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Allison Engineering

Innovative Solutions for
Process Control

Process Industry

Nitrogen Blanketing / Solvent Recovery

Tank blanketing with nitrogen is a common safety technique used throughout the world. The inert Nitrogen is used to prevent the creation of potentially flammable atmospheres and the amount of nitrogen pumped into or released out of the tank’s vapour space is controlled by a predetermined pressure set point. As product is pumped from the tank, the vapours inside expand and the pressure falls below the set point, more nitrogen is then introduced. As the vessel is filled, the vapours begin to compress and the nitrogen vapours are released and usually sent
to a vapour recovery system.

However, without accurate measurement and control of the nitrogen, too much gas results in wasted money and possible tank or component damage and too little gas is ineffective. Furthermore, variations in liquid level combined with changes in temperature and pressure mean mass flow measurement is the preferred choice to ensure accurate and repeatable nitrogen delivery.

The ST100L can accurately measure Nitrogen mass flow over a wide 100:1 turndown & is both ATEX approved & SIL rated. In addition, limited straight pipe upstream is not a problem due to its unique Vortab static plate flow conditioner.

Direct monitoring of the pressure relief valve that feeds to solvent recovery unit is also possible with the FLT93 flow switch, SIL2 rated, no moving parts & capable of very low flow detection.

Key Features

SIL RATED  / ATEX certified

Flow measurement & Flow switches

No moving parts

316 st/st or Hastelloy C276 wetted parts