August 27, 2018

Rupture of sulphuric acid tank

On 4th February 2005 a storage tank containing 16,300 t of 96 % sulphuric acid ruptured. The entire contents of the tank were spilled out into the bund and then overflowed out into the nearby dock. The environmental consequences of the accident were quite significant,the sulphuric acid emission had a serious effect on local flora in the inner and deepest parts of the harbor and harbor entrance area. When the sulphuric acid came into contact with the salt water an exothermic reaction occurred, producing a vapour cloud consisting of hydrogen chloride that drifted northwards along the coastline in the direction of the wind. Fortunately, the wind was blowing towards the sea and away from populated land areas and the cloud diluted very quickly. After the spill approximately 2,000 t of contaminated sulphuric acid remained in the bund. The acid also soaked into about 100,000 square metres of the ground surrounding the spill.
The cause of this incident was a leak in an underground coolant supply pipe of reinforced concrete installed over forty years before that resulted in a weakening of the ground under the tank farm. Apparently, water forced its way out of the pipe, eroding the ground near and around the sulphuric acid tank. This erosion damaged the ground under the tank which ultimately failed due to the lack of support of the tank floor. A study of the appearance of the involved part of the coolant supply pipe suggests that the corrosion was a result of an acidic attack on the concrete.
Important findings
• The damage indicates that the acid exposure occurred over a long period of time. However, it was not possible to determine the exact duration of the exposure.
• The pipe had been in use over many years and the operator had mno suspicion that the pipe was suffering severe degradation. The inspection of the failed pipe after the incident detected little or no internal corrosion, but heavy external corrosion to the concrete. In certain places the concrete had corroded so severely that the reinforcing steel was exposed.
• According to the German standard, DIN 4030 (equivalent to the European standard, EN 260) a strong attack on concrete occurs if the pH level in surrounding water is < 5.5 and a very strong attack can occur if the pH level is < 4.5. Fifteen years before the accident a ground pollution study was carried out in the area, during which one of the sample taking points was close to the failed coolant supply pipe. At this point the pH level was measured at 4 in the shallow groundwater. With this knowledge the company drew the conclusion that this pH level entailed risks for strong acidic attackson the concrete.
Lessons learned
• The uneven corrosion on the outside of the pipe can possibly be explained by the fact that it lay partly in groundwater flow. In this environment, the acid can pass through the barrier more easily, and the reaction products (gypsum) formed can be more easily dissolved. As such, the concrete barrier was not as effective as on the part of the pipe that remained in drier surroundings. Therefore, concrete piping exposed to ground water should be should be subject to protective measures, monitoring and inspection to take into consideration the increased risk from groundwater exposure.
• Similarly, underground piping that entail risks to foundations should be inspected and measured..
• There are a number of strategies that can be applied to piping where there is accelerated potential for degradation or where there are high consequences should significant degradation occur.
Pipes may, for example, be tested for stability (remains in place) and hydraulically checked on a regular basis. Alternatively, consideration should be given to positioning the pipe above ground. The pipe could also be placed in casings, especially where a leak may cause damage to the surroundings or where pressure and ground deformation may cause damage to the pipe.
Source: European commission

August 24, 2018

Confined space fatality

Confined space fatality – Sharp LadyThe Isle of Man Ship Registry has published Casualty Investigation Report No. CA118 on a confined space entry fatality that occurred on a crude tanker. The incident occurred after discharging crude oil. Equipment was lost at the bottom of a tank. It was decided that once the discharge was finished and crude oil washing completed, the equipment should be retrieved before loading the next cargo into this tank, to avoid any potential damage to the ship’s equipment.

The Chief Officer and Cadet entered the cargo tank after an enclosed space work permit and risk assessment had been completed. When the Chief Officer and Cadet reached the bottom of the cargo tank they felt debilitating effects of hydrocarbon vapour present at the lower level of the cargo tank. Both the Chief Officer and Cadet attempted to activate their Emergency Escape Breathing Devices (EEBD) and exit the cargo tank.
The Master observed the Cadet in difficulty and quickly entered the tank, ignoring the advice of a fellow crew member. The Chief Officer successfully exited the cargo tank but the Cadet had collapsed unconscious on the tank bottom. When the Master reached the tank bottom to aid the Cadet he was overcome by hydrocarbon vapour and collapsed.
The alarm was raised and a rescue was quickly initiated. The Master and Cadet were retrieved from the bottom of the cargo tank and brought to the main deck where first aid was administered. The report concludes that the Master died and the Cadet was injured as a result of entering the cargo tank containing a concentration of hydrocarbon vapour at the bottom of the cargo tank. The ship’s safety procedures for enclosed space were not fully complied with and the risk posed by the hydrocarbon vapour measured in the cargo tank was not appreciated by those involved in the tank entry preparations.
The report also concludes that opportunities were missed on board to stop the tank entry by several crew members and that the death of the Master could have been prevented had the safety procedures on board been followed in full.
The full report can be found at


August 18, 2018

Cross sensitivity of detectors

During an examination of a liquefied natural gas (LNG) carrier whose cargo tanks contained ethylene vapors, CO (Carbon Monoxide) gas alarms were received which were traced to an eight-inch crack on a cargo vapor line.
It was noted that the molecular weight of Ethylene (28 g/mol) was identical to the molecular weight of CO, which accounted for the CO PPM readings.  Coast Guard personnel contacted the manufacturer who confirmed that gases such as methane, propane, ethylene and mercaptan, could actuate the CO sensor without ever coming into the range of the LEL limits.

As a result of these events the Coast Guard “strongly reminds all surveyors, marine inspectors, port state control examiners, and any other persons utilizing portable gas monitors and detectors while working onboard on Liquefied Gas Carriers to remain acutely aware that the ethylene gas vapors can exhibit cross-sensitivity.  This issue is not limited to the monitors that the Coast Guard uses but also those made by other manufacturers.  Everyone using a monitor must be aware that if the CO alarm goes off it may be an indication of dangerous gases or chemical vapors and not the presence of CO.  When the alarm sounds users must take corrective action to minimize exposure risks.”
Courtesy: USCG

August 5, 2018

Level gauge and Bromine Transportation incident

Mixed acid charging in the reactor was in progress. Level gauge of mixed acid measuring vessel broke and mixed acid splashed on the body of two employees, injuring them seriously. Root Causes: Inadequate preventive maintenance, Employees not aware about potential hazard involved in the operation.

Transportation of Bromine carried out in glass bottle having 3 Kgs capacity in wooden box by goods vehicle. During transportation few bottles broken & started leaking. Due to leakage near by area affected with bromine gas. People around the area were affected due to inhalation. Root Causes: Inadequate packing of bromine bottle. Untrained driver.

Courtesy: A.G.Shingore, National Safety Council