Advanced Couplers Can Help Optimize the Handling of Hazardous Chemicals

Closed-loop systems are the safest way to prevent the leakage and spillage of hazardous chemicals and a portfolio of dry-disconnect coupler technologies is available to aid in that task.

By David Morrow, Director of Sales – OPW Engineered Systems

Without butadiene, individuals would not be able to drive cars, cover floors with carpet, or go scuba diving. Butadiene is one of those substances that most people have never heard of, but without it, there would not be the synthetic rubbers and elastomers that are integral components in the manufacture of vehicle tires, shag carpeting, and wetsuits to name just a few of many consumer goods that list butadiene as one of their indispensable ingredients.

At the same time, butadiene is also a chemical that its producers and transporters know must be handled with care at all times.

Butadiene is a colorless, non-corrosive gas with a mild, gasoline-like aromatic odour that is a by-product of the production of ethylene and propylene. As such, it is listed as a potential occupational carcinogen by the National Institute for Occupational Safety and Health (NIOSH), and both short- and long-term exposure to it can cause a host of health issues. It is also extremely flammable in both its liquid and vapour forms, requiring butadiene transporters to take the highest precautions when handling it.

Butadiene is just one of many chemicals that come with a similar list of caveats from NIOSH that demand that they be produced, transported, and stored in the safest manner possible, with no risk of physical exposure to technicians or release to the environment. This article will illustrate how using dry-disconnect coupler technology can help reduce, or even eliminate, the risk that a chemical- release incident might occur during or after the loading and unloading of trans- port vehicles – most often railcars and tank trucks – into a storage vessel.

The Chemical Transport Challenge

As noted, the main challenge in trans- porting chemicals is keeping them adequately contained. This is especially true if the chemical is transported as a liquefied compressed gas in a pressurized railcar. If any of these substances exceed their so-called boiling point during transport and begin to revert to a gaseous state, it will expand, thereby putting the ability of the transport vehicle to contain the chemical at risk. This could lead to a product release and, in the worst case scenario, an explosion, depending on the chemical’s characteristics.

The overriding challenge for the transporters of chemical substances is to prevent them from 1) escaping the transport vehicle, whether in liquid or gaseous form, and 2) reverting to a gaseous state, if applicable, during transport.

The challenge is made more difficult by the fact that many chemical transporters continue to rely on outdated coupler technology and “open loop” systems to connect transfer hoses from the transport vehicle to the storage vessel. In many cases, this technology comes in the form of nothing more than a technician inserting a “stabber” pipe at the transfer point with a pipe wrench. These connections have some operational shortcomings that prohibit them from being the absolute best dry-disconnect choice. Mainly, open-loop systems do not possess the ability to ensure that a leak-free connection has been made or to prevent residual product from remaining in the coupling connection when the hose is removed.

A much better alternative to an open-loop system is the “closed-loop” system. In the closed-loop system, there is significantly less risk that any product will remain in the coupler as it is disconnected, which lowers the exposure risk to almost zero, resulting in a safer chemical transfer process.

Experience from the field dictates that there are two main obstacles to getting chemical manufacturers and transport­ers to convert from an open to a closed system of product transfer. The first in­volves mindset, or “this is the way it was always done” thinking, that can hamper efforts to convince people there is a bet­ter way. The second – and much harder to overcome – is physical: most of the rail cars that are used to transport chem­icals are owned and operated by third-party carriers, not the actual manufactur­er. This means that the storage terminal must be able to adapt its operations to meet the needs of each railcar that ar­rives. Since the product-transfer connec­tions “live” on the railcars, the challenge is to get manufacturers and operators to buy into the benefits of closed-loop loading and unloading systems, thereby making advanced dry-disconnect equip­ment standard on their fleets.

The Dry-Disconnect Solution

Aiding the cause in convincing chemi­cal manufacturers and transporters to upgrade to a closed-loop system is a comprehensive portfolio of advanced dry-disconnect couplers that are now available to the chemical-transport mar­ket. The foundation of this product port­folio is innovative flat-face poppet and double-ball-valve designs. These meth­ods of construction help reduce the risk that residual fluid will be trapped within the coupler, lowering the risk of spills and giving the liquid virtually no place to collect or hide, which eases cleaning. Typically, there will be less than 0.5 ml (0.02 ounces) of fluid left on the face seal of the coupler upon disconnection, an amount that is less than one-quarter the volume of a single teardrop.

These couplers feature multiple safety interlocks that allow the valve to open and close only through a deliberate ac­tion by the user, helping prevent acci­dental opening, which is critical when transferring hazardous materials. For extremely sensitive applications, an optional keyed interface locks out and isolates transfer lines. This ensures that a specific coupler can only be used with a specific hose or loading arm, prevent­ing cross-contamination.

Finally, the couplers are quick and easy to maintain because they have fewer parts, allowing them to be repaired on-site without needing time-consuming and costly returns to the manufacturer or interpreting complicated and confus­ing maintenance instructions.

Here is a closer look at three specific advanced dry-disconnect technologies, along with the benefits that each can of­fer to chemical transporters, all of which can be modified to fit the unique needs of the end user’s operation:

• Flat-Face Poppet Dry Disconnects: These couplers, which can be mounted in any orientation, are the most com­monly used advanced coupler technol­ogy because they feature a rugged de­sign, excellent flow characteristics, and heightened product control. The flat-face poppet ensures minimal product loss at disconnection, while the fully interlocked double-safety connection system pre­vents opening if the coupler is not mated properly. Some models allow closure from both the coupler and adaptor side, which significantly reduces the risk of retention and spillage of any residual product at disconnection, helping keep hazardous substances inline and out of the environment. The locking handle on some models is also designed to remain in a locked position, to prevent accidental opening or closing of the valve. Addition­ally, an automatic locking mechanism that is signified by an audible “click” provides added protection, with detach­ment accomplished with an easy tug on the lock release. These couplers can be constructed of stainless steel, aluminum, Alloy 20, or Hastelloy C, making them compatible with a wide range of chemi­cal compositions. Many models have also been approved for use by the Asso­ciation of American Railroads (AAR) and Canadian Registration Number (CRN) regulating authorities.

• Double-Ball-Valve Dry Disconnects: This design gives the coupler double-shutoff reliability, which allows them to deliver the lowest product-loss rates in the industry. Multiple inte­grated interlocks help eliminate unin­tentional disconnects and the result­ing product releases that can threaten worker safety and damage the envi­ronment The coupler’s unrestricted flow path creates no turbulence dur­ing product transfer for full-flow op­timization. Optional keyed couplings isolate transfer lines to provide further defense against cross-contamination. They are typically constructed of 316 stainless steel or Hastelloy C.
• Quick-Connect Dry Disconnects: These couplers have been designed to be ex­tremely user-friendly due to quick, easy connection capabilities while also deliv­ering minimal product loss at disconnec­tion. Quick-connect couplers have also been designed to be interchangeable with other dry-disconnect models and are manufactured in accordance with NATO STANAG 3756 standards. They are usually constructed of 316 stainless steel and feature an integral heavy-duty swivel that minimizes hose wear, along with fully integrated interlocks and lock­ing mechanisms that increase safety. Optional keyed couplings minimize the risk of product cross-contamination oc­curring when the same transport vessels are used to ship different chemicals.

Conclusion

Hazardous chemicals are indispensable in­gredients in any number of products that are ever-present in our daily lives. At the same time, these dangerous chemicals must be handled with extreme care, lest the user or environment become harmed as a result of a leak, spill, or catastrophic release. Integral components in the safe handling and transfer of industrial chemi­cals are the couplers that help facilitate the transfer-hose connection point between transport vehicles and storage vessels. In this case, the use of advanced dry-discon­nect technologies can greatly reduce the risk that hazardous chemicals will leak, drip, or nest within the coupler during and at the conclusion of their transfer, resulting in a safer, more reliable handling process for some of the world’s most significant – and potentially dangerous – raw materials.