Human factors during hydraulic torqueing of bolted joints

 SOURCE: https://www.stepchangeinsafety.net/alerts-moments/high-value-learning-hydraulic-over-torqueing-of-bolted-joint-equipment/

 Description of Incident

Two incidents have occurred during the hydraulic torqueing of bolted joints on assets operated by two different operators in the UKCS. In one instance, the event caused significant damage to the bolted joint; in the other event, the over torqueing value was identified before serious damage could occur.

In both instances the hydraulic torqueing equipment was wrongly set to a torque level higher than the bolted joint design value.

Common issues in both incidents include:

• The torqueing value was entered incorrectly (~1000psi higher than design)
• Both gauge faces involved contained both Bar and PSI scales
• Both torqueing sets were in a position where reading the gauge could be problematic due to the low angle
• No verification of equipment settings was carried out prior to torqueing equipment being operated

Good Practice Guidance

• Consider whether the gauge on the equipment you use is required to carry both Bar and PSI. Could it cause confusion?
• Consider whether your processes are sufficiently robust to prevent a similar incident occurring
• If you contract out this activity, consider how you assure yourself on the competence of the operators provided

Failure of the gear box “anti-rotation” pins of fire water pump

Source: https://www.stepchangeinsafety.net/alerts-moments/high-value-learning-failure-of-a-fire-pump-clutch-as-a-result-of-a-gear-box-anti-rotation-in-failure/

Description of Incident

A failure of a diesel engine driven fire pump clutch occurred during routine pump start up. Clutch components were released at high speed into the fire pump room. This resulted in damage to the fire pump room and to the engine and its ancillary systems. Lubricating oil pipework was damaged, resulting in the release of approximately 100 litres of lubricating oil within the room. There was no further consequence of this release (i.e. fire or explosion). No personnel were present, so there was no harm to people. The fire pump assembly was unavailable for several months whilst an investigation and corrective repair was carried out.

The event was investigated with support from the package OEM and supplier. Investigation of the event revealed that the clutch failure was the result of damage which had occurred within the right-angle gear box (connecting the line shaft fire pump to the clutch / diesel engine). A failure of the gear box “anti-rotation” pins had occurred, which caused the gear box to seize and ultimately led to failure of the clutch in operation.

The investigation determined that:

• The O&M instructions for the gearbox state that anti rotation pins should be clean, oil free and free to travel (rise / fall) within their locating slots.
• On inspection, the damaged pins were found to be contaminated with oil.
• Assembly records indicate that when the pins were installed they were not lubricated and travelled freely.
• Oil migration from the thrust bearing assembly within the gearbox to contaminate the anti-rotation device and pins was possible.
• The company maintenance strategy for gearboxes did not identify anti-rotation pin as a failure mode and no specific maintenance or inspection tasks were scheduled or in place for the installation where the failure occurred.
• The OEM manual for the gearbox and the fire pump package did not recommend any specific maintenance or inspection for the anti-rotation pins, only a check of the gear box oil level.
• An anti-rotation pin failure had occurred on another of the company’s installations several years prior, due to corrosion of the anti-rotation pin causing it to stick / seize the gear box. Periodic inspection and pin replacement was being carried out on this installation but had not been shared across asset or used to update the equipment maintenance strategy.

Following the investigation, a series of recommendations were made which include:

• All fire pump anti rotation pins inspected in field for circumferential cracks (all installations).
• Revision to company maintenance strategy for gear box anti-rotation pins. Periodic inspection and replacement maintenance routines scheduled going forward.

Good Practice Guidance

Consider review of maintenance strategies for fire pumps / gearboxes to determine if:

• Anti-rotation pin failure is a considered failure mode.
• Maintenance routines and inspections are in place to mitigate potential failure of anti-rotation pins and the subsequent consequences.

 

H2S kills at a plant producing algae based natural food additives

Gases with hydrogen sulphide (H2S) contents killed 2 employees at a plant producing algae-based natural food additives. The insoluble fractions stemming from the extraction of gelling agents with no direct usability were being treated on a porous soil (composed of perlite) and then pressed. The filter cakes were leached (to dissolve the salt) over a 0.5-ha zone prior to composting. The drippings were channelled into two sumps, one of which was fitted with an accelerator pump for the in-plant treatment of effluent. 

The discharge hose separated at times, thus requiring that the sump be drained and the pump be adjusted. The two employees were performing this task when the accident occurred. The warning was sounded 3 hours later, once it was confirmed that the two men had not returned; both of them would be found at the bottom of the sump. H2S concentrations in excess of 500 ppm were measured. 

The gendarmerie conducted an investigation into the matter, supported by an expert appraisal. This type of accident often goes underestimated and can arise from any anaerobic fermentation of sludge or compost in the presence of cavities that allow gas to accumulate in confined spaces. High contents (6,000 ppm and above) can overwhelm personnel to the extent that the sense of smell is lost and fainting happens almost instantaneously. In this case, heavy rainfall had prevented handling the accumulations and stimulated the formation of H2S; the proportion of soluble gas in the effluent created an additional hazard.

Source Aria

INCOMPATIBLE REACTION DURING PREPARING ACID CLEANING SOLUTION CAUSES H2S RELEASE

On March 29, 2023, at approximately 5:05 p.m., toxic hydrogen sulfide gas was accidentally released at a paper mill in Kentucky. Exposure to the hydrogen sulfide gas seriously injured one operator and injured two other operators.
At the time of the incident, three operators were tasked with circulating an acid-cleaning solution through process equipment to remove the buildup of solids impairing its performance. This task required an operator to stand directly over a tank and pour solid sulfamic acid powder into its opening.
When these operators added the sulfamic acid powder, the tank should have contained water, but a valve had been left open. This allowed a “weak wash” process stream to enter the tank before the operators added the solid sulfamic acid. The weak wash contained sodium sulfide, which reacted with the sulfamic acid, generating the toxic hydrogen sulfide gas.
Operator 1, who was standing directly over the tank opening, lost consciousness from exposure to the hydrogen sulfide gas that evolved from the tank. Operator 3 was able to call for help over the plant radio system but lost consciousness soon after. Operator 2 was seriously injured after losing consciousness (while trying to help Operator 1), falling to the floor, rolling through a guardrail system, and falling about 11 feet to a lower area of the structure.

Two other Domtar employees heard the distress call and entered the room to help the operators. All three operators regained consciousness. Operator 1 and Operator 3 were able to walk outside without assistance. Emergency responders transported Operator 2 to a hospital for treatment.The company reported that about 25 pounds of hydrogen sulfide were released.
 

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the hydrogen sulfide release was the reaction between the added sulfamic acid and the sodium sulfide in the tank. The company's procedures did not indicate that the weak wash valve should be closed during normal operation, which contributed to the incident. Had the weak wash valve remained closed (or more robustly isolated), sodium sulfide could have been kept out of the tank, preventing the reaction that generated the toxic hydrogen sulfide.

Source:CSB.gov

Chiba, Japan,2011 (earthquake)

Chiba, Japan,2011 (earthquake) On 11 March 2011, the Magnitude 9 Great East Japan earthquake triggered multiple fires and explosions at the Liquefied Petroleum Gas (LPG) storage tank farm of a refinery in Tokyo Bay. At least 5 explosions occurred, the biggest of which created a fireball of about 600 m in diameter. Missiles from the exploding LPG tanks damaged asphalt tanks located next to the storage area, leading to asphalt leakage into the ocean. 

The accident also caused other effects when debris impact and LPG dispersion triggered fires in two neighbouring petrochemical installations. The fires burned for 10 days. At the refinery, six people were injured, while three injuries were reported in the facility adjacent to the LPG tank farm. Overall, 1,142 residents in the vicinity of the industrial park had to be evacuated. 

Onsite, all 17 LPG tanks were destroyed and the refinery returned to full operation only 2 years after the accident. 

Sources: Krausmann, E. and A.M. Cruz (2013), Impact of the 11 March 2011, Great East Japan earthquake and tsunami on the chemical industry, Natural Hazards, vol. 67, p.811 Cosmo Oil (2011), Overview of the fires and explosion at Chiba refinery, the cause of the accident and the action plan to prevent recurrence, Press Release August 2, 2011, http://www.cosmo-oil.co.jp/eng/press/110802/index.html.

CSB PROCESS SAFETY TRAINING APPLICATION - FREE

The CSB has developed a new interactive training application focused on OSHA's Process Safety Management, or PSM, regulation. The training covers the 14 elements of PSM using the 2005 explosion at BP’s Texas City refinery as a model. You can download the program from this link. It is 1GB size.

You can also give feedback to them on further improving it. Kudos to the CSB!

 https://www.csb.gov/news/csb-process-safety-training-application-/

Natech incident - chlorine tank lifted due to flooding

4 tanks with 80 m3 storage capacity for liquefied chlorine in a store housing 5 tanks. The tanks contained different amounts of chlorine with some containing only gaseous chlorine as a residue after discharging, and some being filled up to 20% of their capacity. Each chlorine tank was located in a concrete basin designed to retain the entire tank contents.

This tank with a capacity of 80 m3 was involved in the chlorine release on 23 August 2002.

Description

After being flooded with water exceeding the 'hundred year water level' by 1.3 m, the empty and less filled tanks were lifted by the buoyancy forces according to Archimede's law and displaced from their normal positions. The upwards movement of the tanks deformed and lifted the walkways situated above the tanks.

The safety fittings of the full tank got caught in the walkway and were completely torn off as the walkway kept moving upwards. As a consequence of the valves being torn off from the full tank, a massive leakage of chlorine occurred.

 The plant had implemented 100-year anti-flooding measures. However, the flood exceeded the 100-year flood by 1.3 m, and the severity of the flood was not forecast by authorities and was hence not expected by the plant.

Lessons Learned

Lessons Learned on Equipment

After the accident, a guide-rail structure for vertical guiding of the tanks was installed. This will avoid unwanted horizontal motion of the tanks in case of displacement. This measure was accompanied by a segmentation of the walkways which will move together with the tanks in case of floating.

Lessons Learned on Organisational Aspects

Chlorine storage was reduced to 50% of the capacity before the accident and therefore to one storehouse only, thereby significantly reducing the accident risk.

Also, prior to each scheduled shutdown of the sodium hypochlorite plant, chlorine is removed from the manifolds and pipelines, and before each scheduled power outage or disruption of cooling water supplies, the pipeline connecting the tanks in the storehouse must be disassembled.

Partial leakage of hydrochloric acid due to earthquake

 About 11:35 on December 17th, 1987, a strong earthquake occurred during usual operation of a vinyl chloride monomer plant. The substation was stopped by a malfunction of an over-current relay due to the earthquake during emergency shutdown operation. Although the emergency power generator started, fluctuations of cooling water caused by the earthquake were incorrectly interpreted as a fall of a liquid level. The emergency power generator was stopped immediately by an interlock that mistook an abnormality with cooling water. Following the total power failure, the alkali circulation pump of the absorber stopped, and the gas was discharged.

Read the incident in this link

Leakage and fire of hydrogen during exchange of a dehydrogenation catalyst at an alkylbenzene manufacturing plant

A catalyst in the dehydrogenation reactor, which usually was operated under hydrogen atmosphere, was changed with separating the reactor and its peripheral part from the slightly pressured part by closing a 20-inch remotely controlled valve. The hydrogen pressure of the peripheral part was set at 20 KPaG, and the reactor was opened to the atmosphere. Considering some hydrogen leakage, suction from piping was done with a vacuum device and, in addition, nitrogen sealing was performed. In piping restoration work after changing the catalyst, flames spouted from the clearance of the flange and two workers got burnt. The cause of the fire was mal management of the method of catalyst changing.

Read about the incident in this link

Fire at an acetylene hydrogenation section on rapid re-startup after an emergency shutdown at an ethylene plant

On July 7th, 1973, an explosion and a fire occurred at an acetylene hydrogenation section of T factory ethylene plant of I petrochemical company. Because of a restart error after an emergency shutdown, there was an error in hydrogen feed control. As excessive hydrogen was injected and it hydrogenated ethylene, the reactor reached a high temperature. In addition, there was an exothermic ethylene decomposition reaction. A large fireball (60 m in diameter, duration time 5 seconds) was produced by an explosion of 1200 kg of ethylene.

Read about the incident in this link

Lessons Learned from Accidents in the Chemical Industry in Japan

 https://www.scirp.org/pdf/OJSST_2014092613341419.pdf

Burst of a phenolic resin reactor due to abnormal reaction

 Raw materials were charged into the reactor that manufactured dihydroxydiphenylmethane by a reaction of phenol with formaldehyde at night on the previous day. By putting in the catalyst in the morning of the day, the contents were heated to the fixed 80 °C, and heating was stopped. However, the temperature continued to rise, so cooling was attempted, but a runaway reaction occurred. As a result, the internal pressure of the reactor increased and the reactor burst. One operator was injured. Although the cause cannot be specified, it is supposed that the temperature was raised too high initially, agitation was started while the temperature was rising, and vapor pressure was increased because cooling water piping was blocked, and so on.

Read about the incident in this link

Lessons learnt from process safety incidents

 https://www.aiche.org/sites/default/files/cep/20150323.pdf

Safety Critical Task Analysis (SCTA)

"Human activities are involved in different aspect of operation of a chemical facility. Starting from design, construction, commissioning, operation, maintenance till decommissioning, human is involved. For safe and reliable operation, high human reliability is required in all phases of lifecycle of the facility. However human errors have contributed to many major industrial accidents in Chemical facilities in the past. Few examples are listed" in this link

Explosion caused due to a catalytic effect of contaminant in the reactor at a resin intermediate manufacturing plant

  "An explosion occurred at a plastic intermediate plant. Raw material was decomposed explosively by contaminant on heating and agitating after charging the raw material into the reactor. The reactor exploded and a fire occurred. Due to imperfect valve operations during vacuum distillation work for a previous run, sodium hydroxide for exhaust gas neutralization flowed in reverse to the reactor. As this alkali became a catalyst, a runaway reaction occurred. "

Read about the incident in this link

DANGERS OF STARTUP AND SHUTDOWN OPERATIONS

 https://int-enviroguard.com/blog/dangers-of-start-up-and-shutdown-operations/

Lessons learned from reactive chemical incidents

https://www.aiche.org/resources/publications/cep/2022/february/spotlight-on-safety-lessons-learned-reactive-chemical-incident

“Even a simple task can turn deadly if it is not performed properly,”

"The accident took place in July 2021 at the LyondellBasell Industries complex in La Porte, near Houston, in the acetic acid production unit. The facility is the third-largest acetic acid producer in the US. The CSB’s report found that the inadvertent removal of pressure-retaining components of a valve caused the release of nearly 75,000 kg of an acetic acid mixture. The incident killed two contract workers, severely injured a third, and sent some 29 others to hospital.


“Even a simple task can turn deadly if it is not performed properly,” CSB Chairperson Steve Owens says in a press release. The incident involved a common plug-valve system, and CSB found similar serious incidents in which these valves were taken apart when removing connected equipment."

Read the article in this link

How to prevent runaway chemical reactions - EPA

" PROBLEM: Many industrial chemical processes involve exothermic (heat generating) reactions. Uncontrolled, or runaway, reactions can occur as a result of various situations, such as mischarged raw materials, failure of a reactor's cooling system or the presence of contaminants. If the heat generation exceeds the reactor's ability to remove it, the reaction can accelerate - or run away - and cause the temperature and pressure to increase. A sudden energy release from such an uncontrolled reaction has the potential to harm workers, the public, and the environment. The following Case Study aims to increase awareness of possible hazards connected with exothermic reactions."

Read the article in this link 

Runaway reactions

"A typical runaway scenario involves reactants being charged into a reactor at room temperature and heated with stirring until the reaction temperature is reached. Temperature is held constant to optimise cycle time and yield. On completion, the reactor is cooled and emptied. However, if no provision is made in the process to account for cooling failure at reaction temperature e.g. due to power failure or operator error (forgot to start the stirrer), etc. then unconverted material still present in the reactor may react at an uncontrollable rate proportional to the amount of unreacted material. This may lead to over-pressure in the vessel and subsequent rupture by virtue of the normal reaction exotherm. Alternatively, a secondary decomposition reaction may be initiated and the heat so produced may lead to yet a further increase in temperature and eventual runaway conditions1 . The prime causes of runaways are associated2,3 with – process chemistry – inadequate design – substandard operational procedures – lack of training – raw-material quality control – temperature control – agitation – mischarging of reactants – maintenance – human factors (which may impact all of the foregoing)".

Read the article in this link