Lessons Learned from a Hydrogen Explosion

Lessons Learned from a Hydrogen Explosion: On January 8, 2007, a hydrogen explosion at the Muskingum River Power Plant’s 585-MW coal-fired supercritical Unit 5 caused one fatality, injuries to 10 other people, and significant damage to several buildings. The explosion occurred during a routine delivery of hydrogen when a hydrogen relief device failed, which allowed the contents of the hydrogen tank to escape and be ignited by an unknown source. This article covers the findings of the incident investigation and the actions the plant has taken to prevent a reoccurrence.

Small bore tubing incident

A gas leak occurred at a compressor station when small bore pipework fractured. The incident resulted in a small natural gas release that was successfully resolved without harm, although the licensee identified the potential for the situation to have escalated if it was not for the careful inspection prior to works being undertaken.The small bore pipe that failed was a low point in the drain system located in a pit that was not readily accessible.The root cause was identified as the small bore pipe that failed had not been designed to handle vibration resulting from high gas flows and decreased suction pressures. The small bore pipe’s limited accessibility resulted in it being missed on previous site reviews specifically undertaken to identify potential points of failure due to vibrations.

Source:https://www.dmp.wa.gov.au

HYDROGEN FIRED BOILER EXPLOSION

Bypassing of safety interlocks during start up of boilers have caused many explosions around the World, killing many people. I had investigated one incident where a hydrogen fired boiler was being commissioned and the trips were bypassed as they were causing some problem. The boiler exploded and the operator was killed. Read about another hydrogen fired boiler explosion in this link:

 https://www.dmp.wa.gov.au/Documents/Safety/PGS_SIR_01-2016.pdf

Explosion in molten sulphur tank

Molten sulphur tanks are often not given the importance they deserve. because of the nature of the product, they are dangerous and have to be handled with precautions. This safety alert explains the case of an explosion in an molten sulphur tank. Ensure the learnings are shared. Read the safety alert in this link:

https://epsc.be/epsc_media/Learning+Sheets/2019/19_06+EPSC+Learning+Sheet+_+H2S+explosion-p-660.pdf

Inspection frequencies and OSHA

The most commonly cited equipment for non-compliant inspection frequencies (of any type, not only thickness measurements) have been piping circuits followed by pressure vessels, relief devices, and monitoring alarms. As part of the inspection program, an appropriate inspection frequency must be established for equipment in order to determine whether pipe/vessel thickness is decreasing as expected. API 570 identifies three classes of piping services and recommends a thickness measurement inspection frequency based on the class. For example, Class 1 includes:

• Flammable, 
• Pressurized services that may rapidly vaporize and explode upon release,
• Hydrogen sulfide, 
• Anhydrous hydrogen chloride, 
• Hydrofluoric acid 
• Piping over water of public throughways, and
• Flammable services operating above their auto-ignition temperature.

As discussed in API 570, Class 1 requires a thickness measurement inspection frequency of at least every five years. Classes 2 and 3 require a thickness measurement frequency of at least every 10 years. The inspection interval for specific piping is established by the inspector or piping engineer in accordance with the owner/user’s quality assurance system, but not to exceed the limits set by API 570

Source:Osha.gov

OSHA ASSET INTEGRITY OBSERVATIONS

Examples of equipment cited for violations of the PSM MI requirements that OSHA found during NEP inspections include:

• A broken gate valve caused a level gauge to not work properly, which rendered visual verification of liquid level for the vessel ineffective. This deficiency went uncorrected.
• The installation of an engineered clamp failed to correct a deficient piece of process piping, which was a 90-degree elbow that was outside acceptable limits. The employer continued to use the leaking 90-degree elbow as part of a piping circuit that conveyed waste hydrogen sulfide gas.
• Hydrogen sulfide monitors were not inspected and tested on a regular basis to correct deficiencies in alarms that were outside acceptable limits due to bad sensors, loose wiring, or monitors that needed to be replaced. Work orders were not managed by a tracking system to ensure that deficiencies were fixed in a timely manner. Some work orders marked “fix today” or “ASAP” were not fixed for a week or longer.
• Six relief systems in an alkylation unit were incorrectly sized and were not corrected in a timely manner when the deficiencies were reported. No Management of Change (MOC) was performed to justify the decision to delay replacing the deficient systems.
• Grounding cables were removed from equipment, such as a heat exchanger and pump motors, but were not replaced. 
• Excessive vibration was observed on motors with visible movement of structural steel decking and supports. Also, two 1” pipes and one 4” pipe containing flammable liquid were not adequately supported

Source: Osha.gov

ASSET INTEGRITY ISSUES

Failure to correct equipment deficiencies that are outside acceptable limits39 is one of the leading causes of PSM non-compliance in the petroleum refinery sector. Non-compliance for equipment deficiencies broke down into four major groups:

1. Lack of proper maintenance or repair, 38. 29 CFR 1910.119(j)(1)(i)-(vi)39. 29 CFR 1910.119(j)(5)OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION18
2. Inappropriate installation (such as inappropriate sizing),
3. Missing protective system (such as not including relief devices), and
4. Insufficient structural support.

Equipment most commonly cited for deficiencies were relief devices, followed by piping circuits, pressure vessels, and alarm systems.

Source:Osha.gov

 

Dust collector system explosion

Employee #1 was feeding 400 lb of granular polyalphamethyl styrene (CAS 25014-31-7) through a Mikropal #3 micropulverizer (equipped with a .032 in. screen) into a Mikropal Mikro-Pulsaire dry dust collector. The Mikro-Pulsaire unit has a continuously self-cleaning bag filter located inside the building and had no provision for explosion relief or venting. Apparently a piece of metal between 1 and 2 in. got past the magnet in the micropulverizer, ignited the dust in the system, and caused a fire and explosion that blew open the access door to the dust collector. Employee #1 was standing about 10 ft from the door and sustained second- and third degree-burns on his hands and face. 

Source:Osha.gov