In This Issue

Failures of Excess Flow Valves (EFV’s) in Hazardous Materials Service

The Environmental Protection Agency (EPA) has recently issued an Alert as part of its ongoing effort to protect human health and the environment by preventing chemical accidents. The alert is available on RCP’s website here. Major industry and commercial accidents cannot be prevented solely through regulatory requirements. Rather, understanding the fundamental root causes, widely disseminating the lessons learned, and integrating these lessons learned into safe operations are also required. EPA publishes Alerts to increase awareness of possible hazards.

The primary issue in the alert was that companies who have processes that rely on the EFV for release control alone might be positioning themselves for sustaining an unnecessary risk. There were three clear issues that need review.

The first is the practice of inherently safer design. When EFV’s are selected for hazardous material service, they need to be designed and installed in a fashion that allows the device to function as intended.

  1. Orientation is critical for ball check design. The EFV must be installed in the vertical orientation and with the device so that the ball moves upward against the seat to stop/restrict flow
  2. Spring loaded, ball check, or other technology designs for EFV devices are installed following a design review of potential of:
    1. Particulate entrainment in the process fluid that would prevent operation
    2. Process conditions that would result in solids formation preventing closure of the device
    3. Vapor/liquid two phase flow conditions that could develop causing
      1. Cavitations and loss of face to face material resulting in material bypass
      2. Brittle fracture engagement if temperatures achieved resulting in mechanical failure
      3. Failure to reach sufficient force to operate the device, and
      4. Other process specific concerns
    4. By-product or contaminants that could result in accelerated or pre-mature failure
    5. Flow restrictions or operating pressures upstream or downstream that may prevent the device from operating as desired (i.e. flexible hoses in unloading systems to determine if the flow resistance in the intervening piping might prevent the EFV from closing)
  3. Design installation so that the device can be maintained and inspected.

The second concern to address is to ensure in existing EFV installations that a proper inspection and maintenance program is employed to ensure reliable service or device, especially when it is needed most. Previous history (not only in-house, but others industry and companies that may lessons to learn from) may provide insight into how and when to service or inspect these devices. The Natural Propane Gas Association (NGPA), the Chlorine Institute (CI), International Institute of Ammonia Refrigeration, American Chemical Council, American Petroleum Institute, and other have sources of information/meetings where issues are addressed and questions answered that will help in identifying maintenance/inspection needs.

The third concern was with careful analysis and additional measures based on the risk related to the release of the material. The company should evaluate the frequency versus consequence if the EFV fails and it was the only layer of protection provided. Several examples are given in the alert that address failure and consequence of real life events that occurred.

The conclusion is that companies relying only on one layer of protection, one device between control and catastrophe, should carefully look at there applications and see if the right measures are in place to prevent the potential for accidents that could cause loss of life, employee exposures, loss of operations, and their community harm.

RCP, Your Regulatory Compliance Partner, has subject matter experts that can assist in evaluations and risk analysis for this and process related concerns for Process Safety Management, Risk Management Programs, Pipeline Integrity Management, and other concerns. For more information contact Dan Shelledy or call (713) 655-8080.