[ safety ]
Purge Inlet Pressure Gauge
Gas Supply Temperature Element
Inlet Isolation
To Gas Train
Drip Leg
Y-Strainer
Fig . 1 . Gas train entrance arrangement , including an initial drip leg immediately followed by a Y-strainer and instrumentation .
normally open but can be closed for maintenance purposes without affecting the upstream process . Two simple separation methods are used in conjunction with regular maintenance and cleaning to remove any contamination .
A chamber with ample volume and drain connections over which the fuel gas is passed , also known as drip leg , is first used to trap any unwanted debris and moisture that could damage downstream instruments or affect the operation of the burner . Then a Y strainer follows the drip leg , providing a physical barrier to capture any solids missed by the drip leg . A pressure gauge and temperature element are also used near the gas inlet to ensure the gas is within the operating conditions of the burner and gas train .
Considering that the gas train is used for hydrogen service , it is essential to purge the entire volume with an inert gas , such as nitrogen , in several situations . These include during initial installation , before the first use , between any changes in service , before any maintenance , modifications , or repairs , and prior to returning the system to service . An inlet port for the inert purge gas , equipped with its own dedicated isolation valve , should be positioned immediately after the first isolation valve . This arrangement ensures that when the purge gas is introduced into the system , it will purge the entire volume of the gas train . The system should be purged until the hydrogen concentration is below 1 vol %. Starting with a concentration of 100 % hydrogen , a total of 5 volumes of inert purge gas would be required . The inert gas supply can be obtained from a standalone cylinder or canister manually connected to the gas train , or from a permanent inert gas supply system serviced by a larger onsite inert gas storage vessel . The arrangement of the inlet to the gas train is depicted in Figure 1 .
Upstream of the gas train , hydrogen is typically stored and transported at high pressures to ensure appropriate density and mass flow rate , given its low molar mass . However , the supply pressure to the burner is likely much lower and needs to be controlled . A pressure regulator should be used in tandem with a pressure indicator ( optionally also a transmitter ) to ensure
26 Hydrogen Tech World | Issue 11 | August 2023