Mechanical

System Failures

Process Tank Implosion

Mechanical System Failures

Process Tank Implosion

Mechanical System Failures

Process Tank Implosion

Late in the construction phase of a North Carolina candy factory, a large stainless-steel process water tank imploded during system testing.  The subject tank was designed to hold hot, fresh water at sub-boiling temperatures for use downstream in the ingredient mixing process.  A combination of valves and system control elements were designed to operate the system, maintain water temperature, and control flow as required.

Factory Tank Farm

During the site inspection, the EIS engineer assigned to the project learned that the building management system had not yet been fully setup, so there was no historical controls data available to provide clues as to the state of the system prior to the failure. Through conversations with the construction team involved in system testing at the time of the loss, it was discovered that the subject tank had been filled to about the midpoint with 200°F water shortly before the incident.

Subsequently, the construction team was using the control system to individually actuate various valves throughout the system. Through review of the construction drawings and system schematics, it was determined that the heat exchanger was not activated when the valve to the tank opened, which allowed cold water to be dumped into the tank.

The tank was inspected and found to be equipped with an atmospheric vent at the top, designed to provide relief in the event of a sudden pressure change. Disassembly of the vent revealed that it was equipped with an internal filter. During post-inspection analysis, it was discovered that the filter media used

Paper Filter

in the vent did not meet the project specifications.  Specifically, the specified filter media was to be approved for use in a wet environment; the paper filter media observed during the site inspection was not for use in such an environment.

Through inspection and analysis, it was determined that the 200°F water residing in the tank just prior to the failure caused a column of water vapor to develop in the upper half of the tank.  The vapor column reasonably caused the paper filter media of the atmospheric vent to become wet.

Moments later, when the valve was opened, cold water poured into the tank from the top.  The cold water caused the water vapor in the tank to instantaneously condense, thereby collapsing the vapor column.  The collapsing vapor column created a negative pressure spike within the tank.  Such a pressure spike would normally have been equalized through the tank’s atmospheric vent.  However, the wet paper filter media prevented air from passing through the vent.  As a result, pressure equalization was alternately achieved when the tank imploded.

Imploded Tank

Late in the construction phase of a North Carolina candy factory, a large stainless-steel process water tank imploded during system testing.  The subject tank was designed to hold hot, fresh water at sub-boiling temperatures for use downstream in the ingredient mixing process.  A combination of valves and system control elements were designed to operate the system, maintain water temperature, and control flow as required.

Factory Tank Farm

During the site inspection, the EIS engineer assigned to the project learned that the building management system had not yet been fully setup, so there was no historical controls data available to provide clues as to the state of the system prior to the failure.  Through conversations with the construction team involved in system testing at the time of the loss, it was discovered that the subject tank had been filled to about the midpoint with 200°F water shortly before the incident.

Subsequently, the construction team was using the control system to individually actuate various valves throughout the system.  Through review of the construction drawings and system schematics, it was determined that the heat exchanger was not activated when the valve to the tank opened, which allowed cold water to be dumped into the tank.

The tank was inspected and found to be equipped with an atmospheric vent at the top, designed to provide relief in the event of a sudden pressure change.  Disassembly of the vent revealed that it was equipped with an internal filter.  During post-inspection analysis, it was discovered that the filter media used

Paper Filter

in the vent did not meet the project specifications.  Specifically, the specified filter media was to be approved for use in a wet environment; the paper filter media observed during the site inspection was not for use in such an environment.

Through inspection and analysis, it was determined that the 200°F water residing in the tank just prior to the failure caused a column of water vapor to develop in the upper half of the tank.  The vapor column reasonably caused the paper filter media of the atmospheric vent to become wet.

Moments later, when the valve was opened, cold water poured into the tank from the top.  The cold water caused the water vapor in the tank to instantaneously condense, thereby collapsing the vapor column.  The collapsing vapor column created a negative pressure spike within the tank.  Such a pressure spike would normally have been equalized through the tank’s atmospheric vent.  However, the wet paper filter media prevented air from passing through the vent.  As a result, pressure equalization was alternately achieved when the tank imploded.

Imploded Tank

Late in the construction phase of a North Carolina candy factory, a large stainless-steel process water tank imploded during system testing.  The subject tank was designed to hold hot, fresh water at sub-boiling temperatures for use downstream in the ingredient mixing process.  A combination of valves and system control elements were designed to operate the system, maintain water temperature, and control flow as required.

Factory Tank Farm

During the site inspection, the EIS engineer assigned to the project learned that the building management system had not yet been fully setup, so there was no historical controls data available to provide clues as to the state of the system prior to the failure. Through conversations with the construction team involved in system testing at the time of the loss, it was discovered that the subject tank had been filled to about the midpoint with 200°F water shortly before the incident.

Subsequently, the construction team was using the control system to individually actuate various valves throughout the system. Through review of the construction drawings and system schematics, it was determined that the heat exchanger was not activated when the valve to the tank opened, which allowed cold water to be dumped into the tank.

The tank was inspected and found to be equipped with an atmospheric vent at the top, designed to provide relief in the event of a sudden pressure change. Disassembly of the vent revealed that it was equipped with an internal filter. During post-inspection analysis, it was discovered that the filter media used

Paper Filter

in the vent did not meet the project specifications.  Specifically, the specified filter media was to be approved for use in a wet environment; the paper filter media observed during the site inspection was not for use in such an environment.

Through inspection and analysis, it was determined that the 200°F water residing in the tank just prior to the failure caused a column of water vapor to develop in the upper half of the tank.  The vapor column reasonably caused the paper filter media of the atmospheric vent to become wet.

Moments later, when the valve was opened, cold water poured into the tank from the top.  The cold water caused the water vapor in the tank to instantaneously condense, thereby collapsing the vapor column.  The collapsing vapor column created a negative pressure spike within the tank.  Such a pressure spike would normally have been equalized through the tank’s atmospheric vent.  However, the wet paper filter media prevented air from passing through the vent.  As a result, pressure equalization was alternately achieved when the tank imploded.

Imploded Tank