Formula for the tightening force of fastening bolts for explosion-proof electrical appliances - News - Global IC Trade Starts Here Free Join

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In addition to the necessary locking force, the fastening bolts of the explosion-proof electrical appliance are also subjected to the explosion pressure. This paper mainly introduces the calculation formula of the tension bolt of the explosion-proof electrical appliance, as follows:
Q=1.3Qo(N)
For the stop structure Q=1.1Qo(N)
Qo=QP/Z(N)
QP=PA
Where Qo - the calculated stress of each bolt, N;
QP - the total pressure the bolt is subjected to during the explosion, N;
Z——the number of bolts;
P——includes the compressive stress experienced during the explosion, MPa, 1.5 MPa for IIC, and 1.0 MPa for the rest;
A - the effective area under pressure, m2.
The spacing of the fastening bolts of the explosion-proof electrical enclosure is related to the shape, material and presence or absence of the outer casing. For the planar structure, the IIC level is generally not more than 70-80 mm, and the other explosion-proof grades are generally not more than 120 mm. When the structure is stopped, it is generally not more than 140mm. The number of bolts is generally not less than four for a planar structure, and the number of anchors should not be less than three.
The screw-in depth of the explosion-proof electrical bolts is at least 1.25 to 1.5 times the bolt diameter for the cast iron casing; the steel casing is at least 1.0 times the bolt diameter.
Thread allowance for the housing fastening bolts: The remaining threads of the washer washer thickness must be left after the bolts are tightened so that the outer casing can be tightened after the gasket is lost.
The thickness of the non-transparent screw hole on the outer casing shall be greater than 1/3 of the diameter of the screw hole, but not less than 3 mm.