May 2, 2011 | Mark Paradies

Monday Accident & Lessons Learned: Acid – Not What's On the Label

OGP Safety Alert


Incident Date: 1 February 2011 

 Safety Safetyalerts Alert Images 233 S233 Img1

During the preparation for an acid job, multiple leaks were observed on the transfer connections moving the raw acid from the transport tank into a storage tank. Several days later the storage tank developed several leaks. Additionally during the mixing and pumping of the acid multiple leaks were observed in the equipment. On diluting the acid down to the required concentration (15%) a violent reaction was seen from the mixing tank, at the same time vapor was observed coming from the outside of the coiled tubing string. The leaking tanks and the violent reaction at mixing caused large quantities of acid to be disposed of.

What Went Wrong?
On investigation it was found that the location had ordered 32% HCL for the job. The paperwork supplied by the supplier and all drums indicated that the acid was indeed 32% HCL. On testing the raw acid after the incidents the specific gravity (SG) was determined to be equivalent to 50% HCL. Knowing that that concentration of HCL is not possible, further testing was performed and the acid was determined to be a mixture of HCL, Sulfuric Acid and Nitric Acid. This mixture of fluids had a significantly higher reaction and corrosion rate than the anticipated 32% HCL.

– Raw acid Quality Control testing was not performed on reception of the product, as such the only indication as to what the drums contained was the labeling and accompanying documentation.
– Quality Control requirements at the well site required the final mixture to be tested vs specific gravity. Coincidently the SG of the final mixture was in the expected range of the 15% HCL required.
– The initial leaks while transferring were not adequately reported, as such the initial investigation into the tank leak considered this an isolated mechanical problem.
– The acid supplier was approved to perform cleaning and servicing of the tanks, they were not approved as an acid supplier, as such the required controls were not in place.
– The neutralization process and exposure to personnel could have been compromised as the Emergency Response Plan was written and in place to deal with HCL contingencies.

Corrective Actions and Recommendations
– Ensure that there are adequate processes in place for quality assurance of delivered products. When such products come from locally approved suppliers recognize the additional exposures this may pose.
– Ensure that the Quality Control process is such that all products are cross checked at the time of receipt for compliance to the order.
– Ensure Supply Chain clearly defines the services/products for which a supplier is approved. Purchasing non-approved items must be forbidden.
safety alert number: 233

OGP Safety Alerts

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