The importance of 'O' rings in process safety

I read an article about the importance of secondary seals to prevent leaks. Mr Larry Bachus, in his article mentions the following:
'About half of all pumps in the maintenance shop today were pulled out of service because they were leaking or wouldn’t hold pressure. This is most likely a leaking gasket or o-ring. The o-ring is the rubber component of most pump seals and most instrumentation fittings. The o-ring controls the temperature, pressure, and chemical limits of the device. The difference between a flowmeter in alcohol service and a flowmeter in condensate service is the o-ring. It is not the stainless steel, or the strict tolerances, or the flange bolts. The difference between a mechanical seal in ammonia service and a mechanical seal in propane service is the o-ring. The people who assemble instrumentation devices and parts for the chemical process industries install o-rings that are adequate to perform the static pressure and vacuum test on the part at the factory, which is normally done with water or air. The ultimate user must verify that the factory-installed o-rings are correct for the pumped product application (take into account temperature, pressure, chemical compatibility, and shelf life)".
Read the full article in this link.

Hydrogen peroxide accident kills two

Thanks to Abhay Gujar for sending information about an accident in a chemical unit in Hyderabad tht has killed two women. As per the Times of India article, "The incident took place at 11.30am when the two workers were mixing hydrogen peroxide, methyl ethyl ketone and sodium sulphate to produce a chemical substance used in the manufacturing of asbestos sheet moulds and coolants. The high intensity of the explosion damaged a portion of the chemical unit's roof and severely injured both Venkata Lakshmi and Kalpana". Read the article in this link.

The MSDS of hydrogen peroxide warns of the following:
"Soluble fuels (acetone, ethanol, glycerol) will detonate on a mixture with peroxide over 30% concentration, the violence increasing with concentration. Explosive with acetic acid, acetic anhydride, acetone, alcohols, carboxylic acids, nitrogen containing bases, As2S3, Cl2 + KOH, FeS, FeSO4 + 2 methylpryidine + H2SO4, nitric acid, potassium permanganate, P2O5, H2Se, Alcohols + H2SO4, Alcohols + tin chloride, Antimoy trisulfide, chlorosulfonic acid, Aromatic hydrocarbons + trifluoroacetic acid, Azeliac acid + sulfuric acid (above 45 C), Benzenesulfonic anhydride, tert-butanol + sulfuric acid, Hydrazine, Sulfuric acid, Sodium iodate, Tetrahydrothiophene, Thiodiglycol, Mercurous oxide, mercuric oxide, Lead dioxide,
Lead oxide, Manganese dioxide, Lead sulfide, Gallium + HCl, Ketenes + nitric acid, Iron (II) sulfate + 2-methylpyridine + sulfuric acid, Iron (II) sulfate + nitric acid, + sodium carboxymethylcellulose (when evaporated), Vinyl acetate, trioxane, water + oxygenated compounds (eg: acetaldehyde, acetic acid, acetone, ethanol, formaldehyde, formic acid, methanol, 2-propanol, propionaldehyde), organic compounds. Beware: Many mixtures of hydrogen peroxide and organic materials may not explode upon contact. However, the resulting combination is detonatable either upon catching fire or by impact.
EXPLOSION HAZARD: SEVERE, WHEN HIGHLY CONCENTRATED OR PURE H2O2 IS EXPOSED TO HEAT, MECHANICAL IMPACT, OR CAUSED TO DECOMPOSE CATALYTICALLY BY METALS & THEIR SALTS, DUSTS & ALKALIES. ANOTHER SOURCE OF HYDROGEN PEROXIDE EXPLOSIONS IS FROM SEALING THE MATERIAL IN STRONG CONTAINERS.UNDER SUCH CONDITIONS EVEN GRADUAL DECOMPOSITION OF HYDROGEN PEROXIDE TO WATER + 1/2 OXYGEN CAN CAUSE LARGE PRESSURES TO BUILD UP IN THE CONTAINERS WHICH MAY BURST EXPLOSIVELY."

Hazards and precautions while handling sulphuric acid

Sulphuric acid is used in many chemical plants. NorFalco, as part of their "Responsible Care" commitment have published a very good reference called " Sulphuric acid handbook" which is available in this link. (it is a 3.8 MB pdf file)

Fire in pesticide unit in AP

Thanks to Abhay Gujar for sending info on a fire in a pesticide manufacturing unit in A.P. The article mentions the following: "In a major industrial mishap, two persons were charred to death in a fire and blast in a reactor of a pesticides manufacturing company at Cheruvukommupalem in Prakasam district in the wee hours of Wednesday.The fire broke out in the third production block at about 2.30 a.m in the third floor of the plant following suspected "electric short circuit", resulting in a blast in one of the four solvent distilling reactors at the Bhagiradha Chemicals & Industries Limited (BCIL), Revenue Division Officer K Naga Babu said. Four others working in the ground floor fled to safety".
Read the article in this link.

Distilleries are Dangerous!

I have visited many distilleries in sugar plants. When compared to chemical plants, the operators knowledge of process safety is limited. In one of the distilleries, the operators were not aware of the reason why the water level was being maintained at the bottom of a flare tower. As experienced people leave the organization, it becomes all the more important for management to implement a process safety management system in distilleries. An incident in a distillery which experienced a nitric acid spill and was subsequently closed is given in this link.

Static electricity and CO2 extinguishers

Thanks to Mr Harbhajan Singh Seghal for sending this incident:
"During the plant round of Shift Incharge at Compressor House, it was observed that there is smoke and spark on Non-Drive side bearing of Cooling Tower No.1 – Pump No.D. Immediately this pump was stopped. After stopping the pump fire took place at that place which was extinguished by CO2 Fire Extinguisher. While carbon dioxide cylinder was opened for extinguishing the fire, it was observed that there was continuous spark from the surface of the horn (Outlet Black Nozzle) of the Carbon Dioxide Cylinder. This was informed to Fire Section. As per Fire Section, this is due to static current".

A safety bulletin prepared by the safety advisory group mentions the following:
"The Safety Advisory Group, SAG, has been informed of several fatal accidents caused by explosions which occurred while using CO2 during inerting equipment and storage tanks that had previously contained flammable materials. In most cases the flammable
materials were liquids or gases but dust explosions may also be triggered by the same cause.
Examples of fatalities:
• Two navy firemen were killed in an explosion while attempting to inert an 18,9 m3 Jet Fuel tank by use of portable CO2 fire extinguisher.
• Four persons were killed in an explosion on board the tanker Alva Cape while inerting naphtha tanks using CO2 cylinders.
• Twenty nine persons were killed in an explosion while witnessing the demonstration of a newly installed CO2 fire-extinguishing system for a partially filled 5000 m3 jet fuel tank, in Bitburg, Germany.
Subsequent investigations have shown that, during the inerting process, static charges of several tens of kV were generated and accumulated at the end of the piping connected to the tank. Voltage of this nature is sufficient to produce sparks which act as points of ignition for the flammable mixtures. When liquid CO2 expands up to absolute pressures of less than approximately 5 bars, the result is the formation of small particles of solid CO2 (dry ice). As the two-phase solid/gas flows through the piping, static charges are produced by the particles rubbing against other particles, between themselves, piping and equipment. Subsequently, these charges accumulate in the zones that are not earthed/grounded at the end of the pipelines, most often in valves and nozzles. The sizes of these fields, as determined by experiments, can reach values of between 50 and 180 kV/m. Similarly, static electricity can be generated by the dry ice particles after they leave the discharge nozzle.
The pressure and impurities in the CO2, equipment materials in transfer line hoses, etc. all influence the generation of static electricity".
Read the safety bulletin in this link.

Another Chlorine leakage incident

Thanks to Mr Harbhajan Singh Seghal for sending this incident:
On 18.8.2010 a message was received from Emergency Control Room regarding chlorine leakage in one of the consumers near Vadodara. Immediately the emergency team was sent to attend the problem.
PROCESS / ACTIVITY : The consumer was filling liquid chlorine from 900 kgs to 100 kgs. Cylinders by keeping on weigh balance. The tonner (900 Kgs.cap.) was pressurized with Nitrogen from upper valve. Lower valve of the tonner was connected with the withdrawal pipe fitted with filling valve to 100 kgs. Chlorine cylinder. There was a provision to release withdrawal pipe gas in 200 ltrs. drum containing caustic 100 kgs.
CAUSE OF INCIDENT: During transferring process from 900 kgs. to 100 kgs. liquid chlorine in 900 kgs. tonner exhausted. Pressure of the tonner suddenly gone up due to nitrogen padding. This resulted in very heavy vibration in the withdrawal pipe. Due to this, connection at the both ends was disturbed and damaged the corroded fittings and filling valve due to physical impact. This resulted in heavy gas release from the tonner and cylinder side.
ACTION TAKEN :

• Both the valves of 900 kgs. tonner and 100 kgs. Cylinder were closed after wearing the SCBA (Self Contained Breathing Apparatus).
• Fire hydrant team sprayed water externally to restrict gas in the outer area.
• Police Deptt. controlled the external public for further exposure.
• 10 persons affected with gas during the process were admitted in the hospital which were discharged after first aid.
• Spilled chlorine hydrate was neutralized with Caustic Soda gradually.
• All the tonners were brought back to the plant as per the advise of Explosive Deptt. and depressurized.

All the tonners condition and valves were checked and found perfectly in working order. TECHNICAL / LEGAL LAPSES :

1. Filling of liquid chlorine from 900 kgs. to 100 kgs. was not authorized from Deptt. of Explosives.
2. 900 kgs. Tonner was pressurized manually with Nitrogen pressure from cylinder (max. pressure 150 kg/cm2).
3. Max. pressure required to transfer liquid chlorine to toner is about 10 – 11 kg/cm2 where as uncontrolled pressure was applied manually. It disturbed the transfer process due to high pressure in tonner.
4. There was no well set chlorine neutralizing system. Neutralization was done in 200 ltr. Drum containing caustic.
5. Brazing of copper tube and chlorine valve used for filling was badly corroded and brazing workman ship was very poor. The fitting was not tested at desired pressure.
6. No safety equipments were maintained by the consumer to control any emergency.

LESSONS LEARNT :

1. Filling of liquid chlorine into the tonners can be done after getting the necessary approval from the Deptt. of Explosives.
2. A well set system has to be provided for filling and neutralizing from safety point of view. It is a very unsafe process to transfer liquid chlorine without proper facilities and competent persons
3. Corroded fittings are not be used. Withdrawal pipes needs to be tested and replaced regularly.
4. Provision of pressure regulator and pressure gauge in the line / header is a must.
5. All the safety equipments and gas mask should be readily available.
6. Provision of vacuum system connected with chlorine neutralization system can help to control chlorine hydrate gas due to liquid chlorine spillage.

Electrical area classification

Many plant operations, electrical maintenance and process engineers often get confused about electrical area classification. Electrical area classification is an important part of process safety. Read a succinct explanation of electrical area classification in this link.

Process safety and security - facility siting

A news article mentions the presence of a warehouse containing ammonium nitrate near refineries and fertilizer plants in Visakhapatnam. Recently, the Govt. of India has recently brought Ammonium Nitrate under the explosives act after its usage by terrorists.
The article mentions the following:
"At the time of setting up of this facility in 2007, there was a furore. After the environment assessment report was presented before the MoEF (ministry of environment and forests), the matter went for public hearing, which saw many local residents protesting storage of this hazardous substance, backed by some political parties as well. "But like in many other cases, public objection was overlooked and the government cleared the project, which is again illegally built on the CRZ (costal regulation zone) area," said Mr Sarma.
"Vishakhapatnam is a busy and an important area," he added, "it is a major Coromandel port, it houses the headquarters of the Eastern Naval Command, is an ecologically sensitive zone and is an industrial and commercial hub. Several incidents—from the 26/11 massacre to the sinking of MV Rak—have shown us how vulnerable our coastlines are. In such a situation, storage of explosive substances like ammonium nitrate is a big risk, especially when there are no checks on it."
Read the article in this link.

The importance of lube oil

Many process incidents have been initiated by a shutdown of a critical equipment due to problems in the lube oil system. A short but good article titled "3 reasons why lube oil fails" written by Jeremy Wright highlights contamination, oil degradation and additive depletion as the 3 reasons why lube oils fail. Read the article in this link.

Hydrogen cylinder fire incident

A fire in a plant in the US where hydrogen cylinders on a trailer caught fire has been reported. See the photos of the fire in this link. Apparently a supply line was being repaired at the time of the incident.

Sodium nitrite explosion kills 2

A blast in an disinfectant manufacturing unit in China has reportedly killed two persons. The unit uses sodium nitrite. A fire is reported to have caused the explosion. The MSDS of sodium nitrite mentions the following:
"Special Remarks on Fire Hazards:
When in contact with organic matter, it will ignite by friction. May ignite combustibles.
Special Remarks on Explosion Hazards:
Explodes when heated over 1000 F (538 C). Sodium Nitrite + thiocyanate explodes on heating. A mixture of sodium nitrite and various cyanides explodes on contact. Mixture of sodium nitrite and phthalic acid or anhydride explode violently on heating.Fusion of urea with sodium nitrite Interaction of nitrites when heated with metal amidosulfates (sulfamates) may become explosively violent owing to liberation of nitrogen and steam mixed with ammonium sulfamate form. Violent explosion occurs if an ammonium salt is is melted with nitrite salt. Shock may explode nitrites. must be carried out exactly as described to avoid risk of explosion".
Read the news article in this link.
See the MSDS of sodium nitrite in this link.