Firing Wire 3K-4-093

Firing Wire (1 packet of 5)

The firing wire is used in the complete lid assembly for calibration of calorific determination. The firing wire is used in an oxygen bomb calorimeter inside the bomb or vessel for the purpose of igniting a substance in an oxygen atmosphere.

Packaging: Firing Wires are packaged in packs of 5 wires.

Compatibility: CAL3K-A / CAL3K-AP / CAL3K-F / CAL3K-S / CAL3K-ST / 3K-4 Vessel / 3K-5 Vessel / 3K-5S Vessel / 4K-4 Vessel

Life Span: Between 5-20 firings. The firing wire should be replaced between 5-20 firings, depending on the sample being tested.

The substances can be any material as long as it burns. For the ignition to happen a current is sent through the firing wire, the firing wire gets hot and ignites the sample substance directly or ignites a “fuse” made out of cotton.

The firing wire material is nichrome or platinum. Nichrome has a melting point of -1400 degrees Celsius. Platinum melts at -2000 degrees Celsius. Platinum is seldom used because it is very expensive. The firing wire lasts only for a defined amount of ignitions. The firing wire lasts for 5 to 50 firings. The number depends on the sample material, the burning pattern and the ignition current. The current is adjustable from the oxygen bomb calorimeter to suit your application. The adjustment is done by experimenting.

The practical application of the firing wire : It is connected between the two electrodes and the cotton thread is tied to it. The firing current, which makes the firing wire glow, it adjusted by the firing voltage setting in any of the DDS Bomb Calorimeters.

A firing voltage of 25V is a good start. The voltage should be adjusted up if miss fires are experienced, and the cotton thread is lying in the crucible. In this instance the sample must be discarded and the determination repeated with a new sample and cotton thread.

The firing voltage must be adjusted down if the firing wire breaks (melted) too often, but not as a result of a violent combustion. It can happen that the sample burns with a flame directed at the wire, thus heating it up beyond the melting point of the firing wire, and the wire breaks and lands up in the crucible as molten pearls of nichrome.

Even when the firing voltage of the bomb calorimeter is correctly adjusted the wire will not last forever. The wire oxidizes and gets thinner with every firing, and eventually falls and needs to be replaced.

This is done by pushing the ferrules up, removing the wire ends, and inserting the new wire in the slits. The new wire is secured by jamming the ferrules over the wire. It is advised to keep spares of firing wire handy.

It is advisable to use the supplied firing wire because it is performed and of constant length and diameter. Any other diameter could damage the firing electronics.

The electrical energy used to heat up the firing wire can be compensated.