Presentation

Procedure

Storage tanks

Storage tanks

Many different sizes and types of tanks may be used to store 2-EHN. Heat must be allowed to dissipate.

In most respects, vertical tanks are the most practical overall solution. The low auto-ignition temperature (130°C) of 2-EHN can lead to an air-vapour explosion in the headspace of vessels, which can rupture, spilling the contents. Vapour-air explosions release less energy per unit volume than those resulting from self-reaction of the liquid. Peak blast force is a key design criterion. Vertical tanks can be fitted with a frangible roof to minimize damage in case of a pressure blow-out. API 650 is a widely used standard that can serves as a reference for specifying such tanks. Vertical tanks are also easier to configure with water deluge systems.

Horizontal tanks are used for the storage of 2-EHN. However, they have no ‘roof’, so the fitting of a frangible roof is not an option. If the contents are heated above 100°C, then there is a risk of tank failing at the dished ends, thus forming a « missile » with potentially catastrophic effects. Safety principles should be strictly applied to prevent heating of the product.

A fire in the storage area will heat the storage tanks. A fixed cooling-water deluge system to supply cooling water in event of fire is mandatory to minimize this risk. API 650 standard indicates that a system that delivers a cooling-water flow rate of at least 15 litre/minute/m2 of storage tank surface area can achieve effective cooling. If this volume of water is not continuously available for cooling purposes, additional non-insulating fire cladding of the tank walls could be considered within the context of the overall risk assessment of the storage facility.

Risks of tank bursting under pressure should be minimized.

Heat protection

The principle here is to protect the product from heat.

A deluge system provides the best protection against product overheating. No heating system of any kind should be installed, and existing heating systems must be permanently disabled. When laying out the route for new pipe work to carry 2-EHN, the designer should avoid sources of heat and potential fire. When using existing pipe work facilities, the designer should ensure that heated pipes are not used for 2-EHN.

As a general principle, locating 2-EHN storage tanks in an open area, away from inhabited buildings, is recommended. The site should be remote from possible fire hazards to minimize their exposure to external heat and fire impingement if fire breaks out. The extent of this separation is a local decision to be determined by the site risk assessment. For example, the NFPA 30 standard may be used to help determine the appropriate distance from other storage tanks and equipment, to maintain protection in case of fire.

Firewalls between the tanks will improve thermal protection. If sufficient space is not available for firewalls, then non-insulating tank-wall fire cladding may provide additional protection. Screening walls and non-insulating fire cladding may be combines to achieve acceptable protection. The better the protection, the longer the stored 2-EHN will endure external heating, and the lower the risk of thermal decomposition within the storage system. Instrumented fire and heat detection systems should be installed.

Venting

Bulk storage vessels should preferably be vented directly into the atmosphere, far from ignition sources, if local regulations permit. Conservation vents with frangible roof seams are also acceptable. For smaller equipment, standard engineering practices for design of emergency discharge should be followed.

Tanks containing 2-EHN should preferably be at atmospheric pressure. The vent outlet is to be positioned in a safe area, sufficiently high and far from ignition sources.

Containment wall or bunding

To minimize the consequences of a spill and leakage into the environment, a containment wall (bund) should surround tanks, with a minimum capacity to handle tank contents and deluge water.

Drum storage

Ensure good ventilation during drumming / de-drumming.

Filled drums are to be stored far from heat sources and other flammable products, and protected by firewater. Special care should be taken when opening drums, as they may be pressurized.