Total s Golden rules

Transcription

1 Total s Golden rules

2 Golden rule No. 8: Confined spaces

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4 Confined spaces A confined space is a hollow volume, completely or partially enclosed (a place, structure, piece of equipment or machinery) and usually not designed to be permanently manned. In some cases, a building can also be considered a confined space. However, it may be necessary to move through such spaces or work inside them for maintenance or cleaning operations, occasionally or regularly. The defining characteristic of a confined space is the particularly limited natural exchange between the air inside and outside it, which can lead to risks of suffocation, poisoning, fire and explosion. Because of these risks, serious or fatal accidents sometimes occur when work takes place in confined spaces.

5 Open and closed confined spaces Confined spaces may be open or closed. Open confined spaces are narrow in relation to their length or depth. There may be no particular difficulty accessing this type of confined space but, because of its geometry, the atmosphere inside is not easily renewed. Closed confined spaces are characterized by possible access difficulties.

6 Here are some examples of confined spaces that may be open or closed: wells, pits, pipes, drains, collectors with manhole access, inspection chambers or valve chambers, some manholes, buried structures: pumping station, long, narrow galleries, cisterns, tanks, vats, screening units, mud processing or storage spaces, chlorination or ozone treatment units, storage spaces for certain chemicals, etc. Whenever air exchange is limited and there is a risk of toxic vapors or actual gas accumulating, the volume must be considered as a confined space. This may also apply to a room in a building or workshop.

7 Are there places in your work environment that might be confined spaces? Which ones? Generally speaking, what kinds of spaces in our activities might be considered as dangerous volumes, and why? Give some examples.

8 The risks of carrying out work in confined spaces There are three types of risk associated with working in confined spaces: 1. Asphyxia (suffocation), anoxia, hypoxia 2. Poisoning 3. Explosion and fire

9 Asphyxia, anoxia, hypoxia Asphyxia: cessation of breathing due to a lack of oxygen. Anoxia: temporary or permanent absence of oxygen supply or use in a cell, tissue or the whole body. Hypoxia: a reduction in the oxygen reaching body tissues. 21% NORMAL LEVEL (AIR) These factors are caused by reduction in the oxygen content, which can result in death. 19% 17% 16% 12% 6% TOLERANCE THRESHOLD LOWER LIMIT FLAME EXTINCTION UNCONSCIOUSNESS / FAINTING CESSATION OF BREATHING HEART STOPS

10 Poisoning Poisoning is the inhalation or absorption of a gas or toxic product (e.g. hydrogen sulfide, carbon monoxide, hydrocyanic acid, etc.) that can cause death. Explosion and fire The presence of flammable gas (e.g. methane, butane, hydrogen sulfide, hydrocarbon vapors ) or dust creates fire and explosion risks.

11 Questions We have looked at the different risks and seen examples of products concerned. Complete the following table with the products you have learned about, which can take the form of gases, vapors or fine dust and which are likely to be present in the confined spaces you have identified on your site. Asphyxiating Toxic Flammable

12 Other risks Risks due to performing work: fall risk (same-level and from height) mechanical, electrical, thermal (high or low temperature) risks noise biological agents (infections ) dangerous products lighting handling, physical activities risks due to difficulties in exiting the space possible risk of drowning, etc. Risks due to behavior: panic risk (anxiety, for instance) risks arising from instinctive and uncontrolled reactions which compound the initial accident.

13 Before performing work (1/2) Identify the location, environment and nature of the work, but also its current or previous use and the products likely to be found in it. Make sure the work to be done is essential. Assess the risks. Remove or reduce them before the operation. Raise the necessary permits and authorizations: fire permit, right of entry permit, etc. Designate a safety attendant for the operation, with the ability, knowledge and competencies to initiate emergency action in the event of an accident or incident, while keeping watch from a safe area outside the confined space. Check that the sources of energy or fluid connected to the confined space have been isolated by the appropriate means (lockout, blinding, etc.) Create a natural flow of air in the structure by opening all possible access points, ensuring that this does not generate other risks such as a fall risk.

14 Before performing work (2/2) Clean the space if necessary, and from outside it (for wells and pits). Ventilate the structure by mechanical means before entering, by blowing air in through the lower part. Bring a portable or transportable atmosphere-testing device into the vessel from outside it. Take several atmosphere measurements appropriate to the space layout (different levels, bearings, single points and so on). Halt work if the alarm sounds: prohibit access and move to a safe place. If a descent is necessary to enter the structure, install suitable access means: tripod (or jib crane) with a winch designed to carry people.

15 During the work Ventilate the structure by mechanical means throughout the work, maintaining air flow around the person working. If the work area is at the same level as the entry, the person working should be connected to the outside by a lanyard and extension cable so s/he can be brought out of the area. If the operation involves a descent, each worker should be connected to a lowering device (winch) with a fall-arrest system. Throughout the work, the operators should each have a portable atmosphere-testing device and a self-rescue respirator attached to their belts. Ensure that contact (visual, aural, physical ) is maintained at all times between inside the confined space and outside it, and that the ventilation is effective.

16 Personal protective equipment Wear systematically: Suitable work clothing (gloves, safety shoes, safety boots etc.), A hard hat. Use, where appropriate: Safety glasses, hearing protection A harness with a fall arrester A compressor with a scrubber and a hood, that can produce breathable air A portable atmosphere-testing device A self-rescue respirator Handling equipment (tripod, ropes, tackle etc.) Means of communication between workers doing the job and between the work site and their base.

17 PPE and other equipment used in confined spaces Mobile gas detector Self-rescue respirator Safety lanyard Head torch or portable lamp Safety harness Fluorescent vest Mobile mechanical ventilation system Hard hat, safety glasses or face shield Self-contained breathing Apparatus (SCBA) Telephone (mobile or at hand, outside the work area) Warning signs / barriers for the site Safety shoes / boots First aid kit Walkie-talkie Chemical-resistant coveralls Life jacket Tripod with motorized winch Equipment bag Gloves Winch featuring a fall-arrest device

18 Respirators There are several types of breathing apparatus, used in different domains according to their technical characteristics. For example, for work carried out in a confined space we must use: an escape-only respirator or self-rescue respirator (which workers must keep attached to their belts), carried when the work presents no known risk of dangerous gas being present (and put on and used immediately if the gas detector indicates an unexpected arrival of pollutants). a routine-use respirator, when dangerous gas is actually or foreseeably present. When this is the case, the quality of the risk assessment and procedures (including possible refusal of the intervention) are all the more important.

19 To sum up Jib crane or equivalent Means of ventilation Winch with fallarrest system Protective barrier Physical or visual contact Harness to hold the wearer in position for the work and to protect against falls Self-rescue respirator Atmosphere-testing device

20 Serious accidents Have you heard before of any serious or fatal accident that occurred during work in a confined space? Regrettably, many happen in our industry. Nitrogen and H 2 S are often the cause, but the presence of flammable gases also results in operators being killed. It would take too long to relate, or even simply list all such accidents; so we will mention only a few. Extract from Safe Talk QHS&E journal June 2011 : The tanker truck was transporting bitumen, which apparently had enough hydrogen sulfide in it to create a lethal concentration. The first of the operators killed was only going into the tank for a few minutes to complete a simple task. There was no proof of any atmosphere test having been done. He had no breathing apparatus within reach. Nobody was on hand to intervene or keep a check on the work area. No emergency equipment was available. One person tried to go to the rescue taking inappropriate equipment with him, which resulted in the loss of a second life. This accident took place in under an hour from start to finish. At 4:30, the two men were alive and well. By 5:30 (perhaps even 5:00), both were dead, and the lives of their families and friends were irreversibly changed

21 Accidents Other accidents that have arisen in the industry are summarized in safety directive DirSec 04 ( Interventions in confined spaces ). Here are some extracts from it, illustrating the different types of risk. Manhole accident The facts An inspector put his head into a reactor. He lost consciousness and collapsed, with his head inside, and died. Entry without a permit The facts A tanker truck driver wanted to inspect the tank after it was stripped. As he leaned over the manhole, he dropped a personal item. He climbed down into the tank, where he was later found dead. Semi-confined spaces (pits, shelters, buildings, etc.) The facts Two sewage workers went down to inspect an eggshaped chamber: both were killed. Two welders were tasked with working on a tap line from a tank. To protect themselves from bad weather, they erected a tent. Both welders died from suffocation. What happened? The reactor was being swept with nitrogen. A single breath of it was enough to make the inspector pass out. What happened? Vapors from products heavier than air created a very oxygen-weak atmosphere at the bottom of the tank (very frequent accident). What happened? Methane released from the fermentation of organic matter. The tank was being nitrogen swept, which reduced the oxygen level in the tent.

22 Accidents Semi-confined spaces (pits, shelters, buildings, etc.) continued The facts Explosive atmosphere detected in a trench. An inspector went down into a concrete-lined pit housing compressors. After a few minutes he was feeling faint. What happened? The polluted soil was giving off flammable vapors. Liquid Freon was leaking out. As it was heavier than air on vaporizing, it replaced the air in the pit. Insufficient isolation The facts Nitrogen was detected in a reactor containing an agitator, despite the fact that the reactor had supposedly been fully blinded. Even after a vessel had in theory been fully blinded, the oxygen level inside gradually fell; the workers were alerted by their personal monitors. What happened? The agitator had a mechanical seal with a nitrogen barrier. Isolation of this device was not included in the blinding plan. The vessel had a level gage, based on delta P, and a nitrogen bubbler. Isolation of this device was not included in the blinding plan. Poor atmosphere testing Special dangers The facts An operator descended into a mixer. Though the atmosphere measurement taken was OK, he lost consciousness. The facts A worker fell into a column and drowned at the bottom of it. What happened? The atmosphere was measured only at the entry hole. The hydrocarbon vapors, heavier than air, had accumulated at the bottom of the mixer. What happened? The column had been washed overnight and the water at the bottom of it had not been emptied out.

23 Accidents Hidden or underestimated dangers The facts As he cleaned a tank in winter, the worker concerned was poisoned by benzene vapors. What happened? The atmosphere test that morning had not picked up the benzene frozen in the tank s branch lines. As the morning passed, the benzene thawed with the rising temperature, leading to toxic vapors forming in the tank. Works-related dangers The facts Faintness while performing work in a vessel, despite forced ventilation. Isolation of energy sources The facts A worker was killed when the agitator of the mixer he was cleaning started up. What happened? The ventilator s air inlet was positioned near a compressor on the worksite; the compressor s exhaust gases were sucked in and then blown out inside the vessel. What happened? The agitator had not been locked out. In another case, the wrong mixer was locked out. Special dangers The facts An operator was using a ventilated hood connected to the plant s instrument air network. He died suddenly during the work. What happened? The instrument air network was backed up by the nitrogen network in the event of air compressor failure.