Tanker Couplings

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One of the most common incidents that can happen with potentially disasterous conequences involving chemical storage and handling is the inadvertent filling of a tank with the incorrect chemical. Not only does this cause process problems, but it can also be dangerous if the chemicals react.

Attempts have been made to prevent these incidents by seperating tanker fill points, locking away the fill connections, and having operators present at the time of chemical transfer. These however all do still carry a risk of human error.

Hazard prevention relies heavily on engineering controls to prevent incidents.

KemKey couplings instead of standard camlocks provide an engineered prevention of inadvertent connections and the resulting potentially disasterous situations.

KemKey safety couplings use different colours and stenciling to inform users as to what chemical is in any given tank. Based on the colour of the fittings, from a distance anyone can tell the general class of chemical located in each tank. Each colour has a definite shape associated with it. The shapes make assure that no matter how hard someone tries, they cannot connect an incorrect hose to a tank and make a chemical transfer.

Different connectors simply will not fit.

A short list of reported incidents

11 People Hospitalized from fumes at Darigold dairy in Southeast Portland

Eleven people have been sent to area hospitals following the morning mix-up at a Darigold plant in Southeast Portland.


The leak has been contained although firefighters are keeping an eye on the tank where the liquids were inadvertently combined.

11 workers overcome by chemical fumes at Darigold dairy in Southeast Portland After a truck driver offloads a corrosive agent used to clean tanks at the Darigold dairy into the wrong tank, the chemical reaction created a type of chlorine gas that caused respiratory distress to a total of 11 workers. All 11 were taken to area hospitals for evaluation.

A driver was unloading a corrosive liquid from a tanker truck but he put it into the wrong tank, said Portland Fire spokesman Paul Corah. The liquids mixed. The resulting fumes affected the driver, his assistant and nine other people.

The company has 35 people at the Southeast 6th and Division Place building. The rest of the employees were evacuated safely.

HazMat workers are keeping an eye on the tank, which has heated to 160 degrees and needs to cool down. They’ve surrounded the tank with hoses.

Evacuated employees, some with masks, were gathered at a nearby parking lot.


Whitehall, Michigan June 4, 1999

About 3:30 a.m. on June 4, 1999, a Quality Carriers, Inc., truck driver arrived at the Whitehall Leather Company1 tannery in Whitehall, Michigan, to deliver a load of sodium hydrosulfide solution. The truck driver had never been to the plant before. Upon arrival, he asked a tannery employee for assistance. The employee called the shift supervisor, who met the driver at the plant employee’s work station.

The shift supervisor stated that the only chemical shipment he had previously received on the third shift was “pickle acid” (ferrous sulfate).

He said he had not been told to expect the delivery of another chemical on the shift, so he assumed this load was also pickle acid. The supervisor stated that because the driver did not know the plant’s layout and was unfamiliar with where to unload his cargo, he walked the driver through the plant and out to the pickle acid transfer area.

The supervisor did not verify what chemical was being delivered. The shipping documents identified the cargo as sodium hydrosulfide solution.

The shift supervisor showed the driver the ferrous sulfate connection (the only working transfer connection at that location) so he could deliver his product. The shift supervisor then unlocked a gate to allow the driver to bring his vehicle onto the plant property. The driver asked the supervisor to sign the shipping documents so he would not have to find the supervisor after the transfer was completed. According to the supervisor, he signed the paperwork without reading it and left the area.

The signature block that the supervisor signed stated the following: “I have checked the documents for this shipment and verify that there is adequate storage room to receive this shipment and connection has been made to the proper storage facility.”

Figure 1.

No plant employees were in the vicinity of the transfer area. When the driver arrived at the transfer area, a transfer hose was already connected to a pipe, marked “FERROUS SULFATE,” on the side of the transfer building. During the post-accident investigation, investigators found the other end of the transfer hose connected to the cargo tank and determined that sodium hydrosulfide solution had been transferred from the cargo tank into the storage tank containing ferrous sulfate. (Sodium hydrosulfide solution reacts with ferrous sulfate solution to produce hydrogen sulfide, a poisonous gas.)

Figure 2.

About 4 a.m., an employee in the basement of the tannery building smelled a pungent odor and lost consciousness. The employee said that after regaining consciousness about 10 minutes later, he made his way out of the tannery to an area adjacent to the south parking lot, where he found other employees on break. One of these employees called 911.

The driver was found unconscious inside the tannery building approximately 230 feet from the transfer area. He was pronounced dead at the scene and was later determined to have been overcome by hydrogen sulfide gas. No telephone or other means of communication was located near the transfer area that the driver could have used to notify plant personnel of an emergency. Post-accident investigation revealed that both the emergency valve at the rear of the cargo tank and the compressed air valve, located inside the tannery building approximately 40 feet from the transfer area, were closed and secured.

Chemical Accident

August 1993

There was a release of chlorine gas at the Vanadisbadet (Vanadis outdoor swimming pool) in Stockholm. Sodium hypochlorite is used for purifying the swimming bath water. When refilling the tank with sodium hypochlorite the driver who was delivering the chemical filled it with phosphoric acid by mistake, instead of hypochlorite, whereupon chlorine gas was formed.

He realized his mistake and stopped filling. Some 5 m3 (approximately fourteen kilos) of chlorine gas was formed. Large sections of the area had to be cordoned off and 14 fire service units participated in the rescue work. In all, 13 persons were taken to hospital, however none with serious symptoms. According to calculations by the Swedish Defense Research Establishment (FOA 1997) chlorine concentrations that could have inflicted serious injuries (30 ppm) were reached at a distance of some 10 m from the tank, and concentrations that give irritation (15 ppm) some 25 m from the tank.

Had all the phosphoric acid been transferred to the tank, approximately 40 m3 (approximately 112 kg) of chlorine gas would have been formed and then probably the medical consequences of this accident would have been considerable. According to FOA’s calculations, in that case, directly lethal concentrations (some 300 ppm) would have been reached some metres from the tank, life-threatening concentrations (150 ppm) approximately 10m from the tank, concentrations giving serious injury (30 ppm) some 50 m from the tank and irritation (15 ppm) just under 100 m from the tank. Had all the phosphoric acid and sodium chloride being carried in the tank been transferred to the swimming pool tank, some 80 m3 (approximately 224 kg) of chlorine gas would have been formed and then there could have been directly lethal concentrations (300 ppm) 20–25 m from the tank, life-threatening concentrations (150 ppm) at a distance of just under 50 m, serious injuries (30 ppm) just under 100 m from the tank and irritation (15 ppm) approximately 150 m from the tank. The calculations assumed that the leakage was for some 15 minutes.
The wind speed was 1.5 m/s and the measurements were taken approximately 1.5m from the ground. The distances are in the direction of wind.


Louisville, Kentucky November 19, 1998

About 7:15 a.m. eastern standard time on November 19, 1998, a truck driver driving a Matlack, Inc., cargo tank truck arrived at Ford Motor Company’s Kentucky Truck Plant in Louisville, Kentucky, to deliver a liquid mixture of nickel nitrate and phosphoric acid (a solution designated CHEMFOS 700 by the shipper). A plant employee told the truck driver to park his vehicle next to the chemical transfer station outside the bulk storage building and wait for a pipe fitter to assist him in unloading the chemical.

According to testimony, a short time later, the pipe fitter arrived at the transfer station and told the driver that he would assist him in unloading the cargo tank. The pipe fitter opened an access panel containing six identical pipe connections.

Each pipe connection served a different storage tank, and each connection was marked with the plant’s designation for the chemical stored in that tank.

The driver told the pipe fitter that he was delivering CHEMFOS 700 and then went to the driver’s side of the cargo tank and took out a cargo transfer hose. The pipe fitter connected one end of the hose to one of the transfer couplers, while the driver connected the other end of the hose to the cargo tank’s discharge fitting. Unknown to the pipe fitter or the truck driver, the pipe fitter had inadvertently attached the hose to the coupler marked “CHEMFOS LIQ. ADD” instead of to the adjacent coupler marked “CHEMFOS 700.” The storage tank served by the coupler marked “CHEMFOS LIQ. ADD” contained sodium nitrite solution.

The driver climbed to the top of the cargo tank, connected a compressed air hose to a fitting, and pressurized the cargo tank. The driver and the pipefitter then reviewed the cargo manifest and bill of lading. The pipefitter signed three different certifications on the cargo manifest, one of which certified that the transfer hose was “connected to the proper receiving line.” The pipefitter asked the driver how long it would take to unload the contents of the cargo tank, and the driver told him the transfer would take about 30 to 40 minutes. The pipefitter then left the loading area, leaving the driver to complete the unloading by himself.

About 8:15 a.m., after the air pressure was built up in the cargo tank, the truckdriver started the transfer. When the nickel nitrate and phosphoric acid solution from the truck mixed with the sodium nitrite solution in the storage tank, a chemical reaction occurred that produced toxic gases of nitric oxide and nitrogen dioxide. The driver stated that about 10 minutes after he started the transfer, he saw an orange cloud coming from the bulk storage building. (See figure 1.) He said he closed the internal valve of the cargo tank to stop the transfer of cargo and waited for someone to come out of the building. After several minutes, the pipefitter ran out of the building and gestured for the driver to stop the unloading process.


Figure 1. Postaccident view of the bulk storage building (center) with vapor cloud visible.

As a result of the incident, about 2,400 people were evacuated from the plant and surrounding businesses, and another 600 local residents were told by authorities to remain inside their homes. Three police officers, three Ford Motor Company employees, and the truckdriver were treated for minor inhalation injuries. Damages exceeded $192,000 USD.

MGPI Processing, Inc. Toxic Chemical Release

Accident Description

Accident: MGPI Processing, Inc. Toxic Chemical Release

Location: Location: Atchison, KS

Accident Occured On: 10/20/2016 | Final Report Released On: 01/03/2018

Accident Type: Release

Investigation Status: The CSB's final investigation was released on 1.3.2018.

On October 21, 2016, a chemical release occurred at the MGPI Processing plant in Atchison, Kansas. MGPI Processing produces distilled spirits and specialty wheat proteins and starches. The release occurred when a chemical delivery truck, owned and operated by Harcros Chemicals, was inadvertently connected to a tank containing incompatible material. The plume generated by the chemical reaction led to a shelter-in-place order for thousands of residents. At least 120 employees and members of the public sought medical attention.

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Last Updated: 27 March, 2014