What To Know About CNG Car Cylinders
The most expensive single component of your CNG car conversion will most likely be the high-pressure CNG fuel tank, also known as the “cylinder”. We do not recommend trying to save a buck and getting a used one. The are lots of sizes and types. The most common is for trucks and it is a 21″ x 60″ with about 20 gallon capacity of CNG. It mounts in the truck bed where a tool box would go behind the cab. Cost for a Type 4 carbon fiber tank this size is $3900 (good for 20 years).
CNG Cylinders Aren’t Just Air Tanks
Around the world there are many different types of cylinder requirements and certifications. You can learn more details about the CNG car cylinder standards here. Cylinders are used all around the world. The most common pressure rating in the world (on car cylinders) is 3000 psi (200 Bar pressure) (pounds per square inch). For whatever reason, the American standard for pressure rating on car CNG cylinders is 3600 psi (250 bar pressure). The filling stations in the USA are being built to accomodate these higher gas pressures. It is very important to know the pressure rating of your cylinder. The higher the pressure, the more CNG you can hold and the longer you can drive.
The cylinder usually has between 5 and 15 gge (gasoline gallon equivalent) and the 15gge tank can easily be about 19 inches diameter and 60 inches in length. One “gge” of CNG will get the same mileage as a gallon of gasoline, assuming your CNG conversion was installed correctly.
Remember, you will most likely install it inside your trunk or in the bed of your truck. The cylinder will have an expiration date and one will usually last over 15 years, although visual inspections are required every 36,000 miles or 3 years, whichever comes first. With the proper installation using heavy duty mounting straps you can rest assured your cylinder is perfectly safe to drive around. Again, we encourage you to learn more about the various CNG car cylinder standards.
Four Types of CNG Tanks for Your Car Conversion Kit
Click here for pricing on type 2, 3 and 4 tanks. We can help you get the best pricing and save on expensive shipping costs. It can easily cost over $150 to ship a tank cross country.
Type 1: All steel
These are the most common CNG cylinders. They are relatively cheap, yet very heavy. A full Type 1 cylinder could easily weigh over 350 pounds. A 10 gge Type 1 cylinder could cost around $1,000. A bonus about steel cylinders is that they can pass inspections easier.
They are allowed to show a little bit of wear, dings, and scratches, etc. The other 3 types are held to a higher standard of visual damage.We suggest American CNG for Type 1 steel tanks.
Type 2: Hoop Wrapped Composite
Type 2 cylinders have a metal liner and a composite “wrap” or reinforcement along the straight sides. The metal liner is designed to withstand the high-pressure all by iteself, but the wrap provides additional support and safety. These two components are a compromise between the heavy Type 1 and much lighter Types 3 and 4.
Type 3: Fully Wrapped Composite
The Type 3 has a seamless metal liner that is completely wrapped on all surfaces by a composite reinforcement. The full wrap provides almost all of the strength of the CNG cylinder. You have probably seen Type 3 cylinders without knowing it as they are common in SCUBA and medical oxygen storage. They are much lighter weight than Type 1.
Type 4: Fully Wrapped and Non-Metallic Liner
Very expensive compared to Type 1. $3,000-$5,000 for the cylinder alone. These have a plastic liner and a full wrapping of carbon fiber or mixed fiber. The liners are a permeation barrier only. Even large 15-20gge tanks of type 4 only weigh about 100 pounds when empty.
The strength is in the carbon fiber wrapping. These cylinders are actually not gas tight, but they leak so slowly that nobody worries about the permeation. The Type 4 is fitted with impact protection on the domes for more strength. These are most common on small engine cars like a Civic or like a bus where weight is more important. See images of all types of tanks including PRICES from SkyCNG.