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Lighting design guide of clean workshop

Clean workshop is also called dust-free workshop, clean room, dust-free room. It has high demands on contaminant, temperature, indoor pressure, air flow distribution and lighting etc.

Clean space is applied to all kinds of factories and laboratories such as electronics, micro-electronics, optics, instruments and apparatus, precision manufacturing, aerospace, biology, medical treatment, medicine, daily chemical and food and beverage etc.

DESIGN AND WIRING OF CLEAN LIGHTING

In order to create a lighting design of high cleanliness class in clean room, let me introduce cleanliness class of clean workshop and airflow pattern of clean air first.

Cleanliness of clean workshop:

Chinese standard GB50073-2013 Code for design of clean room adopts the relevant regulations on international standard ISO14644-1, and its air cleanliness class is divided into nine grades.

airflow pattern of clean air

The so called airflow pattern means to design pattern and distribution of airflow inside clean room reasonably. We should try to avoid or reduce vortex, which can help eliminate pollutants quickly, restrict and reduce to the greatest extent the spread of dust and bacteria from indoor pollution sources, and maintain the air cleanliness class required by indoor production environment.

When the required air cleanliness class is 1~4, we should use vertical unidirectional airflow.

When the required air cleanliness class is 5,we should use vertical or horizontal unidirectional airflow.

When class is 6~9, we should use non-unidirectional airflow.

Accordingly, we carry on lighting design based on cleanliness requirement of clean room and airflow pattern.

Clean room of non-unidirectional airflow:

Regarding clean room of non-unidirectional airflow, it is best to use ceiling slim panel light, cassette ceiling fluorescent light is also acceptable. We should avoid using streamline lighting fixture which can create disordered vortex and prevent dust accumulation.

Clean room of horizontal unidirectional airflow:

Regarding clean room of horizontal unidirectional airflow, air supply outlet and return air inlet are both installed on flank wall, the ceiling is convenient for lamps collocation and we can use ceiling slim panel light. If we choose traditional fluorescent lighting fixture, since the fixture is quite thick, it should be embedded-installed, thus try to reduce influence on airflow.

Clean room of vertical unidirectional airflow:

Regarding clean room of vertical unidirectional airflow, the ceiling has a lot of air outlets and has small mounting area, thus we often use tear-type fluorescent lighting fixture, we can also use more advanced tear-type LED lighting fixture which has better lighting effect.

In regards to lamps collocation, it’s best to use continuous or intermittent light band, and collocate it together with detector for fire alarm system and the air inlet and outlet. During installation, pay attention to use sealant and gasket, thus to ensure seal installation, maintain pressure differential of clean room and protect it from pollution.

Considering the light and dark adaptation of production workshop, the illumination of aisle and rest room in clean room can’t have much difference than that of working space, generally it is suitable to have difference of 1~2 grade, but it can’t be lower than 100lx.

Besides setting up general lighting, we should also set up local lighting according to requirement, but the illuminance ratio of local lighting to mixed lighting can’t be too high, so as to avoid a sharp change between light and dark.

Same as all kinds of electrical wiring and profession piping, the wiring of lighting should follow the principle of concealment.

With different airflow pattern of clean room, the building structure is also different, but the lighting fixture is generally installed on the ceiling, the wiring of lighting is usually on technique interlayer. The lighting distribution box is in central location of technique interlayer. In this way it is near load center, and the horizontal wiring is short which can be easily hidden.

For lighting distribution box and switches etc. which must be installed in the clean room, their installation should be concealed. The electric wires, cables and pipelines that go through suspended ceilings must have sealing treatment, so as to prevent dust and bacteria from entering into clean room.

Energy-saving lighting design of clean workshop

Generally the illuminance requirement in clean workshop is higher than normal workshop, the indoor ceiling is relatively low, and the energy consumed in lighting is large. In design, the power density must meet the requirement of standard of energy conservation. The concrete measures in energy-saving lighting include:

1、Choose high-efficient light source

 

Traditional clean workshop usually use fluorescent tube for lighting, which has low luminous efficiency and high watts, at present we can choose high-efficient three primary color tube equipped with high-efficient electronic ballasts. As technique of solid-state lighting is matures, now we should choose high-efficient LED light source as a priority.

2、Choose reasonable illuminance standard

 

Different manufacturing technique and assignment requirement has different illuminance standard, in order to choose reasonable illuminance, we not only need to know technical requirement, but also need to be familiar with lighting products. many designers arbitrarily raise the illuminance standard and lower maintenance factor, such kind of things should be avoided.

3、Choose suitable lighting method

 

The technical process of clean space is complicated and usually its lighting requirement has different levels. In order to lower energy consumption effectively, the designer should fully communicate with the owner and confirm the technological process and assignment requirement in different districts. In places where has high illuminance requirement we can use mixed lighting, thus to provide basic illuminance through general lighting, and to ensure enough illuminance through additional local lighting.

4、Choose intelligent control method

 

For lighting design in clean room, we should both consider switch and control method, controlling light in separate zones and properly increasing lighting switch are relatively traditional method.

As technology improves, time control according to operation period, optically control according to lighting situation, infrared induction according to people flow, even intelligent control method based on Internet of Things, these are all optional control methods.

Emergency lighting of clean workshop

Clean workshop is a relatively sealed object, the route of personnel traffic indoor is complicate, in order that people can leave the scene as quickly as possible and ensure safety under emergency conditions, we should set up guidance lighting for personnel evacuating.

The Chinese standard has regulated that evacuation indicatory sign is better to be put at top of exit door, or on the wall which is less than one meter height above the floor in places of evacuation walk and its corner, the distance between indication signs should not be bigger than 20 meters. The standard illuminance value of escape lighting on the aisle shouldn’t be less than 0.51lx.

But according to particularity of clean workshop, we suggest to set up lighting lamp for escape route, of which the illuminance should be raised to 5lx. Because generally the clean workshop is working three-shift 24 hours day, so we should use everlasting lamp as the escape lighting.

The fire-firing access is entrance of building for firefighter to put out a fire. Code for design of clean room has regulated that red emergency lamp should be set up in fire-firing access, but in in actual projects it is often omitted, so we have to pay attention in drawing check and construction.

In clean room we should set up emergency and stand-by lighting. Emergency and stand-by lighting is to ensure continuing normal activity. We can use house generator for power supply, we can also use transformer which is different from that of supply main from general lighting, or we can use a way in which the low voltage distribution panel(or bus-bar) is separate from that of supply main from general lighting.

The stand-by lighting inside clean room should be uniformly arranged in proportion whose illuminance can’t be lower than 10% of general lighting. The selection of fixture can be same model as general lighting fixture in clean room, but it should has accumulator inside. Usually it is used as general lighting, during power cuts it automatically turns into emergency lighting, in this way it has independent function and simple wiring. It has flexible application and has little restriction from external power source.

Another favored way at present is centralized power type emergency lighting, it uses battery power unit to supply power to dispersive emergency lighting lamps(without battery), in general situation we use commercial power supply, when the power cuts, it automatically changes to emergency power. When the commercial power supply h

Conclusion

The clean room has many pipelines, its professional technology is complicated, it has strict requirement, its design requires cooperation of different professional skills. It is an engineering design with very strong comprehensiveness, and lighting is an important part. The confirmation of illuminance the selection of light souce and lighting fixture, the set up of lighting fixture and building, and the coordination of equipment are all important projects in lighting design of clean room.

ave electricity again, the power automatically changes to commercial power.

For a good lighting design of clean workshop, we should create a bright space with proper illuminance, and use the ceiling space reasonably. We should also decorate cleverly so that the lighting fixture can be classy, comfortable, with uniform illuminance and reasonably organized airflow. With all these finally we can ensure the cleanliness requirements of clean workshop, which is both energy-saving and easy to maintain.

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