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-/