September 18, 2018

Leak due to vibration

A specialized rubber manufacturing plant experienced leakage of a hexane solution from a pump discharge flange during use. The hexane vapor was ignited by a st atic electricity spark and a fire occurred. Apparently, the flange was loosened by vibrations from the pump.Routine operations were being carried out on site at the time of the accident.
The operation involved the transfer of a hexane solution from an un-reacted raw material recovery tank to the washing process through the outlet of the first flange of the pump. The hexane solution
leaked, ignited, and burned. The financial costs of recovery and lost production were significant.
The cause of the accident was a loose flange that resulted in leakage of a flammable substance. During the operation, a previously undetected cavitation in the pump produced significant vibration
which loosened the flange. As a cause of the ignition it was considered that the hexane was charged when it spouted from the flange, and static electricity was discharged; then hexane vapor ignited
and a fire occurred.
It was considered that the vibration might have been intensified by the passage of an insoluble polymer lump through the pump, a malformation in the substance generated on the piping wall. In addition, a reducer connected a 3-inch (~75mm) flange of the discharge pump to 6-inch (~150mm) piping. The looseness of this flange might have been accelerated when the force
of vibration was added on the piping.
Lessons learned
Vibrating equipment can increase potential for stress fractures and gaps from loosely fitting interfaces, all of which can be sources of leaks that, if undetected, may result in an accident. It is necessary to pay sufficient attention to vibrating equipment, especially pumps that may be found in many processes throughout the site. Control measures to mitigate potential risks could include regularly scheduled inspections in line with existing technical standards or in-house experience, particular attention to small-bore piping (vulnerable to fatigue), installation of a  vibration monitor to detect and locate abnormal vibration patterns, as well as other measures available in guidance
on vibrations from numerous sources.
Source: European Commission

September 14, 2018

Common Causes of Gasket Failure

Common Causes of Gasket Failure: During the course of our 50 years in business, Associated Gaskets has seen many different types of gasket failures. Sometimes these were seen late at night when we were called out to help with an emergency, other times it was when one of our own gaskets was returned after failing …

September 6, 2018

Global warming and its effect on process incidents

As the effects of global warming are being felt, chemical industries must acknowledge the fact for planning for natural disasters. The "Fire from ice" video about the Valero refinery incident and The Arkema incident due to Hurricane Harvey are two examples related to climate. Cyclone maximum wind speeds are increasing and past weather data may not be a reliable predictor about the future. What are you doing about it?

September 3, 2018

Gasket failure incident

On 5th January 2008 a production operator discovered a fair sized phenol leak in the phenol pump house next to the phenol storage tank. One of the gaskets on the flange connection on the outlet pipe of the tank had failed. The head of the operations department tried to stop the leak by tying a rubber belt around the flange. In the meantime, an operator sprayed water on the flange to avoid contact with phenol as much as possible. The phenol that had leaked was collected in a catchment pit of 20 m3 underneath the pump house. This catchment pit had a high level alarm, but it was not functioning at the time of the leak. The company was not aware of the malfunction because the alarm was not subject to periodic inspection.
An attempt was made to close the only manual valve on the pipe,located between the inner and the outer tank shells, but the valve spindle broke off during this manipulation, so the line could not be
shut off. After the temporary repair of the flange connection, three leaks continued to release phenol, which were also collected in the catchment tank. It was not allowed for the employees to enter the
pump house while the phenol was leaking. To clean up the catchment pit, the company provided a waste tank big enough to contain all the leaked phenol. When starting to pump the phenol from the catchment tank to the waste tank, it was discovered that the catchment pit had overflowed. Part of the
phenol/water mixture had passed over the rim of the open pit into the municipal sewer system. At the time, it was not yet known how much phenol had leaked to the sewer system.
On 7th January 2008 it was decided to start up the phenol-based batch production to consume all phenol in the storage tank since the phenol tank had to be taken out of service in order to replace
the gasket on the flange. On January 8th, after a few batch productions, it was found out that the level indicator in the phenol storage tank had become stuck since the last control of the level on 4th January (comparison of manual level measurement with level indicator). Only at that moment did the company realize that 25t of phenol had leaked out of the tank. The catchment pit probably
collected most of the release, but more than 5t of the phenol spilled into the municipal sewer. No consequences were reported as a result of the release into the municipal sewer. A specialized
company was hired to repair the remaining phenol leak.
In this case, a variety of causes contributed to the accident. The direct cause was the degradation of gasket that caused the leak. After the flanges and valves were replaced following the accident, it
was discovered that the valve broke down because the gasket next to it had been reacting with phenol over the course of many years, leading to a solid deformation that prevented the valve from moving,
hence, the valve could not be closed. The spindle of the manual valve at the tank broke off as a result of the deformation of the adjacent gaskets.
Source: European commission