Transformer cover plate bolt torque

[kamalakamala]

Dear All,
What should be tightening torque for the cover plate bolt for 50 kVA sealed type transformer? the cork packing thickness is 6 mm and bolt type is 10Mx40mm. Spacing between two bolts is 50 mm. Flanger openning is 940x396 mm . Width of flaner is 50mm. Strenth class of the bolts is 4.8

Thank you.
BR

 

[7anoter4]

See:
thread404-306912

 

[oldfieldguy]

In addition to the normal torque considerations for bolts, you also need to consider the gasket installation.

I've seen bolts torqued to THE standard specification and the pressure squeezed the gasket completely out of position. Please refer to your transformer manufacturer's instruction.

Absent that information, you want a torque value that gives good gasket compression and security.


old field guy

 

[PHovnanian]

Right. What oldfieldguy said. Its a matter of properly compressing the gasket. The bolts have most probably been selected with a tensile strength/torque margin, making the bolt max torque a bad number to use in this situation.

Absent the transformer maintenance manual, you might be able to consult with a gasket supplier to get the proper gasket pressure in PSI or Pa for the cork gasket, or better yet compression thickness. You can then calculate the required bolt torque or fractions of a thread turn beyond contact needed to achieve the requisite gasket loading.