Design Options for Overfill Protection for Aboveground Atmospheric Tanks - Best Practices

"Overfilling of a tank is an important safety hazard.  It may result in loss of tank fluid and potentially severe consequences if the fluid is flammable or environmentally sensitive.   Additionally, it is necessary to preserve the mechanical integrity of a tank.   This article first looks briefly at various ways liquid may overfill a tank, and then describes different design options as best practices to take care of situations where overfilling is a possibility.   The main paper will contain diagrams and appropriate references."

 See this link https://www.aiche.org/academy/videos/conference-presentations/design-options-overfill-protection-aboveground-atmospheric-tanks-best-practices

DONT UNDERESTIMATE OVERFILLING RISKS

 "Loss of level control has contributed to three significant industrial incidents:

 In Australia, the Esso Longford explosion in September 1998 resulted in two fatalities, eight injuries, and A$1.3 billion (more than U.S. $ 1 billion) in losses [1];In the U.S., the BP Texas City explosion in March 2005 caused 15 fatalities and more than 170 injuries, profoundly affected facility production for months afterwards, and incurred losses exceeding $1.6 billion on BP [2]; andIn the U.K., the Buncefield explosion in December 2005 injured 43 people, devastated the Hertfordshire Oil Storage Terminal, and led to total losses of as much as ₤1 billion (about $1.5 billion) [3, 4]."

Read the article at https://www.chemicalprocessing.com/articles/2010/143/

2019 Significant Process Safety Incidents

2019 Significant Process Safety Incidents: Use this summary of 2019's process safety incidents to learn and to help prevent incidents at your facility, whatever your industry. This video is a summary of significant process safety incidents during the year 2019. The purpose of maintaining awareness and sharing process safety incidents each year is to promote the Risk Based Process Safety (RBPS) approach to lessons-learned and to encourage industry to maintain a sense of vulnerability. This allows our members to be up to date on the latest news regarding process safety as we strive to be strong, smarter, and more effective in the ongoing effort to reduce process safety incidents to zero.

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

SIL and functional safety in rotating equipment

 SIL (safety integrity level) is a very important safety indicator that has been extensively discussed, described and often misunderstood within the industry over the past years. The purpose of this article is to provide operators, reliability engineers, instrumentation engineers and department managers with a practical overview of the areas where SIL and functional safety are important in their daily business life. Note that, in the light of the International Electro-technical Commission (IEC) and most other safety relevant standards, risk is strictly defined as “harm to health safety environment” (HSE).

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Process safety time for fired heaters

The fired heater is a common unit operation in the refining and petrochemical industries that is used to increase the temperature of a process fluid. Fired heaters are required when a process-to-process heat exchanger or a utility exchanger (steam condenser, hot oil heater) cannot provide sufficient driving force to raise the temperature of a process fluid for downstream processing. There are numerous applications for fired heaters, from preheating feed to process units to reboiling distillation towers.

During the course of normal operation a fired heater will be exposed to disturbances in the supply of fuel, combustion air, or process fluid that may lead to a potentially hazardous condition developing. To manage these disturbances and take appropriate action to safely operate and control the fired heater, several layers of protective systems are normally provided.¹ These protective systems are designed to take independent action that will prevent the fired heater from reaching a hazardous condition.

 Continue reading at Process safety time for fired heaters

REFINERY FIRE INCIDENT

Incident at Visakh Refinery Date of incident : 23.08.2013 Time: 16:46 hrs Entity: HPCL Location: VRCFP Cooling Tower, Visakh Refinery, Vishakhapatnam

Description:On August 23, 2013, one of the cells of the Salt Water Cooling Tower of Visakh refinery was being commissioned. During the opening of the water line at about 16:46 hours, there was a minor explosion and fire. The cooling tower burned down and collapsed. Due to the fire, workers working near other cells and surrounding area sustained burn injuries. There was one fatality (company employee) and 39 persons sustained injuries and were shifted to INS Kalyani and other hospitals in the city. On the next day, another 6 dead bodies were found in debris. 

Observation:

•One new cell was added to the existing cooling tower, and the existing cells were under maintenance.

•Hot jobs were going on in the nearby area.

•The ingress of hydrocarbon in the cooling water was due to leakage of cooler / condenser in process units connected with this return line.

•There was imbalance in load of two distribution headers on the top of cooling tower cells. To reduce the load on the cooling towers, a process modification scheme was issued whereby the cooling water return headers were proposed to be re-routed to the ground level and construction of riser pipes from the bottom header to the top of each cell, for uniform supply of hot cooling water to the Cooling Tower. With this, the load of return header, which earlier was on top of the cell, would be shifted from Cooling Tower structure to the separate supports outside the Cooling Tower.

•There is distinct possibility of entrapped / accumulated light hydrocarbon in the portion of the new line since it is located at an elevation and that there was no escape route for this entrapped hydrocarbon as the other end of the header was closed by valve.

•The entrapped hydrocarbon gushed into the Cooling Tower as soon as the cooling water return line valve to the new cell was opened. The hydrocarbon got ignited by the spark of welding jobs being carried out nearby causing explosion and major fire. The wooden structure of the Cooling Tower got ignited in the process which continued for about 45 minutes till the fire was extinguished by F&S personnel.

•The accident resulted in serious burn injuries and fatality to a number of persons working in the cooling tower area.

Cause:

•Gushing out of entrapped hydrocarbon from the cooling water return header to newcell, which got ignited since hot jobs were being carried out in close vicinity. The ingress of hydrocarbon was due to leakage of hydrocarbon in cooler/condenser in connected process units.

•Not adhering to the practice of stopping all work (especially hot work) and prohibiting all unrelated contractor and company personnel at site, before commissioning a new system/ facility. Also, carrying out hazard analysis/ risk assessment would have probably indicated that there could be trapped HC gas, and prompted commissioning/ operation team to vent out entrapped gases.

•Undertaking commissioning activities, even though several jobs were unfinished: HC and H2S detectors were not installed. Instrument cabling, cooling fan jobs were still unfinished.Decision to go ahead with commissioning was taken at fag end of the day.Improper coordination amongst Operation, Maintenance and Project departments.Non – liquidation of the gaps identified in internal safety audit & operation check-list before commissioning.

Recommendations:

•Do not allow simultaneous hot work and commissioning activity at site as this increasemanifolds the chances of accidents.

•While commissioning activity is planned/ undertaken, it must be ensured that other than the required personnel, nobody should be allowed to be present at the work site.

•Hazard analysis must be done prior to commissioning of any new facility.

•Hazard Identification and Risk Assessment must be carried out before commissioning of any new/ temporary facility / system; this analysis by a multi-disciplinary group can easily identify the risks involved and suggest measures to overcome the same.

•Facility(s) must not be commissioned unless pre-com audit is carried out.•No facility should be commissioned unless it is ensured that internal audit points / precom check-list points are liquidated; further a multi-disciplinary group must carry out the internal audit.

•There must be a proper coordination amongst the various departments; in the instant case there was clear communication gap and lack of coordination amongst Operation, Project and Maintenance Departments.

•No facility must be commissioned unless safety devices like Hydrocarbon or Hydrogen Sulphide detectors are installed.

•Standard Operating Procedure must be prepared; shared with operating personnel and ensured its display at site prior to commissioning.

•Proper house-keeping must be done at the commissioning site; the site should be clear of unwanted materials and debris.

Source: https://www.pngrb.gov.in/pdf/ERDMP/Analysis of incidents reported to PNGRB from July 2013 to Dec 2014

Incident due to ineffective PSM system

 OSHA's inspection identified several serious deficiencies in a company's process safety management program, a detailed set of requirements and procedures employers must follow to proactively address hazards associated with processes and equipment that involve large amounts of hazardous chemicals. In this case, the chemical was acetone, used in a PSM-covered process known as direct solvation. On the day of the explosion, a valve on a transfer line inadvertently was left open, resulting in the release of flammable acetone vapors. The vapors exploded after being ignited by an undetermined source.

"In this case, the company knew from prior third party and internal compliance audits conducted at the plant that aspects of its PSM program were incomplete or inadequate, and misclassified electrical equipment was in use. The company did not take adequate steps to address those conditions,"

"Luckily, the explosion happened when there were few workers in the plant. Otherwise, this incident could have resulted in a catastrophic loss of life."

Specifically, OSHA found that the process safety information for the solvation process was incomplete. The employer's analysis of hazards related to the process did not address previous incidents with a potential for catastrophic results, such as forklifts that struck process equipment, and did not address human factors such as operator error, communication between shift changes and employee fatigue from excessive overtime. In addition, the company did not ensure that a forklift and electrical equipment, such as a light fixture, switches and a motor, were approved for use in Class 1 hazardous locations where flammable gases or vapors are present. 

Source:OSHA.gov