adjective.(biology, anatomy) of, relating to, or having vessels that conduct and circulate fluids.
In the event of a hydrogen leak our system will ventilate the leaked gas.
No more than 1% hydrogen by volume in the container. Hydrogen is flammable in air at 4%-75% by volume. NFPA 2 (Hydrogen technologies code)
First we began with several different paradigms for how we wanted to both actively and passively vent our storage container as well as purge the container in the event of an extreme emergency. As time went along, we learned more about the feasibility of some of our paradigms and began to narrow down our decision making towards our final paradigm that we eventually decided to implement. Below show some of the paradigms that we had presented, and the explanation for why that certain paradigm was something we furthered the refinement of or moved on from.
Active Ventilation: Our first idea we came up with as a group was active ventilation. Initially, as a group, we knew there had to be some form of active ventilation using electrically powered fans to ventilate the container in the case of leaked hydrogen. Active fans would meet the required NFPA 2-6.17 standard of minimum CFM to ventilate our storage container very efficiently. We did not decide to implement this paradigm because we decided the probability of a hydrogen leak is very unlikely, additionally, speaking with other groups, we also decided if there was a hydrogen leak it would likely be very small opposed to a catastrophic leak. Given that, this introduces our next paradigm which was a combination of both active and passive ventilation which should improve the efficiency of our design even further.
Active/Passive Ventilation: Our next design we had to offer was a combination of both active and passive ventilation. As described above, knowing the likely hood of a hydrogen leak is very small, and a large catastrophic leak is even smaller, we decided we can make our system even more efficient by installing a passive ventilation system that will always be running with no power requirement. How this design would work is that wind driven ventilator turbines would always be running and never be drawing power, at 4 MPH winds the turbines drew enough CFM’s to effectively meet the NFPA 2-6.17 hydrogen ventilation standards. Additionally, while the passive ventilation system was working, if for whatever reason the sensors in the container detected hydrogen at about 0.6% by volume, the active ventilation system (electrically driven fans) turned on with capabilities of upwards of 500 CFM. Hypothetically, with the passive ventilation system drawing enough CFM to meet the NFPA 2 hydrogen ventilation standards, the active fans should never be needed. But, they will be installed and be ready in case active ventilation is needed in an emergency. The best part about this paradigm is that, hypothetically, there will be no need for electrical power input to successfully ventilate leaked hydrogen while meeting all the necessary standards. Additionally, if absolutely needed, there will be active fans with more power because leaked hydrogen is not something to take lightly and ultimately, using our house of quality, overall safety was the most important goal in our design.
Nitrogen Flushing: Nitrogen flushing was a very abstract idea to us and we found some evidence of it being a real possibility. We wanted to have an solution for the absolute worst case scenario, and this is what we came up with. The idea of nitrogen flushing was supported by a design report of a NASA article from the early 2000’s but ultimately the funding for this specific program by NASA got cut and none of it ever got implemented. Nitrogen flushing as our only form of purging leaked hydrogen was very quickly seen as something extremely inefficient and unnecessary. The idea was that nitrogen would very quickly displace all the oxygen in the container and not allow hydrogen to burn or react in any harmful way with oxygen. This would be extremely inefficient if used alone because the likelihood of a small leak is much more probable than a catastrophic leak and we’d be purging the container of oxygen with nitrogen each time any form of a leak was detected. Ultimately, this led to our next paradigm which was a 3-stage-integration and would hopefully implement nitrogen flushing in a much more usable and efficient manner.
3-Stage-Integration: The idea of a 3-stage-integration was to optimize a combination of all of our paradigms. With just active venting we felt we could create a more efficient design by including passive venting, so we were left with the active and passive ventilation combination. We felt that we needed an absolute worst case scenario form of ventilation or purging, so we came up with the nitrogen flushing. Finally, we came up with the 3-stage-integration which used passive ventilation as the first stage, being extremely efficient and drawing no power, then we had the active ventilation system which required some power but would purge the container of hydrogen in a larger leak, and lastly we had nitrogen flushing to displace oxygen in the container if there was a leak too large for our active fans. This was our initial design recommendation because the passive ventilation was very likely going to be the only system ever required, meaning no power would go into purging leaked hydrogen, but we also had taken the necessary precaution for any form of a hydrogen leak and had designs to contain those leaks and avoid a catastrophic failure. Once it came down to implementing this design, after we recommended it, we quickly found that nowhere in the most recently adopted NFPA 2 hydrogen technologies code it had any standard for nitrogen flushing. Additionally, it was becoming extremely hard to find a way to dispense the nitrogen when needed. As a group, with all the research we had done, we eventually decided to leave the nitrogen flushing behind as there was no literature to support that idea besides the NASA article from the early 2000’s that got its funding cut. Ultimately, the nitrogen flushing was too much effort for what it was worth, there wasn’t any literature or standards to support that theory, and most designs involving hydrogen only used ventilation systems. So below, after dropping the idea of nitrogen flushing, we have the final design recommendation and what we ultimately implemented and delivered on, a combination of passive and active venting.
Design Recommendation: Active/Passive Ventilation
As described above in our paradigms, active and passive ventilation was a combination of wind driven ventilator turbines and active, electrically powered fans. The idea behind this was that the wind driven ventilation turbines would require no power but meet all the minimum standards and in the case of a larger emergency we were prepared with large powered fans to purge the container of any leaked hydrogen.
The decision came down to which one of our paradigms met all the standards, which one was the safest, and which was the most cost effective and efficient. Using our house of quality, as a group it was quite clear that the active and passive combination of venting would be the most efficient, safest, and most effective. By having wind driven passive turbines that meet the necessary standards according to NFPA 2-6.17, hypothetically the ventilation system would never need any power. Of course there is a possibility there isn’t any wind or whatever else may happen, we have actively powered fans that are well above the minimum standards according to NFPA 2-6.17 to ensure we are prepared for any possible leak. This was also a very simple design to implement, yet very effective. Most of our paradigms were quite similar or built on top of each other, it really came down to what would be the most feasible, what would be the most effective, and what design would maximize our spending.
Effectively meets NFPA-2 6.17 (Ventilation) standards
6.17.1 (Ventilation Rate) – Must be at a rate greater than 1 CFM per square foot of floor space (160 CFM for this container)
220.127.116.11.4.2 – Exhaust must be within 12 inches of the ceiling
18.104.22.168.5 (Recirculation of Exhaust) – Prevent accumulation of hydrogen within the ventilated space
Meets AMCA 99-0401 (Spark Resistance) for all parts
8” Ventilator Turbine: $82.75 x 2 = $165.5
passive ventilation at all times
255 CFM @ 4MPH winds
We found this ventilator turbine to be our best option, getting two of them for $165 is extremely effective. The NFPA standard of 6.17.1 in NFPA-2 requires a minumum CFM of our ventilation system to be 160 CFM. We have two passive turbines that are rated at 255 CFM at very low speed winds, this meets every standard in NFPA 2-6.17 with absolutely no required power input. Most importantly this ventilator turbine met the spark proofing standard.
Direct Drive Aluminum Exhaust Fan: $431.72 x 2 = $863.44
Active ventilation to quickly remove hydrogen
Up to 541 CFM
As a group, we decided on the below fan because it was water proof, it wouldn’t allow any precipitation to enter the container, it didn’t require a lot of power, and it was spark proof. At up to 541 CFM per fan (we purchased two) we were well above the minimum CFM standard required by NFPA 2-6.17.
12” x 12” Intake Louver: $271.00 x 6 = $1,626.00
Allow of air intake
Capable of 310 CFM intake
These intakes were water proof, drain-able, spark proof, and allowed for more intake of atmospheric air into the container than what would be exiting with our active and passive fans combined. These intakes essentially met all the standards required.
TOTAL COST: $3,169.41
Integration with other teams
We have to work with the power team because our active fans will be REQUIRING power, additionally to meet other standards we need to have back up power in the case that we lose power from the grid, our active fans must still be ready to go if need be.
INTEGRATION with the insulation team will be key, there will need to be cutouts for all our vents and fans. Additionally, we need to come up with a way to mount our fans, vents, and turbines in the container and insulation will provide a support for that mounting.
“How to” cut necessary holes in the container:
“How to” install fans and turbines:
Active Fan instillation:
- 4 L-Brackets
- 8 ¼-20-1” bolts
- 4 ¼-20-3/4” Bolts
- 12 ¼-20-nuts
- 4 ¼” rubber washers
- 24 steel ¼” washers
- 7/16” wrench and socket
- 1/4 “ drill bit
- Power drill
After the hole is cut and fitted to the fan:
- Four L-Brackets will be mounted to the bottom of the roof of the container to support the Fan. Place the L-Bracket the optimal distance apart in the trough of the container roof. Mark where the holes need to be with the sharpie.
- Use the punch to make an indention in the middle of your sharpie mark so the drill bit will have a place to start.
- Drill all the holes out using the ¼” drill bit.
- Install the L-Brackets in place with the nuts, bolts and metal washers along with a generous amount of caulking to make sure it will be water tight. Then tighten the nuts.
- Place the fan in the hole temporally, use level to level the fan. Use sharpie to mark where the holes on the fan need to be. Punch and drill the holes.
- Install fan with the bolts, washers and nuts. Use the rubber washers to separate the steel from the aluminum with steel washers behind the rubber washer.
- Caulk around the fan to make the fan water tight.
- C Channel
- Sheetrock screws
- Adjustable fan base
- Power Drill
After the hole is cut and fitted to the fan:
- Install the Adjustable fan base from the inside of the container, push it up until the base is flush with the sheet rock.
- Fabricate 2 pieces of C-channel to fit between and perpendicular to the C-channel studs.
- Place the 2 pieces of C-channel on both sides of the fan hole
- Screw the pieces of C-channel in place and through the flange of the fan mount.
- Fan mount is now installed, place the ventilator turbine on top.
Progress of Building/Miscellaneous:
Cutting the first intake vent hole:
To get a feel for what we were doing, and to break the ice, we cut our first hole in the container using a Sawzall. The details of the process are in the “How to”. It took nearly two hours to cut the hole using the Sawzall, on top of that we had to grind down the cut to ensure proper fit for the vent. We were sure to undercut the hole if anything that way we can grind more off, once it was cut we couldn’t add more material but we could always take more off by grinding. Eventually the hole was cut, it was ground down to fit the vent, and the exposed steel was painted over with primer to prevent rust.
Cutting the rest of the intake vents:
After taking nearly 3 hours to cut and grind the first intake vent with a Sawzall, we had decided it would be faster to use an Oxy-Acetylene torch to cut the rest of the intake vents. In about 30-45 minutes all the vents were cut, in the next two hours we had to grind down each cut to ensure the vent fit as wanted. Additionally, the burned off paint had to be peeled off, cleaned, and then repainted with primer to ensure no exposed metal would rust. At the end of the day, the next 5 vents (6 total) all fit into their respective holes and were cleaned off and repainted with primer, the next step was to permanently install the vents and seal them off.
Cutting the roof holes for fans and turbines:
Very similar to the intake vents, we used the Oxy-Acetylene torch to cut the roof holes for our active fan and passive turbines. The same process was followed, cutting the holes, cleaning them off and grinding down the hole to fit what was going in there. We also repainted any exposed metal with primer to ensure there was no rusting.
Permanent installation of intake vents:
We drilled four holes (2 on top and 2 on bottom) of the intake vents and put nuts and washers to hold them in place. The exact details will be in the above “How to”. Caulking was added where there were small gaps to ensure water proofing and being sealed, expanding construction foam was used where there were large gaps. With the help of the insulation team, slots were cut into the insulating sheetrock to ensure a fit for our intake vents.
Permanent installation of roof fans and turbines:
With the help of insulation, they had built us a bracket out of C-channel to attach to their C-channel for our passive turbine ducting. The passive turbine ducting was pushed through the sheetrock until the bottom of it was flush, the bracket then was installed to hold the ducting in place. The ducting would sit above the top of the shipping container and then the actual ventilator turbine would simply slip right onto the ducting sticking out the container. Caulking was added around the outside to ensure it was water tight and to maximize the efficiency of the ventilator turbine. The exact details are in the “How to”.
For the active fans, we ran into a little bit of trouble by installing these fans AFTER the sheetrock was in place. All hands were needed to help install the sheetrock so unfortunately the fan installation had to get pushed back. For future reference MAKE SURE THE ACTIVE FANS ARE INSTALLED BEFORE THE SHEETROCK. Luckily the passive fans worked better to be installed after the sheetrock installation. We had fitted 90° L-shaped brackets to the bottom of the shipping container roof (inside) but above the sheetrock. Having the sheetrock in place made it very difficult to install the necessary hardware in between the roof and the sheetrock. Luckily we were able to improvise and make it work. Once the brackets were in place and the hardware was caulked (to ensure it was 100% water tight), the fan was then put in place and the vertical end of the L-shaped brackets were aligned with the holes in the fan’s ducting to install the necessary hardware. Likewise, the necessary hardware was caulked to ensure maximum weather proofing. The exact details of installation are in the “How to”. Once again we had to work with insulation for this process to ensure there were holes for our fan ducting, and to figure a way to mount the fans and turbines.
This concludes our whole process of choosing the right design, to choosing the right parts to implement our design, and the build process to actually complete the installation of our design. In the end we delivered on designing an efficient and cost effective, but most importantly safe, ventilation system to purge leaked hydrogen from the shipping container. We also delivered on ordering the right products to implement our design, and finally we delivered on completing the build process to actually install our ventilation system to the hydrogen refueling station. In one semester, the whole process was completed of designing, purchasing, and building/implementing our design.