Pressure and Safety Devices

In this section we will look at regulators used in Gasfitting, where and why they are used.

Natural gas is distributed down high pressure gas pipelines from the main gas/ oil fields in the Taranaki region. These transmission systems are operated at pressures of approx 8600 kPa. These then go to the local distribution systems, these are operated at various pressures that are typically about 2000 kPa - 400 kPa.

LPG is stored and distributed in bottles at pressures of approx 800 kPa.

But an average household using Natural gas only runs at 1.5 - 2.75 kPa and most appliances on Natural Gas run at 1 - 2 kPa.

A household using LPG only runs at 2.75 kPa and most appliances require 2 - 2.75 kPa.

So how do we achieve this?

Regulators

Main roles of a regulator:

• Minimise fluctuations in the gas installation and appliances
• Create the correct pressures required for the installation and appliances
• Protect the installation and appliances from over pressure 

Pressure reduction in most households and smaller commercial installations are done in two stages, larger commercial installations are done in three.

First stage is the regulator on the incoming high pressure side of the installation, either from the gas supplier (before the gas meter) or from the LPG bottles. This reduces to the required pressure needed for the whole installation. This is to ensure adequate gas volume and pressure to run all the appliances with minimal pressure fluctuations.

Second stage is at the appliance or before a group of appliances in larger commercial. This is set to the pressures required by the appliance manufacturer for the appliance to run efficiently and correctly.

Some LPG appliances do not require this regulator as the appliance is designed to run on incoming pressures (2.75 kPa) 

Most modern appliances, except cooking appliances, come with the appliance regulator as part of the internal valve train of the appliance.

Some appliances come with a combination valve (Unitrol) that regulates gas flow, regulates water temp inside the cylinder and also protects the appliance from overheating and the ability to fail safe with any gas interruption.