Downstream derivatives plant is typically continuous, pressurised, upper tier COMAH, and older than the people running it. The engineering challenge is rarely conceptual. It is the practical problem of modifying a large, complex, hazardous and continuously operating asset within a shutdown window that was fixed eighteen months ago.

Projex Solutions provides engineering design, process safety studies and project delivery for downstream petrochemical derivative producers, working on modification, replacement, debottlenecking and turnaround scopes.

What makes this work different

Upper tier COMAH is the normal condition. Safety reports must be reviewed at least every five years and revised ahead of any modification of significance. Engineering change and regulatory change move together, and a project that ignores the safety report will be stopped by it.

Pressure systems dominate. The Pressure Systems Safety Regulations 2000, with guidance L122 (2014), require a written scheme of examination. On new or modified systems that scheme should shape the design rather than be produced afterwards, particularly around access for examination.

The shutdown window is the real constraint. Turnaround scopes are defined long in advance and cannot slip. Design has to be complete, materials have to be on site, and tie-ins have to fit the first time.

As-built information is unreliable. On plant of this age, drawings and models frequently do not reflect reality. Designing a tie-in from an inaccurate P&ID is how a shutdown overruns.

Ageing plant and integrity. Corrosion under insulation, dead legs, and equipment operating beyond original design life all shape what can realistically be modified rather than replaced.

Where we help

  • 3D laser scanning and point cloud modelling of congested plant, so that tie-ins and new equipment are designed against as-built reality
  • Turnaround scope engineering, designed to be constructible within the window available
  • HAZOP and HAZID facilitation, LOPA, and SIL determination and verification to BS EN 61511-1:2017+A1:2017
  • Pressure systems design developed alongside the written scheme of examination under PSSR 2000
  • DSEAR and hazardous area classification to BS EN IEC 60079-10-1:2021 and EI 15 (5th edition), with CompEx-certified engineers
  • Management of change support where a modification interacts with an existing safety report
  • Debottlenecking and capacity studies, including feasibility and FEED with stated estimate accuracy
  • CDM 2015 duty holder support on live COMAH sites, and EPCM delivery under ISO 9001:2015

Typical reasons clients get in touch

  • A turnaround scope needs engineering to a standard that will actually build in the window
  • A modification requires the safety report to be revisited before it can proceed
  • As-built information is not good enough to design against
  • Ageing equipment needs replacement, and the tie-in design is the hard part
  • A HAZOP needs an independent chairman with continuous process experience
  • Debottlenecking has to deliver capacity without triggering a permit or COMAH change nobody planned for

Related

Part of our work across the chemical sector and the energy sector. See also polymer, resin and elastomer production.

Standards and regulations we work to

  • COMAH 2015, with HSE guidance L111 (third edition, 2015)
  • DSEAR 2002, with ACOP L138 (second edition, 2013)
  • BS EN IEC 60079-10-1:2021 and EI 15 (5th edition, October 2024)
  • BS EN 61511-1:2017+A1:2017 for functional safety, underpinned by IEC 61508
  • PSSR 2000, with guidance L122 (2014)
  • Pipelines Safety Regulations 1996 where major accident hazard pipelines are in scope
  • Environmental Permitting (England and Wales) Regulations 2016 (as amended)
  • CDM 2015 (SI 2015/51) for construction on operating sites
  • ISO 9001:2015

Frequently asked questions

Our P&IDs are not reliable. How do you work around that?
We scan. 3D laser survey produces a point cloud of the plant as it actually is, and we design tie-ins against that rather than against a drawing that stopped being accurate several modifications ago. It is usually the single highest-value thing you can do before a turnaround.

Will a modification force a safety report revision?
It depends whether it constitutes a modification of significance. That determination should be made early, because if a revision is required it has a lead time that will otherwise be discovered too late to protect the shutdown date.

Can you deliver to a fixed turnaround window?
That is the normal condition of this work. Scope has to be frozen early, design complete before materials are ordered, and the build sequence has to be realistic about access and permit-to-work constraints.

Do you provide HAZOP chairing for continuous plant?
Yes. Continuous process HAZOP is a different discipline from batch, particularly around start-up, shutdown and abnormal operating modes, which is where much of the risk on derivatives plant actually sits.

How far ahead should turnaround engineering start?
Earlier than most sites plan for. Scope definition, design, long-lead procurement and constructability review all have to complete before the window opens, and compressing that sequence is the most common cause of overrun.

Can you work alongside our existing engineering contractor?
Yes. We frequently provide specialist input such as HAZOP chairing, area classification or 3D survey alongside a client’s incumbent contractor rather than replacing them.

Talk to us about your turnaround. Request a call