Performance Testing Procedure For The Aflastop

Transcript

Performance Testing Procedure for the AflaSTOP EasyDry M500 Dryer AflaSTOP: Storage and Drying For Aflatoxin Prevention April 2016 PAGE 2 OF 16 The AflaSTOP: Storage and Drying for Aflatoxin Prevention (AflaSTOP) project is identifying the most promising storage options to arrest the growth of aflatoxin and designing viable drying options that will allow smallholder farmers to dry their grain to safe storage levels. The project works to ensure that businesses operating in Africa are able to provide these devices to smallholder farmers. It is jointly implemented by ACDI/VOCA and its affiliate Agribusiness Systems International (ASI) under the direction of Meridian Institute. For more information on AflaSTOP and other key reports and resources, visit: www.acdivoca.org/aflastop-publications. This work was carried out as a partnership with Marius Rossouw and Catapult Design to identify potential drying technology suited to support post-harvest handling devices for maize smallholder farmers. For any inquiries about the EasyDry M500, please contact us at [email protected] A video guide on “Important Fabrication Details” can also be found at XXXXX. PAGE 3 OF 16 TABLE OF CONTENTS 1. Product Overview .................................................................................................................................. 5 2. Safety warning....................................................................................................................................... 6 3. EasyDry M500 Dryer Components ....................................................................................................... 7 4. Performance Testing Procedure – Visual Inspection ............................................................................ 8 5. Performance Testing Procedure – Active Evaluation ......................................................................... 13 6. Troubleshooting .................................................................................................................................. 14 LIST OF TABLES Table 1: EasyDry M500 Attributes ............................................................................................................... 6 Table 2: EasyDry M500 Dryer Components ................................................................................................ 7 Table 3: EasyDry M500 Performance Testing Procedure – Visual Inspection ............................................ 8 Table 4: EasyDry M500 Performance Testing Procedure – Active Evaluation ......................................... 13 Table 5: EasyDry M500 Dryer Troubleshooting ........................................................................................ 14 PAGE 4 OF 16 1. Product Overview The EasyDry M500 dryer is a portable, on-farm drying solution that enables smallholder farmers to dry their maize down post-harvest to the recommended moisture levels. It offers a solution that closely resembles the traditional method of lying shelled maize out in the sun to dry, with the major difference in that forced hot air is used as the drying mechanism and is capable of operating under inclement weather conditions since it relies on burning biomass to generate the required heat, and not the sun. Shallow-bed Saturated Drying Air Drying Air Supply Unit The dryer is either transported (as a service) on two motorbikes, a pickup truck, a trailer, or handcart to or stored at the location (as an on-farm investment) where maize is shelled or dried. The dryer can be assembled within 10 minutes by erecting the modular shallow-bed and connecting it to the drying air supply unit. ± 500 Kg of “wet” maize (±10 x 50 kg bags, ±5 ½ x 90 kg bags, ±4 ¼ x 120 kg bags - ± 50kgs will not effect drying performance) are loaded onto the shallow-bed and the furnace is ignited. The heated clean air needed for drying is generated through convection heat transfer by blowing ambient air over heated heat exchanger (HX) channels. The HX channels are heated by drawing hot furnace exhaust gasses through them and out the chimney. The hot exhaust gasses are constantly generated by steadily burning fuel (maize cobs) in the downdraft furnace. The heated air is blown into a canvas plenum with maize suspended on a perforated mesh bed above it. The air pressure builds up in the canvas plenum and forces heated air past the maize kernels with surface moisture drawn away. The maize is stirred at 30 min intervals to allow the moisture trapped in the lower layers closest to the heated air to escape. Once dry, the maize is offloaded for storage. The dryer can dry the 500 kg “wet” maize (~20% moisture content) down a safe storage moisture content of +/- 13.5% within four (4) hours (+/- an hour depending on the actual moisture content of the maize) and 500 kg of maize of ~16% moisture content to below 13.5% within 90 minutes. Multiple batches can be handled per day depending on starting moisture levels and operating hours. A video guide on “Important Fabrication Details” can also be found at XXXXX. PAGE 5 OF 16 Table 1: EasyDry M500 Attributes Attribute Complete Dryer Drying Air Supply Unit Shallow-bed Unit 2.4 m (W) x 3.3 m (L) x 1.8 m (H) 1.0 m (W) x 1.6 m (L) x 1.8 m (H) 1.9 m (W) x 2.5 m (L) x 1.2 m (H) 1.5 m (W) x 1.5 m (L) x 0.9 m (H) 0.5 m (W) x 1.3 (L) m x 0.9 m (H) 1.0 m (W) x 1.5 m (L) x 0.9 m (H) Agricultural colors – Heat resistant 190 kg 120 kg Mild Steel, Cast Iron, Local, low cost material to promote Plastic, Copper, Aluminum sustainability Stock, Painted/ Stock, Painted/ Painted Heat Resistant Painted Heat Resistant Intangible Dry 500 kg wet maize (+/- 20% moisture content) down to 13.5% in +/Consumes 12 - 15 kg cobs four (4) hours (+/- 2 hours depending and 450 ml petrol/hour. on actual moisture content of the maize) Stock PVC and Canvas Agricultural colors - Bed 70 kg Mild Steel, Canvas, Rubber, Leather, Plastic Stock, Painted 5 years 5 years** Tangible Size - Operation Size - Transportation Color/s Weight Material composition Finish Efficiency/Capacity Projected Durability/Longevity* Various 5 years Recommended capacity of 500 kg Lubricate bearings and check engine oil weekly, Projected Maintenance Repair lesions in canvas and Service engine monthly, Schedule coffee mesh as they occur. Replace HX panels every 2 years. * Durability/Longevity with proper care, maintenance and associated cost. ** Canvas plenum and coffee mesh may wear through first and may need repair/replacing more often. 2. Safety warning The EasyDry M500 dryer is a dangerous piece of agricultural equipment that consists of moving components and hot surfaces, posing possible injury risks. Extreme caution is required around the furnace area, the engine and v-belt assemblies. Children should be kept away from the aforementioned components at all times with bystanders minimized around these areas where possible. Children should be kept away at all times while the dryer is in operation. PAGE 6 OF 16 3. EasyDry M500 Dryer Components Table 2: EasyDry M500 Dryer Components 1 x Shallow-bed 1 x EasyDry M500 Dryer 1 x Drying Air Supply Unit 1 x Rainfly 2 x Collapsible Bed Panels 1 x Cob Drying Basket 1 x Canvas Plenum 2 x Transportation Handles 1 x Main Drying Unit Body 1 x Padlock 1 x V-belt 1 x 5.5 HP Engine 1 x Center Support Post 1 x Connection Pin 4 x Collapsible Support Frames PAGE 7 OF 16 4. Performance Testing Procedure – Visual Inspection Table 3: EasyDry M500 Performance Testing Procedure – Visual Inspection Step 1: Initial inspection of all the components. Step 2: Initial inspection of the drying air supply unit – fan assembly tolerances and construction. Inspect the EasyDry M500 dryer to insure all of the components are present and in good working condition. Pay close attention to surface finishes and ensure that all external metal surfaces are properly painted including the primary supply fan and surrounding scroll. Verify that all hinge and pinned components work properly and that all components intended to nest inside others do so with limited effort. Inspect all bolted connections to make sure that they have spring washers/lock nuts and that they are securely tightened. Check each bearing to make sure that the shaft grub screws and grease nipples (and protection if applicable) are installed and facing upwards. Check to confirm that each fan has less than a ¼ clearance to its respective scroll yet does not make contact with any part of its supporting structure when turned by hand. Ensure that all of the fan blades are welded completely to the fan hubs with hubs welded to the shafts and that the fans are balanced. Check each shaft and pulley for any excentrisities and make sure that each pulley is secured to the shaft propperly with its shear key installed. Confirm that all bearings are lubricated with high temperature (150 ºC) lithium grease. Ensure that the internal air supply fan bearing is sufficiently lubricated by viewing the bearing through the spaces of the heat exchanger panels. Step 3: Initial inspection of the drying air supply unit – Heat Exchanger (HX) tolerances and construction. Step 4: Plenum inspection and fit. 1” ½” Check the HX panels at the furnace and exhaust ends to make sure that all the panels are parallel, equally spaced (~1/2” apart) and spot welded in at least 2 places on each side. Similarly confirm that the HX panels are parallel, equally spaced apart at ~1” with no welding. Check to make sure that there are not visible gaps between HX channel panels or the main frame of the dryer body (if possible) or the removable cover plate. Inspect the plenum to ensure that it is sealed at all the seams and reinforced in the proper locations. Confirm that the perimeter rope and the connecting duct with the strap are installed. Check to make sure that each sub component of the plenum are made from the proper material: Base = PE shipping, Sides = PVC, Connecting duct = Canvas and the Rainfly = Raincoat. Make sure that the connecting duct strap is made from cotton or leather and not something plastic that will melt during operation. PAGE 8 OF 16 Step 5: Shallow-bed support frame inspection. Step 6: Interlocking the bed support frames. Unfold each collapsible bed support frame and confirm that they only open to or just under 90º. Ensure that the hinges work correctly and that the two horizontal support members at the same level when collapsed. Compare each bed support member to another and confirm that they are all equal sizes and lengths. Check the top end of the vertical rainfly support to make sure that it has an end cap and that it has soft edged and will not puncture the rainfly when installed. Place each support frame at a corner of the plenum ready for installation. Inspect each bed support frame’s connecting pins and catches to ensure that one receives the others with minimal effort. Ensure that the pin on each bed support member is located in the same position and perpendicular to the horizontal support member and that the groves in the receiving catches are parallel. This will ensure that two connected bed support frames are straight when connected. Repeat Step 6 until the bed support frame is complete. Ensure that all connecting pins are properly engaged and that all corners are as square as possible. Step 7: Inspecting the plenum fit. Step 8: Inspecting the collapsible bed panels. Flat bar overlap After connecting the sidewalls of the plenum to the inside of the bed support frame, confirm that the plenum sits snug inside the support frame’s legs and that the support frame’s clips are softened and will not damage the perimeter rope during operation. Make sure that the perimeter rope is as tight as possible without damaging the canvas or the bed supports. Smooth out the canvas and confirm minimal creasing by checking that the bottom corners of the plenum are close to the bed support frame’s legs. Inspect both collapsible bed panels and confirm that all the edger and corners that will interface with the plenum has been rounded and softened to prevent damage. Check the coffee mesh for damage and make sure that no wires are protruding beyond the panels edges as his will damage the plenum and my cause injury. Confirm that one of the panels has additional flat bar installed in the correct location. Check that the inner corner of each bed has been cut to allow the center post to nest within them. PAGE 9 OF 16 Step 9: Inspect how the collapsible bed panels fit. Step 10: Rainfly inspection Install both bed panels and center post and confirm that the panels’ total expanded lengths match that of the bed support frame. Ensure that collapsible bed panels nest properly onto the bed support frame with the maximum overlap of the perimeter angle iron resting on the bed support square tubing on 3 sides. A ½” gap should remain between the inner vertical edge of the perimeter panel angle iron and the bed support square tubing. Confirm that the inner corners of each bed allows for the center post to fit snugly but not too tight in the middle of the assembly. Ensure that no gaps exist large enough for maize to fall into the plenum within the entire assembly. Inspect the rainfly for damage and confirm that all the seams are properly sealed. Install the rainfly and confirm that it fits the erected shallow-bed. Check that all the seams are properly sealed and for damage. The top corners of the rainfly should be larger than the bed support vertical members with about ½”* if the shallowbed is assembled on level ground. The bottom of the rainfly should be larger than the plenum perimeter rope by at least 2” on each side. This is necessary to allow air to escape during rain since the air pressure will inflate the rainfly, allowing air to escape out the bottom. *This excess will change as the terrain does since an elevation at the center connections of the bed support frame connection will increase the span between the vertical member s and decrease this overage. The opposite is also true for a depression in this area. Step 11: Ensuring a seals between the ground and the shallow-bed Step 12: Inspecting the engine assembly Furnace seal frame Inspect the bottom of the furnace and confirm that the frunace seal flatbars are installed. Connect the canvas connecting duct and ensure that it fits easily around the receiving connection scroll with minimal effort. The connecting duct should not be larger than ½”. Tigten the strap and confirm that the d-ring mechanism work properly. Check that the engine has sufficient oil and remove the assembly from its transportation stowage. Confirm that is has a padlock and that the pin is easily removable. Reinstall it onto the receiving support angles on the opposite side of the furnace and confirm that is installs with minimal effort yet has minimal play in the pinned connection. PAGE 10 OF 16 Step 13: Inspecting the chimney and stamping the SN and QC numbers. Step 14: Installing the v-belt. Stamp the corresponding serial and quality control numbers onto the dryer body below the chimney support member using a number punch set. Install the v-belt onto both fan and engine pulleys and confirm that the engine assembly hangs level under its own weight without making contact with the ground. Confirm the V-belt type corresponds with that of the pulleys (either type A or B) to ensure the belt does not slip when it rains. Confirm that all of the pulleys are aligned within ½” and that the belt runs in a straight line. Check the pulley and make sure that the shear key is installed and that it is spot welded to the engine shaft. Confirm that the bolt securing the pulley to the shaft is tightened and that the threads are not damaged by over tightening. QC number Serial number Erect the chimney by pivoting it upward from its stowing position until it rests securely on the dyer body under its own weight. Confirm that the hinges work properly and that the chimney seals properly on the dryer body. Engage the sliding mechanism at the base of the chimney and confirm that it latches fully and stays in place until disengaged intentionally. Step 15: Inspecting the cob-drying basket. Step 16: Confirming the batch capacity. Remove the cob-drying basket from its stowing location within the furnace and place it on top of the chimney. Confirm that it releases easily from the furnace cavity without catching. Check that the legs slot into the receiving holds within the chimney easily and that all of the feet make simultaneous contact to avoid instability. Inspect the lid hinge and confirm that the lid is able to fold back 270°. Load the shallow-bed with about 500 kg (±10 x 50 kg bags, ±5 ½ x 90 kg bags, ±4 ¼ x 120 kg bags) of maize and confirm that it fits on the bed with at least 2” remaining at the top of the plenum sidewalls once leveled. Listen for maize falling through into the plenum. PAGE 11 OF 16 Step 17: Ensuring consistent furnace fuel. Step 18: Inspecting the ash cleanout door and installing the thermometer. Thermometer Remove, fill and return the cob drying basket from/to the top of the chimney. When firing the furnace, make sure that cobs are fed from the basket into the furnace. Using similarly dry cobs when testing the furnace and HX efficiencies on various dryers is important so that varying performance is not influenced by the cob moisture levels. Inspect the ash cleanout door and ensure that is seals properly with the dryer body. Install a thermometer on the opposite, adjacent end of the plenum in the drying air cavity under the maize bed. Make sure that the thermometer end does not make contact with the plenum sides or the underside of the maize bed. The intension here is to measure the drying air temperature in the plenum before it passes through the maize bed. Step 19: Calibrating the airflow requirement - Part 1. Step 20: Inspecting the engine mounting. “Off” position Place the drying air supply unit on level ground and ensure that the airflow indicator plate (the 4” x 4” plate welded to the thin rod going across the heat exchanger) is just touching the HX panels and not leaning away or against it. Mark the needle position in the protective half circle before the engine is fired with a hacksaw or cold chisel to indicate to “off” position. Prep the furnace and fill the engine with petrol to a point that can be used as a reference to determine how much furl was consumed during the 30 min testing period. Confirm the engine fuel cap has the proper rubber gasket installed. Confirm that there is enough space between the engine and the furnace body to allow for the engine to be lifted to such an extent where the belt tension is reduced and the engine starts with minimal effort. Start the engine and confirm that is runs smoothly without any moving assemblies making contact with their support structures. Turn the engine off and light the furnace. Restart the engine and reduce the rpms close idle. PAGE 12 OF 16 5. Performance Testing Procedure – Active Evaluation Table 4: EasyDry M500 Performance Testing Procedure – Active Evaluation Step 1: Calibrating the airflow requirement - Part 2. . Step 3: Tracking performance-testing metrics. “On” position A 4 paper Once the engine is running comfortably and at an idle, take an A crisp, uncreased A 4 piece of paper and place it on the flat, equal thickness maize bed. This piece of paper should just “float” above the maize bed. If it doesn’t then increase the engine rpms until the paper can be pushed across the bed with minimum effort. If it hovers with excessive movement then decrease the rpms until it is just suspended on a small cushion of air above but very close to the maize. Once this has been achieved you will notice that the airflow indicator needle has moved away from the “off” position”. Once again, mark the “on” position on the protective half circle. This will provide the operator with a guide on what airflow is required regardless of the maize bed depth without having to take a piece of paper to the field. The important thing to remember is that the slower the air, the hotter it is and the faster it will dry wet maize. The flipside is also true where if the airflow is not sufficient to push through the maze then drying will take longer. Step 2: Documenting performance-testing metrics. Two performance-testing sheets are provided in and Excel file named –Appendix A: Performance Testing Worksheets. The first is used as a visual inspection checklist with the second to document the EasyDry M500’s configuration and to track the plenum temperature and the fuel consumption of the 30 min testing period. The following performance testing metrics should be tracked:   Plenum temperatures Fuel consumption of the engine Feed the furnace at a constant cob feed rate with cobs that have been dried/preheated in the cob-drying basket. At no point should the cob level fall below the top level of the furnace grate. Under and over feeding will result in lower furnace temperatures, HX and ultimately drying air temperatures. Always ensure that the furnace is firing as hot as possible by confirming flames through the peepholes on the side of the furnace body. Track the plenum and ambient temperatures in 5 min intervals through 30 min op continuous operation. A difference of at least 35° C should be witnessed between the ambient and the drying air within the 30 min performance testing period. Upon completion of the 30 min testing period, stop the engine and wait for the furnace flames to die out before refilling the engine to the reference point and noting the fuel consumption. The engine should not have used more than 250 ml of fuel during a 30 min period. Note: Tracking fuel over such a short period of time is often difficult since small amounts are being consumed and a reliable method to conduct in the field-testing on such small amounts is lacking. The better approach would be to track the fuel consumption over the entire drying cycle and divide it by the drying time. PAGE 13 OF 16 Step 4: Disassembling and preparing the EasyDry M500 for transport. . Once performace testing has been completed and the furnace has had some time to cool down, diassemble the EasyDry M500 in the reverse order of assembly and return it to its original condition (engine stowed, cob basket nested and chimney collapsed). Only return the engine assembly to its stowing position once the adjacent metal has sufficiently cooled. Fold the plenum and rainfly neatly and place them in the enigne shipping box along with the v-belt, engine manual and tools and a operating manual. Write the corresponding serial number on the box to ensure that components do not get mixed up if multiple units are being perfromance tested at the same time. 6. Troubleshooting A video guide on “Important Fabrication Details” can also be found at XXXXX. Table 5: EasyDry M500 Dryer Troubleshooting 1. 2. 3. 4. Symptom Collapsible bed panel 1 does not fit properly. Shallow-bed Probable Causes Improper bed support frame assembly. Collapsible bed panel 2 does not fit properly. Maize leaking into the plenum. Improper collapsible bed panel 1 installation. Gaps between Collapsible bed panel 1 and 2 and/or bed support frame. Uneven drying throughout the maize bed. Uneven airflow through he maize bed (uneven chaff accumulation is an indication Solution/s Ensure that the all the collapsible bed support frames are connected properly and that the frame as a whole is square. Ensure that collapsible bed panel 1 is nested properly. Ensure that collapsible bed panel 2 has a sufficient overlap with collapsible bed panel 1 and that the perimeter of both panels has sufficient overlap with the bed support frame. Ensure that the maize bed is level and equal maize thickness throughout the bed. PAGE 14 OF 16 of uneven airflow) 5. V-belt is slipping. Drying air supply unit Insufficient belt tension. 6. Noisy bearings. Insufficient lubrication. 7. Fire escaping out the top of the furnace post-initial furnace startup. Insufficient seal between the bottom of the furnace and the ground, ash buildup under the fire grate or the ash cleanout door is open. 8. Excessive smoke from the chimney. 9. Longer than expected drying times. Insufficient combustion air or wet fuel source. Furnace is over fueled or the ash cleanout door is open. Cobs are too wet for efficient combustion. Low drying air temperature, in insufficient airflow or higher than anticipated grain moisture content. Ensure that the engine assembly hangs freely with only the v-belt supporting it. Ensure all bearing are lubricated at all times. Confirm that a good seal is achieved between the furnace bottom and the ground and that no combustion air is being introduces from the bottom. Remove any ash/charcoal that may be obstruction airflow and ensure the ash cleanout door is closed. Ensure that the proper amount of dry cobs (from the cob drying basket) is fed to the furnace at regular intervals. Cob levels should always lie around the top of the fire grate. Ensure that the furnace is always fired as hot as possible. Confirm constant flaming through the heat exchanger through the peepholes on the side of the furnace. Stir the furnace and introduce more cobs if limited flames are visible. Ensure that sufficient drying air passes through the maize bed by ensuring the engine rpms are set to the derided rate as indicated by the airflow indicator. PAGE 15 OF 16 PAGE 16 OF 16