ARE YOUR CRITICAL ALARMS SET CORRECTLY?

On March 14, 2023, at 11:40 a.m., approximately 1,000 pounds of flammable hydrocarbons were accidentally released from a pump seal and ignited (autoignition) at a Refinery in Texas, causing a fire.      The company estimated the property damage from the incident to be over $1 million.                        

During the unit startup approximately five days before the incident, the pump (a centrifugal pump) had operated with low suction (inlet) pressure for nearly two hours due to a low liquid level in the upstream equipment. The low suction pressure caused the pump to cavitate, which vibrated the pump and damaged the pump’s bearings. Five days later, on March 14, the damaged bearings and the resulting stress on the pump’s mechanical seal caused the seal to fail. The hot hydrocarbons within the pump were released into the atmosphere and ignited, causing a fire. The material was released at 590 degrees Fahrenheit (°F) and had an autoignition temperature of 484 °F.
 In addition, on March 11, two days after the unit startup, vibration from the damaged pump triggered a “High Priority Alarm.” The refinery’s usual responsive action to high-priority vibration alarms was to switch pumps. However, the company did not have another pump available and continued to operate the installed pump, as refinery employees believed the pump was still safe to operate. Employees anticipated that a replacement pump would be available on March 13, but the pump was not replaced before the incident on March 14.
Although the pump vibrations continued and worsened, they never triggered the “Critical High High” vibration alarm threshold because the alarm was programmed incorrectly. Had the vibration alarm been programmed correctly, the “Critical High High” alarm should have activated on March 12, two days before the incident.
The company's investigation found that the refinery operators mistrusted the pump vibration alarms due to past nuisance alarms, causing employees to normalize these alarms.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release and ignition of hydrocarbons from a failed pump that had been damaged after it cavitated during a unit startup. Contributing to the incident were unit startup conditions that damaged the pump, incorrectly programmed alarms, and employee mistrust of alarms.

Source: CSB.gov

Watch "Process Alarm Systems Updates to EEMUA 191 by Andy Brazier" on YouTube

 Watch "Process Alarm Systems Updates to EEMUA 191 by Andy Brazier" on YouTube

 https://youtu.be/xh62GMQ53u0?feature=shared

Alarm floods and plant incidents

Most of the incident investigations performed by the US Chemical Safety Board (CSB) cite alarm floods as being a significant contributing cause to industrial incidents. In fact, alarm management has become identified as one of the key issues listed on the cover of recent CSB investigation reports. The British-based organisation Engineering Equipment & Materials Users’ Association (EEMUA) came to the same finding in its report from 1999 when it analysed major incidents around the world, including Three Mile Island, Bhopal and Texaco Milford Haven.¹ Therefore, the connection of alarm floods to incidents has been well documented for over 12 years. On the whole, industrial progress controlling floods in those 12 years has been nil. Many corporations and plant locations are attempting to do so, but many engineers, including alarm management vendors, do not know what it takes to control floods under all operating conditions. This article shows examples of good alarm management programmes and how they successfully control alarm floods under all operating conditions.

 Read the article at Alarm floods and plant incidents

Alarm management

http://www.plantservices.com/articles/2017/automation-zone-alarm-management/

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Setting a new standard in alarm management

 Setting a new standard in alarm management

Contribute to the surviving victims of Bhopal by buying my book "Practical Process Safety Management"

Don't Alarm your operator!

I have been following the subject of alarm management in a DCS (Distributed control system) with great interest. In many process incidents that I investigate (batch and continuous processes), I observe that the flood of alarms that appeared during the emergency effectively negates the usefulness of the alarm. The irony is that we bring in the DCS with its enormous capability and then realize that alarm management in the DCS is a big issue. The root cause of the problem is the misuse of the enormous capability of the DCS. When installing the DCS it is human tendency to assign all probable alarms, thinking that we are using the capability of the DCS! Now the International Society of Automation has brought out a standard called ISA 18.2 - management of alarms in process industries on June 23rd,2009. The definition of alarm as stated in the standard is "an audible and/or visible means of indicating to the operator and equipment malfunction,process deviation or abnormal condition requiring a response". How did we manage to forget this definition?

I was part of a team of process engineers and process operators in a World Scale methanol plant, where we sat down identifying whether each alarm that was provided was really necessary or not. To our surprise, at the end of the exercise, we had reduced the alarms by over 50%!. Today, there are alarm suppression software sold by various vendors, but I feel the solution is simple - DO NOT COMPLICATE THINGS AT THE BEGINNING ITSELF BY PROVIDING TOO MANY ALARMS!
To achieve the goal process Safety I am of the opinion that things must be kept simple. In other words, KEEP IT SIMPLE & SAFE (KISS!)

While on the topic of alarm management, I have also observed the other extreme in few cases - there weren't enough alarms provided. Such issues crop up not in process plants but in storage and transfer facilities where enough thought was not applied in identifying the alarms required.