AIM EngineersProcedure for Process Equipment manufacturing Unit

Title : PROCEDURE FOR TIGHTENING SCREWS & BOLTS Doc.No. AIM-PR-12

Page1 of 2

Rev.No.00

Issued ByProduction Manager

Issue Date12/05/09

Approved ByFactory Manager

Effective From12/05/09

Description

1. Purpose This instruction ensure that screws and bolts are tighten with the correct torque.

2. ScopeThe instruction covers all types of Heat Exchangers , Reactors designed - and specified by AIM Engg.

3. ResponsibilityDepartment AIM Engg. is responsible for information re. torque on all relevant assembly drawings correspond to this instruction.

Employes working with assembly of heat exchangers in manufacturing, laboratory or during service are responsible for use of the correct torque for tighten of all screws and bolts covered by this instruction.

4. InstructionThe tables 1 to 2 in this instruction states torques for screws and bolt assemblies on HEs.

4.1 Assemblies in generalIf nothing else is stated on the drawings the given tighten torque from the tables is valid.The torque for tighten of screws is chosen from the number in the tables and from the screw material and the treaded dimension. It is provided that all the threads are clean and greased lightly with oil or grease.There can be special conditions which gives another torque, as an example a big difference in the strength between the materials to a screw and its counterpart. If this is the case it will be specified on the assembly drawing.

When the assembly drawing specify a special torque, this must be used always and not the number from the tables.

Whenever there is given a torque for tighten of screws on the assembly and whenever the assembly drawing specify a torque for tighten of screws do always use a calibrated torque wrench or similar tools.Uncertainty on the tightening must max be +/- 5% of the given torque.

4.2 Critical assembly

Regarding critical assembly the torque for tighten of screws on the decanter has to be unambiguous stated on the assembly drawing and in the instruction books.

Following assemblies are always considered as critical:1.Tube Sheet to Girth flanges2.Channel & shell flanges3. Floating Head Flange

Critical assemblies must always be tightened with a torque wrench.Table 1: Steel screws with metric thread - Torque in NmThreadQuality class

M8.810.9

6913

82232

104463

1277109

14122174

16190270

20372528

22519722

24640914

279521620

3013141817

3622803150

3929304940

Table 2:

Steel screws with UNC thread - Torque in NmThreadQuality Class

UNCd[mm]8.8

10.9

1/46.351119

5/167.9382238

3/89.5253868

7/1611.11261108

1/212.793163

9/1614.288133234

5/815.875183323

3/419.05322568

7/822.225516909

125.47721360

1 1/828.57510901930

1 1/431.7515302690

1 3/834.92520203550

1 1/238.126504680