Which modular designs allow the retrofitting of heating/cooling jackets or additional sensors?
Retrofitting process plants with sensor technology can be readily achieved in many cases. Retrofitting a heating or cooling jacket, by contrast, is considerably more involved and is not simply a question of modular construction. Particularly with pressure vessels, vacuum plants or hygienic process apparatus, every structural change must be assessed in terms of statics, thermal behaviour and safety.
Additional sensor technology is easiest to retrofit where spare connections were already provided for at the planning stage. Blank flanges, hygienic process connections or prepared measuring ports for temperature, pressure, differential pressure, moisture, fill level or analytical probes are suitable, for example. Such connections allow additional sensors to be installed without having to subsequently cut open the vessel or weld in new connections. In hygienic applications, sensor connections must be flush, cleaning-friendly and designed so that no dead spaces occur. Sensors in vessels should, wherever possible, be installed flush with the inner vessel wall.
Pipeline sections can also be extended modularly. Instrumented spool pieces, measuring coils or T-pieces, for example, allow the retrofitting of flow meters, conductivity sensors, temperature measuring points or pressure transmitters. This requires that installation length, pressure rating, material, sealing concept and cleanability are taken into account. In CIP- or SIP-capable plants, the extension must not create poorly flushed areas, since these can impair cleanability and validatability.
Skid and frame constructions primarily make it easier to retrofit external components. These include heating or cooling units, circulation pumps, valve islands, filters, heat exchangers, condensers, vacuum pumps and additional measuring points in the pipework. An open, readily accessible frame construction creates space for such extensions and simplifies maintenance and later modifications. It does not, however, replace the technical assessment required where the actual process vessel is to be changed.
A heating or cooling jacket can only be added comparatively easily where the vessel was prepared for this from the outset. Structurally provided jacket segments, half-pipe coils, or a separate, retrofittable outer jacket, for example, are possible. In practice, however, wall thickness, permissible operating pressure, vacuum stability, thermal expansion, weld seams, supports, insulation and the controllability of the heat-transfer medium must be checked. A jacket welded on afterward changes the loading on the vessel and can affect conformity with the original pressure equipment design.
With pressure equipment, a substantial modification can mean that the altered plant has to be reassessed and re-documented. Where pressure vessels or assemblies are modified in a way that can affect their conformity, manufacturer obligations under the Pressure Equipment Directive can arise for whoever is responsible for the modification. The technical assessment should therefore be carried out by the original manufacturer or by a competent body.
On the automation side, free inputs and outputs, decentralised I/O stations, spare cabling, control-cabinet reserves and standardised communication interfaces make it easier to integrate additional sensors. Also important are sufficient power reserves, the appropriate ingress protection rating, consideration of ATEX requirements, and adaptation of control software, alarm limits, recipes and batch documentation.
The best retrofittability results from forward-looking planning. Spare ports, free flange positions, empty conduits, additional I/O capacity and space reserves on the skid should already be provided for in the basic design. Sensor technology can then usually be added economically. For heating or cooling jackets, on the other hand, the following applies: a retrofit is technically possible, but must always be planned, assessed and documented as a structural modification of the process apparatus.
Modularity in amixon® plants
amixon® plants are designed on a project-specific basis according to the User Requirement Specification. This makes it possible to provide for spare connections, additional measuring points, free automation capacity and space for later extensions already at the planning stage. Actual retrofittability, however, always depends on the design, material, pressure rating, vacuum design, hygiene concept and the existing automation.
Additional sensor technology is usually the easiest to retrofit. This requires existing process connections, blank flanges, measuring ports or suitable installation positions in the pipework. Temperature, pressure, differential pressure, fill level, moisture or further product-related measured variables, for example, can be captured through these. In hygienic applications, the measuring points must be cleaning-friendly, low in dead space, and matched to the respective sealing and material concept.
Automation can also be modularly prepared. Free inputs and outputs, decentralised I/O stations, spare cabling and standardised communication interfaces make it easier to later integrate additional sensors, dosing units or safety equipment. After an extension, however, control software, alarm limits, recipes, batch documentation and, where applicable, the validation documentation must be adapted.
Heating and cooling jackets
Heating or cooling jackets can only be regarded as a simple retrofit to a limited extent. With VMT and AMT, the mixing chamber and, depending on the design, the mixing tools too can be executed with temperature control. Whether temperature control can be added afterward, however, is not a standard question of modularity but a technical modification of the apparatus.
For a retrofit, the vessel wall, permissible pressure, vacuum stability, thermal expansion, weld seams, material, supports, insulation, heating or cooling power and the control concept, among other things, must be checked. If an existing vessel is modified by a jacket, half-pipe coils or additional connections, this can affect the original pressure equipment design. An assessment by the manufacturer or a competent body is therefore required.
Expandable functions
Depending on the existing base configuration, liquid additions, dosing lances, nozzles, cutting rotors, washing lances, sampling points, discharge devices or additional sensor technology, for example, can be added. Whether such a module can be retrofitted must be checked for the specific machine. The mechanical installation situation, the hygienic design, the electrical power, explosion protection and the effects on process behaviour are decisive.
A mixing tool or a cutting rotor, for example, can change the mixing intensity and de-agglomeration. Such an extension therefore requires not only a mechanical feasibility check but also a process-engineering assessment with the original product.
Trials and documentation
Before a retrofit, it should be checked whether the planned extension delivers the desired benefit. Mixing quality, temperature profile, product movement, cleanability, discharge, energy input and, where applicable, residual moisture are decisive here. Trials with the original product can form the basis for selecting sensor technology, temperature-control power and process parameters.
In regulated applications, the effects on qualification, cleaning validation, software, batch documentation and data integrity must additionally be assessed. A substantial modification to pressure equipment or a hygienic process plant can require a renewed technical assessment and additional documentation.