Effects of additives in anhydrous ammonia nurse tanks or delivery tanks

Purpose

This safety advisory covers important safety information about using additives with anhydrous ammonia in tanks used for the transportation of dangerous goods.

Scope

This safety advisory is for anyone who uses or works with dangerous goods delivery tanks or nurse tanks to transport or spray anhydrous ammonia on farm fields.

What you need to know

Anhydrous ammonia may be used as a fertilizer and is classified as a Class 2 dangerous good under the TDG Regulations. Some users add additives to anhydrous ammonia to improve crop yields, which is becoming more common due to the many different additive options now available.
There are two ways to add additives to the anhydrous ammonia being sprayed on a field:

• injecting the additives into the manifold system using a separate tank and piping system for the additives, or
• mixing the additives directly into the anhydrous ammonia delivery tank or nurse tank before spraying the field.

Recently, Transport Canada has seen evidence that some of the additives added into anhydrous ammonia tanks have led to corrosion of tanks and components, and gumming or fouling of pressure relief devices and valves. On occasion, this gumming or fouling has blocked the flow of the anhydrous ammonia, requiring users to open these components, which could lead to an accidental release of anhydrous ammonia. There is also concern that some of these additives can lead to stress corrosion cracking in older tanks.

Safety advisory

Transport Canada recognizes the positive economic benefits of adding additives to anhydrous ammonia. However, adding some of these additives directly into the tank may cause harm to the tank and its components. Furthermore, while some companies that make these additives clearly state that they should not be added and left in the tank due to corrosion and other concerns, others are not aware of the long term consequences of adding their products into the anhydrous ammonia tank.

While some additives may not contribute to stress corrosion cracking or cause tank corrosion or fouling (gumming) of piping, valves, and pressure relief devices, some clearly negatively affect the tank and tank components. As these products are still quite new, it is recommended that additives not be added directly to anhydrous ammonia in nurse tanks or delivery tanks, unless it can be clearly demonstrated that the additive does not react with the lading, tank, or tank components.

If the additives react with the tank, lading or components, we recommend that they be added in the product manifold system, outside the anhydrous ammonia tank.

If you own or use an anhydrous ammonia tank and have already added additives to it, please stop using the tank if it shows any unusual corrosion or component clogging, and bring it for service to a facility registered in accordance with CSA B620.

You can find such registered facilities by visiting our website.

Regulatory requirements

Part 5 of the TDG Regulations requires that highway tanks and TC portable tanks transporting dangerous goods comply with Canadian Standards Association (CSA) standards referenced therein.  The CSA B622 standard referenced in section 5.10 of the TDG Regulations is the selection and use standard for highway tanks and TC portable tanks transporting Class 2 dangerous goods by road in Canada. Class 2 dangerous goods include anhydrous ammonia (NH3).

As CSA B622 references the CSA B620 standard for the design, manufacture, certification, assembly, modification, repair, testing, inspection, maintenance, and marking of highway tanks and TC portable tanks, the requirements of CSA B620 apply unless CSA B622 or the TDG Regulations state otherwise.

Nurse tanks and delivery tanks transporting anhydrous ammonia in Canada must be in accordance with the TDG Regulations, CSA B620, and CSA B622.

Loading any product into a dangerous goods tank that can harm the tank or components is prohibited in CSA B622-14.

From CSA B622-14:

5.2 Pre-loading requirements

5.2.1 Means of containment

In addition to the requirements in Clause 5.1, a means of containment shall not be loaded with dangerous goods unless the following conditions are fulfilled:
…

(c) it does not contain any compressed or liquefied gas, residues, or foreign materials that could react with the intended lading or otherwise create a hazard; and

(d) those parts that contact the intended lading will not be subject to deterioration by or react with the lading or cause the lading to decompose, and thereby create a hazard.

Questions

If you have any questions, please contact our Transportation of Dangerous Goods Directorate, Regulatory Frameworks and International Engagement Branch:

Email: MOCRegister‑RegistreContenant@tc.gc.ca
Phone: 1-855-298-1520 (toll free)