Parr Fixed Bomb & Bucket Technology Parr Removable Bomb & Bucket Technology

P

arr Model 6300 Calorimeters utilize a design where thebomb and bucket are not removed from the calorimeter during routine operations. This concept has made it possi- ble to provide new levels of automation of not just the data collection and reporting, but of the entire calorimetric determination. Oxygen Filling The oxygen supply is con-nected to the fixed bomb so that the oxygen charge is auto- matically added to the bomb before the preperiod equilibri- um period.

R

emovable bomb calorime-ters are the more tradition-al design most users recognize. In this design the oxygen bomb and bucket are removed from the calorimeter for loading the sample and filling the bucket with the carefully measured amount of water which absorbs the energy released in the combustion. Exhausting the Bomb At the end of the test thegasses in the bomb are auto- matically released while the calorimeter is being returned to its starting temperature. Bomb Closure Recommended Applications The 6300 Calorimeter utilizesa patented closure design which seals and locks the head into the cylinder with simple 23°twist. While these bombs do notfeature the automatic bomb and bucket handling features of the fixed bomb design calorimeters, the removable bomb calorimeter will remain the calorimeter of choice for users with one or more of the following applications or preferences: •Low to medium testing loadswhich will not justify the higher cost of more auto- mated systems.•Student instruction applica-tions with an emphasis on the basic principals of calorimetry.•Applications which requireunusually high pressures, platinum lining or one of the other special purpose oxy- gen bombs. •Combustions which produceunusual amounts of ash or other corrosive residues that would damage the automat- ic discharge system.•Users who chose not to perform the additional main- tenance that the fully auto- matic instruments require.•Users who presently havea number of 1108 oxygen bombs and other acces- sories in their laboratories. Draining the Bucket The hot water in the bucketis automatically drained from the bucket at the conclusion of the test and replaced with cool- ing water to bring the bomb and bucket rapidly back down to the starting temperature for the next test. Measuring and Filling the Calorimeter Bucket The bomb in the 6300Calorimeter is surrounded by a bucket designed to provide smooth circulation and uniform volumetric filling. The bomb head closure action also seals the bucket at the same time the bomb is closed. The unique design of this bomb-jacket combination permits rapid and automatic volumetric filling of the “bucket” water for each test. Washing the Bomb
1108 Oxygen Combustion BombA391DD Oval Bucket At the conclusion of the test the inside of the bomb is washed to remove the products of combustion from the bomb. These bomb washings can be collected if tests will be run for sulfur, chlorine or other ele- ments released from the organ- ic matrix during combustion. The result of the automation of the above steps plus the automation of the calorimetric measurement itself will save approximately six minutes of operator time per tests when compared to any removable bomb calorimeter.
1136 Oxygen Combustion Bomb

Longer Bomb Life

O

ne of the not so obvious advantages of the fixed bomb designs is that the bomb isalways washed as soon as the final temperature rise can be extrapolated. Generally this is within 4-5 minutes of the firing of the bomb. This minimizes the time any acids produced by the combustion can attack the inner surfaces of the bomb. We are seeing much better service life for the 1136 Bombs used in corrosive service because of this.

Materials of Construction

I

n 1911 Professor S.W. Parr developed his Alloy Illium G to resist the hot mixtures of sulfuric and nitric acids produced in the oxygen combustionof coal. This eliminated the need for gold or platinum liners for the bombs and made it practical to do oxygen bomb calorimetry as a routine labora- tory test. While we no longer use Illium G, we use the most corrosion resistant alloys we can find. For routine combustions we build our bombs of Carpenter 20 Cb3 Stainless Steel which is richer in chromium and con- tains three times as much nickel as Series 300 Stainless Steels. For high chloride service we use Alloy G-30 which adds cobalt and molybdenum to resist the corrosive effect of the chloride ion.
6 Parr Instrument Company www.parrinst.com 7