Authorities in North China have implemented an emergency plan due to a temporary shortage of natural gas supplies in recent days caused by transportation and weather problems.

The plan includes limiting indoor temperatures at public buildings and suspending supplies to manufacturers.

China National Petroleum Corp, the country's largest oil and gas supplier and producer, ran into difficulties when unloading imported liquefied natural gas at ports. This caused a temporary shortage of natural gas supplies in northern areas, the Beijing Commission of City Administration and Environment said.

PetroChina, CNPC's listed arm, said on Monday that a vessel carrying 260,000 cubic meters of liquefied natural gas was unable to discharge its cargo as scheduled at the port of Tangshan in Hebei province because of heavy winds and smog.

Lin Boqiang, director of the Energy Research Center at Xiamen University, said there is an oversupply of natural gas in the country, so the shortage in northern areas will be temporary.

The LNG supply is sufficient, and domestic LNG plants are operating at about 50 percent this year due to oversupply.

"The shortfall will be filled very soon by other means, and the problem is likely to be solved in one or two days," Lin added.

China imports LNG mostly from Turkmenistan, Qatar, Australia, Indonesia and Malaysia.

To keep Beijing's heating system stable, the commission launched a contingency plan on Saturday, strictly controlling indoor temperatures at public buildings and suspending natural gas supplies to manufacturers.

There have been difficulties in supplying natural gas to North China, particularly Beijing, recently due to the earlier arrival of cold weather and problems in upstream gas supply, the National Development and Reform Commission said on Sunday.

Authorities have also reduced natural gas supplies to nonresidential users in Shanxi, Shaanxi, Tianjin, Hebei and Beijing.

The top regulator also coordinated with China Petrochemical Corp and China National Offshore Oil Corp to increase natural gas supplies to the pipeline network to ensure supply in North China.

PetroChina said the situation will improve, as it is adopting measures to limit distribution in order to secure natural gas supplies in the region.

"PetroChina will optimize the LNG distribution network and pipeline infrastructure, and at the same time improve load ability ... to secure the supply of gas for domestic use," the company said.

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Special ships use top technology

A typical LNG carrier, also known as "maritime super-freezer", is a tanker ship designed for transportation of liquefied natural gas. These ships represent one of the top shipbuilding technologies in the world, since they are equipped with gas tanks with the ability to withstand extremely low temperatures.

Liquefaction plants convert natural gas to liquid form for transportation to terminals by cooling it to-162 C, giving the gas one-six-hundredth of its original volume.

An LNG carrier has four to six tanks and a double-hull design.

Experts said the LNG carrier is one of the most sophisticated vessels, because if even a small amount of LNG leaks from a pressurized tank or pipe, it could feed a huge fire and possibly cause a massive explosion.

Currently, the world's LNG ship market is dominated by South Korea, Japan and China. South Korea was the world's largest LNG vessel manufacturer last year, with 68 percent of global orders, earlier reports said.

As China's demand for liquefied natural gas has soared with efforts to optimize the nation's energy mix amid mounting pressure caused by air pollution, the fleet of LNG carriers continues to see huge potential for growth.

Currently, only China, South Korea, Japan, France, Italy, Finland, Norway, Spain, Sweden and the United States are capable of building such ships.