Design of explosion-proof control cabinets
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Are there any **international standards that can be followed for the design of explosion-proof control cabinets? What aspects need to be considered for this design? Are there any colleagues with experience in such designs who can share their insights? Project background: A paint factory that uses a PLC-based control system; the control system was designed last year. Now, the client wants it to be converted into an explosion-proof control cabinet. My initial idea is to design a positive-pressure explosion-proof control cabinet, using the clean compressed air available in the factory for purging purposes, in order to prevent flammable and explosive gases from entering the control cabinet. I welcome everyone’s participation in the discussion. Thank you. This post was last edited by LZ Gas Station on 2009-2-4 at 07:35
Positive-pressure ventilation type explosion-proof electrical control cabinets are generally used. In the flameproof electrical control boxes of such cabinets, intrinsically safe wires and non-intrinsically safe wires should be wrapped separately, and the distance between the intrinsically safe end and the non-intrinsically safe end must be greater than 50 mm. It is not allowed to replace, modify, or adjust any components or structures that could affect the explosion-proof properties.
The design and manufacture of explosion-proof equipment require qualified personnel; it needs to be done in accordance with explosion-proof standards – not every organization is capable of carrying out this work.
The rectification here also follows what LZ envisioned: it is changed to a positive-pressure system, with compressed air being fed in from the top of the cabinet to create a positive pressure.
Find an explosion-proof manufacturer to make a casing; most of those available in China are made of cast iron, which is extremely heavy and makes installation very troublesome. Just thinking about explosion-proof devices and their installation gives me a headache.
Why is an explosion-proof control cabinet needed? Is it in a non-explosion-proof area? The phone and monitor should also be explosion-proof, right?
Positive-pressure ventilation type explosion-proof electrical control cabinets are generally used, and they must comply with GB3836.1-83 \"General requirements for explosion-proof electrical equipment used in explosive atmospheres\" and GB3836.5-87 \"Positive-pressure electrical equipment ‘P’ for explosion-proof electrical equipment used in explosive atmospheres\"
In fact, as long as an isolation room is built to house the control cabinet, the requirements regarding its explosion-proof rating need not be that high. Seen in this way, it’s more economical and practical.
Can an explosion-proof cabinet be built by oneself? We have always sought qualified manufacturers to produce them; at the very least, the boxes/containers used on the outside should be made by explosion-proof manufacturers
Yes. The design and production of explosion-proof equipment must be carried out by manufacturers that possess the necessary qualifications and have undergone explosion-proof certification; not any entity can do this.
It’s not possible to make this by oneself; there are professional manufacturers in China. It’s not just a cabinet, but also includes a pressure control system. The pressure is generally kept between 150 and 300 Pa, with an alarm triggered when it drops below 80 Pa, and automatic power shutdown when it falls below 50 Pa
What was said upstairs makes sense, but the pressure doesn’t have to be that high, right? ? According to the specifications, a pressure of not less than 50 Pa should be sufficient. Another requirement is that the gas to be blown in must be instrument air or nitrogen, rather than compressed air that has not been filtered of dust, oil, and moisture
For positive pressure ventilation type explosion-proof control cabinets, the components themselves must also be explosion-proof.
The clean gas in the factory you mentioned must also be an inert gas!
Positive-pressure ventilation type explosion-proof electrical control cabinets are generally used. In the flameproof electrical control boxes of such cabinets, intrinsically safe wires and non-intrinsically safe wires should be wrapped separately, and the distance between the intrinsically safe end and the non-intrinsically safe end must be greater than 50 mm. It is not allowed to replace, modify, or adjust any components or structures that could affect the explosion-proof properties. The design and production of explosion-proof equipment must be carried out by manufacturers that possess the necessary qualifications and have undergone explosion-proof certification. There is also a pressure control system; generally, the pressure is kept between 150–300 Pa, while the air pressure ranges from 0.4 to 0.8 MPa. An alarm is triggered when the pressure exceeds 350 Pa, and the automatic control system shuts off the air supply or opens the exhaust valve. An alarm is issued when the pressure drops below 150 Pa, prompting automatic air replenishment; when it falls below 80 Pa, an automatic audio-visual alarm is activated, and power is cut off when the pressure drops below 50 Pa. For more details, please refer to Jiangsu Hengtong Electrical Instruments Co., Ltd., Gas Section (pages 35–36): http://www.el-ex.com/victory/. Additionally, the gas source is usually purified air or protective gases such as nitrogen. The gas consumption is 2–8 cubic meters per hour, while the air exchange rate is 10–20 cubic meters per hour. I have worked in a workshop that produces hydrogen, where positive-pressure explosion-proof instrument cabinets of the handshake brand were used. This post was last edited by Mobei Yihai on 2009-4-10 at 10:52