LP Flash Purpose

After high-pressure or intermediate flash stages, liquid still contains dissolved light components. LP flash at 1-5 bar releases remaining volatiles preventing vapor generation in storage tanks. Final separation step before liquid stabilization or sales.

Operating Pressure

Typically 1-3 bar, sometimes atmospheric. Low pressure vaporizes trace light ends remaining after upstream separation. Pressure selection balances liquid stability versus vapor handling. Too low pressure flashes valuable components unnecessarily.

Drum Design

Vertical or horizontal vessel with liquid inlet from upstream stage, vapor space for light ends disengagement, vapor outlet to recovery or flare, stabilized liquid outlet to storage, level control. Simple design as vapor volume relatively small.

Vapor Composition

Contains lightest components from liquid - methane, ethane, some propane. Lower concentration than HP flash vapor. Volume smaller making compression recovery economically marginal in many applications. Often routes to fuel gas or flare.

Material Selection

Carbon steel construction suitable for low-pressure service. Lighter design than HP vessels. Operating temperature typically ambient. Design accommodates atmospheric or slight positive pressure.

Liquid Stabilization

Removes volatiles preventing excessive vapor pressure in storage. Critical for condensate, crude oil, and products requiring stable storage at atmospheric pressure. Prevents tank overpressure and atmospheric losses.

Applications

Crude oil stabilization before storage, condensate degassing, NGL final flash, geothermal brine separation, wastewater stripper feed preparation, and any process requiring final low-pressure degassing before liquid handling.

Flash Efficiency

Low pressure maximizes light ends removal. Longer residence time ensures equilibrium. Adequate vapor space prevents liquid entrainment. Simple gravity separation sufficient at low vapor rates.

Level Control

Maintains inventory for downstream flow. High-level protection prevents vapor line flooding. Integration with upstream flash stages coordinates liquid flow through separation train. Simple automated control.

Vapor Handling

Small vapor volume typically routes to fuel gas if composition suitable. Flaring option for upset conditions. Some facilities compress for recovery if economics justify. Decision depends on vapor value and handling costs.

Storage Interface

Stabilized liquid flows to atmospheric storage tanks. Reduced vapor pressure prevents tank breathing losses. Meets pipeline or transport vapor pressure specifications. Final product quality achieved through LP flash.

Construction Standards

Design per ASME Section VIII or atmospheric vessel codes depending on pressure. Materials for hydrocarbon liquid and vapor service. Relief protection against thermal expansion. Complete documentation with flash calculations.

ERGIL LP flash drums provide final low-pressure degassing stabilizing liquids for safe storage and transport in oil, gas, and process operations.