It is alleged the defendant, in particular:
a) Failed to provide and maintain a safe system of work in relation to the shutting down of the acetylene generator at the dissolved acetylene plant and in particular failed to ensure there was a system of checking that all valves including the isolation valve for the ammonia scrubber to the town water supply were closed;
b) Failed to ensure that employees were adequately trained, instructed, informed in and about safe procedures to be followed when alarms sounded for the acetylene generator plant for those times after it had been shut down and unattended;
c) Failed to have in place or maintain any procedures to be followed when alarms sounded in the acetylene generator plant for those times after it had been shut down and unattended;
d) Failed to ensure that there was an automatic cut off to the town water supply to the ammonia scrubber when the acetylene generator was shut down and to ensure that the acetylene generator flashback arrestor check valves were properly maintained;
e) Failed to have systems to restrict the access of employees from entering the acetylene generating room in the event of an uncontrolled explosion, ignition and fire of acetylene gas;
f) As a result of the defendant's failures all of its employees working at the premises were placed at risk of injury.
3 The defendant pleads guilty to the charge.
4 Mr R. Reitano, of counsel, appeared for the prosecution and Mr M. Tooma, solicitor, appeared for the defendant. The prosecution relied upon an Agreed Statement of Facts with the following documents attached:
· Seven factual Inspection reports of Inspector Beacham dated 19 August 2004, 30 August 2004, 21 February 2005, 23 May 2005, 12 July 2005, 28 July 2005, 24 October 2005
· 82 Photographs taken by Insp Beacham on 16 August 2004, 25 August 2004 and Mr Robert Edwards, professional photographer under the directions of Insp Beacham on 27 August 2005
· Video Capture Images dated 14 August 2004
· BOC Acetylene Generator Start Up and Shutdown Check Sheets dated 25 August 1997 and 7 May 1997
· BOC post incident investigation report received by WorkCover 16 September 2004
· Prior Convictions Certificate.
5 The defendant tendered an affidavit of David Hook, Group Manager - Operations Safety sworn 18 October 2006. He is a technical expert in acetylene generators (based in the UK). Relevant documents were attached to the affidavit including documents in relation to the investigation of the incident and the upgrading of the acetylene plant. Also relied upon was the affidavit of Michael Wilson sworn 22 March 2007 together with 17 volumes of annexures outlining the pre-existing policies and procedures for safe working and the corporation's amended, and where relevant, new procedures adopted after the incident to ensure safe working.
6 The Agreed Statement of Facts relevantly reads:
2. At all material times BOC Ltd [ABN 95 000 029 729] was a corporation with its registered office situated at Riverside Corporate Park, 10 Julius Avenue, North Ryde, in the State of New South Wales ("the defendant").
3. The defendant was a corporation which undertook the business of manufacturing acetylene gas, nitrous oxide gas and various gas mixtures. The defendant was a member of the world wide BOC Group.
4. The defendant owned and operated an acetylene generation facility at BOC Limited Sydney Operations Centre at 428 Victoria Street, Wetherill Park, New South Wales ("the premises").
5. The defendant was an employer. On 14 August 2004 there were approximately 50 employees and contractors working at the premises. The defendant employs approximately 1912 people throughout Australia.
6. On the morning of 14 August 2004 at approximately 5:00 am Mr Sakhany Nak, Dissolved Acetylene ("DA") Generator Operator, employed by the defendant, arrived at the premises to perform scheduled overtime until approximately 1.00 pm that day. Also doing overtime at the premises from 5.00 am to 1.00 pm that day were the defendant's employees Mr Jimmy Chaghouri (Process worker), Mr Gary Gollege (Process worker) and Mr Shaun Murphy (Production operator). These employees were to work in the Acetylene Works Building, in various areas of the defendant's DA plant known as the acetylene generating room, the acetylene cylinder maintenance area/ test shop area and the acetylene cylinder filling racks area. and the test shop area.
7. No team leaders or supervisors to supervise the operation of the DA plant at the premises were rostered to work on the day. Mr Joe Xuereb and Mr Dion Bailey were on 24 hour callout for unexpected technical difficulties. Mr Sakhany Nak, who worked in the DA plant that day was unsupervised but was trained as competent in the operational activities of shutting down the DA plant and had operated and shut down the DA Plant for seventeen years.
8. Mr Nak was feeling unwell at the start of the shift . He commenced work and started the acetylene generator. He then loaded calcium carbide into the carbide skip in order to charge an acetylene generator feed hopper. Before raising the carbide skip to the acetylene generator feed hopper, he felt worse and decided he could not continue working. He left the carbide skip parked adjacent to the acetylene generator standing at ground level. He turned the acetylene generator hopper selector switches to off around 5:55 am.
9. Mr Nak allowed the compressors to run reducing the suction pressure until they tripped on low suction pressure. He later stated that the pressure in the acetylene generator, indicated on PI 2109 was reading 0 kPa. He then shut valve V1821 which isolated the automatic drain valve on the acetylene generator and shut V1679 which isolated the acetylene generator and ammonia scrubber from the suction of the compressors. No shutdown checklist was completed on this occasion.
10. The town water supply isolation valve V1950 to the ammonia scrubber which is on the shutdown checklist was left open. This should have been closed as part of a normal acetylene generator plant shutdown.
11. The defendant had a documented "Acetylene Generator Shut Down Check Sheet" dated 7 May 1997 ("the Check Sheet") that required, as part of the daily shut down procedure to the DA Generator plant, for the water inlet valve to the Ammonia Scrubber to be closed and that action to be marked as completed. Relevantly, the Check Sheet stated:
"This check sheet is to be completed DAILY at the end of the operation of the Acetylene Plant by the Generator attendant".
12. Further, the Check Sheet, once completed, was required to be signed by both the Generator operator and the relevant team leader.
13. Mr Nak was trained to fill in the Check Sheet when starting up and shutting down the DA Generator.
14. Mr Nak left the plant around 6:15am. Before leaving he told Jimmy Chaghouri he was leaving as he was feeling unwell.
15. During the acetylene production process, ammonia impurities in the acetylene gas generated are removed by passing the gas through water. For this purpose, town water is supplied to the ammonia scrubber. When the DA Generator is operating at a process pressure of 70 kPa, the automatic water level control valve for the ammonia scrubber will regulate the water level at the bottom of the ammonia scrubber at a constant height. However, when the DA Generator is shut down, the supply of water to the ammonia scrubber is isolated by closing valve V1950. Mr Nak did not close valve V1950 and as a result, the water level in the ammonia scrubber started to increase abnormally.
16. At an unknown time the water level in the ammonia scrubber rose sufficiently to flood the dry leg section of the pneumatic controller connected to the side of the ammonia scrubber. The flooding of the dry leg had the effect of confusing the pneumatic controller causing the automatic water level control valve to shut, whereas it should have remained fully open as the water level increased.
17. Sometime later that morning Mr Murphy, production operator heard an acetylene generator plant alarm sound off. The acetylene generator plant alarm would have triggered, due to the abnormally high water level flooding the ammonia scrubber or an abnormally high level of water flooding the acetylene generator. Mr Murphy observed a fellow employee Mr Golledge pushing an alarm acknowledgement button in the acetylene cylinder filling racks area which silenced the alarm. (Once silenced an acetylene generator plant alarm would not resound but would have a fault light on the enunciator panel located in the generator room which flashes with rapid frequency until the fault causing the alarm has been cleared (fixed) and reset).
18. Mr Chaghouri, Mr Gollege and Mr Murphy finished work and left the premises at the following times:
a) Mr Chaghouri 1.43 pm;
b) Mr Gollege, 1.46 pm;
c) Mr Murphy, 12.43 pm.
19. Over several hours, after the ammonia scrubber had flooded, water gradually filled the acetylene gas process pipe work (abnormal condition) located between the ammonia scrubber and the acetylene generator, passing into the DA Generator and eventually flooding the acetylene generator.
20. Water reached feed hoppers no.1 and no.2 screw feeders (located on top of the acetylene generator) which contained unspent calcium carbide and an uncontrolled exothermic reaction commenced producing acetylene gas which resulted in an increase of acetylene gas pressure in feed hopper no.2 and an increase in the feed hoppers screw feeder temperatures due to the exothermic reaction.
21. At approximately 7:05 pm the hopper lid on hopper no.2 blew off as a result of the increasing internal pressure in the hopper. The vapour cloud of acetylene that emanated from the DA Generator ignited and exploded. The word "explode" or "explosion" is used throughout this agreed Statement of Facts as referring to its every day usage.
22. There was no-one in the DA plant Acetylene Generating Room at the time of the ignition and explosion of acetylene gas released. Group 4 contractor security guard, Mr Bill Skeen was in the gatehouse. Mr Frank Blazejko (Nitrous Plant Operator) and approximately six (6) other employees were in the P & L Plant that was located approximately twenty (20) metres away from the western side of the acetylene works building. The Acetylene Generating Room was located on the opposite side of the Acetylene Works Building from the P & L Plant.
23. Immediately after hearing the sound generated by the ignition and explosion of acetylene gas released Mr Skeen ran to the opened door of the gatehouse and, observing smoke rising from the Acetylene Generating Room, ran to the alleyway entrance to the Acetylene Generating Room and put his head around the corner so as to view the hopper approximately 10 metres away. Mr Skeen, observing flames coming out of the feed hopper no. 2, immediately returned to the gatehouse.
24. Shortly after hearing the ignition and explosion a break glass fire alarm was activated by Mr Blazejko, at the P&L building opposite the Acetylene Works Building. The break glass fire alarm was automatically received by the Fire Brigade at approximately 7.07pm. On return to the gatehouse from the Acetylene Generating Room, Mr Skeen phoned the fire brigade to ensure the call was registered. Mr Jim Davies, Acting Production Manager, was notified by Mr Skeen of the incident.
25. The fire brigade attended the premises with 6 units. A further acetylene ignition occurred at approximately 7.26 pm in the Acetylene Generator Room. At an unspecified time but soon after the fire brigade arrived Frank Blazejko with the permission of the fire brigade entered the DA plant building via the acetylene compressor room and observed through the fire door window at the eastern end of the compressor room what was happening. Mr Blazejko observed flames coming out of feed hopper no.2 and water coming out of two safety relief valves. At some time probably between 7.30 pm to 8.00 pm Mr Xuereb and Mr Bailey, Maintenance Team Leaders, employed by the defendant arrived on site. Shortly afterwards Mr Davies arrived.
26. In order to stop the reaction in the acetylene generator it was agreed to place a nitrogen purge on the no.2 hopper and then commence draining water from the acetylene generator via the opening valve V1822. At about 9:00 pm Mr Bailey and Mr Xuereb entered Acetylene Generating Room to manually connect a nitrogen purge hose, to fill the feed hoppers and feed screws and DA generator with nitrogen to exclude oxygen from the system to prevent a further explosion or ignition. They then left the Acetylene Generating Room. At about 9:30 pm they returned to the Acetylene Generating Room and opened drain valve V1822 at the end of the acetylene generator vessel to drain the water (to stop the reaction). The connection point for the nitrogen purge and drain valves were beneath feed hopper no.2 which had previously ignited and exploded. Thermal imaging by the fire brigade revealed that the screw conveyor housing temperature went up to 190C during the incident. Water was also applied using a BOC Limited portable fire hose to the feed hopper screw housings to cool the feed hopper screw housings. This was done by Mr Bailey and Mr Xuereb entering the acetylene generating room setting up the portable fire hose and then leaving the Acetylene Generating Room.
27. The area was evacuated for 30 minutes to enable the cooling effect to take place. At 10.00 pm to 10.30 pm the hopper housing temperatures were ambient and the situation deemed safe.
28. Upon inspection of the acetylene generating room after the incident by the defendant it was found that no.2 feed hopper lid had blown off. The hopper lid was found in the acetylene generating room after the incident. After the incident it was reported by the defendant that the feed hopper lid weighed approximately 5.2 kgs.
29. The system of work used by the defendant at the time of the incident was for their operators to start up and shut down the acetylene generator plant without supervision and provide shut down check sheets to team leaders after the shutdown. Typically there were no team leaders on the weekends to supervise DA plant operators. On the day of the incident there were no production supervisors or managers on site with a responsibility for DA plant operations.
30. Prior to the incident the defendant did not include in its acetylene generator plant shut down check sheets the shutting of valve V1729 between the acetylene generator and the ammonia scrubber. Also there was no isolation procedure to secure critical valves V1950 and/or V1959 to prevent the flooding of the ammonia scrubber outside of production hours after the acetylene generator plant had been shut down.
31. Prior to the incident there were no documented procedures in place for employees to deal with acetylene generator plant alarms that occur after the acetylene generator plant has been shutdown when DA generator operators or DA plant supervising staff were not present.
32. Prior to the incident Mr Nak was trained and assessed as competent by the defendant to start up, operate and shutdown the DA Generator. Mr Nak had worked as a generator operator for approximately seventeen (17) years at the time of the incident. One of his team leaders Dave Warters had received computer based training ("Traccess") in the operation of the acetylene generator plant but had not been deemed competent in the operation or shut down of the acetylene generator plant. Mr Golledge was provided with no information or training by the defendant in what to do in the event of an out of production hours acetylene generator plant alarm after the acetylene generator plant had been shut down.
33. At the time of the Incident, the Defendant's operational processes included the following:
ACE-01: The Dissolved Acetylene Process;
ACE-02: Supplying Calcium Carbide to the Generator;
ACE-03: Generating Acetylene;
ACE-04: Carbide Lime Treatment;
ACE-05: Purifying, Compressing and Drying;
ACE-06: Filling Cylinders with Acetylene;
ACE-07: Acetylene Cylinders;
ACE-08: Solvents use in Dissolved Acetylene; and
ACE-09: Engineering Guidelines.
34. The above procedures deal with acetylene generation and are comprised of a number of BOC Group wide and site specific procedures, including:
(1) ACE-03-03-BOC - About Rexarc Generators, is a BOC Group procedure which provides an overview of the principles of operation of a Rexarc ATX Acetylene Generator and describes the components for this generator model.
(2) ACE-03-06-SYD - Operating the Acetylene Generator (ACE-03-06-SYD) and ACE-03-08-SYD - Maintaining the Acetylene Generator (ACE-03-08-SYD) are procedures specific to the Premises.
(3) ACE-03-06-SYD describes the DA Generator procedures for:
(a) starting the generator after normal shut-down, after an end of week shut-down or end of shift shut-down;
(b) shutting down the generator for a normal end of week shut-down or end of shift shut-down, including a checklist to be completed by the operator;
(c) routine checks; and
(d) trouble shooting procedures.
(4) ACE-03-08-SYD - Maintaining the Acetylene Generator, sets out detailed work instructions in relation to the work processes required to be undertaken to perform regular maintenance on the Acetylene Generator. This procedure includes a work instruction regarding the replacement of the flashback arrestor check valve if the rubber ball in the check valve is swollen to a point where it restricts the flow of acetylene.
(5) ACE-01-09-SYD - About this Site, relates to the Premises and provides details of:
(a) the layout of the DA area;
(b) emergency equipment to be found in the DA area; and
(c) PPE requirements for the area.
35. Prior to the incident the defendant had performed no maintenance on the acetylene generator flash back arrestor check valves. The acetylene generator flash back arrestor check valves were not on a preventative maintenance schedule. The manufacturer of the acetylene generator had not mentioned a requirement to maintain the generator flash back arrestor check valves in its operating manual nor had they indicated that this was an important safety control from the water backflow perspective. Prior to the incident the defendant's procedure "Maintaining the Acetylene Generator ACE-03-08-SYD" documented the check valve assemblies in the acetylene generator flash back arrestors. The defendant had replacement acetylene generator flash back arrestor check valve assemblies in the BOC SOC engineering store available for use prior to the incident. The defendant has now implemented a yearly maintenance schedule for the Acetylene Generator flash back arrestors.
36. The acetylene generator plant involved in the incident was a Rexarc Model ATX Stationary Acetylene Generator Model No: 10000ATX manufactured by Rexarc Incorporated West Alexandria, Ohio, U.S.A. and had been in operation at BOC SOC for approximately 19 years.
37. Prior to the incident the two pressure safety relief valves attached to the acetylene generator flash back arrestors were adjusted by the defendant to cold set relief pressures of 150 kPa gauge. BOC procedure ACE 03-03-BOC states pressure over 105kPag is excessively high and Australian Standard AS 1210 -1997 Pressure vessels limits this pressure to 109 kPag.
38. Prior to the incident the two safety relief valves attached directly to the acetylene generator were set to cold set relief pressures of 117 kPa. BOC procedure ACE 03-03-BOC states pressure over 105kPag is excessively high and Australian Standard AS 1210-1997 Pressure Vessels limits this pressure to 109kPag.
39. Prior to the incident there was no automatic cut off valve to the town water supply to the ammonia scrubber when the Acetylene Generator was shut down.
40. Prior to the incident there was no restriction of entry by persons to the area of the Acetylene Generating Room where the incident occurred at any time. Employees could enter the Acetylene Generating Room at will. On site security guards could access the Acetylene Generating Room at any time. After the incident controls were introduced such that only persons authorized by the defendant's management were permitted to enter the Acetylene Generating Room. The defendant has now installed signage restricting entry to the Acetylene Generating Room to BOC management, maintenance and trained personnel. All employees of the defendant are provided with formal induction in site functions and operations on the premises including formal training and awareness of emergency procedures. There was no way anyone could have known at the time of the incident whether or not any employees were in the DA plant generator room.
41. Prior to the incident there was no item registration of the Acetylene Generator plant pressure vessels in contravention of the Occupational Health and Safety Regulation 2001. Improvement notices were issued by WorkCover subsequent to the incident in relation to this issue and complied with. Prior to the incident, the Acetylene Generator plant pressure vessels were registered with the Boiler Inspection Authority and received visual inspection every two years by a certified pressure vessel inspector.
42. Prior to the incident the acetylene generator plant alarm system was maintained in good working order and remained turned on after the acetylene generator plant was shut down.
43. Prior to the incident there were no safety relief valves directly attached to the acetylene generator plant feed hoppers no.1 and no.2. The purpose of such safety relief valves being to relieve acetylene gas pressure build up in the feed hoppers preventing hopper lid or hopper pressure vessel failure. The manufacturer (Rexarc) did not provide a requirement to fit such relief valves to their generators, however Australian Standard 1210 of 1997 at 8.1.1 states when any such device or fitting is not provided by the manufacturer the purchaser shall be responsible for ensuring that it is supplied and fitted prior to placing the vessel into service.
44. At some time before the incident the water supply system to the ammonia scrubber was changed from an overhead gravity supply tank to a direct connection to mains pressure town water supply. The effect of this is that pressure in the town water system is capable of suppling more water to the scrubber than the level control valve can remove (particularly under shutdown conditions) and the scrubber can flood. This contributed to the incident. Prior to the incident there was no risk assessment done in relation to replacing the ammonia scrubber overhead tank with a mains pressure supply system.
45. Prior to the incident the Acetylene Generator was fitted with a number of operational safety controls including the following:
(1) actuated vent valves interconnected with the automated hopper purging system to vent the carbide hopper;
(2) an actuated drain valve, controlled by signals from water level inside the acetylene generator;
(3) equalising valve to equalise pressure in the hoppers after carbide charging;
(4) a gauge fitted to the hydraulic system which registers the hydraulic pressure, and a safety valve which protects the hydraulic cylinder from over pressure;
(5) a temperature safety instrument that measures the temperature of the generator tank and closes the alarm circuit when the temperature reaches a set point;
(6) a water inlet control instrument, that measures the temperature of the acetylene in the generator tank and opens the inlet water control valve when the temperature reaches a set point;
(7) a inlet water control instrument air gauge which measures the air pressure applied to the inlet water valve;
(8) an inlet water control valve which opens to allow water to enter the generator through spray nozzles when the generator tank temperature rises to the set point on the water control instrument;
(9) a high water level air gauge which measures air pressure to the high water level pressure switch. When the air pressure drops below 48 kPag, a pressure switch will close causing an alarm, and below 27 kPag, the screw feeder will not operate;
(10) a low water level air gauge, which measures air pressure to the high water level pressure switch. When the air pressure drops below 48 kPag, a pressure switch will close causing an alarm, and below 27 kPag, the screw feeder will not operate;
(11) a temperature safety instrument air gauge, which measures air pressure to the safety instrument panel. When the air pressure to the safety instrument panel drops below 42 kPag, a pressure switch will close causing the alarm to sound;
(12) a high water pilot valve which vents air pressure to the inlet water valve allowing it to close and stop the water flow in the event of a high water level in the generator tank;
(13) a water level alarm which is activated when the water level varies from the normal operating level (higher or lower) and a flapper valve opens allowing air to exhaust;
(14) a water pressure gauge which indicates the water pressure when water enters the generator tank;
(15) three manual water level valves situated at the end of the generator tank for checking water level (high, medium and low) when filling the tank and during routine operation;
(16) two flashback arrestors, fitted to the generator tank outlet lines to prevent an accidental flame from entering the generator tank; and
(17) four safety relief valves fitted to the generator, two on the tank riser and one on each of the two flashback arrestors. If the generator tank pressure should become excessively high, one or all of these safety valves will open to relieve pressure. An interference mechanism connects four valves to a handle, allowing the operator to open four valves manually, if necessary, to vent the tank for any reason.
46. Prior to the incident the defendant's procedures provided:
a) That water in the calcium carbide feed chute of the acetylene generator plant could cause uncontrolled generation of acetylene.
b) That a hot hopper incident can occur if the acetylene gas within the generator undergoes a deflagration caused by water level rising too high and coming in contact with carbide.
c) That Acetylene is a highly flammable unstable compound and could ignite and explode under any number of conditions and that acetylene plants are not operated in any way that could result in a fire and that only a small amount of energy is required to ignite an air and acetylene mixture that could result in an explosion. When combined with oxygen acetylene burns with a very high temperature flame of 3160 C (5720F).
d) That the typical hazards of a calcium carbide fire are: Fire and explosion, flammable acetylene produced if water is used on calcium carbide fire and a secondary explosion of generated acetylene.
e) That in the event of a calcium carbide fire that personnel are to be evacuated from the area to a location 20 metres upwind.
47. BOC procedures prepared after the incident, to be followed if a hot hopper or hot screwfeed is detected, state:
· A hot hopper or screwfeed can be caused by water or moisture entering the screwfeed and/or hopper. Do not open any part of the generator to atmosphere until it is completely cool and made inert. There is a risk of mixing air and acetylene and ignition from a hot spot, causing an explosion.
48. After the incident the defendant amended their procedures to include requirements that:
i Supervision is to be present to double check that acetylene generator operators start up and shut down the acetylene generator plant as per procedures. If there is no team leader or supervisor available the acetylene generator plant will not be allowed to run. If overtime is required in the DA plant on weekends there must always be a team leader or supervisor to oversee the operation of the acetylene generator. A DA plant team leader or a supervisor must be present during a shutdown to physically check that the acetylene generator shutdown as per the acetylene generator check sheet.
ii The shut down check sheet include the shutting of V 1729 located between the acetylene generator and ammonia scrubber as part of a shutdown plus the check sheet has been significantly modified to include valve numbers.
iii A yearly maintenance schedule for the acetylene generator flash back arrestors.
iv Signage be installed restricting the entry to the Acetylene Generator Room to BOC management, maintenance and trained personnel.
49. After the incident the DA plant team leaders received additional training in the operation of the acetylene generator plant. The safety relief valves for the acetylene generator and acetylene generator flash back arrestors have been reset to 105 kPa gauge, a safety relief valve has been installed on each hopper and an automatic valve has been installed to the water supply of the ammonia scrubber to prevent the ammonia scrubber from flooding. The defendant also applied to WorkCover for item registration of the relevant pressure vessels in the acetylene generator plant including the acetylene generator and feed hoppers. The dry leg of the ammonia scrubber water level control system was modified to prevent the control system from unnecessarily shutting the ammonia scrubber water outlet valve.
50. Subsequent to the incident a Hazard and Operability Study (Hazop) was undertaken by the defendant to consider possible causes, consequences, existing safeguards, actions recommended and provided the following information:
· That direct connection of the ammonia scrubber to the town water system contributed to the incident;
· That check valves in the acetylene generator flashback arrestors and operating procedures to close town water to the ammonia scrubber will safeguard against water level rising in the acetylene generator causing acetylene generation overpressure and heating in the feed hoppers;
· That perished rubber in the flashback arrestor check valves allows acetylene gas or water to return to the acetylene generator;
· That the generator when operating at too high a temperature will cause decomposition
· That water flowing into the feed hoppers causes acetylene generation/hot spots in the feed hoppers overpressure/fire;
· That generation of acetylene in the feed hoppers will over pressurize the feed hopper with lid separation and possible fire and consideration should be given to installing safety relief valves to the feed hoppers and venting to high level vent.