How to deal with excessive pressure in LNG storage tanks

When encountering elevated pressure within an LNG storage tank, a multi-faceted approach is essential to restore safe operating parameters. Here's a breakdown of the primary strategies employed:

Initiating Decompression: The initial step involves activating the designated decompression system. Careful observation of the pressure gauge is crucial during this process. Should the pressure remain elevated despite decompression efforts, the pressure gauge itself might be malfunctioning or damaged, necessitating its immediate replacement with a calibrated and reliable substitute. This step ensures accurate readings for informed decisions.

Modulating the LNG Inflow: A critical preventative measure is the meticulous management of the liquid natural gas (LNG) supply. Overfilling the tank beyond its specified capacity can lead to excessive pressure buildup. Therefore, the feed rate must be carefully regulated, ensuring that the tank's safe operating limits are not exceeded. This proactive adjustment helps maintain a stable pressure environment.

Implementing Temperature Reduction: Lowering the internal temperature of the storage tank provides an effective method for pressure management. This is often accomplished by engaging a dedicated cooling system, which extracts heat from the tank's contents. By decreasing the thermal energy within the system, internal pressure is directly reduced.

Controlled Vapor Release: In situations where the pressure has risen significantly, a controlled release of a portion of the vaporized gas is required. This process carefully vents a quantity of gas into a safe location, thereby alleviating the internal pressure within the tank. This procedure must be carefully executed according to established safety protocols.

Evaluating Thermal Insulation Integrity: A recurring pattern of high pressure often indicates a potential compromise in the tank's insulation performance. A degradation in thermal efficiency causes increased boil-off, leading to pressure increase. To assess this, a vacuum integrity test using a specialized vacuum tester is necessary. If the vacuum level is outside the specified parameters, consultation with the manufacturer is vital, as it might point to insulation failure requiring remedial action or repairs.

Conducting Rigorous Leakage Examination: A thorough external inspection of the entire storage tank is paramount to identify any potential leak points. This meticulous examination encompasses checking the seals, flanges, valves, and welds for any anomalies. It's critical to ensure the structural integrity and pressure containment capabilities of the tank, which involves verifying the sealing performance and compressive strength of all connections and components to avert any unforeseen incidents.