Most design failures on a process plant are really interface failures. One consultant issues the P&ID, another models the pipework, a contractor picks up the cabling, and nobody owns the gaps between them. Line numbers do not match the valve list. A cable route crosses the space kept for maintenance access. A relief case rests on an assumption nobody else saw. Faults like these surface on site, in a shutdown window, when putting them right costs most.

Projex Solutions keeps process, mechanical and EC&I engineering in-house and runs them as one multi-discipline team on one design, from one design basis. Designs are produced with the constructor’s reality in mind: what can be lifted into place, what can be prefabricated, what can realistically be installed in the outage you have. We work across the UK in chemicals, pharmaceuticals, food and drink, FMCG and energy.

Process engineering

Process engineering defines what the plant has to do and proves it can do it safely. It sets the numbers every other discipline depends on.

  • Process design basis and calculations – Agreed flow rates, pressures, temperatures, fluid properties and utility demands, then the pipe, pump, pressure drop and exchanger sizing.
  • Process flow diagrams (PFDs) – Major equipment, main streams and stream data, used to agree the process concept before detailed engineering.
  • Piping and instrumentation diagrams (P&IDs) – Lines, valves, inline items, instrumentation and interlocks: the construction reference and the primary document for HAZOP.
  • Process safety and optimisation – HAZID and HAZOP facilitation, LOPA, SIL determination and balance reviews, so hazards are designed out early.
  • Control philosophies – Modes of operation, sequences, alarms, interlocks and shutdown responses, agreed before any code is written.
  • Pressure relief – Overpressure scenarios identified and devices sized to recognised standards such as API 520/521, with discharge routing documented.

Mechanical engineering

Mechanical engineering turns process intent into something that fits the space, can be built by a site team and can be maintained afterwards. Much of it is brownfield work.

  • Concept design – Preliminary layouts, high-level calculations and budget and programme outlines, so options are compared early.
  • Layouts (site, pipework, equipment) – Arrangements confirming everything fits, with maintenance clearances, access and egress and hazardous area zoning.
  • 3D scanning – Laser survey producing an accurate point cloud where legacy drawings are missing or out of date.
  • 3D modelling – Data-rich models of pipework, equipment, steelwork and cable trays, used for clash detection and sequencing.
  • Construction drawings and installation concepts – General arrangements and detail drawings, plus the thinking behind them: access, lifting, modularisation, phasing.
  • Isometrics, line and valve lists – Fabrication-ready isometrics from the model, with lists covering size, material, rating, actuation and testing.
  • Zoning drawings – ATEX and DSEAR zones, fire risk areas, cleanroom classifications and functional zones, driving compliant equipment selection.
  • As built drawings – Documents revised to reflect what was installed, incorporating site redlines and commissioning changes.

EC&I engineering

EC&I design makes the plant work and keeps it safe to operate. Our engineers work from the same P&IDs and control philosophies as the process team.

  • LV power distribution – Main and sub-main boards, final circuits, protective devices, earthing and bonding and load balancing, to BS 7671.
  • Sizing and power calculations – Load assessments, cable sizing, voltage drop analysis, protection device selection and discrimination studies, documented for the installer.
  • Cable routing – Tray, trunking and conduit layouts with power, control and signal cables properly separated and coordinated against pipework.
  • Instrument block cabling and loop sheets – Loop-by-loop records of tags, terminals, signal types and cabling, cross-referenced to the P&IDs for fault tracing.
  • Lighting layouts – Fixture placement and lux levels matched to each area’s task, with emergency lighting and rated fittings where required.
  • Specifications – Functional, environmental and electrical requirements for instruments, cables, enclosures and distribution equipment, giving procurement a clear basis.
  • Control panel and motor control specifications – Component selection, wiring, enclosure ratings, interlocks and factory acceptance testing for panels and MCCs, to standards such as BS EN 61439.
  • CompEx design – Hazardous area design by CompEx-trained engineers: zone classification, Ex-rated equipment, gland and entry methods, inspection records.

Why in-house matters

With three disciplines under one roof, coordination happens as part of the work, not as a separate exercise. The engineer setting a relief case can talk to the designer routing the vent line. The EC&I engineer specifying a motor starter works from the control philosophy the process team wrote. Discrepancies are resolved in a conversation, not a fortnight of emails between three consultancies.

It also removes the commercial grey area. Where scopes are split, every interface is somewhere responsibility can fall through, and nobody is accountable for whether the instrument schedule matches the P&ID. With one team, accountability and revision control sit in one place.

It shows at construction: fewer technical queries from site, fewer clashes during installation, fewer late changes.

When clients typically call us

  • A capital project needs design before an investment decision, and the business case rests on a credible layout.
  • Existing drawings no longer match the plant, and a modification cannot proceed safely until the as-built position is known.
  • A HAZOP or safety review has produced actions needing engineering out: relief, interlock or hazardous area work.
  • A shutdown window is fixed, and the design must be coordinated and fabrication-ready before it opens.
  • Equipment is being replaced or uprated, and load, control scheme and pipework all change together.
  • A design has stalled because separate consultants cannot agree the interfaces, and someone must own it.

Frequently asked questions

Can you take on part of a design rather than all of it?

Yes. We often pick up one discipline alongside your own team or an incumbent contractor. We set out which interfaces we own and which we depend on, so boundaries are agreed upfront.

We have no reliable drawings for the existing plant. Where do we start?

Usually with a 3D laser scan. The point cloud records what is there, and we model the new design against it, so clashes are found before fabrication.

Do you work in hazardous areas?

Yes. We produce zoning drawings and carry out CompEx design for ATEX and DSEAR environments, covering equipment selection, cable entry methods and inspection records.

What do we actually receive?

It depends on scope. A typical detailed design package includes the design basis and calculations, PFDs and P&IDs, layouts and 3D model, isometrics with line and valve lists, loop sheets, specifications and as built drawings.

Related: our engineering design work is one of six areas covered under engineering services. We also work across a range of regulated sectors and industries.

Whether you are at concept stage, planning a modification around a shutdown, or holding a stalled design, we will give a straight view on scope. Talk to us about your design. Request a call