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Covers procedures for using the 1108 Oxygen Combustion Vessel for calorific value determination and sample preparation.
Lists other Parr manuals relevant to bomb calorimetry and safety.
Essential safety measures and operational guidelines for using the combustion vessel.
Details special alloy, chlorine-resistant, and 1108B models.
Defines limits for sample mass and caloric release for safe operation.
Explains how to attach the fuse wire to the bomb electrodes for ignition.
Specifies adding liquid as a sequestering agent and absorbent.
Details the procedure for securely closing the bomb head to the cylinder.
Instructions for manually filling the bomb with oxygen using the 1825 connection.
Connecting ignition unit, firing process, and critical safety warnings.
Procedure for removing and handling the bomb and its contents after firing.
Describes using a luer fitting and syringe for recovering products.
Covers particle size, moisture, combustion aids, and pelletizing.
Types of capsules (stainless steel, silica, Pt-Rh) for non-volatile samples.
Gelatin capsules, foodstuffs, coarse, corrosive, and liquid samples.
Tape-sealed holders, heavy oils, explosives, and high-energy fuels.
Causes and remedies for incomplete combustion in the oxygen bomb.
Guidelines for optimal oxygen pressure for efficient combustion.
Routine care, inspection, and replacement of bomb parts like valve seats and O-rings.
Checking screw cap threads for wear and safety.
When to return the vessel for factory repair, testing, and proof tests.
Checklist for replacing and examining parts after 500 tests.
List of all parts with their corresponding item numbers and descriptions.
List of pre-assembled components and their part numbers.
Detailed list of parts and their descriptions for the ignition unit.
Detailed list of parts and their descriptions for the oxygen filling connection.
The Parr 1108 Oxygen Combustion Vessel is a specialized laboratory instrument designed for determining the calorific values of solid or liquid combustible materials within a Parr calorimeter, or for preparing samples for chemical analysis in a 1901 Oxygen Vessel Apparatus. This manual provides comprehensive instructions for its operation, maintenance, and safety, emphasizing the importance of understanding its capabilities and limitations.
The primary function of the 1108 Oxygen Combustion Vessel is to facilitate the complete combustion of samples in a high-pressure oxygen environment. This process, historically known as Oxygen Bomb Calorimetry, allows for the precise measurement of heat energy released from a sample or the preparation of combustion products for subsequent chemical analysis. The vessel is designed to contain the high temperatures and pressures generated during combustion, ensuring a controlled and safe reaction.
Sample Preparation and Loading: The manual details careful procedures for preparing various sample types. Solid samples are ideally reduced to 60-mesh or smaller and compressed into pellets using a Parr Pellet Press. This pelletization helps control the burning rate and reduces the chances of incomplete combustion. For samples that are difficult to ignite or burn slowly, combustion aids like benzoic acid or ethylene glycol can be mixed with the sample. It's crucial to ensure that the total combustible charge (sample plus any aids) does not exceed 1.1 grams, and never more than 1.5 grams, to stay within safe operating limits.
Liquid samples, especially volatile ones, can be handled using Parr 3601 Gelatin Capsules, which telescope together to provide a secure friction fit. Non-volatile liquids and oils can be weighed directly into open combustion capsules. For volatile samples, tape-sealed sample holders, using a standard 43AS combustion capsule with a flat top rim or a 43A6 platinum capsule with a spun rim, are recommended. The tape, such as Borden "Mystic Tape" No. M-169-C or 3M Transparent Tape No. 610, must be free of chlorine and low in sulfur. A small opening is pricked in the tape before filling the bomb to prevent disc collapse when pressure is applied.
Fuse Attachment and Liquid Addition: A 10 cm length of Parr 45C10 nickel alloy fuse wire (or platinum wire for special procedures) is fastened between the two electrodes of the bomb head. Quick-grip electrodes simplify this process, requiring only insertion of the wire ends into the eyelets and pushing down the cap to pinch the wire. The fuse loop should be positioned slightly above the sample surface, not submerged, to ensure optimal ignition. A small amount (typically 1.0 mL) of distilled or deionized water is added to the bottom of the bomb as a sequestering agent and absorbent for combustion products.
Closing and Filling the Bomb: The bomb head, with the sample and fuse in place, is carefully slid into the cylinder, ensuring the sealing ring is in good condition and moistened for smooth insertion. The screw cap is then hand-tightened firmly to a solid stop, with no threads exposed. Oxygen is charged from a standard commercial tank using the 1825 Oxygen Filling Connection. The initial charging pressure should not exceed 40 atmospheres (590 psig), and the gas should be admitted slowly to prevent sample displacement. The recommended charging pressure range is typically between 25 and 35 atmospheres, as lower pressures often promote better combustion due to higher gas temperatures and greater turbulence.
Firing the Bomb: Before firing, the bomb must be completely submerged in a calorimeter water bucket or a water bath. The 2901 Ignition Unit, connected to a grounded electrical outlet, provides the current for firing. The ignition wires are connected to the bomb head terminals. It is critical to check for any gas leakage while the bomb is submerged; if bubbles are observed, the bomb must not be fired. During firing, the operator must stand away from the bomb, and the firing button should be pressed for about 5 seconds. The indicator light on the ignition unit confirms current flow, extinguishing when the fuse burns off.
Recovery of Combustion Products: After firing, the bomb is left in the cooling medium for at least 3 minutes to allow for complete condensation of residual vapor. The valve knob is then opened slightly to slowly release residual gas pressure over at least one minute to avoid entrainment losses. The screw cap is removed, and the bomb head is lifted straight out. The interior surfaces of the bomb and combustion capsule are washed with distilled water, and the washings are collected for analysis (e.g., titration for calorific tests, sulfur analysis). An optional recovery procedure using a luer fitting and syringe allows for washing the bomb without opening it, ensuring a more complete recovery of combustion products.
Routine Maintenance: Regular maintenance is crucial for the safe and reliable operation of the 1108 Oxygen Combustion Vessel. Key components requiring frequent attention and replacement include the 230A O-ring head gasket, all 238A sealing rings, the 415A O-ring, and the 20VB PCTFE valve seat in the needle valve. These parts should be replaced after every 500 firings or every six months, whichever comes first. For samples containing chlorine, this frequency increases to every 250 firings. The manual provides detailed instructions for replacing the valve seat, including tightening the 397A compression nut to 100 inch-pounds of torque.
The 238A sealing ring in the insulated electrode should also be replaced with the same frequency as the valve seat, and the 411A terminal nut must be kept tight to prevent misfires and unwanted heating effects. The threads on the screw cap should be routinely checked for wear or deformity. A specific procedure is outlined to check the extent of thread wear, and if the vertical deflection exceeds 1/32 inch (0.030"), the screw cap must be replaced.
Corrosion and Cleaning: The 1108 vessel is constructed from a special columbium-stabilized stainless steel, offering excellent resistance to mixed nitric and sulfuric acids. However, burning samples containing halogen compounds can cause corrosion. For such applications, the 1108CL Chlorine-Resistant Bomb, made of a superior alloy, is recommended for its enhanced corrosion resistance. If a corrosive film develops on the bomb surfaces, it should be removed by proper polishing. After each combustion, especially with high sulfur or caustic samples, the bomb should be emptied and washed promptly to prevent etching or corrosion.
Factory Service and Proof Tests: Parr Instrument Company offers repair and testing services for oxygen combustion vessels. A factory test is recommended after every 5000 firings, or if the bomb has been subjected to excessive charge, internal component ignition, machining by non-factory sources, damage from corrosive vapors exceeding 80% of corrosion allowance, or any changes in the cylinder or screw cap threads. The manual provides shipping instructions for returning the bomb for service.
Safety Precautions: The manual emphasizes several critical safety precautions:
By adhering to these detailed operating and maintenance instructions, users can ensure the safe, efficient, and long-lasting performance of the Parr 1108 Oxygen Combustion Vessel.
General| Model | 1108 |
|---|---|
| Material of Construction | 316 Stainless Steel |
| Maximum Temperature | 350 °C |
| Temperature Range | Ambient to 350 °C |
| Capacity | 2000 mL |
| Volume | 2000 mL |
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