Selecting the correct block heat exchanger requires an evaluation of the operating pressure and the thermal requirements of the process. The standard Compabloc range provides a versatile foundation for industrial duties, while the Compabloc+ is engineered for pressure environments up to 60 bar. Both types utilise 316L stainless steel as a base material for heat transfer plates, with options for higher alloys to handle corrosive media.

The standard Compabloc range covers a broad span of process and utility duties. Plate materials include 316L, 254SMO, Titanium grade 1, 904L, Alloy C276, and Alloy C22. Panels are constructed from carbon steel with a lining that matches the plate material to ensure chemical compatibility. Laser welding is the standard construction method for the plate stack on models CP30 and above; models below CP30 use an alternative welding approach per the product documentation.

High-pressure variants and sealing

For applications where the operating pressure reaches up to 60 bar, the Compabloc+ incorporates the +Seal sealing concept. This utilises a fully confined graphite gasket that prevents over-tightening and reduces gasket creeping, which helps avoid external leakage in high-pressure installations. The Compabloc+ is available in three models — CP50+, CP75+, and CP120+ — with plate and panel lining materials of 316L, 254SMO, or HC276, and carbon steel panels. By excluding interplate gaskets from the plate pack, these welded plate and block heat exchangers remove common failure points found in traditional equipment under pressure stress.

Welded plate and block heat exchangers are deployed across sectors where high thermal performance must be balanced with a compact installation footprint. The standard Compabloc range is designed for temperatures from −46 °C to 343 °C, while the Compabloc+ extends the upper design temperature to 370 °C for high-pressure models. The cross-flow arrangement within each pass ensures that the media interacts efficiently, supported by baffles that direct fluid turns to optimise heat exchange.

Refining and petrochemical duties

In refining, the block heat exchanger is used for condensation and reboiling. The large cross-flow area and short flow path suit low-pressure duties, allowing for minimal pressure drops. For condensation duties involving sub-cooling, the unit is typically mounted vertically. Horizontal mounting is used for reboiling or liquid-to-liquid duties where installation height is restricted. This versatility allows engineers to optimise the process layout regardless of physical site constraints.

Energy efficiency and heat recovery

For heat recovery applications, the multi-pass configuration of a fully welded plate heat exchanger allows for temperature crosses and close temperature approaches down to 3 °C. This capability reduces energy consumption by reclaiming thermal energy from process streams. Because the baffling can be re-arranged, the unit can be adapted to new duties if flow rates or temperatures change over time, providing long-term process flexibility. In chemical processing, high-grade materials such as Titanium grade 1 or Alloy C276 for the corrugated plates ensure safe handling of aggressive media. The unique plate-to-plate joints reduce the risk of crevice corrosion in demanding service conditions.

The block heat exchanger operates by directing two media through alternately welded channels formed between corrugated metal plates. These corrugations promote high turbulence, which drives heat transfer efficiency and creates high wall shear stress that helps minimise fouling. In a standard multi-pass unit, the overall flow arrangement is counter-current, though co-current operation can be designed if required. Each pass is separated by a pressed baffle, which directs the fluid between the plate pack and the side panels, ensuring full utilisation of the heat transfer surface.

Key components

The core of a block heat exchanger is the stack of corrugated heat transfer plates, laser-welded together (for models CP30 and above in the standard Compabloc range, and across all models of the Compabloc+) to form a sealed compact block. This core is enclosed by four corner girders, top and bottom heads, and four side panels that are bolted together. Only four panel gaskets are installed in total — one per side panel — which are the only field-replaceable sealing elements on the unit. The plate pack itself contains no interplate gaskets. The girders and heads are fixed items that must never be disassembled from the plate pack; only the panels are removed for maintenance access.

Selection criteria and engineering factors

Selecting a block heat exchanger requires a thorough understanding of the process parameters. Engineers must consider the design pressure, design temperature, required heat transfer area, and the chemical composition of both media streams. The standard Compabloc range spans from the CP15 with a maximum heat transfer area of 2 m² to the CP120 with up to 840 m² in a single unit. The maximum weight of a CP120 unit reaches 60,000 kg. For the Compabloc+, the CP120+ reaches a maximum weight of 63,000 kg. Material selection is driven by media chemistry, with 316L stainless steel as the baseline and alloys including 254SMO, Titanium grade 1, 904L, Alloy C276, and Alloy C22 available for corrosive service in the standard range.

Comparison to shell-and-tube alternatives

When compared to traditional shell-and-tube designs, welded plate and block heat exchangers offer a reduced unit size and weight for an equivalent heat transfer duty, thanks to the high thermal performance of the corrugated plate geometry. From a maintenance perspective, a shell-and-tube unit typically requires substantial axial space for tube bundle extraction, whereas a block heat exchanger requires a clearance of 50 to 120 cm around the unit to facilitate panel dismantling, and 100 cm of free space above the unit for a panel-lifting device. This can make the block design suitable for retrofitting into plants where space is restricted. The high turbulence generated by the corrugated plate channels also helps minimise fouling that can accumulate in the smooth tubes of alternative technologies.

Maintenance and operational reliability

Reliable operation requires adherence to defined start-up and operational limits. System start-ups must be gradual, with temperature change rates not exceeding 60 °C per hour and pressure change rates capped at 1 bar per minute. These limits prevent thermal and mechanical stress that could lead to component fatigue. Panel bolt torques must be verified before initial start-up and after any re-assembly, with pre-tightening performed at 60–70% of nominal torque values before a final tightening to 100% of nominal values. Panels must never be tightened or loosened while the system is under pressure or before panels have returned to ambient temperature.

Regular maintenance includes external visual checks not less than once per week, supervision of key process parameters daily, and external and internal visual control on a cycle of once per 3 years up to once per 6 years depending on equipment criticality. Chemical cleaning agents recommended for specific deposit types include AlfaCaus or Alpacon Multi CIP II for organic deposits, Alpacon Descalent II for calcium carbonate and calcium phosphate, and AlfaPhos for iron oxides. Mechanical cleaning via high-pressure hydroblasting is effective at pressures up to 500 bar; if higher pressures are required, Alfa Laval should be contacted to ensure safe procedures. For units susceptible to water hammer, reinforced baffles and correctly sized PID control valves are used to prevent damaging pressure surges.