Energy-efficient conception of the new exhausting system

The influence of the plant conception on the energy efficiency of an exhausting system was evident in the renovation of the exhaust system in the carpentry shop of the Göttinger Werkstätten by SPÄNEX.

The Göttinger Werkstätten non-profit GmbH is a modern service company with the following range:

  • occupational integration of people with mental or emotional disabilities,
  • related manufacturing of products or provision of services to contracting entities,
  • stationary and ambulant living offers.

The facility is divided into five workshop locations and residential facilities in the city and district of Göttingen.

The equipment of the carpentry includes all common machines for the processing of wood and wood-based materials. This makes it possible to meet a wide variety of customer requirements. In the production of profile strips, all standard strip profiles, also in special lengths, are manufactured for the trades, the construction industry and DIY supplies. In addition to pure production, the Göttinger Werkstätten are also involved in the respective product development of the customers.

The existing exhaust system had been in operation for many years and showed signs of wear and tear. The main disadvantage, however, was the high current consumption. The old plant can be described as follows:

  • exhausting 19 machines,
  • 2 exhaust groups,
  • 2 raw-air side mounted exhaust fans, each with 37 kw,
  • 2 filter units, each with chain conveyor and valve,
  • chips in a container with raw-air side arranged transport fan, engine power 11 kw.

The reason for the very high current consumption was primarily seen in the conception of the old plant. When a machine was switched on, an exhaust fan with a motor power of 37 kw already started. Parallel to this, the rotary valve, the chain conveyor and the transport fan had to be put into operation with a connection power of 11 kw.

Due to these deficits, the Göttinger Werkstätten were advised by the company Melchior Maschinen and SPÄNEX. Together, the requirements for a new exhaust system have been defined:

  • machines to be exhausted: 19
  • grinding table to be exhausted: 1
  • connected air volume: approx. 41,000 m³/h
  • simultaneously working factor: approx. 68%
  • maximum amount of air extracted at the same time: 28,000 m³/h
  • mode of operation: discontinuous
  • air recirculation: 100%
  • chip disposal: container

Further requirements for the new exhaust system were the reduction of electricity consumption, quiet operation and the improvement of the safety technology.

In the next step, the technical data of the existing extraction system were recorded, the operating sequence was analysed with the machine usage profile and a detailed quotation was created on this basis. The solution developed was presented to the responsible persons of the Göttinger Werkstätten. After several rounds of talks, the final system design was defined, which can be described as follows:

  • exhaust pipework system divided into 4 groups,
  • compact filter system with integrated, speed-controlled exhaust fan, consisting of 4 modules,
  • clean air chamber with exhaust fan (37 kw)
  • filter cell with vibration-cleaned filter hoses
  • chip buffer container (contents 6 m³) with automatically controlled discharging unit
  • substructure with type-tested rotary valve (decoupling link) for handing over to the transport system
  • return air duct with hose rupture guard and switching over to waste-air operation with fresh air intake
  • transport system as a ring line for feeding the container, transport fan (4 kw) in the return line
  • electric circuit for the complete system with automatic slide control and speed control for the exhaust fan via a frequency converter

The proposed concept convinced the customer, so that the company Melchior Maschinen together with SPÄNEX received the order for the delivery, assembly and commissioning of the plant.

Specifically concerning the requirements of electricity cost savings, quiet operation and safety technology, the following should be noted:

Savings in electricity costs

By adapting the pipework system to 4 groups, the full saving potential of the speed control can be reached. According to our experience with similarly designed systems, up to 50-60% of the installed motor power can be saved in real operation. After a period of operation of about 5 months, the average power requirement of the exhaust fan was about 15 kw, so that compared to the old plant an annual saving potential of approximately 50,000 kwh is reached.

A further significant contribution to the energy saving is provided by the transport system connected to the buffer container of the filter device. The capacity of the buffer tank is 6 m³, so that the separated chips in the filter device can be stored in between and only once per day for about 0.5 to 1 hour they are pneumatically transported via the ring line in the container placed next to the filter system. In the old plant, the transport fan had to be operated in parallel with the exhaust system, as there was no buffer possibility. The transport fan is arranged in the return line of the transport system. The motor power could be reduced from 11 kw (old plant) to 4 kw. By buffering the chip material, the energy required for the chip transport to the container is reduced to about 4 kwh per day. The savings effect is therefore determined first by the lower required motor power and secondly from the reduced operating time. It is expected that the transport system will save about 16,000 kwh the year.

Altogether therefore an annual energy saving of approx. 66,000 kwh can be assumed.

Quiet operation

The exhaust fan of the system is integrated in the fan cell of the filter device, which is lined with sound protection mats, so that even under full load a noise emission is barely perceptible.

In addition, the transport fan was installed sound-and weather-protected, by arranging it below the container of the filter device. For this purpose, the base of the filter unit was covered with sheet metal panels. The transport fan can be inspected and maintained via an inspection door.

Safety technique

It is a matter of course that the safety equipment of the installation complies with the applicable standards and regulations. As an additional aspect, it is worth mentioning that a part of the pipework system was equipped with a spark detecting and extinguishing system of the company Grecon in Alfeld. A machine-connected collecting pipeline is monitored, in which, according to the risk assessment, there is an increased risk of spark formation during processing. This measure significantly reduces the likelihood of damage in the form of a fire or an explosion in the filter device.

Summary

After almost 5 months of operation, the management of the Göttinger Werkstätten is enthusiastic about the result: "With the new exhaust system the goals that we set ourselves were not only achieved but surpassed. The enormous savings in electricity costs and the quiet operation of the system are particularly impressive for us."

 

 

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