English (United Kingdom) Viet Nam
Introducion and technical Guidance


CNG is compressed natural gas which is exploited from natural gas mines or associated gas in the process of exploiting the oil, through the cleaning equipment to remove contaminants and heavy constituents, transported by pipeline to the gas compressor plant or compressing directly into the ship carrying CNG. Natural gas is compressed to pressure of 200-250 bars, at the environmental temperature to reduce the volume of tanks, increasing efficiency and reducing transportation costs by means of conveyance by land, railway and waterway.
At the place of consumption, CNG is heated and reduced pressure through PRU - Pressure Reducer Unit, to the desired pressure of customers (usually 3 bars).
The main gaseous component is CH4 (84%), C2H6 (12%), while burning low CO2 generated, making the environment cleaner, causing no greenhouse effect. In the future, it will replace fossil fuels such as gasoline, oil... Because it is fuel that is exploited later than crude oil, the current reserves are still in profusion while crude oil is increasingly exhausted.
PRU system is including equipment:
- Gas tanks (trucks 20 feet, 40 feet);
- The system of pressure reducer (depending on the number of charging posts);
- PRU system;
- Boiler system is placed in container 20 feet;
- The Mixer (if the customer needs to instal)
The entrance for tank trucks must be minimum of 7 meters wide, without obstacles, without corner hiding the view of tank car drivers, and must have space for tank trucks making U-turn.
Depending on the capacity of each plant, the number of tank trucks will be required to provide gas, away from residential areas, must have security corridor for other devices (such as electricity networks, devices with capableness of causing explosion of plants, ...).
Minimum area to put PRU:



(Depending on capacity to instal suitable PRU) 








12 – 19 

 10 - 17

 7 – 15 

 20m x 30m (03 tanks)


 19 – 25 

 17 - 24 

 15 - 22

 25m x 30m (04 tanks)

Note: The table is calculated for the distance from the CNG Phu My Factory to customers less than 100 km.
1. Sub-Station Topographic Investigation
 1.1. Equipment Installation Sites (PRU, LPG tanks, Mixer, CNG tanks...)
 1.2. Customer's gas receiving location ( flange connection to gas inflow pipe )
 1.3. Gas trailer access road
 1.4. Electric and water, lightning protection and grounding, high power system
 1.5. Providing overall premises (CAD file)
2. Providing preliminary design
   Plan drawings of installing position, walls and foundations of Pressure Reducer Unit
3. Proposed implementation progress (Detail Schedule)
   Progress of construction, installation, testing and necessary legal formalities
4. Installing gas pipeline from the gas station to the device
   - Installing pipelines
   - Testing pressure
   - Providing verification records of pipeline
5. Building premises of Pressure Reducer Unit
   - Walling masonry (brick wall of 200mm thick and 2,500mm high)
   - Pouring concrete on foundation (subject to vehicle load of 40 tons)
   - Providing water system (Ø27 PVC)
   - Providing electrical system (10KW)
6. Providing complete profile
   - Drawings of  pressure reducer Unit
   - Description of fire preventing and fire fighting
   - The process of coordinating operations
7. Installing Pressure Reducer Unit
   - Processing and installation of PRU
   - Testing pressure
8. Running test
   Supplying gas to the device using gas of customers
9. Acceptance test and handing over
   Minutes of testing and acceptance test

1. Locating the position of PRU as designed.
2. Building suitable foundation for CNG tank trucks (40 tons).
3. Walling masonry surrounding the area of PRU.
4. Making canopy of PRU, oulet pipes.
5. Supplying water to Boiler system of PRU.
6. Supplying power (10KW) to the electrical panel of PRU.
7. Making lightning-resistant systems for PRU.
8. Building gas pipeline system from PRU to the area of production.
9. Replacing the combustion heads appropriated with CNG.
10.Applying for license of fire preventing and fire fighting.
11. Coordinating operations of the system

1. Awaring to safety work:
- When installing new equipment, ensuring equipment is designed in accordance with conditions of use and fully compliance with the provisions of the safety standards of the state.
- Equipment shall have to be manufactured from materials conforming with working conditions of CNG.
- Technological process was also selected so that the operation is simple and highly automated.
- The repair and maintenance shall have to comply with the process engineering which was setting up closely and made by the technicians having the knowledge, skills and expertise. Maintenance and repair process is closely monitored. The equipment is checked and acceptance test after carrying out the works.

2. The management, operation and maintenance of equipment:
- Understanding clearly operating conditions of devices, such as pressure, temperature, time of operation, etc.
- Understanding the parameters limiting the scope of safety operation of the equipment as well as all other equipment related directly or be controlled directly by pressure equipment.
- Drawing up the processes and operating instructions and processes to coordinate to deal with detailed troubles for each component as well as the entire equipment system.
- Ensuring the machine operators, repair and maintenance department and all the personnels related have been instructed, trained and inspected completely to operating process and troubleshooting.

3. The protective and warning devices are always in good working state:
- The equipment such as safety valves, pressure gauges as well as detectors of smoking, gas and fire are in good working situation.
- Periodically pressure devices are adjusted and checked in accordance with technical requirements and requirements on safety standards of the state.
- The automatic discharging devices such as safety valves, explosion protection film (tank trucks) with discharging pipe led to a safe place.
- Ensuring only those with sufficient responsibilities and authorities will be allowed to change the setup parameters of protective devices, as well as production equipment in general.

4. Maintenance process of equipment:
- The Company has actively planned maintenance and repairs for the entire system of pressure equipment in the unit. The plan of maintenance also take into account the specifications of each device, or equipment unit such as working life, operating characteristics, work environment of the equipment etc.
- Always interested in the abnormal denotements in system of gas loading/discharging. Every weekend technicians shall inspect the working conditions for each equipment unit in the factory as well as at the stations of customers (e.g, if safety valves are regularly effected, it means the system was overpressure unusually or safety valves are not good).
- Before performing the maintenance and repair, making sure the system was discharged pressure, cleaned, discharging gas, filling with Nitrogen...
- Fulfilling safety process during repair and maintenance.

5. Training and instructing:
- All employees in operation, maintenance, repair and especially the new employees are fully trained and instructed.
- The training is redone in the following cases:
• When changing jobs
• When changing device or operation process
• After a time of stop working or switch to do something else.
• After periodic annually.

6. Periodically testing equipment:
According to the provisions of the state, the following devices are periodically tested:
- Pressure tanks
- Pressure pipelines
- Safety valves
- Barometer
These devices are registered the security audit by the Centers for verification and registration for use in the local Department of Labor, War Invalids and Social Welfares before putting into use and be audited periodically by the Center for verification in the using process. The period of verification is stipulated in the current safety engineering standards.

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