Shenzhen Zhongnuo Inspection & Technology Co., Ltd. is based in South China and specializes in explosion-proof certification and coal safety certification application consulting services, offering one-stop explosion-proof technology consulting services.
The meaning of explosion-proof ratings is crucial for understanding and selecting the appropriate explosion-proof equipment. Below is a detailed explanation by Shenzhen Zhongnuo Testing Technology Co., Ltd. on the significance of explosion-proof rating letters:
I. Basic Composition of Explosion-Proof Markings
Explosion-proof markings are typically composed of letters and numbers, and mainly include the following parts:
"Ex" marking: Indicates that the equipment has passed the explosion-proof certification and complies with explosion-proof standards.
Explosion-proof Type: Typically a letter used to indicate the type of explosion-proof protection adopted by the equipment.
Gas Groups: Specify the gas group(s) applicable to the equipment, such as I, IIA, IIB, IIC, etc., which represent different explosive gas environments.
Temperature Groups: Indicated by a letter "T" followed by a number, where the number represents the high surface temperature of the equipment during operation. Commonly used are T1 to T6.
Equipment Protection Level: Indicates the Equipment Protection Level (EPL), typically used for further subdividing the safety performance of equipment in explosive environments.
II. Specific Meanings of Explosion-Proof Grade Letters
Explosion-proof protection type:
"ia" and "ib" denote the explosion-proof types of equipment. The "ia" rating ensures that the equipment cannot ignite an explosive gas mixture under normal operation and in two fault conditions, whereas the "ib" rating prevents ignition under normal operation and one fault condition.
Gas Group Letter:
I: Used in coal mine gas environment.
IIA: Applicable to gases of lower hazard.
IIB: Suitable for ethylene and other medium hazard gases.
IIC: Suitable for gases of equal or higher hazard.
Hazard levels increase sequentially, i.e., IIA < IIB < IIC.
Temperature group letters and numbers:
T1: Equipment surface temperature does not exceed 450°C.
T2: Equipment surface temperature does not exceed 300°C.
T3: Equipment surface temperature shall not exceed 200°C.
T4: The surface temperature of the equipment does not exceed 135°C.
T5: The equipment's surface temperature does not exceed 100°C.
T6: The equipment's surface temperature does not exceed 85°C.
Equipment Protection Level Letter:
Explosive gas environment equipment with a "X" protection level, not a source of ignition during normal operation, anticipated failure, or rare faults.
Gb: Equipment for explosive gas atmospheres, with "high" protection level, not a source of ignition under normal operation or expected fault conditions.
Explosive gas environment equipment with a "normal" protection level, not a source of ignition during normal operation.
Protection levels increase in order: Gc < Gb < Ga. Ga can be used in Zones 0, 1, and 2; Gb can be used in Zones 1 and 2; Gc can be used in Zone 2 only.
III. Example
For example, with the explosion-proof marking "Ex ia IIC T6 Ga":
"Ex": Indicates that the equipment is explosion-proof.
"ia": Indicates that the equipment's explosion-proof grade is a high level within the intrinsic safety category.
"IIC": Indicates that the equipment is suitable for IIC-level explosive gas environments.
"T6": Indicates the surface temperature of the equipment does not exceed 85°C.
"Ga": Represents the protection level of the equipment, applicable to Zones 0, 1, and 2.
In summary, understanding the meanings of explosion-proof ratings is crucial for selecting and using explosion-proof equipment correctly. Shenzhen Zhongnuo Testing Technology Co., Ltd., as a design and testing service provider for explosion-proof products, can offer you comprehensive testing and certification services for explosion-proof products to ensure your equipment meets relevant standards and requirements. For any inquiries or needs, please feel free to contact us at any time.

List of Domestic Explosion-Proof Certification Institutions:
1. Nanyang CNEX
2. Shanghai Coal Research Institute
3. National Electrical Appliance Quality Supervision and Inspection Center
4. Guangdong CQCEx National Explosion-Proof Equipment Quality Supervision and Inspection Center
5. National Coal Mine Explosion-Proof Safety Product Quality Supervision and Inspection Center
6. Jiamusi Explosion-Proof Institute
7. Tianjin PCEC
8. Shanghai NEPSI
9. Beijing Coal Research Institute CCRI, etc.
For applicants, what type of explosion-proof and what level of explosion-proof to choose is actually the same across all authorized institutions. They are all institutions that have been certified and authorized by the state, possessing testing conditions that meet the required standards, adhering to the same standards, and conducting the same testing. Under the same conditions, the trend is inevitable to choose institutions that offer more cost-effective services at a lower price. This is also an important reason why emerging explosion-proof companies are increasingly popular.

Intrinsically safe equipment has explosion-proof ratings of IA, IB, and IC, determined based on intrinsic circuit evaluation considering both counted and uncounted faults. IA rating is used in Zones 0, 1, and 2; IB rating is suitable for Zones 1 and 2; IC rating is only applicable in Zone 2.
Additionally, intrinsic safety equipment can be used in mining environments as well as in explosive gas and dust atmospheres not related to mining. It primarily operates by limiting the energy in the circuit, ensuring that it cannot ignite the surrounding explosive environment under normal operating conditions or in the event of a fault, thereby providing inherent safety and is thus referred to as intrinsic safety type.
If you have more questions about the design and certification of intrinsically safe equipment, Shenzhen Zhongnuo Testing Technology Co., Ltd. can continue to provide you with answers.

Sample requirements for applying for explosion-proof certification:
The sample units submitted by the company for inspection must match the approved drawings and be fully assembled. The number of units inspected should meet the requirements.
If special disassembly tools are required, they should be sent along with it.
For potting-type electrical equipment, a set of both potted and unpotted products should be submitted.
Observing window transparent pieces should be sent separately, with at least 3 pieces, and an additional 5 pieces.
The transparent parts of the lighting fixtures should be sent separately in an additional 8 pieces, with at least 5.
The rubber aging test should provide 3 to 5 pieces of 35156 rubber blocks.
Two 15060mm diameter plastic sheets are required for the insulation resistance test of the plastic shell. If the dimensions permit, the test can be directly conducted on the plastic shell.
1-2 finished products are generally required.
Explosion Proof Certification Application Consulting Service - Shenzhen Zhongnuo Testing Technology Co., Ltd.