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Flameproof (Ex d) enclosures are constructed in such a way that an internal ignition of a flammable atmosphere will not be transmitted outside the enclosure and thereby preventing the ignition of surrounding flammables. The large Ex d enclosure was designed for gas group IIB explosive atmosphere with the help of MATLAB and ANSYS software and further a study of stress analysis due to internal pressure had been carried out on the plates and cover by keeping the thickness of body plate and cover constant. The study showed that stress was observed more in the center of the plate and reducing toward the edges of plates. The value of the length and breadth ratio (a/b) was found out with the help of the curve fitting method to calculate maximum stress (σmax) in the designed Ex d enclosure. The calculated maximum stress of all the plates was less than the simulated results, so the simulated results indicated that the designed enclosure is within the safety limit and suitable for hazardous area.

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Increased safety (Exe) motors are widely used in zone 1 and 2 areas. Exe high tension (HT) motor is designed in such a way that it cannot produce any arc/spark and temperature of any part of motor in normal operating condition and specified abnormal condition. The risk assessment of Exe HT motor was introduced in the year of 2008 by ET22 Committee of Bureau of Indian Standards in IS:6381-2004 standards in India. The Exe motors were designed and risk assessment of ignition was carried out as per new standards. All necessary test on the Exe HT designed motors are also described in this paper. The starting time or blocking time in normal or abnormal condition of Exe motor depends on the insulation system of motor. Time t E of rotor or stator winding depends on some design parameters like mass of rotor winding, rotor copper loss, starting torque etc. Time t E is very critical for any HT Exe motor and it should not be less than 5 s as per IS:

The increased safety (Ex e) high tension (HT) motors are widely used in the petroleum industries and area where explosive atmosphere is present. The time t E and I A /I N ratio value is very important for Ex e motor. The time t E of rotor and or stator winding, I A /I N ratio and temperature rise can be affected by increasing the stator coil pitch. The coil pitch of stator were increased for three different ratings of three phase HT Ex e induction motors and redesigned for analyzing the temperature rise, t E and performance. The relevant tests were performed and performance characteristic of motor was compared with normal design motor.