EnergySafe Magazine Spring 2017, issue 48 | Page 12

12
Gas
News
LPG cylinder valve consulting
meeting
By Jason Treseder, Senior Gas Engineer
Gas regulatory authorities and Gas Energy
Australia recently hosted a meeting with
stakeholders to discuss safety concerns
with the current Type 21 POL LPG
cylinder valve and propose a change
to an alternative, safer connection.
Each year, we record a significant number
of incidents involving portable LPG appliances,
like barbecues. In many cases, gas has leaked
from the connection (e.g. barbecue) to the cylinder
valve, ignited and resulted in damage to property
and injury to surrounding people.
In these instances, the connection of
LPG appliances to a cylinder is generally
made by untrained people who have a limited
understanding of its associated risks. Similarly,
when heading to refill cylinders, many transport
their cylinders inside vehicles.
For many years, the Type 21 cylinder valve
outlet connection has been the default LPG
cylinder connection. The outlet connection on
the cylinder valve consists of an internal thread
leading to an internal cone.
The mating fitting on the hose assembly
consists of a matching external thread, and a
round nipple with a 19mm radius. A leak tight seal
is achieved via compression of the radius against
the internal cone.
Historically, the nut fitting was provided
with spanner flats, and tightening was
achieved by using a spanner to apply
sufficient torque to the nut.
The connection was subsequently revised
to permit soft seals on the nipple to assist with
sealing, meaning a hand wheel was sufficient
to make a leak tight seal, simplifying the
connection process for end users.
However, a recent review of the Type 21
connection found four major design elements
that have contributed to incidents.
» » Open cylinder valve. Here, gas can flow
when the cylinder valve is open without a
gas tight connection. An open cylinder valve
can release a large volume of gas in a short
amount of time. The environment around
small cylinders is generally uncontrolled,
and the risk of gas igniting from a nearby
ignition source is high.
When transporting cylinders inside vehicles,
the risk lies when a cylinder valve is knocked
open during transport, and gas is released in
an enclosed compartment with many ignition
sources. Incidents have occurred where an
operator has assumed the cylinder is empty
and attempted to disconnect an appliance
from the LPG cylinder, without shutting off
the cylinder valve, resulting in uncontrolled
release of gas.
LPG cylinders have also been used as a
threat where the ability to freely open cylinder
valves to allow uncontrolled release of gas
was misused.
» » Left hand thread. Historically, connections
with flammable gas have been designed
with left handed threads to reduce the risk
of incorrect connections. To open and close,
left handed threads are turned in the opposite
direction to conventional threads.
It is likely that untrained users of cylinders may
be unaware of this difference, or forget under
stress. In one instance, an individual operating
a barbecue heard a noise at the regulator.
Concerned it was leak, they attempted to
tighten the cylinder connection while the
barbecue was in operation, not recognising
the left hand thread and ultimately loosened
the connection.
The escaping gas ignited and caused
serious burns to the operator.
» » Exposed sealing faces. The design of the
Type 21 connection is such that the sealing
face on the nipple is exposed to possible
damage, both mechanical and environmental.
Damage to the sealing face such as cuts
and abrasions can prevent a gas tight seal.
» » Soft seal degradation. Many Type 21
connections use soft seals (e.g. rubber bull
nose, O-ring) to provide a sealing face and
enable a gas tight seal to be made by hand,
using a hand wheel or similar.
Exposure to sunlight can cause some soft
seals to degrade prematurely. Degraded
seals can harden and crack, and frequently
detach from the connection. Degraded and
missing soft seals are often not identified and
compatible replacements are at times not
readily available.
The preliminary meeting included
stakeholders representing state regulatory
authorities, LPG supply companies, fire
authorities, suppliers, retailers, wholesalers,
manufacturers, service stations, caravans and
consumers. All attendees reviewed the safety
concerns and incidents related to the current
Type 21 connection.
GEA presented on a range of alternative
LPG cylinder valve connection designs that were
assessed against known causes of incidents
to establish how effectively the new connection
method would prevent incidents from occurring
as well as other features and risks.
Three connection designs were ultimately
shortlisted for more details review.
» » Type 21 connection with the introduction of
a check valve to prevent flow, unless a positive
connection is made.
» » QCC fitting, as used in New Zealand and USA.
» » QCC fitting modified to remove the Type 21
compatibility.
While each of the options were found to
provide a safer outcome when compared to
the current Type 21 fitting, they also maintain
different benefits and potential risks that need
to be managed, if introduced.
It was also noted that there have been
fewer incidents involving bulk cylinders (45kg
and larger). These cylinders are typically part
of a controlled installation with relatively fewer
disconnections and controlled clearances to
ignition sources.
As a result, the proposal to change the
cylinder connection is limited to the smaller
portable domestic cylinders with sizes
ranging from 3kg to 9kg.
Stakeholders generally acknowledged
the need for change and the potential safety
benefits that may be achieved. Feedback
was also provided during the meeting on the
potential risks that will require managment
during a transitional program.
This feedback will be considered and a
decision on a new connection will be made in
consultation with stakeholders and enable a
detailed transitional plan to be developed in
the near future.