Re: [MW:4633] Bolts failure

Metric Bolt Torque Table Estimated with clamp load as 75% of proof load as specified in ISO 898-1
Property Class	8.8		10.9		12.9 Socket Head  Cap Screw
Minimum Tensile  Strength MPa	M6 - M16:  800 M20 - M30:  830		1040		1220
Nominal Size and Thread Pitch	Bolt Torque Specs in Foot Pounds or (Inch Pounds)
	Dry	Lubed	Dry	Lubed	Dry	Lubed
M5 x 0.80	(54)	(41)	(78)	(59)	(91)	(68)
M6 x 1.00	(92)	(69)	(133)	(99)	(156)	(116)
M7 x 1.00	(156)	(116)	(222)	(167)	(260)	(195)
M8 x 1.25	(225)	(169)	(333)	(242)	(377)	(284)
M10 x 1.50	37	28	53	40	62	47
M12 x 1.75	65	49	93	69	108	81
M14 x 2.00	104	78	148	111	173	130
M16 x 2.00	161	121	230	172	269	202
M18 x 2.50	222	167	318	238	372	279
M20 x 2.50	314	235	449	337	525	394
M22 x 2.50	428	321	613	460	716	537
M24 x 3.00	543	407	776	582	908	681
M27 x 3.00	796	597	1139	854	1331	998
M30 x 3.50	1079	809	1543	1158	1804	1353
M33 x 3.50	1468	1101	2101	1576	2455	1842
M36 x 4.00	1886	1415	2699	2024	3154	2366
Lubed means cleaned dry bolts lubricated with a standard medium viscosity   machine oil. Lubricate all contact areas of the bolts and washers. Lubricating  the bolts is the suggested method.  Thread Engagement

Metric Bolt Torque Table Estimated with clamp load as 75% of proof load as specified in ISO 898-1
Property Class	8.8		10.9		12.9 Socket Head  Cap Screw
Minimum Tensile  Strength MPa	M6 - M16:  800 M20 - M30:  830		1040		1220
Nominal Size and Thread Pitch	Bolt Torque Specs in Foot Pounds or (Inch Pounds)
	Dry	Lubed	Dry	Lubed	Dry	Lubed
M5 x 0.80	(54)	(41)	(78)	(59)	(91)	(68)
M6 x 1.00	(92)	(69)	(133)	(99)	(156)	(116)
M7 x 1.00	(156)	(116)	(222)	(167)	(260)	(195)
M8 x 1.25	(225)	(169)	(333)	(242)	(377)	(284)
M10 x 1.50	37	28	53	40	62	47
M12 x 1.75	65	49	93	69	108	81
M14 x 2.00	104	78	148	111	173	130
M16 x 2.00	161	121	230	172	269	202
M18 x 2.50	222	167	318	238	372	279
M20 x 2.50	314	235	449	337	525	394
M22 x 2.50	428	321	613	460	716	537
M24 x 3.00	543	407	776	582	908	681
M27 x 3.00	796	597	1139	854	1331	998
M30 x 3.50	1079	809	1543	1158	1804	1353
M33 x 3.50	1468	1101	2101	1576	2455	1842
M36 x 4.00	1886	1415	2699	2024	3154	2366
Lubed means cleaned dry bolts lubricated with a standard medium viscosity   machine oil. Lubricate all contact areas of the bolts and washers. Lubricating  the bolts is the suggested method.  Thread Engagement

Dear Soliman,

Bolting Procedures

• Place the gasket on the flange surface to be sealed.
• Bring the opposing flange into contact with the gasket.
• Clean the bolts and lubricate them with a quality lubricant, such as an oil and graphite mixture.
• Place the bolts into the bolt holes.
• Finger-tighten the nuts.
• Follow the bolting sequence in the diagrams above.
• During the initial tightening sequence, do not tighten any bolts more than 30% of the recommended bolt stress. Doing so will cause cocking of the flange and the gasket will be crushed.
• Upon reaching the recommended torque requirements, do a clockwise bolt-to-bolt torque check to make certain that the bolts have been stressed evenly.
• Due to creep and stress relaxation, it is essential to prestress the bolts to ensure adequate stress load during operation.

Torque Tables

These tables were developed to be used with Garlock spiral wound gaskets. They are to be used only as a general guide. They should not be considered to contain absolute values due to the large number of uncontrollable variables involved with bolted joints. If there is doubt as to the proper torque value to use, we suggest that the maximum value be used.

All bolt torque values are based upon the use of new nuts (ASTM A194, GR 2H) and new bolts (ASTM A193, GR B7) of proper design, acceptable quality and approved materials of construction as well as metallurgy. It is also required that two hardened steel washers be used under the head of each nut and that a non-metallic based lubricant (i.e. oil and graphite) be used on the nuts, bolts and washers.

The flanges are assumed to be in good condition and in compliance with ASME B16.5 specifications. Special attention should be given to seating surface finish and flatness. See "Recommended Flange Finish".

Only torque wrenches that have been calibrated should be used. The proper bolt tightening pattern must be followed with the desired ultimate torque value arrived at in a minimum of three equal increments. All bolts in the flange should then be checked in consecutive order in a counterclockwise direction. See "Gasket Installation".

The contact dimensions listed are taken from the ID and OD of the windings, which are different from the ASME ring gasket dimensions.

No provisions have been made in these tables to account for vibration effects on the bolts. These tables are are based on ambient conditions, without compensation for elevated temperatures. If conditions different from these exist, we suggest that further analysis be performed to determine the appropriate torque values.

 

Regards,

 

Yadav Shiva Chelliya,
Inspection Engineer,
Doha Qatar,
+974-6166465

n Tue, Mar 30, 2010 at 9:07 AM, Soliman, Mohamed (kuwait) <Mohamed.Soliman@worleyparsons.com> wrote:

 

 Dear all ,

 

I have a case for the bolts and nut Grade 8.8 ,Carbon steel material according to EN 20 898.Those bolts and nuts are failed during the tightening and some of the nuts are loose .

 

What tests can be carried out to ensure the soundness of those bolts .

 

Best Regards

M.S

 

 

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