STANDARD OPERATING PROCEDURE: Use of Autoclaves for Hydrothermal Experiments  

Oregon State University, Department of Chemistry
Standard Operating Procedure (SOP): Use of Autoclaves for Hydrothermal Experiments (ver. 1.0)
Author: Mas Subramanian (mas.subramanian@oregonstate.edu)
Safety Web Inception Date: 4/19/2011
Revised: N/A

Chemistry Department Safety Office: Gilbert Hall Room 153
Emergency Medical Services: 911
Campus Student Health Center: 541-737-9355
Poison Control: 9-1-800-222-1222
OSU Environmental Health and Safety: 541-737-2273
Campus Security: 541-737-7000

A. Introduction

A1. General: This document discusses procedures and safety guidelines for the use of Teflon-lined, stainless steel laboratory autoclaves manufactured by the Parr Instrument Company (formally named acid digestion vessel). The autoclave is a closed stainless steel vessel with an internal cup and lid made of Teflon. The instrument can be charged with reagents, and closed. Under external heating, the contents will be raised to higher temperatures and pressures than within an unsealed container. The autoclaves are specifically designed for harsh chemicals, high temperatures and high pressures. This SOP is intended to inform on safe working practices to follow whenever autoclaves are utilized in the research laboratory for hydrothermal/solvothermal experiments; however, it is not a substitute for hands-on training by an experienced co-worker. The SOP should be read and understood prior to the commencement of relevant work and used to complement supervised practical familiarization with the various techniques described.

A2. Scope: This procedure applies to all staff, students, and visitors of the Subramanian Research Group in the Department of Chemistry at Oregon State University that work in the laboratory and have the potential to use the autoclave for solvothermal or hydrothermal experiments.

 

 

B. Hazard Identification, PPE, training requirements, emergency response, spill clean up, and general precautions

B1. Hazards: A risk of explosion or implosion exists when using autoclaves. In addition to the dangerous destructive force of such equipment failure, these events are also likely to result in the release of hazardous materials. Accordingly, personnel who operate the autoclave must be trained to understand proper packaging, loading, labelling, as well as operation and emergency procedures.

B2. Personnal protective equipment (PPE): Appropriate eye and skin protection must be worn during all stages of the operation, as follows:

(a) Eye protection: chemical splash goggles or safety glasses that meet ANSI standard Z-87.1 must worn whenever using the autoclaves. Ordinary prescription eye glasses will not provide the necessary level of protection unless they also meet the same ANSI standard. A face shield, worn over safety eye wear, is required in addition if there is a possible risk of explosion.

(b) Skin and body protection: heat-insulating gloves must be worn when moving autoclaves to and from the oven. A fully-buttoned knee-length laboratory coat must be worn to protect the body at all stages of operation. In addition, fully enclosed shoes which cover the entire foot (with no holes in the top) must be worn.

B3. Training and competency: Only trained laboratory personnel are allowed to operate the autoclaves. The trainee must have already mastered an understanding of and have been given instruction in the use of autoclaves by an approved trainer (the instrument supervisor or any trained member of the Subramanian Research Group). Competency will be assessed by close observation of the trainee by the instrument supervisor or an approved trainer. A record of trained personnel is maintained by the Subramanian Research Group.

B4. Emergency response: If any injury occurs seek first aid or, if necessary, seek medical assistance (call 911). If clothing is soaked in hot water/steam, remove clothing and cool the injured part in cool water. Place a notice on the autoclave indicating that it is not to be used until the cause of the incident is determined, procedures enacted to prevent future incidents, and the autoclave is deemed safe for operation.

B5. Spill clean up: Spills may occur from a boil-over or breakage of containers.The operator is responsible for clean-up of any spills resulting from their experiment. Prior to beginning clean up, the autoclave and materials must be allowed to cool to room temperature and all relevant Material Safety Data Sheets (MSDS) should be re-consulted to determine what protective equipment, spill clean up, and disposal protocols are necessary. If the operator is in any doubt that he/she may not be able to safely handle the spill, OSU's Chemical Hygiene Officer should be contacted immediately (Lance Jones: 541-737-2274; EH&S front desk: 541-737-2273).

Visibly inspect the autoclave and inside of the oven prior to cleaning ruptured equipment and use a spill kit to absorb and contain dispersed materials ready for disposal. Chemical waste should be disposed of following the protocol appropriate for the material. If materials have been intermingled, follow the clean up and disposal protocol for the most hazardous component of the mixture. No operation of the autoclave is allowed until the spill is completely cleaned up.

B6. General precautions:The following general safety guidelines MUST be followed.

1. Reagents used in the vessel must not react to release gas. This will lead to excessive pressure build-up.

2. Before every use both the stainless steel shell and the Teflon liner should be visually inspected for cracks, pitting, rust, metal creep or excessive wear. Steel shells that are cracked or flawed in any way must be discarded. Worn or distorted Teflon liners should be replaced.

3. When charging the autoclave with reagents, the Teflon liner should never be filled more than 66 percent (filling fraction, ~15 mL). This will ensure that there is sufficient headspace for vapour formation and fluid expansion when the vessel is heated.

4. Nitric acid should not be used with organic materials to prevent the formation of nitro explosives.

5. Reactions which are highly exothermic or which release large quantities of gas (such as an oxidant and an organic compound) should not be performed in the autoclave.

6. Perchloric acid should NEVER be used in the vessel.

7. Do not overheat the autoclave. The maximum temperature is 250 �C.

8. Do not exceed the pressure limit for each run. It should be verified if the pressure expected is within the limits of the device. Check relevant vapour pressure tables (Parr Instrument Company Acid Digestion Vessels Operating Instruction Manual, pg 8).

9. This model has a spring-assisted pressure plate system that will release energy should the pressure within the vessel exceed the autoclaves specifications. Nothing must ever be done to inhibit the function of the pressure plate system. The spring must be replaced if it shows signs of excessive wear.

10. After heating, the autoclaves must be allowed to naturally air cool on a heat-resistant plate.

11. The autoclaves should NEVER be quenched in water.

12. After use, the autoclaves must not be opened until they are fully cool. Even then, they should be opened with care because the contents may still be under pressure.

13. Owing to the risk of explosion or implosion, samples should not be autoclaved if they:

• contain radioactive material,
• contain or are suspected of containing hazardous chemicals (solvents or corrosives),
• contain chemicals that will become unstable/volatile at elevated temperatures,
• are contaminated by sharps.

 

 

C. Procedures for the safe use of autoclaves for hydrothermal/solvothermal experiments

C1. Equipment maintenance: Stringent visual inspections of the autoclaves are to be performed every six (6) months to examine their structural integrity. The autoclave should be taken out of use if there is any evidence of damage, deterioration or metal creep on the thread of the autoclave body, lid or other stainless steel components. In addition, carefully note the following:

1. Autoclaves are marked with unique numbers.

2. Only matched autoclave parts are to be used. No mix-matching of lids to bodies is allowed.

3. No person shall operate the autoclave unless the autoclave is in good repair.

4. Users are not to make repairs. Autoclaves shall be maintained and repaired by qualified persons.

5. If the autoclave does not operate exactly as expected, a notice shall be placed on the autoclave indicating that it is not to be used until the problem is diagnosed and corrected.

 

 

Figure 1. Parr acid digestion vessel model 4749.

 

Figure 2. Holding fixture and Hook spanner.

 

C2. Loading autoclave and running hydrothermal experiment: Before starting please note that signage indicating “Hazardous Process Underway” must be displayed when autoclaves are in use. Each oven has signage indicating the temperature, DO NOT change the temperature without verifying that the oven is not in use. Replace the signage to reflect the set temperature.

1. Place the desired reagents into the Teflon Liner (charging).

• Do not mix incompatible materials
• Do not overload; leave sufficient room for steam circulation. The maximum volume allowed is 66 percent and 1 g total of solid material.

2. Place the stainless steel Bottom Plate into stainless steel Autoclave Body and ensure that the Bottom Plate is in the correct place.

3. Ensure that the lip of the Teflon Liner is free from any liquid/solid by gently cleaning with a Kimwipe.

4. Place the Teflon Lid onto the Teflon Liner. Nothing should impede good contact between the lid and liner.

5. Gently place the charged Teflon Liner into the Autoclave Body.

6. Place the Corrosion Discs (first thin then thick) onto the Teflon Lid

7. Place the Lower Pressure Place onto the corrosion plates with the spring cavity facing upwards the place the Spring into the spring cavity of the Lower Pressure Plate. Only undamaged springs should be used.

8. Place the Upper Pressure Plate onto the Spring/Lower Pressure Plate/Autoclave Body assembly spring cavity side down.

9. Screw the stainless steel Screw Cap onto the Autoclave Body assembly until finger tight.

10. KEEP VESSEL ON BENCHTOP TO TIGHTEN, do not pick up to tighten. Spilling can occur out of the cup.

11. Then secure holding fixture into a vice and tighten the lid with a spanner.

• Do not over-tighten – no more than 1/8th turn after tight.
• Do not cross-thread the Autoclave Body and Screw Cap.

12. Transport the autoclave assembly/s to the reaction ovens (Room 209).

• Do not excessively tilt the autoclaves. Spilling into assembly may occur.
• Warning – charged autoclaves are heavy.

13. Commence hydrothermal/solvothermal reaction by placing the autoclave assembly/s into the reaction oven. The oven may be preheated or cold. Wear heat-insulating gloves when placing autoclaves into a preheated oven.

14. Record materials used in the reaction and vessel number in the Log, found in the Hydrothermal Vessel Instructions and Log book.

C3. Unloading autoclave and working up hydrothermal experiment:

1. Put on appropriate PPE including heat-insulating gloves and safety glasses and/or face shield prior to handling heated autoclaves.

2. Open oven door and gently remove the autoclave/s and place them on a thermal-resistant plate or ceramic brick to cool down.

• Allow the autoclave/s to cool down naturally. 
• DO NOT QUENCH THE TEMPERATURE BY PLACING THE VESSELS INTO COLD WATER. 
• Shut down the oven if necessary prior to removal of autoclave/s.

3. After completely cool, secure the holding fixture in a vice and unscrew the Screw Cap of autoclave using the spanner.

• Only open an autoclave when completely cooled.

4. Gently remove the Pressure Plate/Spring/Teflon Liner assembly from the Autoclave Body by slowly pressing the Bottom Plate upwards. Remove the Pressure Plates, Corrosion Discs and Spring prior to removing the Teflon Liner and Teflon Lid.

5. Remove the reactant from the Teflon Liner and process as required.

6. When complete, clean the Teflon Liner and dry. Place the autoclave assembly into the designated storage box. Ensure that all matched autoclave parts are stored together (screw cap, pressure plates, autoclave body, etc.).

C4. Waste disposal: Dispose of used solvents in the appropriate labelled waste containers (i.e., segregated into water soluble waste solvent, water insoluble waste solvent, and halogenated waste solvent).

 
   

D. Further reading

1. Advanced Porous Materials Laboratory, School of Chemistry, The University of Melbourne, SOP Version 1.0, 07/14/10.

2. Parr Operating Instructions: Parr Acid Digestion Bombs, Parr Instrument Company, No. 249M.

 

 
This chemical safety advisory document was prepared solely for the use of researchers affiliated to Oregon State University. As stated above (Section A), the content is designed to inform on good working practices and it is not intended to replace hands-on practical training in the techniques described. It is the responsibility of the Principal Investigator to see to it that his/her co-workers are properly trained and informed on hazard management, including the possibility of customization of the information herein as appropriate to meet specific needs. Neither Oregon State University, nor any of its employees (including the author), makes any warranty, express of implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, or represents that its use would not infringe privately owned rights. Reference herein to any specific commerical product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by Oregon State University.