Detonation Arrestors for Unstable Detonation Conditions in Piping Systems

For production processes with flammable substances, flame arrestors are important safety devices that allow gases to pass through but prevent flames in order to prevent a larger fire or explosion.

A recent Control Engineering Europe article, Detonation arrestors reduce complexity and increase safety, highlights considerations in detonation arrestors, which are flame arrestors designed to prevent the transmission of a detonation in a confined system. These confined systems include piping systems that are manifolded or have long run-up distances (maximum attached pipe lengths).

The EN ISO 16852 standard, Flame arresters — Performance requirements, test methods and limits for use specifies:

…the requirements for flame arresters that prevent flame transmission when explosive gas-air or vapour-air mixtures are present. It establishes uniform principles for the classification, basic construction and information for use, including the marking of flame arresters, and specifies test methods to verify the safety requirements and determine safe limits of use.

The article’s author notes that, according to this standard:

Arrestors designed only for stable detonations require up to two additional independent measures of protection…

This requirement is because:

…stable-only detonation arrestors alone do not provide adequate protection against the most severe detonation events.

Flame-PropagationFlames in these confined systems:

…normally start as a slow deflagration, a flame front moving at subsonic velocity and if the system allows, will accelerate to a detonation via a phenomenon known as ‘Deflagration-to-Detonation Transformation’ (DDT). DDT will occur when the highly pressurised vapours ahead of the flame front come in contact with the flame.

Upon this event, an:

…explosion occurs and the pressure wave ahead of the flame front becomes a shock wave. This shock wave produces tremendous compression of the gases both upstream and downstream from the initial point of DDT. A detonation is a flame driven shockwave at or above the speed of sound in the unreacted medium as measured at the flame front. As the flame propagates farther down the pipe, it goes into a dynamic state known as an unstable or overdriven detonation.

Highly localized pressure can result from the flame propagation traveling at supersonic and hypersonic velocities. Bends, elbow, tees, and final control elements such as check valves can induce additional turbulence.

Detonation arrestors are designed and tested for these unstable detonations and should be used in applications that have multiple turbulence inducing devices. It is:

…not possible to predict where DDT might occur within the piping system. Therefore, it is not appropriate to use detonation arrestors that have been tested only for stable detonations, since they are not able to effectively stop detonations that might occur at or between the DDT and the point at which the detonation becomes stable. If conditions are right, a galloping detonation can occur.

Using:

…detonation arrestors designed and certified for both stable and unstable detonations protect against the most severe detonation events without requiring any utilities, control devices or operator intervention.

You can learn more about flame and detonation arrestors in a whitepaper, ENARDO Flame Arrestor Technology. You can also connect and interact with other pressure regulator and flame arrestor experts in the Regulators group in the Emerson Exchange 365 community.

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Modernizing and Optimizing Experiences to Share

Emerson ExchangeLet’s highlight a few more of the accepted presentations from Emerson experts presenting at the October 12-16 Emerson Exchange conference in Denver. You can download a spreadsheet with the entire list of accepted abstracts here. These presentations share experiences, lessons learned, and tips to help you improve your plant or production facility’s performance.

Emerson's Sudhir Jain


Emerson’s Sudhir Jain will present, Operational Improvement – By Modernizing World’s Largest Crude Oil Stabilization Facility. His abstract:

Saudi Aramco-Abqaiq Plants decided to upgrade and modernize their control system for columns, NGL [natural gas liquids] and Utilities, with an objective to have major operational improvement. This is accomplished by:

  1. Migrating PROVOX to DeltaV
  2. Migrating Triplex Regent ESD System to DeltaV SIS
  3. Planned cutover to have no impact on production
  4. DeltaV Zones to enhance flexibility to operate
  5. Engaged Control Performance Consultants to identify bad actors and used tools for improved performance of regulatory loops
  6. Deployed Cyber Security and automated patch management
  7. Added centralized backup and recovery

Continue Reading

Instrumenting for Increased Performance

Yesteryear, energy and water were relatively inexpensive, waste disposal carried little cost, emissions did not incur fines and people willing to work in harsh manufacturing plant and production facility environments were abundant. Today, energy and water costs are high, waste disposal is expensive, emission fines are high, and people with the right skills to work in these facilities are more difficult to find and keep.

Emerson's Jonas Berge


Instrumental-to-SuccessEmerson’s Jonas Berge makes these observations in a Control Engineering Asia article, Instrumental to Success. He highlights how the prior environment impacted the way plants and production facilities were instrumented:

But when existing plants were first built all those years ago they were only instrumented for production and safety. Plants were not instrumented for long-term reliability, maintenance and field operator productivity, energy efficiency, or safety and environmental incident monitoring.

Given the demands of today, adding more sensing devices is critical to address these challenges. Jonas makes the analogy of how digital pictures have transformed the way we do things. Where in the film era, pictures were for special occasions, today they are used for many things:

…where we parked the car, of the directory map at the mall, a beverage we liked, or the spare part, or produce we need to buy.

Similarly, additional sensing devices beyond basic process control and safety shutdown open up new opportunities never before envisioned. Using wireless sensors to monitor simple safety devices is one example: Continue Reading

Measurement and Final Control Technology Announcements from OTC

The news was flowing fast and furiously from the recent Offshore Technology Conference (OTC) in Houston, Texas. I wanted to highlight some of the news from Emerson in case you missed it.

To help protect subsea well and pipeline integrity and support metering/allocation strategies, the Roxar subsea Wetgas Meter allows:

…the earliest possible detection of water from gas wells… The meter detects changes in water content of the flowing well at as little as 0.2 ppm (parts per million) – sensitivity that has never been reached before and that represents less than a droplet of water finely distributed in a volume equal to that of four car fuel tanks.

Emerson's Svein Erik Gregersen


Emerson’s Svein Erik Gregerson explained that more and more operators are making wet gas metering an integral part of their future flow assurance, production optimization and hydrocarbon allocation strategies.

The meter provides real-time, accurate hydrocarbon measurement for operators’ fiscal allocation obligations and accurate salinity and formation water measurement. Continue Reading

Gain a Competitive Advantage–While Wearing Pajamas

Emerson's Jocelyn Sexton


Author: Jocelyn Sexton

Across a variety of industries, manufacturing plants must meet rigorous production goals in order for companies to remain competitive. Especially in today’s economic climate, everyone is looking for the best cost options to make improvements without sacrificing quality. However, endless technology changes and complex processes make it challenging to keep up.

Do your engineers know how to maintain, configure, troubleshoot and pull data from your system? Does your staff understand how to use all the features in the technology you’ve invested in? And are you following best practices? The right training can help ensure a facility’s peak performance levels and profits.

Virtual-ClassroomAlso, a gap may exist between your soon-to-be-retiring workforce and young engineers or technicians who lack experience. Taking courses via Virtual Classroom may be the best use of your time and money to deliver the much-needed education that will help your staff make critical decisions about your system when something goes wrong.

When it comes to training, I have three tidbits of information to share:

Fact: Projects that dedicate 6–10% of their budget to training were twice as successful as projects that invested 4% or less to training.

Fact: More than 62% of petroleum engineers polled in a 2012 survey said they were waiting to receive technical training that they feel they should have already received.

Fact: Companies can reduce their training budget by up to 40% when eliminating travel… and having students attend classes in their pajamas.

OK, I made the last part of the third fact up — the type of clothes you wear while attending a class does not impact how much money you can save. But if you can receive important training without walking into a formal classroom, wearing pajama pants and a comfy t-shirt while sitting at home may be another big plus! Manage your training budget — and get the training you need, when you need it — by eliminating the need for travel expenses. Continue Reading