Articles
Applying Safety Instrumented Systems To Raw Natural Gas Complexes
January 30, 2009
•Case Study: Applying Safety Instrumented Systems To Raw Natural Gas Complexes
by Allen Hood, Pressure Product Manager, ABB Inc.
In the production of gases from natural gas wells, safety instrumented systems (SIS) can protect critical piping and dehydration processes from high pressures, while minimizing the risk of undesirable emissions. Raw natural gas commonly contains varied concentrations of methane, carbon dioxide, hydrogen sulfide, nitrogen, helium, and water at high pressures. The raw gases contain both free and entrained water; dehydration systems remove the water.
Removing water
Dehydration facilities typically collect the raw natural gas from multiple wells that are miles apart. Their purpose is to minimize the corrosive nature of the gas. Following dehydration, the gas goes to a plant that separates the dried gas into its various components in a form suitable for marketing.
Raw gases often flow from the well field in insulated underground pipes at pressures that can range upwards of 3000 psi. Typically, they first enter production manifolds that mingle the gases from several wells. Here a basic process control system, in conjunction with expansion vessels, reduces the gas pressure substantially, permitting free water to drop to the bottom of the vessels for disposal.
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