Water pump
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Executive Summary
Primary Stakeholders and Product Needs
The major stakeholders are the customer and the shipper. In the typical American urban household, the main use of this type of pump is to pump water out of basements or to water grass. To meet these needs the product has to be able to pump water from a lower source, the basement, to a higher final place, such as through a window and outside into the grass. It has to be durable and simple to use which means that anyone can use it. The shipper needs the product to be as light and small as possible to cut down on weight, which cuts fuel costs. Also smaller products mean that more can fit in the same space and also reduce shipping costs. These two groups are the main stakeholders of the post production section.
Product Use
How the Product Functions Mechanically
First plug in the motor with the appropriate voltage selected. The electricity runs through the pressure sensor and then to the motor. The motor turns an internal shaft which is connected to a buffer spring. The spring is connected to the impeller which is connected to an nozzle that goes to the inlet. So the motor shaft, spring, impeller, and nozzle are all connected into one shaft driven by the motor.
When the motor turns it creates a suction which draws the water through the inlet and nozzle to the impeller. The spinning impeller then throws the water out into the iron chamber causing a vortex to develop. This vortex then causes the pressure to increase inside the iron chamber and forces the water through the outlet. It is the pressure created from the spinning water that is actually pumping the water.
The pressure sensor is connected to the iron chamber and when the pressure reaches a certain threshold, it causes a mechanical switch to cut the power to the motor. The pressure sensor threshold can be adjusted by setting a spring to a predetermined compression. Then when the pressure increases it compresses the spring more, which will cause the circuit to break through various mechanical linkages.
Bill of Materials
Design for Manufacture and Assembly (DFMA)
Failure Mode and Effects Analysis (FMEA)
Because of the number and complexity of system components, a typical single-stage, mechanically coupled centrifugal pump can fail in approximately 600 ways (Mechanisms). To narrow pump failure modes to the most likely component failures, it was assumed that the most likely causes of pump failure would take place in the moving parts of the system, located along the shaft. The stationary components were assumed to be less susceptible to fatigue and stress failure, unless noted in the dissection and use study as in the case of the inlet nozzle and pump casing.
The inlet nozzle, the motor, the pressure switch and the mechanical shaft seal were determined to have the highest combined RPN value. The inlet nozzle is crucial for pump function and was observed to fail under long term use. The motor is the most complicated assembly and can be dangerous if it fails due to overheating or if water leaks in. The pressure switch and the mechanical shaft coupling both have multiple modes of failure and can easily become fatigued or broken with pump misuse.
It was noted during the dissection and use study that the tip of the inlet nozzle was broken off inside the housing, indicating fatigue as a mechanism of failure for the nozzle. The inside of the pump housing chamber was extremely rusted and the water circulated through the pump became contaminated, which is a system failure for intended use as a well pump.
To prevent overall component failure, it is most important to properly assemble the pump and have narrow tolerances, particularly on the shaft components because a misaligned component will be subjected to high stresses and causes vibrations in the system. It is also important to prime the pump before use because mechanical seals will overheat and permanently fail due to increased friction. Debris in the water is a cause of multi-component failure because an occlusion in any part of the pump will result in high system pressure. The addition of a filter and rust-prevention measures, such as internal coating or an easy way to empty the pump of water would be beneficial to include in redesign. It would also be beneficial to redesign the pump such that it is easy to disassemble and replace fatigable parts, such as the shaft seal. However there are trade-offs because the addition of these design changes would increase system cost.
Design For Environment (DFE)
The DFE analysis showed that the pump system can easily be recycled and does not waste many materials. The motor and pressure sensor do not appear to be specifically designed for this system and so they could potentially be used in other products. The pump’s iron casing can be recast and the plastic parts can be recycled. The entire system was not built to be disassembled because it is difficult to take apart and a seal has to be broken in order to fix any internal parts. The chosen materials are robust, therefore it seems that it was meant to last a long time without failure, but not be fixed after breaking. There are several suggestions for improving the design. Possibly make the pump solar powered or have a battery pack that could be charged using solar power. The iron casing could be made thinner as the current component could withstand extraordinary pressures. Also instead of using iron, aluminum would still be strong enough and since its lighter, would cut down on shipping costs. The pump could be redesigned to only have one chamber, which would cut down on materials, assembly time, and shipping costs. DFE Guideline Good Aspects of Competitor Product and Ideas for Improvement 0. New Concept Development · De-materialization · Increase shared use · Integration of functions · Functional optimization · Other solutions: pipes, fan, buckets, mops/towels · Possibly make a solar powered battery pack (if small amount of water to pump) · Add a mesh filter before the intake in order to stop debris from clogging the impeller 1. Select Low Impact Materials · Avoid toxics · Avoid ozone depleters · Avoid hydrocarbons · Leaner materials · Renewable materials · Low energy content materials · Recycled materials · Recyclable materials · Could use old car parts create pump · Use recycled plastic and iron 2. Reduce Material Amount · Reduce weight · Reduce transport volume · Reduce iron casing (currently very thick) · Decrease water cavity size · Possibly add smaller baffles instead of the large one 3. Eco-Manufacturing · Chose alternate production processes o Low emission production o Use materials efficiently · Eliminate production steps o Net shape casting vs machining o Integrated surfaces to avoid painting · Reduce energy consumption · Use renewable energy · Reduce production waste · Fewer/cleaner production consumables · Different metal, such as aluminum, does not need to be painted and is lighter so it would reduce transportation costs · Make the impeller snap-together instead of glued · Possible redesign of the shape/size of the casing could reduce components needed for the sameso that the plastic chamber is not needed (make it a 1 chamber system instead of 2 chambers)
4. Optimize Distribution · Less/cleaner/reusable packaging · Energy efficient transport mode · Energy efficient logistics · Cornstarch packing peanuts · Transport on trains · Make correctly sized boxes 5. Reduce Use-Phase Impact · Lower energy consumption o Default power down o Programmable clocks o Reduce mass of movable products o Insulation · Cleaner energy sources o Winds, solar, renewable, low sulfur coal o Rechargeable batteries · Reduce consumables o Batteries, fluids, etc o Minimize leaks o Reusable consumables · Cleaner consumables · Reduce consumable waste · Solar or micro-wind power and rechargeable battery pack could provide sustainable power · Pressure sensor shuts off when the pump is not needed · Only consumable is electricity 6. Maximize The First Life · Increase reliability and durability (FMEA) · Easy maintenance and repair o Indicate procedure for disassembly, cleaning, maintenance o Indicate subassemblies that wear and locate for easy access · Design for modularity · Avoid trendy designs · Promote product-user relationships · Pump is not designed to be disassembled, but can unscrew nuts and bolts and use a crowbar to break seal and remove metal chamber cover so can be repaired during product lifetime. · Robust materials used to reduce wear rather than designing for disassembly · Product-user-relationship is simple because it is installed once and connected to an electricity source and provides continuous water pressure 7. End of Life · Reuse of product · Re-manufacturing/ refurbishment of product · Recycling of materials · Safer incineration · Design for disassembly · Use recyclable materials for which a market exists · Prefer recycling to “Down cycling” · Integrate functions into fewer parts · Avoid large variety of materials · Avoid elements that interfere with recycling · Mark part material · The outer iron covers, motor, and pressure sensor could be reused in other devices/pumps · Metal covering and two types of plastic were used · Iron casing could be melted down/ recast · Designed to disassemble in a linear fashion once the cover is removed
Team
References
List of 600+ Mechanisms of Pump Failure. http://www.lifetime-reliability.com/free-articles/reliability-improvement/pump-failure-modes-list.html
How to Adjust Water Pump Pressure Control Switch. http://inspectapedia.com/water/WaterPumpAdjust.htm
Mechanical Shaft Seals for Pumps: http://net.grundfos.com/doc/webnet/waterutility/_assets/downloads/shaft_seals.pdf
Electric Motor Failure Modes. http://blog.machineryhealthcare.com/bid/47114/Electric-motor-failure-modes
How our pump works: fill it with water, plug it in, motor spins, turns impeller, creates pressure differential, pumps water. Use cases: - Mechanical/how it works - Jenny - Household use in America - Christina - Centrifugal pumps - Kyra - Piston/suction pumps - Eva - Torque info - Jerry
