Clariant Life Science Molecules (UK) Limited. The Board of Clariant Life Science Molecules (UK) Limited require you, as their health and safety specialist, to recover the company's position following the accident, which involved a 50 litre capacity autoclave. In particular, they wish you to prepare comprehensive documentation, in order to convey the key information to the Board of Directors, as follows:
The criteria, which should be used to select a suitable replacement autoclave (50-litre capacity; Power Rating not to exceed 10kw).
A written, 'Periodic Maintenance Schedule', which should be applied to this equipment by a competent person.
A detailed 'Safe System of Work', which can be applied to autoclaving operation, based on the company's legal obligations, including a set of autoclave operating instructions for the shop floor staff.
An indication of your recommendations for any training requirements, to facilitate the implementation of the 'safe system of work.
Introduction
A pressure vessel is generally taken to mean a closed vessel which operates at a pressure greater than atmospheric pressure (Stranks, W. 1997).Which is includes the autoclave that maintains saturated steam for a period of time at high temperature and pressure, used to sterilize equipment and materials by destroying potentially infectious agents. When the autoclave was invented in 1880s by Charles Chamberland, the sterilization of materials using steam and pressure considered a dependable procedure for the destruction of all forms of microbial life. However, the autoclave must be properly used and understood to be effective. (oomyceteworld.net). When installing new equipment, we should ensure that it is suitable for its intended purpose, and that it is installed correctly, and all the workers know how to operate it safely by following safe system of work to minimizing the accidents as possible that may result from the pressure in the system, the type of gas or liquid and its properties, suitability of the equipment and pipework and the age and condition of the equipment. Pressure equipment if fails in use, it can seriously injure or kill people nearby and cause significant damage to property. About 150 dangerous occurrences involving such unintentional releases, around six of these result in fatal or serious injury each year in Great Britain. (HSE 2002).
To reduce recurrence of the accidents like what happened with Giancarlo Coletti when he injured his right arm by failing of the clamping system on an autoclave (pressure vessel), causing the lid to fly off and hit him. The replacement autoclave should have some criteria that will be useful for the ease and safe operating system of this autoclave to prevent injuries and accidents.
The criteria to select a suitable replacement autoclave 50-litre capacity:
The type of autoclave loading, there are two types of autoclaves loading, top and front loading, the front loading easier in loading, and unloading and it is perfect with small capacity of 50L. Even top loading have the greater capacity due to increase in height recently becoming less popular due to health and safety issues involving lifting of possibly heavy baskets and containers. ( www.priorclave.co.uk).
What kind of chamber should autoclaves have cylindrical or rectangular, the Pressure inside the chamber naturally attempts to make the chamber round. A cylindrical chamber can have thinner walls and has less metal to heat up. It, therefore, weighs less and costs less to manufacture and operate, and it is better steam circulation on front loading models. Because of the circular profile of the working chamber and the 'square' profile of most autoclave loads there will normally be space around the sides of the load for steam circulation. (www.priorclave.co.uk).
The autoclave can be heated by three principle methods, steam heated from an external steam source, dedicated steam generators and electrically heated by heaters inside the chamber which is the preferred type, especially with small capacity autoclaves, because it is Simple and easy to maintain and service as the heaters are visible and accessible within the chamber and less complex and therefore, less expensive and requires less servicing. (www.priorclave.co.uk).
The type of door required to open and close the autoclave it is better to be a manual door with single action closure because it is less complex than powered door closures, and so requires less servicing and is less expensive, faster and easier to operate than hand bolt doors that may cause accidents because of failure of the clamps when over-tightened, causing them to break.
The cycle of autoclave operation can be controlled by pressure and time, which is no longer common with the advent of more reliable temperature systems. It can lead to under-temperature cycles if air remains in the autoclave but temperature and Time control, mostly used nowadays, which is ensuring adequate temperature sterilizing conditions if air remains in the autoclave.
The following dimensions are advised if possible where the small and medium sized autoclaves are often castor mounted and with flexible connections can be moved to enable service work to be carried out.
Around the Autoclave at least: Sides 1 meter
Rear 300mm
To prove sterilization method of recording the cycle includes Integral Data Printers, which is inexpensive and uses the same sensors as the autoclave. These can be faster and quieter than other systems.
The picture below for the Swift lock Compact Autoclaves that comes in different capacities.
Source: (www.astell.com).
A written, 'Periodic Maintenance Schedule', that could be applied to this equipment by a competent person.
The periodic Maintenance Schedule written below should be followed by the employees and competent person to make sure that the autoclave is working properly and accidents caused by the faults or damage of any part of the equipment prevented, referring to the Pressure Systems Safety Regulations 2000.
Minimum daily maintenance schedule.
- checking for cleanliness of autoclave parts, for example, internal chamber, fittings, door seal, etc. and cleaning where necessary.
- Visual checks for steam and water leaks.
- Disinfect the exterior surface of the autoclave.
- Clean the interior walls with either tri-sodium phosphate or another mild detergent.( www.ucl.ac.uk).
Minimum weekly maintenance schedule
The following checks be made weekly by the competent person
- Check the door gaskets for wear and the operation of indicator lamps
- Temperature and pressure gauges and correlation of temperature gauge against
pressure gauge during a cycle.
- Inspection of recordings for abnormalities.
Minimum quarterly maintenance schedule
Checks every three months are recommended to be done also by a competent person.
- inspect control instrumentation as it may require recalibration or replacement.
- Check valves, for example, if there is a steam-pressure reducing valve present -
does it need cleaning or replacement?
- inspect all electrical heat terminal points and joints in piping and chamber for corrosion and wear.
- check for cleanliness of the water and steam line main strainers - if fitted and the pipe work and drains to waste to ensure they are clear and operating.( www.ucl.ac.uk).
Minimum annual maintenance schedule and inspection
The following checks and activities should be undertaken annually:
- check service history for recurring faults and corrective action;
- Inspect and remove any scale from the chamber by a method approved by the manufacturer.
- Check the water-level control and indicator systems and operation of temperature indicator and pressure gauges.
- Test the operation of safety valve(s)
- During a cycle with the chamber empty, check all control functions including correlation of pressure and temperature gauges against known references.
- should carry out thermometric tests of typical laboratory loads as during original commissioning and validation.( www.ucl.ac.uk).
As well as autoclave monitoring and maintenance is an important aspect of a properly functioning autoclave. Following the manufacturer's recommendations for preventative maintenance.
Safe System of Work
To maintain a high degree of safety and minimize accidents and injuries, all material which must be stored outside while awaiting autoclave treatment must be labeled with the name and contact information of the person responsible for the job. Ensure that any primary containers, which are the containers that are in direct contact with the contaminated material, permit steam penetration.
Any caps or lids must be loose or partially open, and plastic bags should be opened slightly.
All containers may be filled to a maximum of 2/3 of their capacity and the secondary containers are used to contain any spill that may occur.
Loading:
• When operating an autoclave proper personal protective equipment must be worn to protect against burns and scalds. Shoes with closed toes and heels must be worn at all times, and it is recommended that a lab coat be worn. Heat-insulating gloves must be worn when loading and unloading. If there is a splash risk, goggles and/or a face shield should be worn as well.
• make sure that autoclave pressure gauge is at zero and carefully open the autoclave door and place materials inside the autoclave, in a secondary container to protect the autoclave (e.g. place flasks with liquid inside a deep tray). Making sure not to overload the sterilizer, thereby allowing for steam circulation.( www.uottawa.ca).
• Close the autoclave door and make sure that it is properly closed and fill in the Autoclave Log with all required information.
Select the Settings:
• Choose the appropriate cycle time and type for sterilization from the control panel.
• Start the autoclave and do not attempt to open the door while the autoclave is running.
• Make sure that the autoclave reaches the desired temperature before leaving it unattended. If the door begins leaking steam, abort the cycle and tighten the door further.
• If you must abort, press the abort button on the control panel. Wait for at least a minute before cautiously cracking open the door to let out steam. Once the steam has been released, reopen the door fully. (www.chembio.uoguelph.ca).
Unloading
• Make sure that the pressure gauge is at zero, stand back from the door and crack it open, allowing steam to dissipate before opening it fully.
• Check if liquids are bubbling, leave them to cool further before moving to avoid boil over.
• Remove the items and place them in a safe location and record any problems encountered in the Autoclave/Problem Log.
Do not load incompatible materials (some plastics, flammable materials, radioactive materials, substances which may emit toxic fumes, etc.).
General Autoclave Safety Practices:
1. Check inside the autoclave for any items left by the previous user that could pose a hazard (e.g. sharps), before using the autoclave,
2. Clean the drain strainer before loading the autoclave and then load the autoclave properly..
3. Individual glassware pieces should be within a heat resistant plastic tray on a shelf or rack and never placed directly on the autoclave bottom or floor.
4. Be sure that the door of the autoclave is fully closed and the correct cycle has been selected before starting the cycle and when the cycle is complete, open the door slowly. Keep your head, face, and hands away from the opening.
5. When removing items from an autoclave, a rubber apron, rubber sleeve protectors and heat-resistant gloves should be worn. (www.ehs.sc.edu).
Safe Practices for Autoclaving Liquids:
When running an autoclave cycle with liquids, the cycle time is longer, but uses lower temperatures to minimize evaporation of the liquids being sterilized.
The caps of containers with liquids must be loosened before loading. To prevent bottles from shattering during pressurization.
To contain the contents and catch spills use a tray with a solid bottom and walls
Before removing autoclaved items, wait 10 minutes for autoclaved liquid loads and let liquids stand for a full hour before touching with ungloved hands. Be sure others in the area know a heat hazard is present. (www.ehs.sc.edu).
Safe Practices for Autoclaving Dry Loads:
Add 1/4 to 1/2 inch of water to the tray so the bottles will heat evenly.
Check plastic materials to ensure they are compatible with the autoclave.
Before removing autoclaved items, wait 5 minutes for loads containing only dry glassware.
For dry loads, let the glassware cool for 15 minutes before touching it with ungloved hands.
Autoclave Training:
The general requirement of Health and Safety at Work etc 1974 (HSWAct) apply to all autoclaves. These require the provision of a safe system of work, and properly trained operators.(HSE 2006). Mistakes in autoclaving may result in having to re-autoclave material, or modify the cycle conditions (length of exposure time or temperature).Unfortunately, lack of diligence during the autoclave process can be very costly in terms of personal injury, down time, lost experimental data, expensive and/or length repairs, so that is why training is absolutely required prior when using the autoclave. Not only will minimize the risk of personnel being harmed, but it is essential to ensuring a successful decontamination or sterilization of your material. Training will also help minimize the risk of damage to the equipment. That is why employees must receive training for the autoclave that they will be using, working within adequate operating procedures to ensure the system was used correctly. (www.uwindsor.ca).
Accidents could happen when the workers not trained well how to use the autoclave properly and
each workplace must develop and implement an autoclave safety training program. All users must be trained before operating an autoclave and the supervisor is responsible for ensuring each person in the place is appropriately trained and all training must be documented, and records should be maintained with other safety training certificates. (HSE 2002).
Recordkeeping: Operators should maintain documentation of any autoclave preventative maintenance or repairs. These records should indicate who performed the work, the type of maintenance or repairs conducted, and the date the autoclave was serviced. The records should be maintained either in the room with the autoclave, or signage should be posted indicating the location of any records that document autoclave maintenance or repairs. (HSE 2000).
Conclusion
Autoclaves generate extreme heat and high pressure. Users should understand and respect the hazards these can create, with choosing good autoclave criteria and preparing a periodic maintenance schedule reviewed within suitable intervals make any defects to be discovered before accidents happen. The operator should be familiar with the safe system of work that includes a set of autoclave operation instructions, which presented by appropriate training.
