Distribution systems

The gas supplied through natural gas and LPG distribution systems must have adequate pressure, quality, and odour and must be accurately measured.

Natural gas distribution systems take gas from the point at which the transmission system delivers gas to the “city gate” station to various consumer points of supply. Transmission systems and distribution systems are generally constructed of either steel or plastic to specific standards. Transmission systems are operated at pressures upwards of 2000 kPa. Distribution systems can be operated at various pressures that are typically up to about 400 kPa, although higher pressures are sometimes used.

Liquefied Petroleum Gas (LPG) is supplied by bulk tanker or in cylinders to supply depots and consumer installations. When stored and supplied in containers, LPG is in liquid form. It is vaporised by withdrawal from the tank or cylinder.

While most LPG supplied in New Zealand is delivered in bulk form or in cylinders, there are some small LPG distribution systems in the South Island.

Supply pressure, gas quality and odour

The gas pressure available to each installation must be sufficient for the safe supply and use of gas at that installation. Gas suppliers are responsible for ensuring consumers have sufficient supply pressure. In practice, suppliers will indicate the supply pressure available.

In order to ensure that the gas supplied is suitable for appliances available in New Zealand, the gas supplied must meet the relevant specification. For natural gas, this specification is NZS 5442 Specification for reticulated natural gas. LPG must comply with NZS 5435 Specification for liquefied petroleum gas (LPG).

Gas must have a distinctive and unpleasant odour so that the presence of gas in the atmosphere is readily detectable at and above 1/5th of the lower explosive limit of the gas. This requirement is fundamental to gas safety.

Gas measurement

The regulations specify limits for accuracy of measurement of gas for revenue purposes. The requirements of NZS 5259 Gas measurement must be met unless there is written agreement between the seller and the purchaser.

When a gas meter (gas measurement system) is placed into service the uncorrected error must be no more than plus or minus 2%. Before being placed into service the meter must be tested for accuracy and sealed by a competent organisation.

Safety Management System (SMS)

Gas supply systems that supply or are intended to supply an annual consumption greater than 10 TJ of gas are required to maintain an SMS

Safety Management System (SMS)