Process Safety Moments
This page contains brief descriptions of situations that have occurred at process facilities which can teach important lessons. Questions are posed to help focus on the key points.
New moments are added regularly so check back periodically.
Contractor Awareness of Hazards
The fourth floor of the main processing building at a facility was being repaired. Cement was being pumped from the ground level. The cement truck was located next to the facility's tank farm. A crane was used to hold the cement hose above the tank farm which contained two large storage vessels of chlorine gas. When asked, the cement truck driver and crane operator did not know what was contained in the vessels or if the contents were hazardous.
Repairing floors and pumping concrete are not covered operations under OSHA's process safety management (PSM) standard. However, performing work within or in close proximity to a PSM-covered process requires proper awareness of the hazards present. In this particular situation, the cement truck driver and crane operator were subcontractors. The main contractor failed to share basic information about the process with those companies working for it.
The provisions of the PSM standard, and certainly the impacts of the hazards of an operation subject to PSM, apply not only to employees but also to visitors, contractors and subcontractors. Anyone present on-site needs to know the hazards present in areas where they will work and adjacent to them, and the provisions of the emergency action plan that pertain.
Is this true for your facility?
Protection of Hot Oil and Other Systems
At a pilot plant facility, a hot oil heating system did not have a low flow interlock. A switch failed “on” so that the oil continued to heat while not circulating (electric heater). Because of their location in the system, neither the pressure nor temperature interlocks were effective. The steel encasing the oil failed releasing hot oil, which ignited in the room only minutes after security passed through on rounds. At a plant owned by the same corporation, a similar incident occurred with a full-scale system, killing several workers. Hot oil systems must be designed with low-flow interlocks. Electric heating elements, unless designed to fail at low temperatures, can continue to heat until a failure occurs.
Does your facility recognize the need to protect hot oil systems with sensors that will operate in "no flow" situations? Are there similar situations with other protective measures where they will not function under various foreseeable circumstances?
Human Factors in the HMI
On investigating an incident involving high temperature heat transfer fluid at a facility, it was discovered that from approximately 2:00 to 4:00 in the afternoon, the operators could not see the control panel due to glare from the fall sun.
Do your human factors reviews recognize and correct deficiencies in the human-machine interface (HMI)? Do you have a system in place to respond effectively to operators' concerns about their working conditions?
At a solvent spun synthetic fibers facility, operators did not recognize for over 36 hours that a 60" duct carrying solvent laden air at 70% LEL had physically blown an end off and was releasing the mixture to the environment. Relying on detection and correction of an abnormal situation solely by operating personnel is a weak safeguard.
Are your operators well enough trained to recognize and respond to unusual process upsets in a timely manner? Does refresher training reflect lessons learned in recent incidents?
Expecting the Unexpected
A batch nitroglycerin process at a Government Owned – Contractor Operated (GOCO) facility exploded after having been operated without incident for forty-six years, proving once again that, “we have never seen anything like that,” is not a sufficient criterion for ruling a scenario out in a PHA.
Do your PHA teams understand that their charge is to identify the potential incidents that haven't happened but might? Are your risk tolerance criteria, and your culture, sufficiently rigorous to deal with rare events?
A series of PHA studies identified the possibility of the nitrogen blanket on flammable storage tanks being turned off so that the tanks might collapse during pump-out. Each scenario was judged to be acceptably safe individually. About 4 years later, one of the events occurred, and the company questioned the validity of the PHA. On review, they found that the tank collapse should have been expected based on the aggregate risk from all the tanks. They had no system to look at the aggregate risk and determine if they still met their safety criteria.
Does your company look at aggregate risk from similar scenarios that occur in multiple PHAs? If not, does management have a false sense of security?
Confined Space Created by a Tarpaulin
A work crew used a tarpaulin to provide protection from the weather while performing work on process piping. Inadvertently, they created a confined space but did not follow the company’s confined space procedure. One fatality occurred.
How will your employees know if they have created a confined space? Are they able to recognize when they encounter a confined space?