Alas, have you ever thought about why the surveillance screens with red light in chemical plants will not explode in high temperature and high pressure environments? Last year, a friend who was in the mining industry suffered a great loss. He bought an ordinary LED screen for cheap and installed it in the mine. As a result, the equipment was short-circuited and sparked, which almost caused an accident... Today, let's talk about the door to the explosion-proof surveillance screen. Novice can avoid at least 80% of the pit after reading it!

What is the difference between explosion-proof screen and ordinary screen

Many people think that explosion-proof is just adding an iron shell, but​ ​Explosion-proof certification structure​ ​It's the core. A truly qualified explosion-proof monitoring screen must do these two things:

1. ​​Sealed and anti-seepage​ ​: There must be double-layer silicone strips at the joints of the box, and even gaps of the thickness of hair should not be available to prevent combustible gas from drilling into the equipment.
2. ​​Energy-limited design​ ​: Even if the internal circuit is short-circuited, the heat released instantly is lower than the critical value of igniting dangerous gases

I have seen some counterfeit goods, and the shell looks quite thick. As a result, when measured with a vernier caliper, the diameter of the heat dissipation hole exceeded the standard by 0.5 mm - this error is enough to cause explosions in an oil and gas environment!

Three parameters determine life and death

When buying explosion-proof screens, don’t just focus on the price. These three indicators must be inspected on the spot:

• ​​Explosion-proof sign​ ​: Identify the code combination of Ex d IIC T6 Gb, and no alphanumeric characters can be wrong (Ex represents explosion-proof, d is explosion-proof type, and IIC level is suitable for the most dangerous gases such as hydrogen)
• ​​Surface temperature​ ​: The maximum temperature of the shell must be more than 20℃ lower than the on-site combustible material ignition point, for example, for coal mines, it must be controlled within 85℃.
• ​​Impact resistance level​ ​: Only withstand the impact resistance of 6J or above can the equipment room tool fall. Take a 500g steel ball and smash it from a height of 1.2 meters. The screen body must not have cracks.

Last time I helped the refinery inspect the goods and took a photo of the infrared thermal imager, I found that a screen with a nominal IP65 was found. After half an hour of running, the local temperature of the junction box soared to 117℃. This must be installed in the pump area and turned into a time bomb in minutes!

Hidden minefields for installation and maintenance

Even if you buy a qualified product, something will happen if you don’t install it. Let me tell you a real case: The explosion-proof screen of a chemical factory has clearly passed the inspection, but it leaked after three months of operation. Later, I took a look at it.​ ​The installation team actually used ordinary screws instead of explosion-proof certified fasteners​ ​, thermal expansion and contraction lead to seal failure…

Here is the key point:

1. The wiring must be carried out with explosion-proof flexible pipes, and ordinary PVC sleeves are looking for death
2. The grounding resistance should be <4Ω, don't believe what some installers said, "Just be almost the same.""
3. Every six months​ ​Do airtightness testing​ ​, apply foaming agent to the joints, and stop immediately if bubbles appear

Price Mist Cracking Guide

The price of explosion-proof screens can range from 8,000 to 50,000 per square meter, and the price difference is mainly in these places:

There is a trick: ask the supplier to provide it​ ​10% redundant lamp beads​ ​design plan. For example, if you buy a P4 screen, you will actually arrange the lamp beads at P3.6 spacing. Even if it is damaged later, it will still maintain the complete display after re-jumping the wires - this solution can extend the screen life by more than 3 years.

Unpopular tips for choosing suppliers

In addition to reading the qualification certificate, I will teach you two operations that talents in the industry know:

1. Let sales live demonstration​ ​Fault injection test​ ​, for example, unplugging a power module, see if the system can automatically switch the backup circuit
2. It's been nearly three years​ ​Explosion-proof certificate annual review record​ ​, Some manufacturers do not conduct annual inspections after obtaining the certificates, which is equivalent to waste paper.

Remember to focus on the control system​ ​Fault tolerance rate​ ​. A good explosion-proof screen should be done: a single control card failure will not affect other areas, and the switching time of the main and backup signal source is ≤0.5 seconds - this is too important for the monitoring center that operates 24 hours a day!

Now do you know why some manufacturers dare to quote low prices? Save a explosion-proof junction box to cut off 2,000 yuan, but this is a bet on life! A truly reliable explosion-proof monitoring screen is all about the thickness of the steel plate to the torque of the screw. Next time you purchase, remember to bring a vernier caliper and torque wrench to inspect the goods - this trick can make 90% of the corners come true!

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