Identifying The Best Coupler For Butadiene-Handling Applications

By OPW | Jun 14, 2021

Though there are no direct consumer uses for 1,3-butadiene (more simply called “butadiene”) it is one of those chemicals that most people have never heard of, but without it we would not have the synthetic rubbers and elastomers that are integral components in many consumer goods that count butadiene as one of their components, from vehicle tires to shag carpets.

It is also a chemical that its listed as a potential occupational carcinogen by the National Institute for Occupational Safety and Health (NIOSH), and one that is extremely flammable in both its liquid and vapor forms. This means that butadiene must be treated with respect at all times, and its transporters must take the highest precautions when handling it. 

The main challenge to transporting butadiene is keeping it adequately contained. This task is made difficult for two reasons:

  • Vapor Pressure: Butadiene, according to NIOSH, has a vapor pressure of 2.4 atmospheres, which means it is under 2.4 times more pressure than a normal gas. Upon release, butadiene will enter the atmosphere and expand quickly, which increases its risk factor for humans and the environment.
  • Exposure Limits: According to the American Chemistry Council, the permissible exposure limit over an 8-hour total weighted average for butadiene is 0.5 parts per million (ppm), which essentially means that occupational exposure should never be allowed to occur. 

Therefore, butadiene is usually transported in pressurized railcars in the form of a liquefied compressed gas. In its liquefied state, butadiene must be kept at a temperature below 24ºF (-4.5ºC). If allowed to reach a temperature higher than 24ºF, it will exceed its boiling point and begin to revert to a gaseous state. This will cause it to expand, which could lead to a product release and, in the worst-case scenario, an explosion.

That makes a “closed-loop” system the best alternative when transporting butadiene. In the closed-loop system, there is significantly less risk that product will remain in the coupler as it is disconnected from the transport vehicle, which lowers the exposure risk. Key components in an effective closed-loop system are the dry-disconnect couplers that make the connection between transport vehicle and storage tank.

OPW Engineered Systems, a product brand of OPW, currently offers a four-model portfolio of dry disconnects that can fit the unique needs of a butadiene-handling operation:

  • Drylok® Dry Disconnects: These couplers, which can be mounted in any orientation, feature a rugged design, excellent flow characteristics and very little product loss. The flat-face poppet ensures minimal product loss at disconnection, while the fully interlocked double-safety connection system helps prevent the coupler from opening if it is not mated properly.
  • Kamvalok® Dry Disconnects: Their flat-face poppet action provides closure from both the coupler and adaptor side, significantly reducing the risk of spillage of residual product at disconnection. The locking handle is also designed to remain in a locked position, which prevents any accidental opening or closing of the valve.
  • Epsilon Dry Disconnects: The Epsilon’s double-ball-valve design allows it to deliver the lowest product-loss rates in the industry. Multiple integrated interlocks help eliminate unintentional disconnects and resultant product releases, while the coupler’s unrestricted flow path helps prevent turbulence during product transfer for full-flow optimization.
  • Twist-Lok Dry Disconnects: This is OPW’s newest dry-disconnect coupler and it has been designed to be extremely user-friendly due to quick, easy connection capabilities, which also result in minimal product loss at disconnection. Twist-Lok couplers are also interchangeable with other dry-disconnect models and have been manufactured in accordance with NATO STANAG 3756 standards.

For more information on OPW Engineered Systems’ complete portfolio of Dry Disconnect Couplers, please visit


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