Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 2 Proposed Development
designed to reduce the oil in water content (OIW) from typically 100‐500 ppm on the inlet to less than
25 ppm on the outlet.
The level of PW in each vessel is controlled by interface level controllers. The position of the interface
may be readily adjusted, to suit operating conditions and water cut, to achieve sufficiently clean
discharged water.
Each PW flow is measured. Each line is also provided with corrosion monitoring probes and a sample
point.
2.7.5. FLARE SYSTEM
The flare and vent systems are provided to collect releases of hydrocarbon gas from process systems
under normal and emergency conditions and dispose of them safely.
The flare system collects releases of a significant rate which are burnt, whereas the vent system
collects small quantities of gas vented as a result of ‘breathing’ of low‐pressure tanks, and releases
these directly to atmosphere without being burnt. Flare gas is burnt at the end of a boom
cantilevered from the northeast corner of the platform. Vent gas is released at a point halfway up
this boom.
In general all relief valves fitted to process systems, which prevent mechanical failure due to
overpressure, are directed into flare collection headers.
Flared gas is collected, has condensate removed, and is burnt in two separate systems:
HP system, which takes gas from all moderate or high‐pressure sources. The gas flows via
the HP knock‐out drum, V2501, to the HP flare tip where it is burnt. The HP flare tip is a low
emissivity type. It operates at high velocity to burn gas efficiently and without smoke.
LP System, which takes gas from low‐pressure users which cannot flow into the higher
pressure HP System. It also takes gas releases from blowdown of gas compressors (where a
very low final pressure is required to prevent compressor seal leakage). The LP flare gas flows
via the knock‐out drum, V2502, to the LP flare tip where it is burnt.
The HP and LP flare tips are mounted as a single assembly at the end of a 73.5 m long boom, which is
positioned at the north east corner of the platform and angled at 45° to the horizontal. Boom length,
position and angle were chosen to take advantage of prevailing wind direction in blowing the flared
gas away from the platform, and minimise radiation levels and the effect of hot flare plume on the
platform.
Total fluids flared on the Clyde platform in 2010 was 17,755 tonnes (EEMS, 2010).
2.7.6. POWER GENERATION AND FUEL USE
The main power is generated by seven gas turbine generators. Auxiliary power, produced by two
diesel driven generators, is available to maintain supplies to priority services in the event of failure of
the main stream. The primary power generation systems on the Clyde platform are outlined in Table
2‐11.
A further level of emergency support is provided by the uninterruptible power supplies system. This
is battery powered and ensures that life‐support and safety systems are maintained under emergency
conditions. The batteries are kept charged during normal operations by the main electrical supply.
2‐ 18 D/4114/2011