Page 65 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 1 Health and safety practices and systems

● Cylinders should be transported only on purpose-designed trolleys of the
correct size. Three-wheeled trolleys are safer than two-wheeled.
● Trolleys for transporting cylinders should be manufactured to BS 2718.

Equipment used with oxy/fuel gases
As well as the bottles themselves, there are several other pieces of equipment
that we need before we can start using our oxyacetylene bottle set. The main
components of oxy/fuel gas equipment are shown in Figure 1.33.

A pressure regulator fitted to the
outlet valve of the gas cylinder,
used to reduce and control gas
A flashback arrester to protect cylinders pressure. Most modern regulators
from flashbacks and backfires. Flashback work with a two-stage system: the
arresters (also called flame traps) must be initial stage dispenses the gas at a
fitted into both oxygen and acetylene gas set rate from the storage cylinder;
lines to prevent a flashback flame from the second stage handles the pressure
reaching the regulators.
reduction. On a two-stage system,
the device has two pressure gauges.
One gauge tells how much gas is
remaining in the cylinder, and the
other tells the pressure of the gas
being released.

A control valve to shut off or isolate
the gas supply, usually situated at the top
of the cylinder. It has a square key to open
and close the valve. As a general rule, when
using oxyacetylene, both the oxygen and Cylinders of oxygen and fuel gas
acetylene bottles should have their own key,
which should be left on the bottle during the (propane or acetylene).
welding process so that the bottle can be
isolated quickly in an emergency.

Non-return valves to prevent
oxygen reverse flow into the fuel
line and fuel flow into the oxygen
line. The valves can be used to
Flexible hoses to convey the gases from prevent conditions leading to
the cylinders to the blow pipe. Hoses between flashback, but should always be
the torch and the gas regulators should be used in conjunction
colour-coded: red for acetylene and blue for with flashback arresters.
oxygen. Fittings on the oxygen hose A blow pipe or other burner device
have right-hand threads (non-flammable gas), where the fuel gas is mixed with
while those on the acetylene hose oxygen and ignited.
have left-hand threads (flammable gas).
p Figure 1.33 Oxyacetylene set

KEY TERM
Flashback: where the flame burns in the torch body, accompanied by a high-
pitched whistling sound. It will occur when flame speed exceeds gas flow rate
so that the flame can pass back through the mixing chamber into the hoses.
Most likely causes are incorrect gas pressures giving too low a gas velocity,
hose leaks or loose connections.

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