LPG and PNG Gas Piping for Factories: Design, Safety and Approvals

Fuel gas is one of the most useful utilities in a factory — furnaces, ovens, boilers, heat treatment, canteens — and one of the least forgiving when it is installed badly. A gas system is not plumbing with a different medium. It is a pressure system carrying a flammable fluid through occupied buildings, and every part of it is designed around that fact.

LPG or PNG: where the gas comes from

LPG (liquefied petroleum gas) is delivered and stored on site, in cylinders connected to a manifold or, for larger consumption, in bulk storage vessels. The plant holds its own fuel, which is both its advantage — supply independent of a pipeline — and its responsibility, because storage brings its own safety distances and approvals.

PNG (piped natural gas) arrives through a city gas distribution network. The supplier brings the gas to a metering point at the site boundary; from there the plant's own internal network takes it to the points of use. There is no storage on site, but the internal system still has to be designed, installed and tested to the same discipline.

From supply to burner

Whatever the source, an industrial gas system follows the same logic:

• Supply. A cylinder manifold bank with changeover between duty and standby banks, a bulk LPG installation with vaporisation where demand requires it, or a PNG metering skid.
• Pressure regulation. Gas is reduced in stages from supply pressure to the pressure each appliance needs, with regulators and safety devices at each stage.
• Distribution piping. Usually welded steel, routed where it is protected from damage, supported properly, and kept away from ignition sources and from spaces where leaked gas could collect.
• Metering. Where the plant wants to know which line or area uses what, metering is designed in, not added afterwards.
• Isolation at every appliance. Each point of use can be isolated locally for maintenance without shutting down the rest of the plant.

Detection and shut-off: the system that watches the system

A gas system is not safe because it has been built well; it is safe because something is watching it. Gas detectors are placed where a leak would accumulate — low down for LPG, which is heavier than air; higher up for natural gas, which is lighter. They are wired to alarms and to emergency shut-off valves that cut the supply automatically when gas is detected, and that can also be operated manually from a safe location.

The detection layout, the shut-off logic and the electrical work that connects them are as much a part of the gas system as the pipe itself.

Testing before gas is introduced

Before any gas enters a new line, it is pressure tested to prove it is tight, and then purged — usually with nitrogen — so that gas is never mixed with air inside the pipe. Commissioning brings each appliance on line in turn, checking regulation, flame and safety interlocks.

Approvals

LPG storage and handling in India falls under the regulatory oversight of PESO (the Petroleum and Explosives Safety Organisation), which governs gas cylinder installations and bulk storage vessels and the safety distances around them. PNG supply is governed by the city gas distributor's own requirements up to the meter. The plant's fire authority will also look at the gas installation when it inspects the site. A design that anticipates those approvals from the start avoids re-routing pipe after the inspector has seen it.

Why gas belongs in the same contract as everything else

A gas line crosses the civil work, the structure, the electrical system that powers its detection and shut-off, the fire protection system, and the equipment it feeds. VPSTEC delivers LPG and PNG piping, metering, cylinder manifold banks, and gas detection and emergency shut-off as part of the same contract as the plant's other utilities. On a multi-year appointment at an operating industrial gas facility, our piping, electrical and safety systems were integrated with the existing utilities without interrupting production.