressure differ- ential can be determined with high accuracy over the full range of 0 to 4 inches of water. Instead of Magnehelic gages, inclined/vertical manometers were con- sidered. This type of manometer has increased resolution at low pressures, the same as the two-gage system described above. Manometers are often used as a primary standard and the readings obtained with them are usually trustworthy in 2-5 ------- ! r. Figure 2-3. Control Unit, Back Cover Removed ------- contrast to gages which require calibration. However, manometers contain liquid which could spill during shipment or handling of the control unit, or inadver- tently be blown into the pressure sampling lines. For these reasons Magnehelic gages were used. Umbilical Line Connections The umbilical line between the control unit, oven, and probe makes the following connections with the control unit: Multi-point connector with a.c. power leads to oven, fan, and probe; Five dual-pin thermocouple connectors for the stack, probe, oven, and impinger thermocouples; Two Swagelok connectors for the pitot tube. The umbilical line also connects to the vacuum pump. The outlet of the pump is connected to the "inlet" fitting located on the Control Unit. The sample gas then passes through the gas and orifice meter in the manner of the typical Method 5 sampling train. A quick-disconnect fitting is provided at the sample "exhaust" outlet. A length of tubing can be connected at this point for leading noxious sample gases away from the control unit area. Power Inlet Connectors Two power connectors are shown. One provides the power for operating all equipment located in the control unit and the fan. The other connector pro- vides power for the probe and oven heaters. The vacuum pump has a separate power line and power switch. The power lines were divided in this fashion to assure that the system could be connected to several separately fused lines to obtain the necessary three kilowatts of power. The control unit has a removable back cover. This feature provides ease of access for assembly or repairs, and for setting the orifice size on the three- position orifice meter (right side, Figure 2-3). Three orifices are used for high accuracy measurements over the following flow ranges: 0.5-1.9 cfm 1.4-4 cfm 2.2-6 cfm 2-7 ------- The pressure drop for each of the above ranges is typically 0.5 to 4 inches of water at the specified flow rates. 2.2 OVEN The oven contains the cyclone and filter and supports the probe and im- pinger train (Figures 2-1, 2-4, 2-5, 2-6). It is a sturdy, double-walled box with two inches of fiberglass insulation. When the oven interior is at 500°F, the exterior is safe to touch. The maximum power dissipation of the single sheathed heating element is 1200 watts. This is sufficient to bring the oven up to 500°F in less than fifteef minutes. A circulation fan increases the heat transfer rate to the cyclone sep- arator and filter so that these too are heated within the fifteen minute warm-up period. The fan can also hasten cooldown when the heater is off and oven door is left open. A cyclone separator is used when the sample stream contains particles larger than 3.5 microns in diameter. The filter attaches to the cyclone or di- rectly to the end of the sampling probe in the event the cyclone is not used. Both the filter and cyclone are constructed of stainless steel. The interior of the filter housing is coated with teflon to prevent the filter from sticking to the housing. The filter has a standard 142 mm diameter which can be purchased ready-cut from several filter manufacturers. While the oven can easily be heated to 500°F, it is intended that the max' imum temperature be limited to 450°F. This is to assure a long life for the silicone rubber gaskets on the door jamb. A rack is provided beneath the installed filter for placing a second fil- ter. The second filter is thus preheated and ready for quick replacement of the first filter if the latter becomes excessively clogged. 2.3 PROBE The probe can be mounted on the oven in any of the following configura- tions: Probe body horizontal (usual position) Probe body vertical (Figure 2-7) Probe tip assembly rotatable through 360° (Figure 2-8) With this flexibility in probe orientation, nearly any sampling situation can be accommodated. 2-8 ------- - - I Figure 2-4. Oven with Carrying Case ------- Figure 2-5. Oven with Cyclone Separator and Filter in Position for Use 2-10 ------- Figure 2-6. Details of Filter Housing and Cyclone Separator ------- HORIZONTAL TRAVERSE. en CD tv) I to VERTICAL Figure 2-7. Probe Mounting for Vertical or Horizontal Traverses ------- l/v s to I PROBS THROUGH Figure 2-8. Rotation of Sampling Probe ------- The principal probe details (Figure 2-9) are as follows: Stainless steel sampling tube Fiberglass insulated strip heater Round probe body Strain relief for all electrical, thermocouple, and pitot line con- nections Interchangeable probe tips with diameters from 1/4 to 3/4 inch. The round probe body is an important feature not usually found on sam- pling equipment. Because the body is round, the sampling port can be sealed very easily. A good seal is necessary as part of proper sampling practice and for the safety of nearby personnel. 2.4 IMPINGER TRAIN The impinger train has several functions listed below in order of impor- tance: Cooling the sampled gas to a temperature level safe for the pump and gas meter Condensing for the purpose of determining water concentration Collection of particulates too fine to be trapped by the filter Chemical analysis The above ranking is not arbitrary. Cooling the sampled gas stream is an essential feature of the impinger train. Moisture concentration must be de- termined as part of Method 5. The impinger train method is a convenient way for determining moisture concentration. The use of impingers for the collec- tion of very fine particles is presently being argued. Some specialists claim that fine particulates may be formed as chemical precipitates or by condensation in the impinger liquid. Thus the fine particulates collected may not actually be present in the gas stream being sampled. Chemical analysis by means of impingers has been ranked last because chemical analysis is not always performed concurrently with particulate sampling. The impinger method is useful, however, when searching for trace metals and a wide variety of other chemical compounds. In this case, however, the virtues of isokinetic sampling at high flowrate are not important and a smaller impinger train for the exclusive purpose of chemical analysis is more useful. 2-14 ------- to M U1 PROBS TEMP T£. HEATER POVMEE Figure 2-9. Probe Details ------- The familiar all-glass Smith-Greenberg impingers could not be used above 3/4 cfm because of water carry-over. The glass parts were also too fragile for the rough environment in which stack sampling is performed. The impingers were therefore increased in size, demisters added, and the glass parts were replaced by Lexan plastic or stainless steel parts (Figures 2-10, 2-11). The impingers can be used at flowrates up to 8 cfm. The interconnections between the impingers are made with stainless steel tubing and Swagelok fittings. This is a rugged, neat method for connecting the impingers as compared to glass tubing and ground-glass spherical joints with clamps. The impingers are sealed with large diameter caps using "0" rings. Thus the interior of the impinger is completely accessible for flushing or cleaning. The "0" rings make better joints than the more common ground glass joint used on impingers. The "O" rings do not require a layer of grease for sealing and they do not seize as ground glass joints can. The Lexan plastic is inert to most commonly encountered gases and sol- vents. In the rare case when Lexan can't be used, the simple cylindrical shape can be produced in glass or teflon. Other features of the impinger train are the following: Impinger rack constructed of PVC plastic Thermocouple mounted on cap of last bottle for monitoring outgoing gas temperature Stainless steel cap on first impinger to withstand high temperature gas Fiberglass carrying case also serves as ice bath Carrying case accommodates impingers, rack, and a 25-foot umbilical line Impinger train is separable from the oven. The feature of being able to separate the impinger train from the oven is useful .* because not all sampling situations involve high temperature gas streams. 2.5 VACUUM PUMP A vane-type vacuum pump, Gast Model 1022, is used. This pump has a 3/4 h.p. motor, flowrate of 10 cfm at 0 in. Hg, and weighs 59 Ibs. including all fittings (Figure 2-12). The features of this pump are as follows: Smooth, pulse-free flow High vacuum capacity 2-16 ------- H si Figure 2-10. Lexan Impingers with Combination Ice Bath/Carrying Case ------- 1! L^B « >«MW W^^ MM Figure 2-11. Lexan Impinger Dimensions 2-18 ------- SJ - 10 Figure 2-12. Vacuum Pump Assembly ------- Self-lubricating carbon vanes Special shaft seal Coarse and fine flow control valves located on pump Carrying handle Operates in open air for good cooling Unbreakable metal filter and muffler jars Vacuum gage to indicate filter condition Quick disconnect fittings* The pump is relatively heavy compared to the lifting capacity of an in- dividual. However, the pump is quite compact and the carrying handle makes its weight manageable. We explored ways for lightening the vaccum pump/ including the following: Use diaphragm pump Have special pump head fabricated from a lightweight alloy Use smaller pump operated at higher rpm Substitute a high performance induction or universal motor for the standard motor. A Thomas Model 2727BA39 diaphragm type vacuum pump was evaluated. This pump has two diaphragms, a flowrate of 7 cfm at 0 in. Hg, and weighs 27 pounds. The low weight, as compared to a vane pump, is mostly the result of using lightweight die castings for the pump head. The diaphragm pump was not satisfactory because of its pulsating flow. It is possible that a surge tank could have been used to reduce the magnitude of the pulsations. However, the additional weight of a surge tank would negate the advantage of low weight in the pump itself. At one point the leak-free characteristic of the diaphragm pump was considered a strong point. The seals on a vane pump were reworked, however, re- sulting in a negligible leak rate. The possibility of a special lightweight pump was also considered. This was not a practical approach because the pump manufacturer (Cast, Inc.) had no interest in producing small quantities, i.e., less than 1,000 units, of a special pump. The same response resulted when we asked for a corrosion-resistant stain- less steel pump. The last two possibilities for reducing pump weight remain practical. As much as 15 Ibs. could be saved by operating a small pump at high rpm using 2-20 ------- a high performance induction motor. However, the cost of developing a lightweight Pump/motor combination was not justifiable on this program. One of the major reasons for using a vane pump rather than diaphragm pump 18 *-ne better flow/weight ratio at high vacuum for the vane pump. Above 7 in. 9» the vane type pump actually weighs less than a diaphragm pump of the same flow capacity. 2.6 UMBILICAL LINE The umbilical line provides all power, thermocouple, and pneumatic con- nections between the probe, oven, and impingers and the Control Unit (Figure 2-1) ne significant features of this part are as follows: Quick disconnects and plugs at each end Strain reliefs to prevent inadvertent opening of connections or wearing of lines Smooth, kink-free, waterproof sheath for enclosing all lines Mating ends of connectors configured so that umbilical line length may be increased by plugging in additional line. The basic umbilical line has a length of 25 feet. 2'7 TRAVERSING STAND The oven with probe attached is supported from a roller-carriage running °n a track in the traversing stand (Figure 2-1). Thus the probe can easily be 9Ulded across the stack being sampled. The stand can be erected in two configurations, one for horizontal probe traverses, the other for vertical traverses (Figure 2-13). The height of the stand is adjustable over a distance of 7 feet for horizontal traverses. The and breaks down into pieces for convenience in shipping. 2 R ° COMPARISON OF ACTUAL SAMPLING SYSTEM TO DESIGN OBJECTIVES The design objectives were to construct a Method 5 type of sampling train aving a flow capacity of 5-10 cfm, portability, ruggedness to resist the rigors shipment, and ease of set-up and handling. The oven and probe were to be eatable to 500°F. The system was to break down into modules weighing no more th*n 50 ibs. The sampling train actually constructed samples at a maximum rate of °ut 6 cfm, limited by the vacuum pump capacity. With a larger vacuum pump, 2-21 ------- K) N) N» H- vQ C K (D to I [_, u> 1-1 n 01 (U U) 0) H- I 3 ill CO ft (a CO a rt o M h H- N O rt P) HORIZOMTAL VERTICM. TRAVERSING STAND SETUP ft H- O ------- ne capacity can be increased to 8 cfm when the flow is limited by water carry- Ver in the impinger train. The oven and probe may be heated to 500°F, although °r long life of the oven door gaskets, 450°F is a better limit. The heaviest in the system are the control unit, 66 Ibs., and the pump, 59 Ibs. While modules are heavier than desired, they are quite manageable because of the handles provided. Rugged shipping cases are provided for all parts of the system: high ^pact strength fiberglass for the control unit, oven, impinger train, and vac- Um Pump; steel reinforced plywood for the probe and traversing stand. The entire system can be unpacked and set up for use in less than one °Ur- Heating time for the probe and oven is less than 15 minutes. 2-23 ------- SECTION 3 RECOMMENDATIONS FOR FUTURE WORK The two most useful objectives for future work are weight reduction and simplification of operation. To illustrate, the present high volume sampling system has a weight of 300 Ibs. including 90 Ibs. of shipping containers. The valve adjustments and computations for establishing isokinetic sampling condi- tions are repetitive, tedious, and require the abilities of a skilled technician Fortunately, weight reduction and simplification of operation are complementary objectives. One of the main contributions to the weight of a stack sampling system is the meter used for measuring total sample flow. A 6 cfm sampler, for example, requires a bulky meter weighing about 20 Ibs. The reason for using this type of meter is that it is simple and inexpensive. If the instrumentation is changed so that an electrical signal corresponding to flow rate is produced, then elec- tronic flow integration becomes possible. The gas meter is thus replaceable by an electronics module weighing a few ounces. There are further advantages, how- ever. The sampling system can now be made to automatically maintain isokinetic sampling conditions. Since all parameters are available as electrical signals, e.g. stack temperature, velocity, sampling rate..., it is feasible to automate the recording of data also. (See Table 3-1 for comparison of manual and auto- mated sampling systems.) The concept for an advanced, automated particulate sampler would not have been very practical two years ago. It was about then that small, versatile computers for process control and low-cost digital displays began to appear on the marketplace. A sampler based on a digital computer would have these capabilities: Continuous, automatic control of sampling rate Compensation for stack temperature variations Control of probe and oven heaters Continuous digital display of all important test parameters Data logging on magnetic tape cassette Data logging on digital printer 3-1 ------- TABLE 3-1 SUMMARY OF SAMPLING SYSTEM CONCEPTS System Type Description Estimated Cost* Dollars Manual Data taking and adjustment for isokinetic sam- pling entirely manual. System is heavy, re- quires skilled operator. Because of simplicity easy to comprehend its use and maintenance re- quirements. Currently most common type of sampling system. 2,500-6,000 Semi-automatic Adjustment for isokinetic sampling automatic, but manual data taking. Simplifies operation of sampler, reduces skill level required of oper- ator and chances for error. Isokinetic con- ditions and flow regulation determined by simple analog or digital computer. Electronic flow Integration. System bulk and weight re- duced to half that of manual system. Adaptable to continuous monitoring applications. 4,000-12,000 Automatic Adjustment for isokinetic sampling and data taking are automatic. Data recorded on tape cassette for rapid data reduction. Cassette interface with computer for data print-out, calculations, or curve plotting, e.g. temper- ature and velocity profiles. Lightweight system requiring minimum of skill to operate. Adaptable to continuous monitoring applications, 6,000-14,000 Automatic Sampling and Probe Traversing All the features of the automatic sampler with the additional advantage of automatic probe positioning. A single operator can monitor several units simultaneously. Adaptable to continuous monitoring of large stacks. 7,000-15,000 n9 small quantity production, e.g. 10 units 3-2 ------- Some of the features of the automated sampling system are considered below (Figure 3-1). First, it should be noted that the operator must initially supply some basic data to the computer, e.g., stack pressure, molecular weight of the sampled gas, and the desired probe and oven operating temperatures. The operator must also select the appropriate sampling nozzle diameter. The sample flowrate is measured with a turbine flowmeter. This type of flowmeter is usable over a flow range of at least 10:1, has a digital signal corresponding to volumetric flowrate, and is nearly insensitive to gas viscosity. The flowmeter is placed in the oven, together with the cyclone, filter, and motorized control valve. Thus none of these components are affected by con- densation of water or other vapors. A gas-to-air heat exchanger would be used instead of an impinger train for cooling the sample gas. This would eliminate the need for ice and result in a lighter weight cooling system than the impinger train. The vacuum pump is located downstream from the turbine flowmeter. With this positioning of components, the leakage characteristics of the pump are not critical, assuming the pump can handle the required flowrate and vacuum. Because the leakage characteristics of the pump are not critical, there is an opportunity to reduce the transported weight of the system in a novel way. The pump can be purchased as a piece of plant equipment and left permanently on site. All of the important test variables are displayed digitally. The operator can thus verify that all conditions are normal. The data can be automatically recorded on a tape cassette. Using a cassette, the data can be fed into a computer, perhaps over a telephone line, for the determination of velocity pro- files and particulate concentrations. A digital printer could be used as a back- up of a tape cassette data logger. Probe traversing can also be done automatically since all that is required is motion along a straight line. A signal indicating probe position would be into the system for recording regardless of whether the probe is moved manually or automatically. The weight of an automated system would be about 140 Ibs., assuming the vacuum pump and heavy vacuum line are left at the sampling site. The greatly simplified operation will free the test personnel so that they can make subjec- tive evaluations of sampling conditions, or conduct other measurements, e.g.r chemical analyses. 3-3 ------- TUEBiNE I STACK. PITOT PfZOSE I DIFFERENTIAL PRESSURE TRAKJSPUCER i PKOBE POSITION SIGNAL. STACK RELAY OVEN HEATER. RELAY t MOLECULAR WEIGHT STACK PRESSURE I OVEN) PROBE TEMP6RATUBC CC-MTKOL. SllSNJAl- DIGITAL. DATA OUTPUT MANUAL DATA INPUT SWITCHES VACUUM PUMP TIMS STACK, TEMPE|?ATUee STACK VELOCITY SAMPLING RATE TOTAL SAMPLE FLOW OVEN PROBe 1 DIGITAL j I PRINTER I I I A- 837 6 Figure 3-1. Automated Particulate Sampler ------- An automated, portable particulate sampling system would undoubtedly be useful. A system of this type would have even greater usefulness for continuous monitoring applications where the system is permanently installed on the stack. 3-5 ------- APPENDIX A INSTRUMENTATION FOR STACK SAMPLING Isokinetic stack sampling with an EPA type of sampling system requires the following measurements: Stack temperature Temperature at orifice meter Stack pressure Sample flowrate and cumulative flow Stack velocity Humidity The various ways for performing these measurements are indicated in Tables 1~4. In the future, stack sampling can be expected to become more automated and The measurement methods suitable for the current EPA sampling train will ot necessarily be appropriate for the more advanced equipment. For example, it 8 currently feasible to measure temperatures with glass-stem or bi-metallic ther- °toeters. it is more convenient, however, to measure temperature with thermocouples. temperatures of concern can then be displayed at a single location, sensor place- is Simple in the case of thermocouples, and the temperature is observable as a °ltage suitable for recording or as a control signal. The measurement of flowrate and total flow is another area where improve- ent is needed. The orifice meters used for measuring flowrate are accurate only QVev a narrow range of flow conditions. Three separate orifices are necessary, r example. to cover the 0-6 cfm range of the Aerotherm high volume stack sampler. ML. "etter way to measure flowrate is with a turbine flowmeter. A single turbine n cover a 10:1 flow range easily. The electrical signal produced by the turbine °wmeter is useful as the input to a controller which automatically maintains kinetic sampling conditions. The flowmeter signal can also be" integrated elec- °nically, thus eliminating the requirement for a heavy, bulky gas meter. Stack velocity is usually observed with Magnehelic gages or inclined/verti- i manometers. The pitot differential pressure displayed by these instruments is ^ectly related to the stack velocity. A direct indication of stack velocity 1(3 be useful. This can be obtained by measuring differential pressure with a Ure transducer. The pressure signal would then be processed along with stack rature in an analog or digital computer having stack velocity for the output. A-l ------- Table 1. Measurement of Temperature Measuring Device Glass-stem thermometers Mercurv-fllass thermometer Atcohol-gtass thermometer Pcntane-glass thermometer Jena or quartz mercury- nitrogen thermometers Gas thermometers Resistance thermometers Platinum-resistance thermometer Nickel-resistance thermometer Thermistors Thermocouples Pl-Pt-Rh thermocouple Chromel-alumel thermo- couple Iron-constantan thermocouple Cofiper-constantan thermocouple Chromcl-constaotan thermocouple Beckman thermometers (Metastatic) Bimetallic thermometers Pressure-bulb thermometers Gas-filled bulb Vapor-filled bulb Liquid-filled bulb Application Temperature of gases and liquids by contact Primary Standard Precision; remote read- ings; temperature of fluids or solids by contact Remote readings; temperature by contact Standard for thermo- couples General testing of high temperature; remote rapid readings by direct contact I! 1! Same as above, especially suited for low temperature For differential temperature in same applications as in glass stem thermometer For approximate temperature Remote-testing I II Range, ° F Precision. ° F Limitations 38/575 Less than 0.1 In gases, accuracy affected to 10 -100/100 -200/70 -38/1.000 by radiation -459/1.600 Less than 0.01 Requires considerable skill to us* -320/ 1 ,800 Less than 0.2 High cost; accuracy affected to 5 by radiation in gases -150/300 0.3 Up to 600 0.1 Accuracy affected by radiation in gases 500/3,000 0.1 to 5 High cost: also, requires Up to 2,200 0.1 to Up to 1.500 0.1 to Up to 700 0.1 to expensive measuring device 15 Less accurate than above 15 'Subject to oxidation 15 5°C difference 0.01'C Must be set for temperature to be measured 0/1,000 1 usually much Time lag; unsuitable for remote more use; unreliable -200/1,000 2 20/500 2 -50/2,100 2 taut-on must be exercised s° that installation is correct Optical pyrometers Radiation pyrometers Seger cones (fusion pyrometers) Indicating crayons Melting and boiling points of materials For intensity of narrow spectral band of high temperature radiation (remote) For intensiry of total high-temperature radiation (remote) 1,500 upward Any range 15 Approximate tern perature 1.000/3,600 (within temperature source) Approximate temperature (on surface) Standards 125/900 All except ex- tremely high temperature 50 ±1% Extremely precise For laboratory use only A-2 ------- Table 2. Measurement of Absolute Pressure Measuring Device McLeod gauge f Irani gauge Thermocouple vacuum gauge Absolute-pressure manometer Diaphragm gauge Barometer, mercury- nianometer type Differential manometer and barometer Evaporation liquid temperature Pressure transducers - strain Oage. capacity, potentiometer. crystal, magnet, and others ' Application Range Very low absolute. 0-0.1 in. Hg pressure Moderately low absolute 0-30 in. Hg pressure or above 0.1-20 mm Hg Atmospheric pressure Moderately low absolute 0-450 in. Hg pressure .or above On refrigeration machine Depends on and for use during liquid evacuation Remote reading, responds 0.05 to 50.000 to rapid changes of pressure psi Precision Limitations 2-5% Not direct reading; vapors tend to condense out Must be calibrated for gas composition on which used 0.01 in. Not readily portable 0.05 mm Hg Direct reading 0.001-0.01 in. Not readily portable 0.01 in. Awkward observation; requires two readings 1% Liquid must be kept supplied; can be used only where liquid evap- oration will not damage system 0.1% Table 3. Measurement of Differential Pressures Measuring Device Micromanometer Draft gauges Manometer Swinging-vane type gauge Bourdon-tube type Pressure transducers - Strain gauge, capacity. Application Rang* Very low pressure 0-6 in. H,O differential Moderately low pressure 0-10in. H,O differential Medium pressure 0-100 in. H,O differential or Hg Moderately low pressure 0-0.5 in. H,O differential O-20 in. H,O Medium to high pressure Any differential usually to atmosphere Remote reading, responds 0.05 to 50,000 to rapid changes of psi Precision Limitations 0.0005 in. H3O Not readily portable; not easy to use with pulsating pressure 0.005 in.- Must be leveled carefully 0.05 in. H,O 0.05 in. Where used with liquid must be compensated for liquid density 5% Generally usable to atmospheric pressure only As high as 0.01 Subject to damage due to over- psi or 0.01 % of pressure shock or pulsation full scale 0.1% tIOmeter, crystal, magnet pressure A-3 ------- Table 4. Measurement of Humidity Measuring Device Application Range Precision Limitations Wet-bulb thermometer with dry-bulb thermometer (Psychrometer) Dew-point apparatus Condensation type Fog type Electrical conductivity type Hygrometer (for relative humidity) Hair hygrometer Hygroscopic material other than hair Electrical conductivity Infra-red Radiation Standard salt Chemical analysis Absorption and weighing Room of building, out- side air, air moving in ducts: standard method 0 to 500 0.1 to 1 Occasional laboratory work; not widely used -180 to 200 Simple wide range method 100 to -I- 100 Accurate measurement of 0-200 dew point; suitable for remote use 2 1 For direct relative humidity (rh) in air where motion is slight Same as above also for high sensitivity For remote use While usable at all temperatures, it is uniquely applicable to extremely low temperatures For standards 0 to 100% rh- -40 to 150F 3%rh Oto100%rh -40 to 150 F 2 to 5% rh Should be used in air stream moving 1,000 to 1,500 fpm or correction m*de. Thermocouple may be used at lower velocities. Difficult to use at sub-freezing temperature. Cumbersome, expensive, difficult to use with precision; unsuitable for remote use Series of readings necessary for determination Unusable below 20° F and below 15% rh or for any moderate humidity at temperature under 0° F Considerable lag; low sensitiv- ity; adversely affected by temperature above 125DF and rh below 20%; frequent calibration required when used t extremes of range Frequent calibration required when used at extremes of range. Requires frequent calibration Requires the use of very costly equipment Cumbersome process Note: Tables 1 - 4 are from the article "Significance of Errors in Stack Sampling Measurements" by R. T. Shigehara, W. S. Todd, and W. S. Smith. A-4 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) 1. REPORT NO., EPA-650/2-74-067 2. 3. RECIPIENT'S ACCESSION NO. 4. TITLE AND SUBTITLE Design, Development, and Fabrication of a Prototype High-Volume Particulate Mass Sampling Train 6. REPORT DATE May 1974 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) W. F. Lapson and H. J. Dehne 8. PERFORMING ORGANIZATION REPORT NO 7079 9. PERFORMING ORGANIZATION NAME AND ADDRESS Aerotherm/Acurex Corporation 485 Clyde Avenue Mountain View, CA 94042 10. PROGRAM ELEMENT NO. 1AB012; ROAP 21ADJ-080 11. CONTRACT/GRANT NO. 68-02-1339 12. SPONSORING AGENCY NAME AND ADDRESS EPA, Office of Research .and Development NERC-RTP, Control Systems Laboratory Research Triangle Park, NC 27711 13. TYPE OF REPORT AND PERIOD COVERED Final: 6/26/73 - 4/30/74 14. SPONSORING AGENCY CODE 18. SUPPLEMENTARY NOTES 16. ABSTRACT The report gives results of a program to develop a high-volume sampling train with the following characteristics: 5-10 cfm sampling rate, modular, portable, 500 F probe/oven temperature, and conforming to Federal Register Method 5 basic requirements (standards of performance for new stationary sources). The program included a study of the overall requirements of stack sampling instrumentation, concluding with recommendations for portable, easier to use systems that are effective over a wide range of sampling rates. i. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.lDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group Chemical Analysis Air Pollution Sampling Particles Flue Gases Measuring Instruments ^article Density (Concentration) Stationary Sources Particulates Mass Sampling 13B, 07D 14B 21B 8. DISTRIBUTION STATEMENT Unlimited 19. SECURITY CLASS (ThisReport) Unclassified 21. NO. OF PAGES 40 20. SECURITY CLASS (TMspage) Unclassified 22. PRICE > Form 2220-1 (9-73) T-l ------- |