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Design Analysis
Abstraction & Modeling
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Solution Development
The customer's goal is to have the bridge motorized. The major constraints are cost and lifespan. Lifespan is essentially a cost too, but it can be mitigated by finding a solution that is low maintenance and has a long period between repairs. For this assignment the choice of motor and other necessary mechanical components will not be explored. The detailed inner workings of the bridge are unknown and I am assuming a low variability in the mechanical options. Thus we will assume for the following options will have the same mechanical components. To power the bridge there are 3 options:
Battery/Hydropower: This design would see the bridge being powered by a relatively large battery. The battery could be recharged via turbines placed in the river.
Pros:
Environmentally friendly
Self-sufficient, doesn't rely on utility companies for power
Cons:
Short Lifespan, the Tesla Powerwall which is comparable to the kind of battery the bridge would use only has a lifespan of 10-20 years.
Complex design, the customer only needs a design for the bridge to be motorized but this solution would require a design for the power source and a charger for the power source.
If there are large number of operations in a short time the battery may become drained forcing Conrail to operate it manually.
High cost
Generator: This design would see the bridge being powered by a gasoline or diesel generator.
Pros:
Self-sufficient, doesn't rely on utility companies for power
Short refueling time, in the event the generator runs out of gas there are stations within 5-10 minutes of the bridge.
Moderate lifespan, 20-40 years
Cons:
Not environmentally friendly, CO2 emissions and potential fuel runoff into water.
Standard Grid Connection: This design would see the bridge powered by utility lines likely via underground cables.
Pros:
Long lifetime, electrical cables can last 50-70 years
Limited exposure to the elements, unlike the other two options which would require relatively large above ground components
Environmentally friendly
Cons:
High initial cost, there aren't any utility feeds in the vicinity of the bridge so a significant amount of excavation and cable would be needed.
In the event of a power outage the bridge would have to operated manually
Problem Formulation
Research
Rather than doing a Source/Cause or statement-restatement technique to find out the problem I spoke with the customer. My initial thoughts were correct in that the bridge is antiquated and needs to be modernized. However, the customer's needs where smaller in scope than I had thought. They only want the bridge to be motorized, but not autonomous or remotely operated. The design must comply with federal, state, and municipal regulations like the National Electric Code.
PS-DS Method
Present State: The bridge must be operated manually which puts physical strain on the operators and increases risk of injury.
Desired State: Normal operation of the bridge without physical strain placed on the operators.
Kepner-Tregoe Analysis
How?
How is the problem related to other problems? - Aging infrastructure is a widespread problem across the U.S. Thousands of structures and systems are falling into disrepair which makes them more dangerous for citizens and employees alike.
How is the problem not related to other problems? - Unlike roads and their bridges the South River railroad bridge is infrequently used and only presents a risk for a few Conrail employees rather than the public at large.
Why?
Why is there a problem? - The bridge has always been somewhat of a thorn in Conrail's side. The newspaper article shows that Conrail has had an interest in motorizing the bridge since at least 2000. We can assume that since the rail line is infrequently used the project did not have high priority and remained dormant until now.
Why is the problem important? - Employee safety is huge priority for companies. Since the project would see a reduction in injury risk it is important.
Why does the solution work? - Removing the physical labor involved with operating the bridge lowers the risk of employee injury.
Where?
Where did the problem occur? - The bridge is located on the South River in Middlesex County NJ on the border of South River Borough and Sayreville Township.
What?
What is known? - A basic understanding of how the bridge operates. The frequency of crossings is known along with federal regulations for the bridge. The customer's needs and desires for the project are also known.
What is not known? - A more detailed understanding of the bridges operation, such as the mechanical load and what may be inside the concrete foundation of the bridge. It is also unknown if the bridge needs any repairs, though it is not a priority of this project it would be an opportune time to do any repairs.
What are the constraints? - The major constraint for this project is cost. The project is maintenance and will only lower potential risk rather than bring in profits. Therefore the customer doesn't want to spend too much on the project. Additional constraints would include any regulations on marine construction and electrification.
What are not the constraints? - The customer is not concerned with the speed of the opening/closing process.
What is the goal? - The goal is to have the bridge safely motorized at a reasonable cost.
What is not the goal? - Despite the title and original intention of the project the bridge will not be fully automated. Originally I was thinking about having the bridge detect or communicate with an incoming train and start closing. However, as the customer is not seeking this goal there is no need to implement it in the design proposal.
When?
When does the problem occur/not occur? - The problem occurs every time the bridge is opened or closed whether it is to allow rail or marine traffic. This occurs about 3 times a week according to Conrail.
When must the solution be implemented? - There is no particular deadline, but it would be best to implement ASAP as the customer is currently pursing a solution as well.
Who?
Who can provide more information? - Conrail
Who cannot provide more information? - The townships of South River and Sayreville are unlikely to have much info. It's also unlikely that I'd be able to get any info from the bridge designer as its over 100 years old. Due its age the designer may no longer exist as a company and documents on the bridges design might not have been preserved.
Who is the customer? - Conrail, and to a lesser extent any company using the rail line.
Who is affected by the problem? - As noted elsewhere the problem affects only Conrail and its employees. The time taken to open and close the bridge are not a large concern. Thus customers using the bridge are not meaningfully affected.
Needs Assessment:
Background - Across the South River in Middlesex County NJ there is a railroad bridge owned and operated by Conrail. The bridge is the last manually operated swing bridge in the state and requires a team of 2 to physically rotate the bridge with a crank.
Objective - The physical labor required to operate the bridge can be strenuous on Conrail employees and puts them at an elevated risk for injury. The goal is to motorize the bridge so it can be operated with the push of a button.
Methodology - Conrail is currently working on this project too so they would likely want it as soon as possible. A 100% design submission would likely be submitted within a year with construction following shortly.
Expected Results - Once the project is complete the bridge will be able to be operated electrically.
Costs - A complete cost breakdown may be out of the scope of this project, but for a large infrastructure project like this the final cost to Conrail could be between $1-3 million.
Hazard Analysis The primary cause for hazards in this project is the fact that the bridge is located in an aquatic environment. Flooding is a common occurrence in the South River and it is likely that the main structure of the bridge may be partially submerged from time to time. During rarer storms like Super Storm Sandy the bridge may become fully or nearly fully submerged. Any implementation will need to be properly waterproofed and would require a motor designed to work in dry/wet conditions. NEMA 6 or 6P enclosures should be sufficient.
Battery Powered Option: Since the battery would likely be mounted inside the frame of the bridge its body and terminals would need significant insulation and waterproofing. The same would be required for any turbines or paddlewheels used to charge the battery. Rust would also be a large concern and may reduce the lifetime or performance of the battery.
Grid Powered Option: This is likely the least risky of the options. Cables could be fed through the ground, river bed, and the concrete foundation of the bridge. While this would make the bridge susceptible to blackouts given the relative infrequency of crossings it would be unlikely to affect more than a single train.
Generator Option: The location of the generator would determine the potential risk. Mounting the generator in or on the bridge would lead to a greater risk of flood damage. That location would also pose a greater pollution risk if the generator potentially leaks.
While there is a no trespassing sign on the approach to the bridge it is largely ignored. Teens occasionally hangout on the bridge and there are fishers from time to time. Although people rarely. if ever, cross the bridge as it doesn't lead anywhere of significance. The current design of the bridge is well protected as all the important equipment is located within the bridge and it can only be operated with a special tool. Any interface, like a button or switch, used to operate the bridge would need protection. Requiring a key for operation would likely be sufficient. If the generator was mounted on land it would likely need to be locked or fenced in.
The electrical system would need to be interlocked such that the bridge cannot be turned while the rails are in the locked position. By extension this would prevent the bridge from turning while a train is crossing.
Ethics and Liability
If I were actually in the position to see this project fully realized it would have to be inspected and approved by a professional engineer. Professional engineers must uphold a high level of ethically responsibility and therefore the proposal must do the same to be approved. The bridge must not cause harm to any person. The electrical systems will be interlocked to avoid any components being powered on or moving in a dangerous situation.
From a legal standpoint the area is off limits to any non-Conrail personnel who do not have consent and approval from Conrail to be on the bridge. Anyone meeting the aforementioned criteria would be considered a trespasser and Conrail would not be liable for any potential injuries. However, the potential for any civilian injury should be minimized anyway. To do this any interfaces or panels employees use to operate the bridge will be physically locked and/or require a key to operate. Any additional electrical equipment will be locked as well with appropriate warning information.
The proposal must also take into account environmental ethics as well. It is a priority to prevent and pollutants from seeping into the river. In this regard the best solution would likely be connecting the bridge to the existing power grid. Both a battery and generator could leak hazardous materials into the water. Proper waterproofing and sealing can also mitigate this risk.
Intellectual Property
As this proposal is simply an infrastructure upgrade there is no intellectual property to deal with. There is no new product or technology being developed. The proposal would just use existing components the contractor would purchase and install. There is nothing to patent, trademark, or copyright.
Synthesis
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