FAQ

Never supply at a pressure above 220 bar (22 Mpa): this is the maximum supply pressure allowed by Ordinance number 32 of 03/06/01 of ANP (Agência Nacional de Petróleo) [National Petroleum Agency]. The maximum service pressure of the cylinder is that at which the gas is stabilized at 21o C; that is, 200 bar. The service pressure is reached when the gas temperature drops, after the supply of the vehicle. Supplying at pressures above 220 bar (22 Mpa) can shorten the useful life of the cylinder and of the remaining of the conversion kit components.

In the first place, we should explain that the correct unit and the unit used all over the world to measure the real capacity of any cylinder and for any monophasic gas is the volumetric capacity of water that is measured during its manufacture and printed on the warhead of the cylinder in liters, as required by all national and international standards. The cubic meter unit is adopted only in the supply system of the station at the time in which the gas is being measured for charging.

Why?

1. As explained above, the physically available volume for filling is that informed on the warhead, in liters of water, since the capacity in cubic meters varies because of several factors.

2. Actually, depending on the supply pressure of the station, one can fill less or more one same cylinder. ANP (Agência Nacional do Petróleo) regulates 220 bar as the maximum supply pressure.
Important: Some stations are supplying at higher pressures, which is contrary to the regulation and, therefore, the practice is unsafe and totally not recommendable.

3. Another very important factor is that the cylinder sometimes gets oil on its inside, derived from the compressors, during the load. This oil takes up useful space, that is, that initial available volume decreases.

4. The molecular friction of the gas derived from the filling speed can also cause heat, thus reducing gas storage capacity in the cylinder.

5. By the time of the first load, the presence of air inside the cylinder is common, which is also a capacity reducer, a fact which tends to be eliminated in the subsequent loads; however, residual gas will remain, which will also reduce the amount of gas placed by the station.

6. But perhaps a fact that few realize is the filling temperature. Just check the ABNT standard – NBR 13200 – and see how complex and variable the gas volume of a cylinder is as a result of the filling temperature. Several charts and formulas can be seen there which, ultimately, lead to the conclusion that filling a cylinder at 20oC and the same at 40oC for instance, can present quite different results in the volume of gas packed in the cylinder.

That is why when we talk about cylinder volume, we must talk about LITERS OF WATER, I repeat, and not in cubic meters. It is not wrong, but that requires a number of assertions to become true.

In order to avoid gas leaks in the connection of the valve with the cylinder, one should imperatively follow the following procedure:

1. Place the valve (without the sealing tape) in the cylinder, threading manually until achieving “manual tightening”. The hands must be protected with gloves and one should count the number of turns until tightening.

2. Remove the valve and place the sealing tape in its thread in a total of 7 to 8 turns, always clockwise.

3. Thread the valve (also manually) again in the cylinder, also counting the number of turns until achieving tightness.

4. Tighten the valve with a wrench in a total of 3 turns plus the difference found between the manual threads with and without the sealing tape, of steps 1 and 3 above.

Note: These instructions were transcribed from the “Handbook of compressed gases” of the Compressed Gas Association – USA.
Important: Valvulation, performed this way, must provide a torque of approximately 150 N.M.(which can be check by means of the torquemeter), as per NBR 11353-1 : Highway Vehicles – Installation of Vehicular Methane Gas (GNV) Revision: Dec. 1999.

It is advisable that sealing tape be used, which works as a lubricant in this valvulation process. Liquid Teflon can also be used; however, cure time instructions must be followed as defined by the manufacturer. Any other material (such as grease, string, etc.) is not recommended in this process.

No. This is a high risk operation. Do not try to remove the gas from the cylinder without adequate equipment for depressurization, since this will imply risks. The cylinder should be handled by technically trained people.

The cylinder should not be re-used and must be destroyed. The exposure of the cylinder to any source of excessive heat or welding should be avoided. Exposed at high temperatures, the cylinders are subject to changes in their characteristics as to their resistance, becoming fragile. Read the Cylinder Manual and the adhesive fixed on the body of the same. The instructions described therein are very important and refer to your safety and preservation of your property.

In case of fire in your vehicle, do not try to extinguish the fire. Get away immediately from the fire up to a minimum distance of 50 meters and call the Fire Department, which must be informed that your vehicle runs by natural gas. Such information will help the work of our firemen.

Never replace the cylinder for another type of reservoir: kitchen gas containers or other compressed air tanks cannot be used together with NGV gas cylinders or replace them, since the NGV cylinders are designed for high pressure storage (200 bar). The MAT cylinders are designed to support this high pressure safely while the other types of cylinders are not designed for high pressure.

No. The behaviors of the gases vary. Some are even corrosive, and may even damage the cylinders internally, cause ruptures, etc. This reservoir (cylinder) was developed specifically for NGV.

Yes. Never expose the cylinder to corrosive products. Be careful with the acids; avoid leaving batteries, for instance, near them.

Never touch the pressure relief device or the safety device of the valves. As the own name says, that is to bring safety. If there is any problem, go to a converter to have your valve changed.

Installation or removal must be performed only by companies registered by Inmetro and qualified to do a good job, which warrants the safety and the intended economy. The user should not allow other non-qualified people to handle this equipment. If it is necessary to remove the cylinder, it must be totally depressurized. In case tin-shop service is necessary on the vehicle, which involves weld or blowtorch near the cylinder, the latter must be removed previously to the service.

Supply only at stations authorized by the Agência Nacional de Petróleo (ANP) and watch the maximum filling pressure: Never supply at pressures above those authorized by ANP (22 Mpa or 220 bar).

Do not allow changes in the original characteristics of manufacture of the cylinder or the valve and never fix anything to the body of the cylinder by means of welding, as this is strictly forbidden. Do not allow “nosies” to change the thread of the cylinder, the valves, the safety devices, the markings, etc.

The standard, which defines the color in which the cylinders must be painted for these gases is NBR 12176: Cylinders for Gases – Content Identification.

1. Two-dome cylinders are quite common in the whole world and for several types of high pressure gases and there is no cylinder standard that forbids them.

2. In the past, we manufactured them for specific exportation given that some were commercialized in the country, when there was no effective regulation yet for NGV by INMETRO. Today, we only manufacture two-dome cylinders for wagons and compressor breathers, since a two-dome cylinder has a production cost higher than one with bottom and dome.

3. These cylinders were also used in pairs, so that the outlets that did not have valves were interconnected by the converter by high pressure piping. When some outlet (a bottleneck that was not interconnected), this was buffered with a stopper.

4. The best way to close this outlet is really the stopper that should no longer be removed, as long as it is in good conditions.

5. However, we stand out that the periodic inspection at 5 years of usage is valid and must be also followed for this cylinder, given that I recommend that the hydrostatic test should be performed with the stopper installed. Of course, at the time of reassembly of the cylinder in the vehicle, after its retesting, just like that of the valve, the other outlet must also be checked as to possible leaks.

Because NGV is not toxic and is lighter than air and, in case of leaks, it rises quickly, reducing risks of explosion or fire. In addition, in order for NGV to ignite, it must be submitted to a temperature of approximately 620 ºC, while gasoline ignites at approximately 200 ºC.

The cylinder has a guarantee of 20 years as of the manufacture date, depending on its correct use. For that, the owner must have MAT’s Quality Certificate and its Invoice.

At each 5 years (maximum period as per ABNT standard 12274), the cylinder must be revalidated through periodic inspection as of the date of manufacture or in case there is corrosion, damages due to thermal, or mechanical causes (dents, hits) or even when there is transfer from one vehicle to another. This should only be performed by companies certified for such by Inmetro. Soon after the inspection services, the inspection company must affix a confirming seal (purple in color) on the warhead of the cylinder. After this requalification, the certifying company starts to answer for the guarantee of the cylinder.

No, never. Such fact makes the thickness of the wall of the cylinder be below the minimum thickness of the project, jeopardizing the user. Even if the cylinder does not present any type of problem with this marking, it must be rejected during inspection, which should occur at each 05 years.

The cylinder valve must be closed immediately and the vehicle forward to a converter registered by Inmetro. The user should not allow other non-qualified people to handle this equipment.

The vehicle must be taken to a converter registered by Inmetro so that the cylinder can be removed and replaced only after the complete service is finished.

Yes. This happens as a result of the compression of the NGV molecules during this operation, causing friction between the same and consequently heat, which will reflect on the wall of the cylinder.

Yes. Usage causes NGV expansion and consequently heat loss, which will reflect on the wall of the cylinder.

The water steam existing in air, in contact with the valve and the cylinder with temperature below that of the environment, forms the characteristic humidity in these cases.