Flex Process carried out a detailed study of an existing relief system for handling a runaway phenolic resin reaction. Using in-house software, we were able to identify the required size of the vents, and ensure that the new design was up to scratch.

1. Consultancy.
Project Delivery.
Innovation.
Case Study: Resin Reactor Vent Analysis
Detailed assessment of reacting two-phase relief
Client: Top Tier COMAH Phenolic Resin Manufacturer

2. Who are we?
Process engineering consultancy
Specialising in advanced modelling techniques, to give answers that
are more accurate, reliable and robust
Decades of process and mechanical engineering experience
Combine cutting edge simulation with real world understanding, to
provide you with solutions that are effective and practical.
Core team of eight engineers, supported by a wide network of
associates.
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3. Project Background
Top tier COMAH site
HSE Regulator questions mechanical integrity of reactor emergency vent
system to withstand a full relief event
Original mechanical calculations no longer available
No process flows to support pipe work dynamic assessment, likely to be
two phase reacting flow
Client no longer has access to internal process/mechanical expertise
Flex Process brought in to help address HSE action
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4. Our Responsibilities
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Site Survey of vessels, pipes and catchment tank
Complete two phase relief calculations to generate process flows
Build pipe stress models for each reactor system and assess against
pipe code (ASME) for thermal, sustained and dynamic cases
Complete vessel nozzle strength calculations
Report findings and agree way forward

5. Site Survey
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General Arrangement
Drawing
Site Measurements
Research Site Data
Records

6. Two Phase Flow Modelling
Use own in-house DIERS based software to calculate two
phase flow through vent lines
Use detailed mechanical survey data
Use physical properties for phenol, water, formaldehyde, resin in
calculations
Input actual calorimetry data
Worst case static or dynamic flow outputs
Flows, temperatures and pressures at various points within vent system
to support detailed pipe stress modelling
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7. Process Data Output
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8. Pipe Stress Engineering
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CAESAR II Simulations

9. Main Conclusions
Significant deviations in thermal, sustained and dynamic cases from the
ASME design code. Simple changes not possible.
Original designs had limited pipe stress analysis, some were site run
Insufficient allowance for pipe thermal expansion (e.g. straight runs)
Incorrectly specified pipe bellows
Insufficient pipe supports for dynamic loads, such as disk rupture
Weak nozzles on heat exchangers, reactors and catchment tank
No supporting calculations for catchment tank foundations
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10. Proposal for Redesign
Redesign vent pipe runs to allow for thermal expansion, minimise
bellows on wetted duty
Install new pipe bellows designed to withstand movement on reactor
nozzles
Change heat exchanger heads with stronger nozzles
Install special pipe supports to withstand dynamic loads
Change catchment tank instead of making repairs to weak nozzles and
adopt new centrifugal design for more effective separation
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11. Redesign Proposal
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Detailed Proposal Drawings
New Vessel General Arrangement Drawings

12. Redesign, Estimate and Programme
Redesign proposal developed in drawings incorporating all the required
changes
Fully checked out proposals through additional site survey, pipe stress
analysis and two phase relief calculations to ensure that relief capacity
not compromised
New, more flexible pipe specification developed that minimises the
requirement for bellows
Detailed capital cost estimate for changes
Installation programme developed, which minimises disruption to
operations
Suggestions made to optimise vent size through further scenario
analysis
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13. Summary
Client had a complex problem involving the HSE
Through a mix of process and mechanical in-house expertise, the
analysis could be completed effectively
Findings were clearly reported and a way forward discussed
Fully checked out redesign completed, costed and installation
programme devised that minimised disruption
Deliverables produced that could be used to support discussions with
HSE regulator
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14. Summary
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Consultancy.
Project Delivery.
Innovation.
Please get in touch to find out how we can help your
business today.
E: enquiries@flexprocess.co.uk W: flexprocess.co.uk
T: +44 1454 629 689