SINGAPORE — Subbaiyan Marimuthu, one of three workers who perished in an industrial explosion in Tuas, was so spooked by an earlier fire at his workshop that he was afraid to work, an inquiry committee (IC) looking into the accident was told on Thursday (23 September).
The 38-year-old Indian national was present when a small fire broke out on the afternoon of 12 February this year at the oil jacket of an industrial kneader or mixer machine. It was the penultimate moment in a series of incidents involving the machine, which sparked a flurry of calls, texts and video messages between the workers of Stars Engrg and their boss Chua Xing Da, who owns the fire protection contractor.
Marimuthu's colleague Mehedi, 22, testified on Wednesday, "It looked like a red-orange flame measuring about 250-300mm high and 150-250mm wide."
Chua, Stars Engrg's sole director, was alerted to Marimuthu's emotional state by production engineer Lwin Moe Tun. He told the IC that he attempted to calm Marimuthu, who was the foreman of the company's Tuas workshop, down via texts and calls, but did not manage to speak to him over the phone.
"I wanted to explain to him then that no one wanted the events of 12 February 2021 to happen and that, if there are issues, we should mitigate and control the situation, before moving on," said Chua in his witness statement, which took more than half a day to read out.
"I do not remember whether Marimuthu got back to me via phone after these messages."
Twelve days later, the blast at the workshop in Platinum@Pioneer industrial building killed Marimuthu and two others, while Mehedi sustained serious burns to 58 per cent of his body. Six other workers were also injured.
Marimuthu left behind his wife and two young daughters. He never got to meet Lithesaa, who was only 10 months old at the time.
Preliminary investigations indicate that the blast was caused by a combustible dust explosion. The dust was in the form of potato starch powder.
Day four of the public inquiry was again centred on the mixer machine purchased by Chua in August 2019 for US$11,700 from Laizhou Keda Chemical Machinery in China via Alibaba. It was used to manufacture a fire clay material with ingredients such as potato starch, boric acid and silicon oil.
The mixture of ingredients was placed in a mixing compartment and heated by an oil jacket filled with thermic oil to make the clay, which would then be wrapped with other materials to assemble the fire wrap.
On Monday, State Counsel Kristy Tan had pointed out the multiple "red flags" in the months preceding the incident that showed that continued operation of the machine posed "huge risk" to the safety of the workers. They included small fires at the machine's heaters, as well as leaks from the oil jacket.
Numerous repairs were also carried out, such as replacing worn out gaskets, welding a base plate to the underside of the machine, and installing insulation on the oil jacket.
On Thursday, Chua was subjected to a grilling by Tan, who pointed out inconsistencies in his statement and questioned his upkeep of the mixer machine.
Multiple issues with mixer machine
Stars, which provides design-built fire protection systems, was started by Chua and his older brother Desmond. The younger Chua oversaw most aspects of the company, including finance, safety and welfare. He also prepared the company's risk assessment (RA) documents, which did not identify the risk of fire and explosion when materials were transferred into the mixer machine.
"I thought that the only combustible material was potato starch, and the quantities involved at 88 kg for each batch of fire clay produced were quite small," admitted Chua, who felt that the risk of fire and explosion was unlikely.
He personally carried out monthly maintenance of the machine, using a checklist which he prepared based on the user guide. But the workers began experiencing issues with the machine from August 2020.
Chua claimed that the machine's user guide lacked specific instructions and that Laizhou Keda staff were unresponsive to his queries. "I was very unhappy with their after-sales service," he said, adding that he had told Sherry, a member of Laizhou's staff, that the machine was "very lousy".
Nevertheless, on 12 February, he asked Sherry for a quote for a new mixer machine.
Inconsistencies in Chua's statement
Tan took issue with numerous aspects of Chua's statement. For example, he claimed that the user guide did not specify how often the oil in the oil jacket should be topped up.
In response, Tan quoted the guide which said, “Pay attention to check that the heat conduction oil in the jacket is added in time with the loss of heat conduction oil”. She added that it could not give a specific timing to top up as it depended on how often the machine was used and how much oil had been consumed.
Tan also cited an incident where Chua had claimed that a worker, in using a dipstick to measure the amount of oil in the jacket, had "only touched a little of the oil inside the curved side of the oil jacket".
However, she showed with a simple mathematical calculation that it required 120 litres of oil just for the amount to touch the curved side - and Chua had already stated that the jacket only contained 40 litres at that point.
Asked by Tan if his claim was "not very credible", Tan said after a long pause, "Yes, Your Honour."
Tan then noted Chua's acknowledgement that he had only measured the temperature in the oil jacket once, while using water instead of thermic oil as the heating medium. Chua responded, "The initial thought is that we want to know what temperature the jacket is operating at. Once we measure, there is no need to use the sensor."
Tan pointed out that the use of water instead would give a "very different reading", which Chua admitted. "You should actually be monitoring the temperature each time you use the mixer machine. That is the safe way to operate it, agree?"
When Chua affirmed, Tan added, "Even if the manufacturer didn’t respond, (measuring the temperature) is really not rocket science, correct?"
"Yes, Your Honour," said Chua quietly. He will resume his testimony on Friday.
First tranche of hearings
A total of 15 witnesses will be heard. Investigators from the Singapore Civil Defence Force's Fire Investigation Unit, as well the Ministry of Manpower, will also testify.
The IC is chaired by Senior District Judge Ong Hian Sun. He is assisted by Lucas Ng, general manager of the plant at Petrochemical Corporation of Singapore, and Dr Peter Nagler, chief innovation officer at A*Star. It was appointed by former Manpower Minister Josephine Teo in March.
Its role is to inquire into and ascertain the causes and circumstances of the accident. It will also determine if criminal proceedings should be initiated against any individuals.
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