HSE's role in gas supply emergencies
The Health and Safety Executive's (HSE) role in gas supply emergencies
- If the forthcoming
winter is severe there is a risk that gas demand will exceed the gas supply
available from Britain's offshore fields, the interconnector pipeline with
Belgium and the Isle of Grain LNG import terminal. Ofgem has made
clear its concerns and monitors the market closely to ensure that
anti-competitive behaviour is not restricting gas supplies. A shortage of
gas, if not managed properly, could give rise to a risk of a gas supply
emergency and this document summarises HSE's role in this regard.
What is a gas supply emergency?
- A gas supply
emergency arises when the pressure of the gas in the pipeline network is
reduced, thus causing a danger to the public.
- Gas has to be
transported at an adequate pressure to ensure that gas appliances work safely.
If the pressure in the network is too low then appliances may not burn the gas
properly resulting in incomplete combustion and noxious fumes. Alternatively, if the appliance does not have an effective protective device,
flames may go out only for the gas to be re-ignited when pressure is restored
resulting in a fire or explosion.
- HSE does not have
responsibility for the security of gas supplies or the wider social and economic
consequences of a shortage of gas. Ofgem's web-site contains more information on security of supply issues and the winter outlook.
How can shortages of gas result in a gas supply emergency?
- For the pressure in
the network to be maintained there has to be a balance between gas supply and
demand. Simply, gas taken from the network by consumers has to be replaced by
gas flowing into the network from producers, gas processing facilities, storage
facilities, interconnector pipelines and LNG import facilities.
- In a severe winter
gas demand goes up as households use more gas for heating and other consumers
(such as power stations) increase their demand on the network. This demand has
to be met but is reliant on gas being available at the right place and time. If
there is not enough gas available, demand has to be cut to maintain the safe
pressure in the network.
Who is responsible for managing the safety of the gas networks?
- There are several
participants in the gas industry. Gas conveyors (also known as transporters)
operate the gas network and transport gas through pipes to consumers. The
network in the UK consists of over 280,000 km of transmission and distribution
pipes transporting gas to some 20 million consumers. Currently there are five
major gas conveyors: National Grid who operate the high pressure transmission
system and four distribution networks, and four other companies each operating a
distribution network. There are a number of smaller gas conveyors who operate
networks downstream of these major distribution networks. Each network operator
is responsible for ensuring safe pressure in their network and for co-operating
where necessary to ensure the safety of other networks.
- The Network Emergency Co-ordinator
[NEC] is responsible for coordinating the actions of all gas conveyors to
minimise the risk of a gas supply emergency. Currently National Grid is the NEC.
The gas networks have to co-operate with the NEC as necessary.
- Gas shippers buy gas from
producers to sell to suppliers. They also employ gas transporters to transport
gas to supplier's consumers.
- Suppliers buy gas from shippers to sell to consumers.
- Consumers purchase gas from gas suppliers. Consumers include large industrial
sites, gas fired power stations, smaller industrial and commercial sites,
hospitals and domestic premises.
- Gas conveyors and the NEC have
the prime responsibility for ensuring safe pressure in the networks. They
describe their arrangements for doing this through their GSMR safety cases.
Gas Safety (Management) Regulations 1996 [GSMR]
- Under GSMR, each gas conveyor
and the NEC has to have a safety case which describes how they manage the safety
of the gas networks. How they minimise the risk of a gas supply emergency is a
key part of the safety case. The safety cases have to be accepted by HSE before
gas can be conveyed in the network. Gas conveyors and the NEC have a legal duty
to comply with their safety cases and HSE inspects the conveyors to verify that
the arrangements in the safety case are in place and working correctly. HSE also oversees industry emergency exercises aimed at testing arrangements for
dealing with a potential or actual supply emergency.
- Gas conveyors and the NEC rely
on other industry participants to enable them to run the networks safely.
Therefore GSMR requires gas producers, processing facilities, storage site
operators, shippers, suppliers and others, including consumers, to co-operate
with them as is necessary, to minimise the risk of a supply emergency. For
example, if demand has to be cut to maintain the pressure in the network because
there is a shortage of gas, the gas conveyors may instruct gas consumers to stop
using gas. There is a hierarchy in which this is carried out so that sites like
hospitals and domestic consumers have gas as long as possible.
- Safely isolating certain
consumers whilst maintaining safe pressure in the rest of the network is not a
supply emergency and forms a key part of the safety case.
Gas in storage
- There are a number of gas
storage sites in the UK used by gas shippers and others to store gas. Gas in
storage plays an important role in minimising the risk of a gas supply emergency
throughout the winter period. Under arrangements in the gas conveyors' and
NEC' safety cases, a minimum quantity of gas is retained in storage to meet
domestic demand, demand from priority consumers and demand from other consumers
who are difficult to isolate safely from the network, such as 'embedded'
industrial and commercial sites. Where necessary, gas is taken from storage to
minimise the risk of a supply emergency to these consumers.
there is not enough storage capacity to meet all demand and some consumers, such
as large industrial sites, may need to be isolated in a safe and timely manner.
Therefore it may be necessary for gas conveyors to direct large industrial sites
to stop using gas both to protect them and ensure the safety of the rest of the
The Gas Safety (Management) Regulations 1996 [GSMR] define a gas supply
emergency being an 'emergency endangering persons and arising from the loss of
pressure in a network...' . The definition of danger is limited to risks
from the gas itself.