Abstract:
An apparatus and method to internally cut vertical slots inside PVC, HDPE, or plastic pipe-riser (blank casing) in existing methane gas recovery wells (extraction wells) that have been installed at Municipal Solid Waste Facilities are described. Vertical slots cut in methane well risers allow methane gas, LFG derived from the decomposition of waste, to enter the existing riser and extraction system. This process saves time and cost associated with drilling additional wells to retrieve methane gas from subsequent layers of the waste body. The process assists in maintaining regulatory compliance by capturing LFG and preventing it from being emitted into the atmosphere.

Description:
PRIOR RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 60/866,699 filed Nov. 21, 2006 entitled “Internal Pipe Slot Tool,” which is incorporated herein by reference in its entirety. 
     
    
     FEDERALLY SPONSORED RESEARCH STATEMENT 
       [0002]    Not applicable. 
       REFERENCE TO MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       FIELD OF THE INVENTION 
       [0004]    The invention is a tool for internally cutting vertical slots in plastic pipe and a method of using an internal pipe cutter to improve methane extraction from municipal solid waste facilities (MSWFs). The method uses an internal pipe cutter to slot existing riser pipe and extract additional methane from methane recovery wells at MSWFs. By internally slotting the methane well riser pipes, the volume and rate of methane extraction is enhanced, the amount of methane extracted from a given landfill unit is increased and less methane is emitted into the atmosphere. Increasing methane capture and production while reducing methane emissions assists MSWFs in maintaining regulatory compliance. Additionally, the internal pipe cutter can be used to rehabilitate methane extraction wells where the screen zone has been flooded, clogged or deemed inoperable. 
       BACKGROUND OF THE INVENTION 
       [0005]    Methane is a primary constituent of landfill gas (LFG) and a potent contributor to greenhouse gasses. MSWFs are the largest source of human-related (anthropogenic) methane emissions in the United States, accounting for about 25 percent of these emissions in 2004. Additionally, these escaping LFG emissions are a lost opportunity to capture and use a significant energy resource. Substantial energy, economic, and environmental benefits are achieved by capturing LFG and reducing greenhouse gasses. LFG recapture projects improve energy independence, produce cost savings, create jobs, and help local economies. LFG is currently extracted from landfills using a series of wells and a vacuum system that consolidates the collected gas for processing. From there, the LFG is used for a variety of purposes including motor vehicle fuel, generator fuel, biodiesel production, natural gas supplement, as well as green power and heating. 
         [0006]    Currently, MSWFs bury waste bodies in layers over time (See  FIG. 1 ). The basic structure is a floor and sidewalls (not shown) of compacted clay, covered with a HDPE polymer liner, filled with layers of waste alternated with clay or soil layers. Once a landfill has reached a certain capacity methane recovery wells are installed and gas is extracted from decomposing waste layers, as the waste body increases in height, riser pipe is added to the existing extraction well, once the waste body reaches the design height or capacity it is covered with topsoil, replanted with natural vegetation and left to decompose. LFG is created as solid waste decomposes in a landfill. This gas consists of about 50 percent methane (CH 4 ), the primary component of natural gas, about 40-49% percent carbon dioxide (CO 2 ), and a small amount of non-methane organic compounds. Landfills must be monitored over time to ensure that LFG emissions, groundwater leachate, and waste from the solid waste unit are not being released and impacting the environment. Methane extraction and recovery removes LFG and prevents emission of these air contaminants. Methane is first produced in the oldest, lower decomposing waste bodies. Subsequent layers produce methane at different times and rates. To extract methane from subsequent layers, wells are drilled to a desired depth or elevation and methane extracted. As decomposition continues shallower and shallower wells are required to reach gasses trapped in upper waste bodies. LFG capture and use is a reliable and renewable fuel option that represents a largely untapped and environmentally friendly energy source at thousands of landfills around the world. 
         [0007]    Recaptured LFG can be used to produce electricity with engines, turbines, microturbines, or other technologies, used as an alternative to fossil fuels, or refined and injected into the natural gas pipeline. Capturing and using LFG in these ways can yield substantial energy, economic, environmental, air quality, and public health benefits. Internationally, significant opportunities exist for expanding LFG recovery and use while reducing harmful emissions. 
         [0008]    Extraction of LFG from upper elevations by drilling shallower wells is a capital intensive process. Multiple wells, pipe, equipment and repeated drilling are required to collect and transport the gas to the collection facility. A method of ventilating existing methane wells is required that would not damage the vertical pipe while allowing methane gas to enter the riser from subsequent waste bodies or subsequent elevations within the same well location. 
       SUMMARY OF THE INVENTION 
       [0009]    The internal slot tool is a cutting tool used to cut vertical slots inside existing methane well riser pipes above the original screen section to allow additional production of gas from upper zones or in wells where LFG production is reduced or completely inoperable. The tool is designed to fulfill the needs of owners and operators at landfill facilities. It provides ventilation to riser pipes initially installed in the waste body and extended with additional riser as waste is added. The amount of riser can reach lengths of approximately 50 feet or more above the original ventilated screen section of the well. 
         [0010]    As used herein “riser pipe” or “vertical pipe” is defined as any length of pipe that is vertical or nearly vertical. Due to shifting waste bodies, imperfections in drilling, and deviation in pipe over time, the pipe may depart from vertical and may even approach horizontal at places within the pipe. Plastic pipe materials include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polyethylene (PE), cross-linked high-density polyethylene (PEX), polybutylene (PB), and acrylonitrile butadiene styrene (ABS), for example. Pipe may also be made from concrete or ceramic. 
         [0011]    The internal slot cutter ( FIG. 2 ) consists of a power supply, body, and cutting apparatus. The power supply may be electric, hydraulic, compressed air, or other non-sparking power supply. The body can be plastic, ceramic or metal. A brass or stainless steel body provides a durable and smooth surface. The motor ( 1 ), ( FIGS. 4 &amp; 5 ) is sealed within the body and may be a sealed electric motor, hydraulic motor, compressed air motor or other non-sparking motor. The cutting apparatus extends from the body of the internal slot cutter. The cutting means ( 34 ) are pushed against the internal walls of the pipe cutting through the pipe and providing ventilation slots allowing LFG to enter the well and increase recovery volume and rate. 
         [0012]    A method of using the internal slot cutter is also described. The cutter is placed within an area of pipe that requires ventilation generally above the original screen zone. The motor ( 1 ) is engaged and the cutting apparatus extended to slot the pipe. The slot is made longer by raising the cutting tool with the motor engaged. Once a desired slot length is reached the motor ( 1 ) is disengaged and the cutting apparatus is retracted. The internal slot cutter is then moved to another area and the process repeated or the tool is removed from the pipe when all slots are finished. 
         [0013]    Sealed electric, pressurized hydraulic, and compressed air power supplies have been developed for a variety of applications. Motors can be selected based on cutting blade size, number of cutting blades, and gear ratio to cut a variety of pipes dependent upon pipe internal diameter and pipe wall thickness. In one embodiment the motor is a pneumatic motor with vented exhaust. In another embodiment the motor is an electric motor. 
         [0014]    The motors may be approximately ¼ horsepower to approximately 10 horsepower, preferably between about ½ horsepower and about 5 horsepower, and most preferably the motor should be approximately 1 horsepower. In another embodiment the motor is about 8 horsepower. A larger or smaller motor may be used dependent upon the size of the pipe, size of the cutter, number of blades, and length of time required to cut through the pipe. 
         [0015]    The tool body or main motor housing ( 11 ) can be plastic, ceramic, metal, carbon steel, cast aluminum, stainless steel, or brass. Cast aluminum, carbon steel, stainless steel and brass bodies provide a smooth, durable surface for the tool. The body may be solid or sectional. In one embodiment the body has a screw-type cap ( 55 ), ( FIG. 5 ) that seals the end of the tool body ( 11 ) as well as providing support for the adapter ( 51 ). Optionally, additional adapters ( 52 ) may also be placed in the end cap ( 55 ) or directly in the tool body ( 11 ). 
         [0016]    The cutting apparatus as depicted on ( FIG. 2 ) can have 2 cutting blades at 180°, 3 cutting blades at 120°, 4 cutting blades at 90°, 5 cutting blades at 72°, 6 cutting blades at 60° apart, or more equally spaced cutting means. Many different cutting blades are known, including circular saws, chain saws, hole saws, and grinding wheels. These can be configured to create slots between 1/10th inch and 1 inch wide. The driving motor worm gear ( 3 ) engages the drive sprocket ( 7 ), rotating chain and cutter sprocket ( 32 ), spinning the cutting blades ( 34 ) at high speeds. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1 : Methane Extraction from Municipal Solid Waste Bodies. The methane extraction well consists of a screen zone in a waste body for methane extraction, a riser pipe that carries the methane to the surface header and subsequent gas collection system. A methane extraction well is drilled into a waste body at a specific depth or elevation. Often the screen zone is installed early in the life of the landfill and risers are attached as the waste height is increased. Solid waste bodies are formed in waste-body layers as the landfill matures. To extract gas from waste bodies added above the original screen zone, additional ventilation is required, perforation slots may be added using the internal slot cutter to ventilate additional waste bodies in the existing riser system. 
           [0018]      FIG. 2 : Internal Slot Cutter. An internal slot cutter is described one embodiment is demonstrated. The internal slot cutter (A) uses a power supply that transmits compressed air, hydraulic, or electrical power through hoses or wires ( 58 ) with one or more connectors ( 56 ) that attach to fittings ( 51 ) on the body ( 11 ). The power supply powers the motor ( 1 ) and drive shaft ( 2 ). The drive shaft ( 2 ) rotates the drive arms ( 26 ) thus rotating the saw blades ( 34 ). Two (B), three (C), four (D) or more drive arms ( 26 ) and retractable blades ( 34 ) may be used. 
           [0019]      FIG. 3 : Retractable Blades. The motor ( 1 ) rotates the drive arms ( 26 ) that rotate the retractable saw blades ( 34 ). (A) The retractable saw blades ( 34 ) may be pressed outward by a movable wedge or pusher arms ( 40 ) that presses against the drive arms ( 26 ) and saw blades ( 34 ) against the pipe when pulled toward the motor. (B) The retractable saw blades ( 34 ) may be pulled outward by a rope, chain, or cable ( 63 ) that is attached to the drive arms ( 26 ). Optional eyes ( 62 ) may be fixed along the body to guide the pull cable ( 63 ). (C) The retractable saw blades ( 34 ) may be pressed outward by pushing the motor ( 1 ) and drive arms ( 26 ) against a fixed wedge ( 64 ) thereby forcing the drive arms ( 26 ) and saw blades ( 34 ) outward. 
           [0020]      FIG. 4 : Description of the Internal Slot Cutting Tool and attachment. The figure shows one embodiment of the tool with a diameter of approximately 4.75 inches and a length of approximately 28 inches. The exterior of the tool is shown in Panel A including the arm median (G) and cutter axis (H). Panel B shows a cutaway of the tool demonstrating the motor, worm gears, arms and cutter details. Panel C shows the arm deployment detail and Panel D shows the one embodiment of the cutter detail. 
           [0021]      FIG. 5 : Itemized part detail. Itemized parts are listed in Table 1. 
       
    
    
     DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
       [0022]    The internal slot cutter is a tool for cutting vertical slots in a plastic pipe. The tool is lowered into a vertical pipe to a target depth and activated. Upon activation, the cutter expands to the internal diameter of the pipe and cuts vertical slots through the pipe casing. The cutting apparatus are positioned on opposing sides of the pipe, either 180° apart for 2 blades, 120° for 3 blades, or 90° for 4 blades. More blades may also be used for larger pipes or where more slots are desired (i.e. 5 blades at 72°, 6 blades at 60°). Wider slots may be generated by increasing the width of the cutting means. Cutting blades can be from 1/10″ to  1 ″ wide, or wider for larger pipes. As the cutting apparatus expands, the blades push equally against opposing sides of the pipe creating vertical slots at each cutting means. Slots may be cut in varying lengths by raising the cutting tool while activated. The size of the slots will depend upon the diameter of the pipe, depth of the pipe, type of pipe, amount of waste body to be ventilated, and the like. In one embodiment the slots are about 1 to about 12 inches long or about 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, to about 30 cm in length; in another embodiment the slots are approximately 6 inches long or 15 cm in length. In another embodiment the slots are several feet or meters long. After the slots are cut to a desired length, the power source is turned off and the cutting apparatus retracted. The tool is lifted and the process repeated until a desired length of pipe is slotted. 
         [0023]    The tool is run in an explosive environment; therefore a non-sparking power source is preferred. In one embodiment air or hydraulic power is used to power the tool. In a preferred embodiment a single pressurized air hose is used to power the tool where the pneumatic motor may optionally be vented to remove the pressurized air from the riser pipe. In another embodiment a hydraulic feed and return line are used to power the tool and recirculate hydraulic fluid. Additionally, a steel cable, rope, or pipe may be attached to the tool. 
         [0024]    In one embodiment, the power source fittings are recessed in the body. The power source fittings may also be coupled, or encased in an end-cap using a variety of connectors known to one of ordinary skill in the art. Connectors include, but are not limited to, screw-type connectors, hydraulic connectors, pressure fittings, and the like. 
         [0025]    The diameter of the tool body must be narrower than the riser pipe. Although ideally the riser pipe would be vertical, the pipe may have bends and obstructions that may intrude into the interior of the pipe. Thus the tool body should be less than about 85%, preferably less than about 80%, more preferably less than about 75%, and most preferably less than about 60% of the pipe&#39;s internal diameter. In one embodiment the tool is less than 5 inches in diameter, in a preferred embodiment the tool is between 2 and 6 inches in diameter. The total diameter of the tool body, retracted cutting blades, and all supply lines may be about 2, 2.5. 3. 3.5. 4. 4.5, 5, 5.5, 6, to 6.5 inches, or about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, to 20 centimeters, or larger diameters. 
         [0026]    The body excluding the cutter should be less than 3 feet long, preferably about 2 feet and most preferably from about 1 foot to about 2 feet in length. The body may be an elongate oval or cylindrical. Body material can be any durable material including plastic, metal, or ceramic. In a preferred embodiment the body is cast aluminum, carbon steel, stainless steel, or brass providing both a durable casing and a weight. The tool may weigh between 2 and 20 pounds. Preferably the tool weighs between 4 and 16 pounds, most preferably about 10 pounds. 
         [0027]    The cutting apparatus needs to expand to the internal diameter of the pipe and cut through the pipe. In one embodiment the internal slot cutter expands about 4 to about 10 inches in diameter (or about 10 mm to about 25 mm). In another embodiment the internal slot cutter expands about 6 to about 8 inches in diameter (or about 15 mm to about 20 mm). In a preferred embodiment the internal slot cutter expands to greater than 8 inches in diameter (greater than 15 mm). The blades must be able to cut about a 0.1 to about 1 inch or about 1 mm to about 3 cm wide slot in the pipe wall. In a preferred embodiment the cutter makes about a ⅛ inch thick slot in the pipe wall. In another embodiment the cutting apparatus makes an approximately ¼ inch slot in the pipe wall. The slots may be about ⅛, 3/16, 7/32, ¼, 9/32, 5/16, ⅓, 11/32, ⅜, ½, ¾, to 1 inch wide, or about 1, 2, 3, 4, 5, 6, 7, 8, 9 to 10 mm wide or approximately 1, 2, 3, to 4 cm wide or greater dependent on the scale of the cutter and the width of the cutting blade. The cutting apparatus can cut a variety of pipe materials including schedule 80 PVC pipe, HDPE, or other plastic pipe materials. Blades may be interchanged dependent upon the material to be cut and thickness of the riser wall. 
         [0028]    An index of parts is shown in Table 1. The parts listed in Table 1 may be substituted with similar parts. For example, a drive sprocket and chain may be replaced with a pulley and belt. A shaft, washer and retaining ring may be replaced with a bolt and nut. A brad may be used to permanently affix two parts instead of screw. A gear box may be substituted for the worm gears. Alternative washers, bushings, bearings, and spacers may be used where appropriate. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Itemized parts list. 
               
             
          
           
               
                 ITEM 
                 QTY 
                 DESCRIPTION 
                 Supplier 
                 PART # 
               
               
                   
               
             
          
           
               
                 1 
                 1 
                 Pneumatic Motor 
                 Atlas Copco 
                 LZB54_3 
               
               
                 2 
                 1 
                 Shaft worm gear adaptor 
                 Rush Gears 
               
               
                 3 
                 1 
                 Worm gear 
                 Rush Gears 
                 WH12QR 
               
               
                 4 
                 3 
                 Machined worm gear 
                 Rush Gears 
                 WB1220QR_Machined 
               
               
                 5 
                 3 
                 Worm gear bushing 
                 McMaster-Carr 
                 6391K178 
               
               
                 6 
                 3 
                 Drive sprocket spacer 
                 Capital Tool 
                 Spacer_Sprocket_28T 
               
               
                 7 
                 3 
                 Drive sprocket 
                 Capital Tool 
                 Sprocket_28T 
               
               
                 8 
                 3 
                 Drive sprocket washer 
                 Capital Tool 
                 Spacer_Thrust_Sprocket_28T 
               
               
                 9 
                 9 
                 Socket head screw cap 
                   
                 SHCS-English-UNC 
               
               
                 10 
                 6 
                 Worm gear bearing 
                 Berg W. M., Inc. 
                 Berg_BR5-2 
               
               
                 11 
                 1 
                 Main motor housing 
                   
                 Housing_Working 
               
               
                 12 
                 1 
                 Bearing 
                 Stafford Mfg. Corp. 
                 5909K18_ThrustWasher 
               
               
                 14 
                 1 
                 Thrust Washer 
                 Stafford Mfg. Corp. 
                 5909K78_Washer_35mm_1mm 
               
               
                 15 
                 1 
                 Thrust Washer 
                 Stafford Mfg. Corp. 
                 5909K91_Washer_35mm_3.5mm 
               
               
                 16 
                 1 
                 Bearing 
                 Stafford Mfg. Corp. 
                 5909K38_ThrustWasher 
               
               
                 18 
                 2 
                 Thrust Washer 
                 Stafford Mfg. Corp. 
                 5909K52_Washer_1.25_.032 
               
               
                 19 
                 1 
                 Linear shaft bearing 
                 Berg W. M., Inc. 
                 Linear_Shaft_Bearing 
               
               
                 20 
                 1 
                 Linear drive base 
                   
                 Linear_Base 
               
               
                 21 
                 1 
                 Linear drive arm support 
                   
                 Arm_Support_2 
               
               
                 22 
                 2 
                 Socket head screw cap 
                   
                 SHCS-English-UNC 
               
               
                 23 
                 2 
                 Flat washer 
                 Grainger Ind. 
                 ANSI B18.22.1-1965, R1990 
               
               
                 24 
                 3 
                 Support arm pusher shaft 
                   
                 Linear_Arm_SetScrew 
               
               
                 25 
                 1 
                 Linear drive 
                   
                 Linear_DrivePiece 
               
               
                 26 
                 3 
                 Cutter arm 
                   
                 Arm_Sprocket 
               
               
                 27 
                 3 
                 Cutter shaft bearing 
                 SKF 
                 4200 ATN9_PART1 
               
               
                 31 
                 3 
                 Cutter shaft 
                   
                 Shaft2 
               
               
                 32 
                 3 
                 Cutter sprocket 
                 Capital Tool 
                 Sprocket_18T 
               
               
                 33 
                 3 
                 Cutter sprocket spacer 
                 Capital Tool 
                 Spacer_Sprocket_18T 
               
               
                 34 
                 3 
                 Cutter 
                   
                 3x.25 Cutter 
               
               
                 35 
                 3 
                 Cutter thrust washer 
                 Stafford Mfg. Corp. 
                 5906K547_Thrust_Washer 
               
               
                 36 
                 3 
                 Retaining ring 
                 Smalley Steel Ring Co. 
                 WSM-37 
               
               
                 37 
                 3 
                 Cutter support washer 
                 Stafford Mfg. Corp. 
                 Washer_Cutter 
               
               
                 38 
                 3 
                 Screw cap 
                   
                 SHCS-English-UNF ¼-28 × ⅝ lg 
               
               
                 39 
                 3 
                 External retaining ring 
                 Smalley Steel Ring Co. 
                 WSM-25, ¼ 
               
               
                 40 
                 3 
                 Pusher arm 
                   
                 Pusher_Arm 
               
               
                 41 
                 3 
                 Pusher sleeve bearing 
                 Berg W. M., Inc. 
                 6338K411_Sleeve_Bearing 
               
               
                 42 
                 4 
                 Pusher thrust washer 
                 Stafford Mfg. Corp. 
                 5906K511_ThrustWasher 
               
               
                 45 
                 1 
                 Pneumatic drive 
                 Atlas Copco 
                 LZB14R_4 
               
               
                 46 
                 1 
                 Linear drive screw 
                   
                 Linear_DriveScrew 
               
               
                 47 
                 1 
                 Drive motor housing 
                   
                 BottomHousing_Working 
               
               
                 48 
                 3 
                 Worm gear shaft 
                 Rush Gears 
                 WormGearShaft 
               
               
                 49 
                 3 
                 Screw cap 
                   
                 SHCS-English-UNC, ¼-20 × 1 lg 
               
               
                 50 
                 1 
                 External retaining ring 
                 Smalley Steel Ring Co. 
                 WSM-50, ½ 
               
               
                 51 
                 2 
                 BSP Adapter 
                 Sanford 
                 38BSP_Adapter 
               
               
                 52 
                 1 
                 BSP Adapter 
                 Sanford 
                 12BSP_Adapter 
               
               
                 53 
                 1 
                 Motor support sleeve 
                   
                 MotorSleeve 
               
               
                 54 
                 1 
                 Spring ring 
                 Smalley Steel Ring Co. 
                 RW-0250-0.144 
               
               
                 55 
                 1 
                 End motor cap 
                   
                 MotorLoader 
               
               
                 56 
                 2 
                 Fitting Adapter 
                 Chamberlin Rubber Co. 
                 16-12_FTX-S_PRT 
               
               
                 57 
                 1 
                 Fitting Adapter 
                 Chamberlin Rubber Co. 
                 20-16_FTX-S_PRT 
               
               
                 58 
                 2 
                 Fitting Hose 
                 Chamberlin Rubber Co. 
                 30 
               
               
                 59 
                 1 
                 Fitting Hose 
                 Chamberlin Rubber Co. 
                 32 
               
               
                 60 
                 1 
                 External retaining ring 
                 Smalley Steel Ring Co. 
                 WSM-125 
               
               
                 61 
                 3 
                 Drive housing spacer 
                   
                 Housing Spacer 
               
               
                   
               
             
          
         
       
     
         [0029]    All parts are commercially available, but may be manufactured to meet the specifications described herein if custom sizes or materials are desirable. Additionally, the tool may be scaled for larger or smaller pipes thus the part selected may be replaced with an appropriately sized part. 
       Example I 
     Pneumatic Cutter Tool 
       [0030]    In one embodiment an airtool was designed to cut ¼″ slots in a 6 to 8 inch diameter pipe. The tool including housing, motor, cutters, pusher motor and housing, is approximately 28″ in overall length and about 4¾ inches in overall diameter. The cutting wheels are shown in their fully deployed position ( FIG. 4 ). The Cutter is held in place on the shaft with a washer and screw. A double row ball bearing is used to support the shaft. The bearing is captured in the arm by an internal shoulder in the arm and a flange on the cutter shaft. The pusher arm is also attached to the shaft to move the cutter out to the pipe ID. Cutter deployment is slowed or stopped when the arm impacts the ID of the tube and cutting begins, the arm is then extended further until a slot is cut through the pipe. A pneumatic motor or electric motor ( 45 ) may be used to deploy the arms ( 26 ). One advantage of a pneumatic motor is that stall does not hurt the motor. With an electric motor, motor current can be monitored to detect stall and control arm deployment. 
         [0031]    The main pneumatic motor ( 1 ) receives compressed air at a flow rate of approximately 37.5 cfm at 100 psi. The supply hoses (forward and reverse) are approximately 1″ outside diameter (OD) or ⅞″ inside diameter (ID), and the discharge hose is approximately 1¼″ OD or 1⅛″ ID. When using a vented exhaust motor, the exhaust hose ( 59 ) must be large enough to prevent back pressure from slowing the motor. Optionally, the end motor cap ( 55 ) houses adapter fittings ( 51 ) that reduce larger supply and exhaust hose fittings ( 58 ) to the motor fittings ( 56 ). Longer hoses may require larger diameter supply and exhaust hoses as the pressure may drop approximately 25 psi over 100 ft of hose length in the supply hoses and 8 psi in the discharge hose. 
         [0032]    In one embodiment, a 0.8 hp motor ( 1 ) is powered by a compressed air supply to rotate at the drive shaft ( 2 ) and worm gear ( 3 ) at approximately 6,700 rpm. At 6,700 rpm the drive shaft worm gear ( 3 ) will rotate the cutter arm worm gear ( 4 ) and drive sprocket ( 7 ), the drive sprocket rotates the chain and cutter sprocket ( 32 ), the cutter sprocket ( 32 ) turns the cutter ( 34 ) at approximately 2100 rpm. 
         [0033]    The cutter ( 34 ) may be a part of the drive chain or may be attached to the cutter sprocket. As shown in  FIGS. 4 &amp; 5 , the cutter ( 34 ) is a 3″ diameter by ¼″ thick saw blade. In one embodiment the minimum cutting speed is about 1500 to about 1800 ft/min, preferably about 1600 to about 1700 rpm, and most preferably about 1650 ft/min. 
         [0034]    The cutting arms are deployed by rotating a second motor located inside an “Arm Deployment Motor Housing”. The motor drives the “Drive Screw” as shown in  FIG. 4B . The drive screw is threaded into the “Arm Pusher”. The “Arm Pusher” is captured within the “Arm Deployment Pusher”. The “Arm Deployment Pusher” rides on the “Linear Base” (not labeled). The “Linear Base” is square in cross section to prevent rotation. The Linear Drive Mechanism is shown in cross section in  FIG. 4B . 
         [0035]    In one embodiment, a M ICRO M O ™ (www.micromo.com) motor provides the power required to drive the pusher arms. The motor about 1″ in diameter and can be selected in a variety of voltages including 6 to 24 V DC motors. The motors are reversible and controllers available from MICROMO™ enhance the ability to manipulate the arms. 
         [0036]    In another embodiment, pressure from the compressed air is used to fill a cylinder driving a push rod. As the push rod extends, the push arms are driven out until the cutter reaches the ID of the riser pipe. Motion can also be achieved with a linear drive pneumatic or hydraulic cylinder. 
         [0037]    Cutter can be of various designs, different widths and diameters. Cutter geometry can be customized to optimize the cutting performance in different materials. A simple cutting blade can be used for PVC and polyethylene. Cement and harder materials may be cut with a diamond-tipped saw. Saw diameter, tooth spacing and material can be optimized for a variety of materials. 
       Example II 
     Electric Cutter Tool 
       [0038]    In another embodiment a sealed electric motor is used to power the internal cutter tool. Electric motors can provide drive and torque from a motor with a smaller diameter. The cutting tool can be scaled to very small diameters using electric AC or DC motors. Brushless motors can minimize the danger of spark or flames. Containing the electric motor in a sealed housing may be an added safety measure. 
         [0039]    In one embodiment a ½ horsepower electric motor rotates a drive shaft bevel or miter gear. The drive shaft bevel or miter gear drives a second miter or bevel gear. The second gear drives a cutter arm belt that in turn rotates the cutter shaft. The cutter shaft rotates one or two cutters, thus cutting a slot or pair of slots into the riser pipe. The cutting arms may be pushed out by the main motor when the motor is activated, or may be driven by a second motor or solenoid. 
       Example III 
     Tool Operation 
       [0040]    Methane wells may be ventilated when methane production from a given well is reduced due to clogging, flooding, pipe damage, or other factors that may make the well inoperable. A riser may also be slotted as upper waste bodies begin to produce methane, or risers may be vented in an effort to reduce total methane emissions. First, a visual inspection of the vertical pipe ensures the riser is continuous and not damaged. A video camera is run down the pipe to identify obstructions, mark depths and identify any bends in the pipe. Depths of target waste body and desired areas for slotting are then diagrammed and the amount of slotting required for waste body length is calculated. The internal slot tool is dropped or lowered down the vertical pipe (or pushed if a solid pipe, bar, or wire is attached) to the desired depth. Cutting is initiated by powering the tool and expanding the cutting apparatus to the walls of the pipe. The tool is raised a desired length while cutting. Once a length of pipe is slotted the cutting apparatus is retracted and the power is turned off. The tool may be rotated to add additional slots at the same elevation or raised to add slots at a different elevation. The tool is removed when slotting is finished. If required a video camera may be used to verify slot depth and length. 
         [0041]    The methane wells are then monitored and compared to methane production prior to adding ventilation slots. The amount of methane produced may increase from about 5% to over 150% above previous production levels. In another embodiment methane production is increased from about 10% to about 100% above previous production levels. When ventilating new waste bodies within each well location, the amount of methane produced may double or triple depending on the length of riser ventilated.