Selecting the Right Air-Powered Pump for Your Landfill Pumping Application

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1 Selecting the Right Air-Powered Pump for Your Landfill Pumping Application David Kaminski QED Environmental Systems Inc. Ann Arbor, MI / San Leandro, CA Copyright QED Environmental Systems, Inc. 2014; all rights reserved. The information contained within this document may not be published, broadcast, rewritten or otherwise distributed without prior written authorization from QED. Today s webinar topics Air-powered pump components Principles of operation and design features Application information and project requirements Factors that affect pump performance Selecting the pump configuration and materials Air compressor sizing and air dryer systems Air & liquid tubing or hose selection and pump fittings Accessories to improve pump performance, reliability and serviceability Special Pumps for Challenging Applications 1

2 2 Air Supply to Pump Air Exhaust Air Filter/Pressure Regulator Liquid Discharge Discharge Check Valve Pump Body Air Valve Mechanism Float Assembly Discharge Tube/ Float Guide Inlet Check Valve Inlet Screen Actuator Rod Automatic Air-Powered Pump Components Air-powered automatic pump: How it works Discharge Cycle When float reaches the top of its travel, exhaust valve closes and air inlet valve opens Air pressure against liquid closes inlet check valve and pushes liquid up discharge tube As liquid level drops, float drops and pulls actuator rod down, closing the air inlet valve and opening exhaust valve to repeat Fill Cycle Fill Cycle Hydrostatic pressure opens inlet check valve As pump fills with liquid, air escapes through exhaust valve and internal float rises

3 3 Air-powered pump design features High-clearance check valves and passages maximize solids handling, liquid viscosity Low-speed moving parts minimize wear Built-in on/off level control - no need for level sensors or float switches Gentle pumping action = less foaming and solids precipitation than impeller pumps Bottom inlet allows for maximum liquid drawdown pump down to 15 (38 cm) No need for cooling can pump liquids up to 250 F (120 C) without failure Wide range of materials handles low ph, high chlorides, solvents, corrosives, etc. Air power safer than electricity in wet or potentially explosive environments (LFG) What s the application? Air-powered automatic pumps can be used in most landfill pumping applications Dewatering LFG wells or dual extraction gas and leachate wells (vertical risers) Pumping from condensate sumps and demister pots Pumping from leachate collection risers (vertical risers) For sloped riser applications, air-powered pumps with surface-mounted controls can be used low-flow wells to pump up to 3000 GPD (11,350 LPD or 11.3 m 3 /day)

4 4 What are the application requirements? Total depth of the well, sump or riser, measured from top of casing Liquid column height (from bottom) or depth to liquid (from TOC) Drawdown level desired (from TOC) or desired maximum liquid column height remaining after pumping (measured from bottom) Maximum drawdown achievable will be reduced if the well is under vacuum by the amount equivalent to the vacuum applied (in inches of water column) Lift requirements above grade - pumping to tanks, ponds, up slopes Type of discharge header gravity flow or force main Gravity flow header may require some additional pump discharge pressure to move liquids the desired distance from the well or riser to the discharge point Force main header connection will require additional pump discharge pressure to overcome header pressure and one-way check valve at header connection Flow rate desired or specified If not known, determine if the maximum flow rate that can be achieved with the selected air-powered pump will handle the desired liquid volume over time Factors that affect flow rate Total head combines pump depth, discharge line elevation above the well and frictional loss in the piping, fittings, and in-line check valves Flow rate decreases as head increases at a given air pressure; increasing air pressure generally increases flow rate Submergence is the liquid level above the top of the pump; controls the pump fill rate Flow rate increases as submergence increases Viscosity is a measure of a liquid s thickness or resistance to flow. Flow rate decreases as viscosity increases at a given submergence, lift and air supply pressure.

5 5 Instantaneous vs. average flow rate Flow curves for airpowered pumps are based on the average flow rate over a period of time, stated in gallons per minute (GPM) or liters per minute (LPM) at a stated depth Discharge header sizing for air-powered pump systems is based on average flow rate, since multiple pumps will discharge and fill at random, not simultaneously Level control in the well: the pump actuation point The point at which the liquid level inside the pump activates the air valve mechanism is called the actuation point The actuation point is the distance from the bottom of the pump to the top of the float travel (top of inlet on top-fill pumps) This varies based on pump length, float length and inlet position and is specified for each pump model The pump position in the well determines the maximum drawdown level in the well

6 6 How vacuum affects the pump actuation point A vacuum applied to the well will RAISE the actuation point above the design point when the pump exhaust is outside the well The increase in the actuation point is based on the amount of vacuum applied to the well, measured in inches (centimeters) of water column (WC) In the example, a vacuum of 20 (51 cm) WC raises the actuation point of the pump from 33 (84 cm) to 53 (135 cm) Options for wells under vacuum To maintain the design actuation point of the pump, the exhaust air line should be terminated inside the well. If exhaust air entering the well is an issue (e.g., O 2 & N 2 in a landfill gas system), the exhaust air line can be terminated outside the well. The pump can be lowered in the well to maintain desired liquid level, or a shorter pump with a lower actuation point can be used if the desired flow rate can be achieved. Where higher flow rates are needed and exhaust air must be outside the well, an equalization valve can be used to direct the majority of the exhaust air outside the well while applying vacuum to the exhaust line to lower the actuation point.

7 7 Selecting the pump configuration Bottom-inlet pump models are most commonly used for landfill applications to maximize drawdown and solids removal from the well, riser or sump Long-body pumps provide the highest flow rates but require the greatest submergence to operate Max14 GPM (53 LPM) flow, 38.4 (98 cm) drawdown Short-body pumps provide nearly the same maximum flow rate as long-body models but have a lower actuation point (more drawdown capability) and somewhat shorter service life Max13 GPM (49 LPM) flow, 26.7 (68 cm) drawdown Low-drawdown pumps have the lowest actuation point for maximum drawdown but provide lower flow rates, and can have a shorter service life when operating at higher cycling rates Max 7 GPM (26.5 LPM) flow, 15.3 (39 cm) drawdown Slider Pump for sloped risers The Slider pump is an air displacement pump with special check valves that work in sloped leachate risers and slant wells The Slider pump uses surface-mounted controls and a bubbler-type level control system to pump up to 3000 GPD (11,350 LPD or 11.3 m3/day) Automatic air-powered pumps are designed for use in vertical risers and wells the float mechanism and check valves won t work in sloped risers

8 8 Pump materials and corrosive conditions Corroded Stainless Steel Pipe Corrosion is often the result of elevated chloride levels (>1,000 ppm), especially at temperatures above 75 F (24 C) and low ph, which can be as low as 1.5 in landfill leachate and condensate QED s air-powered automatic pumps are available in a range of corrosion-resistant material configurations. The pump mechanism is not adversely affected by moderate corrosion. The AutoPump AP4+ Leachate model using stainless steel and PVDF parts is warranted for all typical landfill liquid chemistries at temperatures up to 180 F (82 C) Pump failure due to corrosion Corrosion can also be induced by high sulfides, reducing conditions (low to no oxygen present), and microbial attack from sulfate-reducing bacteria or iron bacteria Corrosion begins at the weakest point pumps made with welded bodies rather than seamless tubing and welded or machined components that haven t been properly treated after machining. WELD FAILURE

9 9 Air system design criteria 1. Determine the air pressure and air flow rate (volume) required for each pump and the total for all pumps 2. Allow for future system expansion if anticipated; costs less than adding a second compressor later 3. Choose the compressor type based on air volume, project length, and desired maintenance intervals 4. Factor in air compressor duty cycle appropriate to compressor type to determine compressor size 5. Determine if an air dryer is required and how much additional air will be required for dryer Flow rate and air consumption curves Each pump model has its own flow rate, lift and air consumption curves that should be based on actual testing, not calculated values 1. Use the pump flow curves to find the flow rate at the desired depth 2. Use the air consumption curve to find the air volume required 3. Multiply this factor by the desired pump flow rate to determine the air consumption per pump 4. Multiply the air consumption per pump by the number of pumps to determine compressor size

10 10 Air compressor types Reciprocating piston compressors are the most common type used. They generally have lower capital cost and are slightly more energy efficient, but are larger, have a lower duty cycle, create more noise and vibration, and require more maintenance over time. Rotary screw compressors are smaller, quieter, and have a 100% duty cycle. They use 5-10% more energy, but maintenance is less frequent and therefore less expensive. Reciprocating Air Compressor Rotary Screw Air Compressor Do I need an air dryer? Air dryers remove condensed moisture from the air system downstream of the compressor to protect air lines, fittings and pressure regulators from damage by corrosion or freezing Should be used at all sites with high humidity (regardless of temperature) and in any climate where ambient temperatures drop below 32 F (0 C)

11 11 Air dryer systems Select an air dryer that will achieve a dew point temperature of 20 F (7 C) below the minimum operating temperature anticipated Refrigerant air dryers are capable of drying air to 35 F (2 C) and don t consume any air from the compressor. Typically used in warm, humid climates where freezing conditions don t occur Refrigerant Air Dryer Desiccant air dryers are capable of drying air to -40 F (-40 C) but consume 15% of the available air from the compressor. Recommended for winter climates. Desiccant Air Dryer QED Flow Rate & Air Consumption Calculator QED s latest web-based tool to help you select the pump that meets your flow rate needs and determines the air system size Input factors for well depth, any additional lift above the well cap, and the desired flow rate The calculator will display the maximum achievable flow rate and the air volume required per pump Entering the number of pumps will display the air compressor size with or without an air dryer qedenv.com/flowratecalculator

12 12 Discharge line sizing and materials 1 (25 mm) and 1.25 (32 mm) OD tubing are most common sizes for down-well discharge tubing Larger diameter provides highest flow rate and lower air consumption per gallon/liter of liquid pumped Surface discharge tubing is typically UV-resistant nylon or HDPE Surface discharge sizing as well as air line diameter can be determined using on-line pipe flow calculators Jacketed tubing or rubber hose? Jacketed Nylon-12 Tubing All lines bundled together, easier to manage High temperature rated to 180 F (82 C) High chemical resistance to many organics Lighter than hose yet very strong Won t kink easily, won t double over in well More economical than rubber hose (40% less) Fuel-Resistant Industrial Rubber Hose Greater bend radius than tubing, can be easily coiled at surface for pump depth adjustment More flexible in very cold weather applications Easier to remove from barbed fittings Resistant to most solvents and fuel additives Used mostly for GW remediation applications Jacketed Nylon-12 Tubing Industrial Rubber Hose

13 13 Easy Fittings faster and safer Maintenance often requires removing pump tubing Cutting tubing and clamps from barb fittings can be difficult, time consuming, poses a safety risk, and shortens tubing length 2-3 (5-8 cm) each time Easy Fittings are high-flow quick connects with quick-release retainer clips Made of high-quality stainless steel alloys with double Viton O-ring seals Saves valuable field time and cost LESS than conventional quick-connect fittings Quick flange removal with the Easy Bolt Removing flange bolts can be a slow and difficult task. Galvanized and plated bolts corrode, and stainless steel bolt threads can gall and seize, often requiring bolts to be cut off and replaced. Easy Bolts fit standard flange holes and tighten using a simple lever action No tools required forget the wrenches and saws! High-grade investment cast stainless steel Only four Easy Bolts needed for 6 & 8 flanges Save labor expense plus replacement bolt cost

14 Air filter/pressure regulator Filter/regulators are installed at each well to protect the pump air valves from large solids and allow for pressure adjustment The regulator allows air pressure to be adjusted to reduce the discharge rate at that well if desired The filter captures solids that may be downstream of the air compressor filter, such as dirt that enters during installation or during routine pump service Moisture is also trapped by the filter, which has an auto-drain valve on the bottom to release water periodically during operation Cycle counter Used to estimate the liquid volume pumped from the well The counter advances one digit with each discharge cycle Multiply the cycle counts by the volume per discharge cycle for your pump model to determine the total volume Also useful for observing pump operation, relative flow rate increase/decrease, and for scheduling maintenance based on total cycles of operation Not subject to scaling or corrosion in leachate or contaminated water like traditional flow meters 14

15 Slowing down the rate at which the pump fills will reduce the rate at which liquid enters the well, which can help reduce the accumulation of silt in the well. Slow fill valve The slow fill valve is installed on the well cap/flange in the air exhaust line and works by controlling the rate at which air is vented from the pump, reducing the fill rate The overall flow rate of the pump will be reduced, since the fill cycle time will be extended Exhaust air equalization valve Installed in the exhaust line below the well cap/flange with exhaust terminated outside the well. Approximately 90% to 95% of the exhaust air is vented through the valve and outside the well. When exhaust line pressure is equal to atmospheric pressure outside the well, the spring loaded valve closes and allows vacuum to be applied to the exhaust line, thereby allowing the liquid level to be pumped down as low as possible. 15

16 Excess Air Flow Valve (auto air shutoff) The Automatic Air Flow Shutoff Valve is a safety feature used in landfill gas wells to prevent pumping air into the well should the air line be ruptured by fire, high temperature or physical damage. The valve is preset to allow the pump to operate at maximum flow under normal operating conditions but will close if the flow exceeds the trigger point. The valve must be manually reset to resume normal operation. Options to improve operation and reduce maintenance in tough applications Teflon-Wrapped Float Entire float assembly is coated with a thin Teflon sheath Greatly reduces build-up of solids on the float, which can extend maintenance intervals Speeds cleaning and reduces chance of damaging float during cleaning 16

17 17 Options to improve operation and reduce maintenance in tough applications Wide Slotted Float Used in wells with very high suspended solids Actuator rod slot is wider and extends through entire float body to prevent build-up Can be retrofit to existing pumps (contact Customer Service for details) Standard Float Wide Slot Float Options to improve operation and reduce maintenance in tough applications Silt and Foam Filter Designed to reduce solids loading in pumps to improve performance and extend maintenance intervals Threads onto pump inlet assembly (replaces standard inlet screen) Filter pad material can be cleaned or replaced Can also improve pump performance and reduce leachate emitting from external exhaust line in wells with foaming leachate

18 18 AutoPump AP4+ * Design Features Easier disassembly: removing four bolts on bottom inlet allows complete pump disassembly in minutes no turning of the inlet assembly or O-ring hang-up/dragging Easier service: quick-release clip on actuator rod allows quick float removal for easier cleaning. Pump body has a high-polish ID finish to reduce solids build-up and precision bore sizing to improve O-ring fit Increased durability: All metal parts are 304SS or higher for improved corrosion resistance; plastic parts are high-strength & hightemperature engineering plastics (PVDF, PEEK) Increased warranty: 5-year full warranty with no pro-rating in later years * Patent Pending QED AutoPump AP4+ Advantages Widest range of pump models and accessories available to handle difficult landfill pumping environments Longer warranty than other types of pumps (5 years) Easier to disassemble for cleaning than other designs All of this comes from QED, the originator of air-powered pumps for landfills, remediation and groundwater sampling Over 100,000 AutoPump systems installed since 1986 Manufactured in the USA Midwest & West Coast Experienced Application Specialists (18 years average) Toll-Free Customer Service and Tech Support Local QED Reps in USA, 20 international distributors Multi-million dollar inventory to meet fast delivery needs

19 19 What to consider when purchasing a pump The bitterness of poor quality remains long after the sweetness of low price is forgotten. Experienced application specialists Warranty length and coverage Designed for serviceability Cast components vs. machined parts Pump weight & ease of removal Ease of disassembly Customer Service and Support Full O&M manual provided with pump Availability of repair parts Troubleshooting & repair phone support Local field service and support availability Machined inlet housing parts must be assembled, higher corrosion potential Webinars, training and online resources One-piece cast stainless steel inlet has increase corrosion resistance, easier to service Questions? David Kaminski QED Environmental Systems, Inc. info@qedenv.com Toll-Free Numbers Ann Arbor, MI: San Leandro, CA: Website