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What size CNG trailer/s do I need for my virtual pipeline project?

Considerations in sizing your mobile natural gas storage trailer/s.

Contrary to much of the advice in the industry which assumes bigger trailers are always better… the actual answer to the above questions is … “It depends.”

In many ways we can look to the aviation industry for similar inspiration. There are business cases for jumbo jets and regional-sized jets alike.

Likewise, CNG and renewable natural gas (RNG) virtual pipeline projects are far too nuanced for a one-size-fits all strategy. Just throwing the largest trailers at the project will certainly work – but may end up costing much more as compared to right-sizing a trailer solution for a project.

CNG Large Storage Trailer

The following are some of the considerations in determining the right size of trailers for your project.

1) How much gas needs to be transported per day?

2) How far is the gas required to travel via virtual pipeline?

3) What pressures are trailers filled to?

4) What pressures will the trailers be de-fueled to? (Also know as the heal pressure of the trailer.)

5) Are there any restrictions to the times of day trailers can be pickup and dropped off?

6) Are there any space limitations to either loading or offloading areas?

7) What are your hazmat hauling logistics capabilities or limitations?

8) What time frame are you looking to for project amortization?

9) Where are you hauling and what are the on-road weight limits? Some states have different permitted weights.

10) What is the CNG trailer offloading to? Are their times when it doesn’t require being connected and defueling?

11) What levels of redundancy (ie additional hours of supply or storage) do you want in your mobile storage solution.

These are just some of the issues to consider when developing your virtual pipeline solution. Let’s take a look at some of these considerations below.

Large Trailer with Less Trips vs Smaller Trailer with More Trips:

Questions number 1 (how much gas) and 2 (how far does it need to be hauled) above are certainly the most importation. In general, the further you need to haul gas via virtual pipeline, the more incentive there will be to utilize larger trailers. That is because larger trailers generally equal less trips required.

At the same time, most Compressed Natural Gas (CNG) hauling projects are less than 200 miles each way – and many in the 25-to 50 mile range. And for projects that have very short hauls – less than 25 miles each way – it may be more cost effective to use a small or medium sized trailer and make an additional trip. Related to question 8 above: what are your amortization goals? The extra CAPX of larger trailers would potentially be more expensive than the extra OPX of additional short trips utilizing smaller trailers with smaller CAPX.

CNG Mobile Storage Trailers for Virtual Pipeline
Consider Advantages of Small vs Large CNG Storage Trailers

Hauling Transporting Logistics Considerations:

Another consideration is your hauling logistics. You can design hauling logistics and trailer rotations as an academic exercise. And then you can design it for sustainable, real-life scenarios where employees work predicable shifts with accommodations for vacations, sick time, etc.

For example, you might require 270,000 SCF delivered each day and a large trailer may hold a total volume of 350,000 MCF of storage. As a result, academically, you require a trailer delivered every 1.29 days (350/270 = 1.29 days of volume or every 31 hours). But designing a real-life logistical support for rotating a trailer exactly every 31 hours could create a very challenging work-life schedule. A rolling schedule every 31 hours will create a schedule with pickup and drop offs that change everyday and eventually roll into the middle of the night for pickups and deliveries. Is it technically doable? Yes. Is it realistic for real-life employee scheduling? Maybe. This ties to question 7 above… what are the hazmat-hauling, capabilities and limitations? If it’s more realistic/feasible from a logistics schedule to rotate a trailer one time per day instead of every 31 hours, then you can likely reduce the size of the trailer and reduce your trailer CAPX/Lease Rate. You would only require a trailer that holds 300,000 instead of 350,000 SCF.

CNG Virtual Pipeline Logistics and Schedules
Consider Virtual Pipeline Hazmat Hauling Logistics

Level of Redundancy/Hours of Storage:

Renewable Natural Gas (RNG) Virtual Pipelines utilize dedicated trailers to a specific renewable gas plant (ie dairy, wastewater, landfill, etc). Having enough buffer storage built into your RNG hauling solution is important to ensure reliability and redundancy. As trailers are being filled and then hauled away from the plant, there needs to be another trailer queued up and ready to fill. If there’s a delay in a trailer returning back to the plant, is there adequate storage at the plant to ensure the plant does not need to be shut down?

For industrial gas supply, redundancy is focused on the hours of natural supply for fueling equipment. The logistics should include additional hours of supply in your trailer solution to ensure there’s room in the operation to help cover for a delay in trailer pickups, delivery and logistics. Redundancy can be accomplished with additional trailer assets planned as backup or permanent onsite buffer storage solutions.

Fuel Remaining Virtual Pipeline
Consider Levels Redundancy & Storage

Trailer Working Pressures vs Your Project:

The industry standard for CNG fueling and compression is set to 3600 PSI in United States. Nearly all CNG fueling stations have compression that will fill cylinders to this working pressure. Some CNG tube trailers are rated for higher pressures – 4000 PSI and even 5000 PSI. These higher pressure trailers can technically hold more gas (due to the higher level of compression) but if your project is utilizing the industry standard 3600 PSI compression, then you are not ever utilizing the higher capacity of the trailer. Said another way, you are likely paying a premium for a higher trailer pressure capability, and never utilizing this premium.

CNG Pressure Gauge
Consider Service Pressure for Your CNG Storage Trailers


It’s important to understand the details of your project to design the most effective virtual pipeline solution. CNG Direct designs, engineers and manufactures CNG tube trailers and provides turnkey trailer maintenance, hazmat transportation/hauling and logistics solutions for industrial and renewable natural gas virtual pipeline services. We customize our solutions around your project specifics. Let's get started on your project.

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