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Types Of CBW Equipment

Tunnel washers are of four general types:

  1. Single skin - Voss, Schultess
  2. Double skin - Cherry Tree, Milnor, Poensgen
  3. Single and double skin - Aqua Trac, Senking
  4. Batch exchange - Poensgen, Senking

The configuration of a tunnel washer and the required number of stages, size, etc. must be full and accurately specified prior to selection and purchase of the machine. Once built it is not possible to modify or re-configure the normal tunnel washer, i.e. change the number of stages or wash parameters. The only system which can be changed is that which consists of a machine assembled in a modular construction with separate, discrete components linked together, e.g. Poensgen.

No one machine has all the desirable features and the machine selected should comprise the maximum plus points for the required use.

Diagram 4

Control Systems

The control of the washing system, individual wash processes and workflow must be closely allied to production planning. The inherent flexibility available to the launderer within a washer-extractor system is not necessarily available for the CBW system. This system cannot be adequately controlled or monitored manually and therefore operations are invariable controlled by their process card readers or full computer programming. The number of individual operations required i.e. load sequencing, process design and inputs, cycle time, press, conveyor and tumble drier interfaces makes any manual alternative method of control impossible.


A tunnel washer does not just replace a line of batch washers, it must be regarded as the core of a wash system. The installation of a tunnel washer should dictate the end of "ad hoc" planning of production through the washroom.


Planning must commence in Sorting as the tunnel washer demands not only a constant supply of work at regular short intervals but work of a category that will be adequately washed by the process installed on the machine.


Loading of the machine must be considered in terms of the weight of the classification in relation to volume, the accuracy of the weight of the load, and in the correct sequence to balance the tumbler operation.

Tunnel Washing

Previously a line of batch washer-extractors has been able to accept a variety of soiling and different classifications by having available different processes catering for different requirements of temperature, chemicals, water levels, time of processing and a variable number of stages within each process. For the tunnel washer it is necessary to study how to merge these different requirements into one average process which will process as much of the work as possible and discard for separate washer-extractor processing, anything that does not fit. We must also study the needs for special requirements such as Bleaching, Starching, Softening, Anti-chlor and Souring.

Press or Hydro-extractor

The press extracts water from the work after washing and rinsing. Inefficient use because of poor maintenance will cause production to suffer. If the tunnel wash machine is being run on a reduced time cycle to produce more work, an increase of moisture retention can occur with possible further delay implications during the drying operation. It is also now possible to obtain a pass-through high speed hydro-extractor unit as an alternative to a press unit. The choice of moisture removal system will depend on production requirements.


These must be balanced to the machine cycle time, otherwise production suffers. Production planning must therefore take account of the number of tumblers and their performance.


The evaporative performance of ironers should be studied to avoid unnecessary conditioning of work thus minimising the use of tumblers and allowing either a shorter machine cycle time or reduced energy usage.

Above all else the batch tunnel washer has to be operated as part of a fully integrated system with each individual element closely linked and tuned to the requirements of the next i.e.

  • sorting - a correct load at each cycle time
  • tunnel washer - receives a load at each cycle time interval
  • press unit (or extractor) - receives, processes and discharges a load within the tunnel washer's standard cycle time
  • tumble drier - receives and processes to part of fully dry any work load presented from the conveyor and discharges this to the required level of dryness and is ready to receive a further load from the conveyor at the required cycle time or multiples of cycle time. It follows from the above that each tunnel washer will require a multiple bank of tumblers to maintain effective production without hold or pause periods occurring.

This information courtesy of Division of Building Technology, CSIR.