In petroleum, chemical, gas and pharma plants, flammable gases may be present continuously or intermittently. Standard hoists create ignition sources through fault arcs, contactor switching, brake friction or impact. A reinforced standard hoist is unacceptable; the design must be explosion-proof from the outset, electrically and mechanically.
"CT4" is Chinese industry shorthand, not a complete marking; it generally means "IIC T4". A full marking includes protection type, gas group, temperature class and EPL: Ex db IIC T4 Gb (IEC) or II 2G Ex db IIC T4 Gb (ATEX). Check the valid Ex certificate and nameplate.
Ex: explosion-proof compliant.
db: flameproof enclosure, IEC 60079-1; older "d".
IIC: most stringent subgroup (hydrogen, acetylene); covers IIA and IIB per certificate.
T4: max surface 135°C (T1–T6: 450/300/200/135/100/85°C).
Gb: EPL, Ga for Zone 0, Gb for Zone 1/2, Gc for Zone 2 only.
ATEX: Zone 1 is normally 2G, Zone 2 may be 3G; North America uses Class I Division 1/2. IECEx, ATEX, Chinese Ex and UL/CSA are not mutually recognized; export projects must meet target-market regulations.
Safety rests on three features. Flameproof joints: controlled gap, length and finish quench internal flame and hot gases. Surface temperature: motor design, load limit, duty cycle and cooling hold the class; T4 is stricter than T3/T2. Non-sparking parts: hooks and trolley wheels in non-sparking material; control boxes flameproof or intrinsically safe.
Selection: confirm area classification (Ex db suits Zone 1/2, not Zone 0), gas type (IIB or IIC), ignition temperature (T3/T4 with margin), capacity, height, duty class and frequency. Export projects generally need an IECEx CoC or ATEX EU-type certificate; China needs GB/T 3836.
Maintenance red lines: never open a flameproof enclosure while energized; never strike, scratch, paint or re-gasket joints; replacement parts must match the protection level.
Zhejiang Vertex International Trade Co., Ltd supplies lifting equipment and customizes gas group, temperature class, capacity, height, voltage, control and mounting, plus OEM/ODM within certificate scope. Send gas type, ignition temperature, area class and lifting needs for advice.
Zhejiang Vertex International Trade Co., Ltd. Parent Companies:
1. Zhejiang Boneng Lifting Technology Co., Ltd. (Former Name: Taizhou Boneng Lifting Machinery Equipment Co., Ltd.)
2. Sanmen Youbang Machinery Co., Ltd.
Reposted for informational purposes only. Due to factors such as timeliness and policy, please refer to the sources mentioned in the content. If you have any questions, please contact us.
