Implosion Prevention and Furnace Draft Exploration
Discovering system pressure and flow changes after equipment updates and ensuring proper controls response can be key in preventing severe structural damage or implosion. TRAX offers a draft analysis study to help clients learn more about potential operating hazards and controls remediation that can be taken to help mitigate those risks.
What Does a Draft Study Do?
A draft study uses mathematical modeling to closely investigate pressure, flow, and temperatures in a power plant or other facility.
When TRAX conducts a study, our clients often want to know about the impacts of a process change and how to lessen or eliminate negative and severe excursions and effects. The dynamic models developed as part of a draft study can be used to verify NFPA 85 compliance, optimize plant operation, and ensure implosion protection. TRAX can even test control logic across the load range, tuning the controls to avoid nuisance trips while retaining the desired functionality.
Implosion can be a risk with newly added environmental equipment. The added pressure drop from the new equipment, aging ductwork, inadequate fan trip interlock logic, and insufficient fuel trip kicker logic can lead to severe negative pressure in the furnace, which can cause the ductwork leaving the furnace to implode, resulting in danger to employees, extensive downtime, lost generation, and expensive repairs. TRAX can retune controls for a safer, more effective response using the client’s specified design limits as guidance.
How does resizing fans affect the plant pressure profile?
Could a different ducting configuration around updated environmental equipment improve losses?
If a plant is retrofitted to gas or a hydrogen blend, will an MFT cause a severe pressure excursion or implosion?
How can the controls be optimized to handle carbon capture additions?
Using a Draft Study: Analyzing New Equipment and Improving Effectiveness of Controls
A furnace draft study begins by building a high-fidelity dynamic model of the existing plant and verifying the accuracy of the model at multiple steady-state conditions, as well as through a dynamic event. These existing configuration tests can often reveal valuable information about current plant behavior that may not be captured by the plant historian due to transmitter range limits or infrequent field readings.
Once we have a validated model, TRAX can begin to examine a client's area of interest. Typically, process follows several key steps:
New Configuration. Modify the model to reflect the proposed equipment and controls changes that the client wishes to investigate. TRAX also performs a full review of proposed controls changes to confirm compliance with NFPA 85 code.
Dynamic Testing. Transient testing begins and the model is subjected to scenarios such as fan trips, MFTs, mis‑operation, or catastrophic equipment failure. Pressures, flows, and temperatures are monitored. The transients allow investigation of plant dynamics caused by actuator stroke time, control system gains, or plant runbacks. The analysis done during the dynamic events can provide specialized information, such as the effects when a vent stack is used, flow reversals, and optimum control system tuning.
Analysis and Reporting. Once the transient tests are complete, the results are analyzed to identify excessive pressure, flow, or temperature, as well as other undesirable behaviors. TRAX then develops and tests process or control logic changes in conjunction with the client’s needs to prevent or reduce the excessive conditions. The figure illustrates furnace pressure during a plant MFT event using the existing control logic, and the same event after implementing TRAX control system recommendations. All findings are presented to the client.
A draft study offers a range of benefits, including assurance that proposed new equipment is sized properly, prediction of system pressures during extreme plant events, and evaluation of existing control logic. Conducting a furnace draft study during an equipment or controls upgrade is an important part of ensuring the safety of a plant in its new configuration.
