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FIGURE 5 ORIGINAL HDPE IP GAS ROUTE FIGURE 6 DRAINAGE CHAMBERS FOUND DURING 40MWE DERWENT SITE PREPARATION

FIGURE 7 150MM CLEARANCE BETWEEN LV CABLE AND IP STEEL FIGURE 8 SCHEMATIC OF DERWENT PHASE 1 GAS PRESSURE FLOW
GAS PIPE AT DERWENT

averages about 10°C. Given the required operating pressure (MOP) of 7bar within site, the demolition of part of the
pressure reduction from 38bar to 7bar, a temperature range of 0°C to 40°C. aforementioned power station revealed
and subsequently to 250/260mbar, a PE100 and multilayer PE100/PE100 existing drainage chambers.
decrease in the temperature of the gas pipes shall not be operated below 0°C. Trial holes were carried out on
was expected at the outlet of the PRS the rest of the gas route to eliminate
from 10°C to about -10°C. This is due to Solution A pre-heater module as shown potential risks around utilities not
the Joule-Thomson effect. in Figure 4 was incorporated to heat up captured on the utility search.
For every bar of pressure reduction, the gas to approximately 23.1°C. Results showed that oil filled cables
there is a subsequent temperature This was prior to the pressure were located between 1.2m and 1.5m
reduction of 0.5°C. This poses a huge risk let down, with an expected outlet below the ground surface which
to the downstream gas infrastructure. temperature of 8.1°C of gas on the discounts a possibility of an open cut
downstream pipework. The boiler installation or directional drill to install
Joule-Thomson effect In 1852, British consumes an average of 82.60kWth of either the gas pipe or the LV cable.
physicists James Prescott Joule and gas at a flow rate of 9,937Nm³/h. This
William Thomson discovered that is subject to weather conditions. Power supply The ultrasonic meter and
temperature change can occur in gas as electronic devices on the PRS and pre-
a result of sudden pressure change over Underground utility services and heater module required a 380V 50Hz
a valve. This is referred to as the Joule- structures UKPR’s proposed 40MWe site AC 3ph 16Amp power supply.
Thomson effect. was situated at the old decommissioned Due to limited information on the
As shown in Figure 3, the Derwent power station. underground utilities, I was faced with
temperature change pertaining to the Unfortunately, the as-built drawing the challenge of installing 305m of
Joule-Thomson effect can occur when a for this site was incomplete and many 95mm AL cable below ground to the
flowing gas passes through a pressure details were unknown. This posed feeder pillar.
regulator, which acts as a throttling a huge risk to the installation of the
device, valve, or porous plug. HDPE IP gas pipe and the low voltage Solution Based on the outcomes of
(LV) cable which would share the same the trial holes, I concluded that the
Risk of temperature to downstream trench as the gas pipe. low voltage (LV) cable needed to be
infrastructure According to Gas Industry The LV cable was required to supply installed above ground on the steel gas
Standard (GIS) PL2:8 and IGEM/TD/3 power to the pre-heater module and the pipe, allowing approximately 150mm
Edition 5, all PE100 SDR11 need to ultrasonic meter. clearance in reference to IGEM/UP/2
be able to operate at a maximum In preparing our proposed 40MWe Edition 3/Clearances. See Figure 7.

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