It is not the purpose of this note to regurgitate the contents of the various standards covering the topic but to provide a personal perspective. AS 2865 2009 is a good reference covering the definition, isolation, cleaning, rescue plan, atmospheric limits, ventilation etc. Some of these comments may be considered controversial.
In the authors opinion, all confined space deaths are avoidable. No one starts the day expecting to end it in a box – “it was just a quick job”. The author views confined space entry as one of the most hazardous activities which can be undertaken. Hazards which exist performing normal activities are amplified because you can’t get away from them. Follow all the rules ++
Cornerstones of effective confined space management
Recognition of Confined Space: The definition is defined in the standards; however, a permit issuer should have the authority to call anything a confined space should he or she feel it necessary
Typical Limits Oxygen 19.5 – 21.5%vol
Flammables Less Than 5% of the LEL or 1% for hot work
Toxic 50% of the TLV or WES
IN the case of AS 2865, an entry may start if flammables are less than 5% LEL but must end if they rise to 10% LEL during the entry. No one should ever enter a flammable atmosphere above these levels, other than voluntarily to perform a rescue (note BA won’t help if it goes bang). Some companies require zero flammables. This, in the authors opinion, is not pragmatic as it takes no account of the practicalities of a slight meter zero error or residual hydrocarbons disturbed during work or cleaning. The concern here is a “blind eye” will be turned which is not recommended. Finally, there are several monitoring pitfalls for the unwary and it is recommended that the standby person receives better training than “if it beeps, get out”.
Standby Person No standby, no entry – absolute The standby person should be spending his or her time controlling and monitoring access and egress, monitoring the atmosphere, checking rescue equipment but never leaving the entry point and NEVER ENTERING THE SPACE – no matter what. This is how multiple fatalities occur. For much of the time the standby person may be sitting, but when the event occurs they suddenly become the most important person in the world. They must be able to recognise signs of danger such as symptoms of low oxygen, and be capable of communicating in an emergency and assisting in the use of emergency equipment. Entry points must be clearly marked “NO Entry” during breaks and when work is suspended to protect the unwary.
Rescue Plan - The availability and training on BA has been commented in the Emergency Response Blog and unless the emergency services have a 4min response time, they wont be able to contribute. Define two or three likely scenarios. E.g. an injury, a medical problem (heart or asthma attack) a gas release or loss of consciousness. State who will carry out the resuce and how they will be contacted in an emergency. They should know they are part of the team and must be available. Roughly state how the rescue will be performed and explicitly what equipment is required and where it will be kept during the rescue. A one-person rescue may be possible. Then test the plan.
Isolation - This is covered in the standards but briefly involves a positive isolation as close to the space as possible. The hierarchy being:
Spacer/spool removal and blank or cap -
Full Pressure Spade or spectacle blind
Double Block and Bleed (locked)
A single valve isolation is not acceptable and the need for proper isolation should be considered at the design stage.
Permits - Separate permits will usually be required for the application and removal of blinds, the entry itself and for the work being carried out inside the confined space all of which should be cross referenced
Equipment - Some emergency equipment requires specialised training such as that required to lower an injured person from a high location e.g. a distillation tower. Providing the equipment without the training has been known to have caused fatalities.