Compabloc CP75 Plate Pack Replacement

01 · The customer challenge

The customer needed a new core, not an unnecessary new installation.

The documented objective was to restore an existing Compabloc CP75 by replacing its internal welded plate pack while retaining the pressure casing. That distinction defines the project. A complete new exchanger can be designed around new nozzles, supports and site connections. A replacement core has to enter an installed mechanical system whose boundaries already exist.

Retaining the casing can preserve more of the installed asset and may reduce changes to surrounding pipework, supports and foundations. Those are practical reasons to investigate a core-only retrofit, but they are not automatic benefits. They depend on the condition of the retained casing and on whether the old and new interfaces can be verified accurately.

The project therefore could not be treated as “CP75 equals another CP75.” Model identification starts the review; it does not complete it. The replacement pack still had to be engineered around the actual dimensional interface, assembled without cumulative drift and checked for leak tightness before shipment.

02 · Interface review

Why a replacement core requires controlled reverse engineering.

A fully welded plate pack is part of a larger pressure-containing assembly. Its outside envelope matters, but so do the locations and orientation of the fluid interfaces, the relationship between the plate block and cover faces, and the clearances needed to install the core inside the retained casing. A pack that is close in overall size can still be unusable if those relationships are wrong.

For this CP75 project, the surviving record confirms a dimensional interface review and manufacture around the existing casing. It also confirms that dimensional compatibility was a fabrication priority. It does not preserve the project drawing, measured dimensions or pass arrangement, so those details are intentionally not reconstructed here.

For a comparable retrofit, HEXNOVAS normally reviews the external plate-pack envelope, port or nozzle locations, plate orientation, flow-pass arrangement, sealing and cover interfaces, assembly clearances and the tolerances that control fit-up. The original drawing is preferred. Where it is unavailable, controlled measurements and clearly referenced photographs are required. This is the same evidence-led approach described on the Compabloc heat exchanger product page.

03 · Replacement engineering

Engineering the CP75 plate pack as an assembly.

Replacement engineering has to connect three groups of requirements: the retained mechanical interface, the internal flow-path geometry and the manufacturing sequence. The outer frame cannot be reviewed in isolation from the welded plate block. Likewise, a plate pattern cannot be copied without confirming how the finished stack locates inside the casing and communicates with the two circuits.

On the CP75 project, HEXNOVAS controlled plate alignment, weld integrity and dimensional compatibility. These controls address a specific risk in a tall welded core: a small positional error introduced early in the stack can accumulate as the block grows. Even when individual plates are within their own tolerances, the final assembly can drift unless datum control, sequence and intermediate checks are built into fabrication.

Fit-up is therefore more than matching external length and width. The finished pack must maintain the intended circuit separation, preserve flow-path continuity and arrive at the retained interfaces in the correct position. For readers comparing technologies, the plate-and-block heat exchanger page explains the broader welded-block construction used for this class of equipment.

04 · Manufacturing control

Plate alignment and welding control were treated as linked tasks.

The project record identifies production quality control, plate alignment, welding inspection and welding integrity as part of the scope. It does not identify a welding process or inspection standard, so no process name or acceptance class is claimed. What can be stated is why these controls matter: welded containment and final geometry are produced together, and a correction made late in the stack may be difficult or impossible without disturbing completed work.

A disciplined sequence checks component preparation, establishes a repeatable datum for stacking, monitors alignment while the block is built and verifies critical dimensions before access is lost. Welding control must also protect the separation between circuits and the integrity of the external boundary. Inspection points therefore belong inside the manufacturing plan, not only at final completion.

The photograph shows the height of the assembly and why cumulative alignment control is important. It also shows the perimeter frame and exposed plate-block faces before installation into the finished casing. The photo is used as project evidence, not as a basis for inferring undocumented metallurgy or welding parameters.

05 · Quality verification

Leak tightness had to be demonstrated before the retrofit reached site.

The surviving project record confirms leak testing and leak-tight verification. In a two-circuit welded core, this concerns both external containment and internal separation. A leak to atmosphere is one failure mode; communication between the two fluid circuits is another. Either can make a mechanically well-fitting replacement unacceptable.

Pre-shipment verification is especially important for retrofit work. Once the core is inside the retained casing, access is more restricted and a defect can consume valuable shutdown time. Testing does not replace dimensional inspection or welding control; it confirms a different part of the acceptance case.

The available record does not publish the test medium, pressure, duration or acceptance criteria. Those values should be agreed for each project from the design conditions, materials, applicable code and customer inspection requirements rather than copied from an unrelated exchanger.

06 · Retrofit decision

When replacing the core is sensible—and when it is not.

A plate-pack replacement is worth evaluating when the existing casing remains serviceable, its critical interfaces can be inspected, and the required duty can still be met within the retained configuration. In that situation the existing footprint, supports and much of the site connection arrangement may remain usable. This project demonstrates that HEXNOVAS has executed that type of CP75 replacement.

A core-only approach should not be forced onto unsuitable equipment. Damage or severe corrosion in the casing, distorted cover or sealing faces, unverified geometry, inaccessible pressure-boundary defects, or a process duty that has moved beyond the old configuration can justify complete replacement. Pressure-code and inspection requirements also have to be reviewed before defining the scope.

Plant owners comparing a welded block with other layouts can also use the technical guide on Compabloc versus shell-and-tube heat exchangers. Other documented retrofit work is available in the HEXNOVAS case-study library.

07 · Required project inputs

Information normally required for a comparable replacement project.

The following is general engineering guidance. It is not a claim that every item survives in the CP75 project archive.

08 · Practical lessons

What this CP75 project demonstrates.

1. A model designation starts the retrofit review; it does not prove interchangeability.
2. The retained casing and its interfaces must be evaluated before committing to a core-only scope.
3. External dimensions alone do not define flow-path and fit-up compatibility.
4. Alignment control has to continue through the complete welded stack because dimensional errors accumulate.
5. Welding, dimensional inspection and leak-tight verification answer different acceptance questions; none replaces the others.
6. The current process duty should be reconfirmed instead of assuming the old core remains thermally suitable.

For additional construction context, see the guide to the Compabloc heat exchanger working principle.