Case Ditails

Scenario
Case Name Rupture of a triethanolamine tank caused due to an erroneous injection of nitric acid
Pictograph
Date January 25, 1996
Place Uji, Kyoto, Japan
Location Electronic part factory
Overview Nitric acid was erroneously injected from a tank lorry to a tank of triethanolamine, which caused an intense exothermic reaction. The tank ruptured due to its increasing internal pressure. At facilities that handle substances with contamination hazards, intrinsically safety design to prevent mixing due to human errors and safety education on chemical substances are required.
Incident Nitric acid carried with a tank lorry was erroneously injected into an adjacent triethanolamine (TEA) tank, and the tank ruptured.
Processing Storage
Substance Triethanolamine, Fig2
Nitric acid, Fig3
Nitrogendioxide, Fig4
Type of Accident Rupture
Sequence 1. The driver of a tank lorry carrying nitric acid erroneously connected it to the inlet of the TEA tank.
2. A factory worker in charge of receiving chemicals opened a solenoid valve of the nitric acid tank to start receiving.
3. The driver found that the liquid level of the nitric acid tank did not rise while that of the TEA tank rose. He informed the factory staff, disconnected the hose to the TEA tank, and discharged nitric acid in the piping.
4. Although the driver informed the staff of the injection of nitric acid in the TEA tank, the worker judged that nitric acid did not enter the TEA tank because the solenoid valve of only the nitric acid tank was opened.
5. The hose of the lorry was reconnected to the nitric acid inlet and injection was restarted.
6. Smoke rose from the TEA tank during injection into the nitric acid tank, and the TEA tank ruptured after five minutes. Eleven adjacent tanks were damaged by debris from the ruptured tank, and chemicals flowed into the tank yard.
Cause An exothermic reaction took place when nitric acid mixed with TEA. As the liquid temperature rose, nitrogen oxides gas was generated, which raised the internal pressure of the tank, and the tank ruptured. Inadequate judgment of the driver, in addition to miscommunication among factory staff, caused the accident.
1. The driver had come to the factory for the first time. He was informed that the injection nozzle for nitric acid was the second one from the left. Nevertheless, because he wrongly believed that the nozzle for nitric acid was made of stainless steel, at his own judgment he made a connection with a stainless steel nozzle, as he found that the indicated nozzle was made of vinyl chloride.
2. Although the factory staff did not open the main valve, another worker opened the bypass valve of the main valve on the previous day and it was left open. This was not informed to the staff in charge of receiving chemicals, or he simply forgot it. As a result, nitric acid entered not only the receiving piping but also the TEA tank itself. The worker concerned made a further mistake by judging that no nitric acid was injected into the TEA tank without confirming the rise in the liquid level of the tank. AS only nitric acid remaining in the piping was removed, it remained in the tank and reacted with TEA.
Countermeasures Communication and confirmation of what has been done should be ensured. In addition, the following also have to be done. (1) Receiving operation should be carried out in the witness of the chief responsible for specified chemical substances. (2) The flange should have a different shape for different chemicals. (3) Lighting should be installed near the inlets. (4) Countermeasures against an accident by an erroneous injection should be defined and training should be provided.
Nevertheless, because it is not possible to stop the reaction between nitric acid and TEA once it has started, it is essential to prevent miss-injection in the first place.
Knowledge Comment Most accidents with chemical substances with contamination hazards are caused due to human errors and a lack of safety knowledge.
Background It was familiar work which led to inattention. It is assumed that there was no sense of danger even though the receiving piping for two materials that should not be mixed were located close to each other. There was no communication that should have been done during usual operation, nor confirmation of the lineup for receiving. On receiving material from a lorry which is done constantly, the witness of a factory staff and confirmation of the line-up are sometimes omitted. Therefore, no information about the opening of a bypass valve was the main factor. It is not clear whether it was caused by an individual error or looseness of attention in the factory as a whole. Including the absence of a factory staff on the site, the following are indicated. (1) The chief responsible for specified chemical substances (defined by regulation) was not present. (2) Confirmation of hose connection was done by a subcontractor. (3) Lighting was poor. (4) Hose inlets for dangerous materials that should not be mixed were located close to each other.
Incidental Discussion There are some cases in which receiving a lorry as a routine operation is carried out by a transport firm in the absence of a factory staff for cost saving. Although this is understandable given the current economic situation, it is not recommended from a safety point of view.
Reason for Adding to DB Example of rupture caused due to a hypergolic reaction from an erroneous injection
Scenario
Primary Scenario Organizational Problems, Poor Management, Looseness of Discipline, Ignorance of Procedure, Disregard of Procedure, Omission of Confirmation, Poor Value Perception, Poor Safety Awareness, Inadequate Risk Recognition, Planning and Design, Poor Planning, No Consideration on Safety Engineering, Malicious Act, Rule Violation, Safety Rule Violation, Bad Event, Chemical Phenomenon, Abnormal Reaction, Failure, Large-Scale Damage, Rapture, Loss to Organization, Economic Loss, Manetary Damage 100 million yen
Sources Japan Industrial Safety and Health Assoc. The details of occurrence of accidents.
Japan Industrial Safety and Health Assoc. Safety and health information center. Accident case No.789. Nitric acid from tank lorry was injected into triethanolamine tank by mistake, then the tank ruptured. The Japan Industrial Safety and Health Assoc. home page
Number of Deaths 0
Number of Injuries 0
Physical Damage Window glass was damaged by the impact of a storage tank rupture.
Multimedia Files Fig2.Chemical formula
Fig3.Chemical formula
Fig4.Chemical formula
Field Chemicals and Plants
Author WAKAKURA, Masahide (Kanagawa Industrial Technology Research Institute)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
Scenario