BS 4791 : 1985
British Standard - Specification for Calorimeter Bombs.
Scope
This British Standard specifies requirements for materials, construction, design and performance for calorimeter bombs used for the combustion of materials as a means of determining their calorific value and the elements present in the products of combustion. Precautions for the safe use of the bomb and its ancillary equipment, together with routine maintenance procedures for keeping the calorimeter bomb in serviceable condition, are described in Appendix B, Appendix C and Appendix D.
Caution - This standard does not apply to calorimeter bombs for the determination of the calorific value of explosives or other samples if a pressure exceeding 50 bar could be generated.
Definition
For the purposes of this British Standard, the following definition applies.
Calorimeter Bomb - a high pressure vessel used for the determination of calorific values of combustible substances such as solid, liquid and gaseous fuels, foodstuffs and biological samples.
Note - The calorimeter bomb consists of a body, a cap and a closure ring. The test sample is contained in a crucible suspended from the cap. Oxygen is introduced through a valve in the cap and the sample is fired using electrodes that pass through the cap.
Warning Note - A known quantity of the given material is burned in the bomb and the heat released by the combustion is measured using a calorimeter. For most materials, it is necessary to introduce oxygen under pressure to ensure complete combustion. However, certain materials, such as pyrotechnics, generate sufficient oxygen for this purpose on combustion, and the introduction of gaseous oxygen in addition to that in the atmosphere is not therefore required and may be dangerous.
Design
The design shall be such that the bomb can be sealed and opened by hand without the use of tools of any kind.
The calorimeter bomb seal shall be so designed that, after tightening by hand, an increase of pressure in the bomb will tighten the seal and prevent leakage. Similarly, the fixings of the valve and the electrodes in the cap shall be so designed as to be leak-proof when the bomb is fired or brought up to proving pressure.
Materials
Bomb Cap and Body
The bomb cap and body shall be made of a material that is capable of withstanding the pressures generated by the combustion process and that shall not be corroded by the products of combustion of the test samples. The bomb cap and body shall each be machined from solid or hollow forgings or bar; they shall not be fabricated from components welded or brazed together. If the bomb cap and body are made of a material other than stainless steel, the material supplier should certify that the material has passed a correspondingly suitable test for resistance to inter-crystalline corrosion.
Closure Ring
The closure ring shall be made of material, such as aluminium bronze, capable of withstanding the pressure generated by the combustion process. The closure ring shall be machined from solid or hollow forgings or bar. It shall not be fabricated from components welded or brazed together.
Plating
The mating screw threads of the body and closure ring shall not be electroplated. Note - The external surfaces of the closure ring may be electroplated to provide protection against corrosion.
Sealing Ring
The ring used to seal the cap to the body shall be inert to the materials which may come into contact with the calorimeter bomb. Note - the ring should be made of suitable resilient material.
Valves
The valve or valves which are used for the admission and/or reverse of oxygen shall be suitable for use with pressures of up to 100 bar within the bomb. Note - Self-sealing valves fitted with high pressure valve core have been proved by experience to be suitable. For information on the availability of suitable self-sealing valves, apply to Inquiry Section (London), British Standards Institution, enclosing a stamped addressed envelope for reply. If a self-sealing valve is fitted, it shall be provided with a screw threaded cap to cover its inlet.
Electrodes and sample crucible
The electrodes and sample crucible shall be made of materials that are capable of withstanding the heat generated by the combustion process and that will not be corroded by the products of combustion of the test samples. Note - Details of the crucible to use for a given sample material will usually be given in the appropriate material test method.
