Aquarium pump
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Executive Summary
The primary purpose of the following information is to gain a complete understanding of a bilge pump and a siphon. The bilge pump is commonly used as an emergency device to evacuate water from a maritime vessel, whereas the siphon is commonly used as a device to transfer fluid from a fish tank to a receptacle such as a bucket. These two devices are being analyzed in depth with the future goal of combining their functions to create a new prototype that uses a manual pump to create a siphon with the application intent of cleaning aquarium tanks.
For both the bilge pump and the siphon, a product study was completed. This process began by analyzing the product's primary use and the customer needs. Then, the analysis proceeded onto product dissection, with identification of part functions shown in the Bill of Materials. Once all parts were identified, a failure mode and effects analysis (FMEA) and a design for manufacturing and assembly analysis (DFMA) were completed. These evaluations provided valuable insights regarding what considerations had been made while initially designing the parts and what possible improvements could be incorporated into future designs. In addition to the FMEA and DFMA, a design for the environment analysis (DFE) was performed in order to gain a better understanding of the effects that the current products had on the environment and whether future improvements could be made bearing in mind environmental considerations. Finally, relevant numerical analyses were completed for both products in order to provide more in-depth information on the product uses and limitations.
This main page summarizes the results of the in-depth analyses for both devices. In addition, there are corresponding pages for both the Bilge pump as well as the Siphon that complete the analysis.
Product Purpose
Hand-Operated Bilge pump: The primary purpose of a bilge pump is to remove water from a maritime vessel. However, the pumping function of the device makes the hand-operated version useful in a range of applications where a liquid must be drawn out of a source and relocated to a different area. Although the use of a device to remove accumulated water from a boat evolved from buckets, to hand-operated bilge pumps, and finally to electric bilge pumps, the hand-operated version of this technology is widely used on vessels as a backup in the event of an emergency. In addition to small boats, hand-operated bilge pumps are used in kayaks, canoes, rowboats, lifeboats, and a host of other personal watercraft applications in which a compact, light-weight, easy to use, and economical pump is required.
Siphon: Like all siphons (which provide a means for draining liquids from higher elevations to lower elevations), the purpose of an aquarium siphon is to transfer water from a fish tank to a bucket located at a lower elevation. In addition, the siphon attachment allows the aquarium rocks to become dislodged in the turbulent flow created within the attachment tube, which cleans off the algae from the rocks before returning them to the bottom of the aquarium.
Customer Needs
Hand-Operated Bilge pump: The principal user needs for a hand-operated bilge pump (as used in its original design context) are as follows:
- Ability to pump large quantities of water in a short period of time
- Compact shape to facilitate storage (especially in the cramped confines of a kayak or canoe)
- Light-weight design for convenient travel
- Ease of use
- Durability (to withstand common use and wear)
- Low cost (to encourage widespread use)
Siphon: The principal user needs to a water siphon (as used in original design context) are as follows:
- Ability to create and maintain a siphon
- Performance reliability (i.e., ability to avoid clogging)
- Compact shape
- Durability
- Low cost
- Ability to pick up rocks for cleaning in attachment (but not allow them to enter the siphon tube)
Stakeholders
As entities (either individuals, businesses, or groups) that have some degree of dependency on the product, the following entities are possible stakeholders for the products listed below.
- Hand-Operated Bilge pump:
- Users
- Designers, engineers, managers, and other employees at company where product is made
- Suppliers of raw materials
- Boating, sporting goods, and outdoor stores
- Siphon:
- Users
- Designers, engineering, managers, and other employees at company where product is made
- Suppliers of raw materials
- Aquarium stores
Consumer Demographics
Hand-Operated Bilge pump: In its original design context, the primary users of this product are individuals who participate in maritime activities in a small vessel or personal watercraft. However, the hand-operated bilge pump can be employed in other settings as well, which would suggest that the targeted demographic could change depending on the application of the device. For instance, if the pump is being modified to empty an aquarium, fish-owning individuals would become the new primary consumer demographic.
Siphon: The primary users of this device are individuals who own aquariums. Secondary users could include anyone wishing to transfer an amount of liquid that would be difficult to transfer by buckets. Some examples of this would be to empty a clogged sink or small pool, or to transfer gas and fuel.
Product Function
Hand-Operated Bilge pump: The functions that allow hand-operated bilge pumps to draw water from a source and deposit the water to another location are relatively straightforward. The rubber flap located at the base of the pump allows water to flow in a unilateral direction away from the removal source. Simultaneously, water pressure forces open a sliding disk valve near the bottom of the moving piston, which allows water to enter the upper portion of the cylinder. For the upstroke of the device, the aforementioned disk valve of the piston is forced closed. The water is concurrently drawn out of the top of the device (typically into a hose that is connected to the water disposal area), while the flapper valve concurrently opens. During this stage, the pressure differential between the atmosphere and the low-pressure section of the lower cylinder causes water to be sucked into the device from the original water source.
Siphon: To use this device, one must place the attachment in the tank and then create a siphon so that water flows out of the tank into a receptacle. Novices can create a siphon merely by sucking on the smaller end of the tube and waiting for water to begin flowing. This method can be difficult and has the obvious disadvantage of the user coming in contact with the water in the tank. An advanced technique is where the user scoops up some of the fish tank water into the attachment end of the tube then proceeds to raise that end so that it is much higher than the opposite end while simultaneously plugging that same end with a finger. Then, the user waits until all the air bubbles in the tube have ascended and released out of the tube until proceeding. Once the air bubbles have released, the user is ready to start a siphon. Carefully, the user places the attachment end into the tank, fills the remainder with water, and then flips it upside down so that the open end is at the bottom of the tank or mixed in with the aquarium rocks. At this point, the tube should be completely filled with water. When the user is ready, he or she can release the finger (which is on the opposite end of the siphon), and water should begin moving out of the tank into the receptacle. The user keeps one hand on the tube by the receptacle and the opposite hand on the attachment end, which is in the tank. To clean the tank effectively, the user can move this attachment around the rocks, which dislodges the pebbles. Every so often, the rocks will be siphoned up the attachment and could potentially clog at the siphon. At this point, the user must plug the small end of the tube with their finger and raise the attachment out of the rocks so they will fall back down. To start the suction, the user releases the finger plug and can proceed to clean the tank. The user can then repeat this process until they are satisfied with the amount of water removal from the tank. To stop the siphon, the user simply raises the attachment out of the water, which stops the suction. Both the novice and advanced method are difficult. The siphon could potentially be lost, needing to restart the process.
Product Use
Hand-Operated Bilge pump: Click here to view a flow chart of the product use for the bilge pump.
In order to demonstrate the use and workings of the pump, our group made videos that illustrate the following product functions:
- Complete Bilge Pump Demonstration
- Partial Bilge Pump Demonstration
- Bilge Pump Operation Description
- Plunger Demonstration
Siphon: Click here here to view a flow chart of the product use for the siphon.
In order to demonstrate the use and workings of the siphon, our group made the following video:
Bill of Materials
Hand-Operated Bilge pump: Click here to view the bill of materials for the bilge pump.
Siphon: Click here to view the bill of materials for the siphon.
Failure Mode and Effects Analysis (FMEA)
The FMEA tables detail our assessment of the most common failures that we anticipate the bilge pump and siphon to experience. These assessments explain how product parts may fail and what the consequences, detectability, and probability of occurence those failures implicate. Addressing these possibilities will allows future designs of these products to be more reliable. Using the Suggested Evaluation Criteria (as found on the FMEA wiki page), we were able to rank the severity from 1-10 (10 being the highest). For the occurrence parameter, we then were able to rank the probability of failure again from 1-10 (with 10 being the highest). Finally, we were able to rank detectability from 1-10 (with 1 being the most detectable). From these three numbers, we were able to multiply them together, which results with the Risk Priority Number (RPN).
Hand-Operated Bilge pump: Click here to view the FMEA for the bilge pump.
The highest RPN value for this analysis was 180 which ended up being the rubber seal losing efficiency. This failure received a 6 for severity, a 6 for probability of occurrence, and a 5 for detectability. The result of this failure would be the pump operating inefficiently, if not at all. From this analysis it can be concluded that even the most catastrophic failure is not detrimental to the user with respect to physical safety and wellbeing. The worst case scenario is the pump losing its functionality, causing the user to have to purchase another such pump. Finally, this analysis also shows that there is room for improvement.
Siphon: Click here to view the FMEA for the siphon.
The highest RPN value for this analysis was 105, which would be caused by overuse. This mode of failure would lead to a hole or rip in the main tube, which transfers fluid from the aquarium to the output source. This failure received a 7 for severity, a 5 for probability of occurrence, and a 3 for detectability. The result of this failure would be the siphon operating inefficiently but perhaps would lead to a complete loss of functionality. From this analysis, it can be concluded that even the most catastrophic failure is not detrimental to the user with respect to his or her physical safety and wellbeing. The worst case scenario is that the siphon would lose its functionality, causing the user to have to purchase another such pump. To fix this failure mode, a possible solution would be to use more durable material in the tube. This example illustrates the fact that the FMEA analysis diagnoses some room for improvement in the overall design of the siphon.
Design for X (DFX)
The concept of DFX refers to considering a specific variable X in the design of a product. Some common variables that are considered are ease of: manufacturing, assembly, use, and maintainability.
Design for Manufacturing and Assembly (DFMA)
DFM and DFA refer to analysis and design strategies that aim to understand how a product is made and how the manufacturing and assembly steps in its production can be improved. The DFMA process is advantageous for a designer's consideration due to the tremendous cost benefits that accompany the simultaneous analysis of DFM and DFA and the interface between the two methods. The use of these methodological tools can reduce costs, decrease labor, cut production times, decrease part counts, and improve the overall design quality.
Design for Manufacturing (DFM)
The primary goal of the DFM process is to analyze the manner in which the component parts of a product are made. By examining how things are manufactured, this process can be optimized so that parts can be produced efficiently and economically while adhering to design constraints. In order to optimize a manufacturing process, cost factors must be taken into account along with time, labor, environmental, and quality concerns. The list below details some ways that DFM could have been or could be applied to the products under investigation.
Hand-Operated Bilge pump: The analysis here suggests that the product has been designed well for manufacturing. The bilge pump design reduces manufacturing costs through its choice of materials, and the usage of plastic for most parts also makes the product durable and useful in its given functions. Also, since a requirement for this part is that it is light so that it can be made to float, the choice of plastic fills this function as well.
Siphon: The analysis here suggests that the product has been designed well for manufacturing. Despite its simplicity, the siphon design manages to reduce manufacturing costs through its choice of materials yet retains a high degree of durability. However, one improvement that might be made is to use an injection molding process to make the siphon attachment converger instead of forging, as this manufacturing switch would allow the process to become more cost effective.
Design for Assembly (DFA)
The objective of DFA is to improve product quality and reduce costs by optimizing a product’s design and assembly process. DFA goals are predominantly achieved through simplifying a product, reducing part counts, and designing components that can be easily managed and installed. The following list describes how DFA may have been, or should be applied to the products under investigation.
Hand-Operated Bilge pump: From the detailed product analysis, it is clear that there are several steps that could be taken to improve the assembly process used to fabricate the bilge pump. Because sleeve fittings are used between most parts, the glue and fasteners could likely be eliminated, allowing for easier assembly and future maintenance of the product.
Siphon: From the detailed analysis here, it is evident that great care has been taken to optimize the assembly process for the siphon. Owing to the straightforward nature of the product design, the design for assembly of the siphon is nearly optimal, as it avoids superfluous complexities and allows for easy handling.
Design for Environment (DFE)
Design for the environment refers to the concept of considering the effect that a product will have on the environment. The entire life cycle of the product should be considered. This includes the manufacturing of the product, the transportation of the product, the use of the product, and end of life.
Economic Input-Output Life Cycle Assessment (EIO-LCA)
One way to assess the effects that a product has on the environment is a process called EIOLCA. This takes into consideration each sector of the economy affected by manufacturing and distributing the product of concern. The economic activity, energy usage, and greenhouse gas emmissions related to manufacture and distribution of the product for each sector is calculated by an EIOLCA software.
For both the hand operated bilge pump and the siphon the sector of "Plastics pipe, fittings, and profile shapes" was used to analyze the environmental effects of the product. For $1 million worth of the product, the total economic activity for all sectors is $2.28 million and for the top five sectors is $1.315 million. The total energy required to manufacture $1 million worth of the product is 11.6 TJ for all sectors, and 6.959 TJ for the top five sectors. The global warming potential for manufacturing and distributing the product is 884 MTCO2E for all sectors and 528.3 MTCO2E for the top five sectors. The price of each seperate product, and the tables found using EIOLCA can be found on the individual bilge pump and siphon pages.
Since there is no energy or waste produced by the product itself during use, this stage in the life cycle has no environmental effects. At the end of life, the product can be recycled since it made essentially of only plastic. While energy is used in recycling the product, the beneficial aspects of recycling outweigh this effect. Thus, manufacturing and distribution of the product has the largest impact on the environment. However, the processes and products use already minimize this effect during manufacturing so there are no environmental concerns left to be addressed in future design.
Quantitative Analyses
To pass through the entire system of the aquarium pump, fluid will:
1. Enter attachment
2. Pass through contraction to enter siphon tube
3. Flow through siphon tube
4. Diverge into pump entrance
5. Diverge again into pump body
6. Go through 90 degree elbow and contraction to pass through pump exit nozzle
In order for the fluid to pass through this system, the pump must provide a certain amount of head, since each of the above steps in the fluid flow is accompanied by a head loss. Most of the head loss in this system comes from what is called minor head losses associated with expansions and contractions in the flow path. The below equations represent the two ways of calculating minor head loss when the mean velocity of the flow is known. Since the velocity of fluid passing through the system may vary depending on the user, the actual head loss of the system cannot be calculated explicitly.
In the first equation, K is the head loss coefficient. In the second equation, f is the friction factor (which varies with velocity of the flow), the quantity Le is the equivalent length of an elbow, and the quantity D is the inner diameter of the pipe. The relevant values for the aquarium pump system are shown in the image to the right.
More detailed numerical analyses of the two component devices can be found with both the bilge pump and siphon information.
Prepared for: 24-441 Engineering Design Course (Fall 2007), Carnegie Mellon University
By Sarah Biltz, John Bistline, and Kimberly Lord
