H-70 Propellant

H-70 (hydrazine, 70% aqueous solution) is used as the propellant in emergency power units (EPU) on the F16 and other single engine aircraft. When there is a loss of engine power, the EPU activates and provides power to maintain the aircraft’s vital functions such as hydraulic and electrical systems.

H-70 does not work like conventional propellants in that it does not burn to provide energy. Instead it is passed over a catalyst bed which causes the hydrazine to decompose into gaseous nitrogen, hydrogen and ammonia. The presence of the water acts to modify the decomposition temperature in order to prevent thermal damage to the catalyst bed and to the turbine parts. As the water removes heat, it is turned into steam which aids in powering the EPU.

Boiler corrosion is costly. Nationally, the bill for metal repairs, lost energy and time lost because of maintenance shutdowns runs into millions of dollars each year. Yet, corrosion in boilers is relatively inexpensive to prevent.

Most boiler corrosion is due to dissolved oxygen carried into the steam generating system with the feed water. The obvious answer to the problem is to get rid of the oxygen before it can cause damage. In most systems, this is done by both mechanical oxygen removal in deaerators, and by the addition of chemical reducing agents. These agents, which combine rapidly with dissolved oxygen to form harmless reaction products, are known as “oxygen scavengers.”

Scav-Ox® 35% hydrazine solution has proved to be an extremely effective oxygen scavenger. At high boiler temperatures it outperforms sodium sulfite, the other most commonly used oxygen scavenger. Calca Solutions has broadened the scope of hydrazine’s advantages with a 35% hydrazine solution that has been catalyzed to react rapidly with oxygen at low temperatures: Scav-Ox® II (organic catalyst).

Since mechanical features, physical conditions and water treatment chemistry of various steam generating systems vary, Calca Solutions’ line is designed to provide the right product for the right purpose. Most important, the catalyzed product has removed the only significant disadvantage of hydrazine – its slowness, compared with sodium sulfite, in reacting with oxygen at low temperatures.

Together, Scav-Ox® and Scav-Ox® II offer effective oxygen removal over a wide range of boiler conditions. In addition, all have further important advantages: