How to determine the tightening torque of a flange?

determinar el torque de apriete

TIGHTENING TORQUE THEORY

In this article we will teach you to determine the minimum torque applicable to the screws that join the flat gaskets and the flanges .

References:

Tightening torque methodology

Orifice gaskets require initial preload in high pressure systems. We must bear in mind that the internal pressure, the moment of thermal concentration and the moment of dead load are the loads that generally cause more losses in the joint.

To apply the torque we will use impact wrenches , torque wrenches or torque wrenches. The torque that we must apply is governed by the following variables:

  • Nut and bolt class
  • Burr of the nuts
  • Lubrication
  • Dust, chips and dirt on bolts and nuts
  • Notches
  • State of the flange surface on which to rotate

Adequate lubrication can increase efficiency compared to an unlubricated assembly of approximately 50% . Heavy graphite or oil mixture will suffice for normal applications.

 

Coefficients of friction of nuts and bolts:

MaterialsLubricantsFriction µ ± 20%
SteelGraphite, petroleum or oil0.07
SteelMolybdenum disulfide grease0.11
SteelMachine oil0.15
Cadmium Plated SteelDoes not require0.12
Zinc plated steelDoes not require0.17
Steel bronceDoes not require0.15
Corrosion resistant alloy or nickel or silver basedDoes not require0.14
Titanium steelGraphite in petroleum0.08
TitaniumMolybdenum disulfide grease0.10

Relevance of preload

The preload in the flanged end holes must be high enough to keep the assembly in contact and under pressure. Decreased pressure could result in leakage of pressurized liquid, loss of seal under cyclic loading conditions, and reduced seal life. In the following image we can see the relationship between the useful life of the seal and the preload .

An axially loaded flanged joint in which no preload was applied to the bolts is represented by the line OAB, in which the stress on the bolt is equal to that exerted on the joint. When the stress on the joint varies between Pa and Pb, the load variation on the bolt is represented by the section on the ordinate Pba and PBb. However, with the application of a preload, the load variation on the bolts will be lighter than that of the joint (as indicated by line PB1A, with less slope than OAB) because part of the load is absorbed as a reduction. compression of the gasket. In this way, the axial load applied to the bolts varies between PBa ‘and PBb’ when the modification of forces on the joint is between Pa and Pb. These conditions result in a considerable reduction of the variation of the cyclical load of the bolts which pays off in an extension of the useful life of the joint.

MONTAJE

ASSEMBLY

For an effective seal, all components of the flange connection must be optimally mounted, the most common cause of a leak is improper mounting. Before starting to assemble, we must pay attention to the angularity and centering tolerances related to the pair of flanges that make up the set. The use of excessive force will lead to a deterioration of the joint with the proclivity to generate losses.

Assembly sequence

  • Place the gasket on the surface of the flange to be sealed.
  • Position the other flange in contact with the gasket.
  • Clean the studs and lubricate them properly, with a mixture of oil and graphite for example.
  • Place these studs in the holes.
  • Approach the nuts by hand.
  • Follow the adjustment sequence according to the figures.
  • Do not exceed 30% of the recommended torque values ​​for the studs, as it may cause a bad seating of the joint.
  • Once the recommended torque according to the table has been reached, make a pass in hourly sequence for verification.
  • Due to stress relaxation and creep, it is essential to pre-tighten the studs to ensure the correct torque value during system operation.
determinar el torque de apriete

CALCULATION OF TIGHTENING TORQUE IN FLAT JOINTS

To determine the torque necessary to apply, first of all we will determine the required surface pressure that must be applied to the joint to achieve an adequate seal, which will be:

Where:
Ecal: Calculated Surface Pressure in Bar.
Emin: Minimum Surface Pressure in Bar.
R: Radial Pressure where R = m. Pd.
y: Set Pressure in Bar.
H: Force that tends to separate the flanges H = Ai. Pd.
A: Gasket contact area.
Pd: Design Pressure in Bar.
Ai: Internal area of ​​the duct.

El torque estará dado por la siguiente expresión:

Where:

Ejun: Surface pressure of the joint in Bar.-
A: Contact area of ​​the joint.
d: Effective diameter of the Stud.
N: Number of Studs.

The torque to be applied to the studs of the flanges equipped with flat gaskets must be the one with the highest value, comparing the minimum with the calculation.

determinar el torque de apriete

DETERMINATION OF TIGHTENING TORQUE FOR SCREWS

First of all, we will calculate the torques to apply to the flange bolts, which allow obtaining a surface pressure to be exerted on the joint, in such a way that a correct sealing of the joint is ensured, based on the pressure of design corresponding to the classes of pipes, their values ​​being the following:

MINIMUM AND CALCULATED TORQUE FOR FLANGES ANSI S-150#

DNDbDrNdideePamPdAiEcal.TcalTmin
pulg.mm.mm.c/u.mm.mm.mm.Bar-Barcm2BarNm.Nm.
1/212.710.17422.034.91.604004.0019.503.80490.861412
3/412.710.17427.842.91.604004.4019.506.07492.122117
112.710.17434.550.81.604004.4019.509.35494.692722
1 1/212.710.17449.673.01.604004.4019.5019.32494.725746
215.912.88461.992.11.604004.4019.5030.09494.0711694
2 1/215.912.88474.6104.81.604004.4019.5043.71498.03136110
315.912.88490.7127.01.604004.4019.5064.61498.30199160
415.912.888116.1157.21.604004.4019.50105.87501.40142114
619.115.758170.7215.91.604004.4019.50228.85510.52276216
819.115.758221.5269.91.604004.4019.50385.33518.23381294
1022.218.5512270.3323.81.604004.4019.50573.83522.82404309
1222.218.5512327.0381.01.604004.4019.50839.82532.54494371
1425.421.2712350.3412.71.604004.4019.50963.77528.26700530

MINIMUM AND CALCULATED TORQUE FOR FLANGES ANSI S-300#

DNDbDrNdideePamPdAiEcal.TcalTmin
pulg.mm.mm.c/u.mm.mm.mm.Bar-Barcm2BarNm.Nm.
1/212.710.17422.034.91.604004.0049.903.80632.501912
3/415.912.88427.042.91.604004.4049.905.73632.333622
115.912.88434.551.01.604004.4049.909.35641.704629
1 1/219.115.75449.673.01.604004.4049.9019.32642.3911471
215.912.88861.992.11.604004.4049.9030.09640.717547
2 1/219.115.75874.6104.81.604004.4049.9043.71650.8610967
319.115.75890.7127.01.604004.4049.9064.61651.5515998
419.115.758116.1157.21.604004.4049.90105.87659.48229139
619.115.7512170.7215.91.604004.4049.90228.85682.81246144
822.218.5512221.5269.91.604004.4049.90385.33702.54406231
1025.421.2716270.3323.81.604004.4049.90573.83714.30474266
1228.624.4516327.0381.01.604004.4049.90839.82739.16678367
1428.624.4520350.3412.71.604004.4049.90963.77728.21666366
1631.827.6220410.3469.91.604004.4049.901322.19759.73865455
1831.827.6224461.8533.41.604004.4049.901674.94748.94965515

MINIMUM AND CALCULATED TORQUE FOR FLANGES S-600#

DNDbDrNdideePamPdAiEcal.TcalTmin
pulg.mm.mm.c/u.mm.mm.mm.Bar-Barcm2BarNm.Nm.
1/212.710.17422.034.91.604004.0096.503.80849.632512
3/415.912.88427.042.91.604004.4096.505.73849.304822
115.912.88434.550.81.604004.4096.509.35868.616128
1 1/219.115.75449.673.01.604004.4096.5019.32868.7515471
215.912.88861.892.11.604004.4096.5030.00865.0410247
2 1/219.115.75874.6104.81.604004.4096.5043.71885.1214867
319.115.75890.7127.01.604004.4096.5064.61886.4621798
422.218.558116.1157.21.604004.4096.50105.87901.80369164
625.421.2712143.7215.91.604004.4096.50162.18862.75624289
828.624.4512170.7269.91.604004.4096.50228.85850.331190560
1031.827.6216221.5323.81.604004.4096.50385.33870.871318605
1231.827.6216276.0381.01.604004.4096.50599.15892.881334598
1434.930.8020327.0412.71.604004.4096.50839.82948.771455613
1638.133.9720410.4469.91.604004.4096.501322.831096.311532559
1841.337.1520461.8533.41.604004.4096.501674.941074.812235832
2041.337.1524513.2584.21.604004.4096.502068.541112.202107758
2447.643.4924615.9692.11.604004.4096.502979.281153.2732721135
3050.846.6728730.3857.01.604004.4096.504188.381041.8154882107

How to determine the tightening torque of a flange?

determinar el torque de apriete

TIGHTENING TORQUE THEORY

In this article we will teach you to determine the minimum torque applicable to the screws that join the flat gaskets and the flanges .

References:

Tightening torque methodology

Orifice gaskets require initial preload in high pressure systems. We must bear in mind that the internal pressure, the moment of thermal concentration and the moment of dead load are the loads that generally cause more losses in the joint.

To apply the torque we will use impact wrenches , torque wrenches or torque wrenches. The torque that we must apply is governed by the following variables:

  • Nut and bolt class
  • Burr of the nuts
  • Lubrication
  • Dust, chips and dirt on bolts and nuts
  • Notches
  • State of the flange surface on which to rotate

Adequate lubrication can increase efficiency compared to an unlubricated assembly of approximately 50% . Heavy graphite or oil mixture will suffice for normal applications.

 

Coefficients of friction of nuts and bolts:

MaterialsLubricantsFriction µ ± 20%
SteelGraphite, petroleum or oil0.07
SteelMolybdenum disulfide grease0.11
SteelMachine oil0.15
Cadmium Plated SteelDoes not require0.12
Zinc plated steelDoes not require0.17
Steel bronceDoes not require0.15
Corrosion resistant alloy or nickel or silver basedDoes not require0.14
Titanium steelGraphite in petroleum0.08
TitaniumMolybdenum disulfide grease0.10

Relevance of preload

The preload in the flanged end holes must be high enough to keep the assembly in contact and under pressure. Decreased pressure could result in leakage of pressurized liquid, loss of seal under cyclic loading conditions, and reduced seal life. In the following image we can see the relationship between the useful life of the seal and the preload .

An axially loaded flanged joint in which no preload was applied to the bolts is represented by the line OAB, in which the stress on the bolt is equal to that exerted on the joint. When the stress on the joint varies between Pa and Pb, the load variation on the bolt is represented by the section on the ordinate Pba and PBb. However, with the application of a preload, the load variation on the bolts will be lighter than that of the joint (as indicated by line PB1A, with less slope than OAB) because part of the load is absorbed as a reduction. compression of the gasket. In this way, the axial load applied to the bolts varies between PBa ‘and PBb’ when the modification of forces on the joint is between Pa and Pb. These conditions result in a considerable reduction of the variation of the cyclical load of the bolts which pays off in an extension of the useful life of the joint.

MONTAJE

ASSEMBLY

For an effective seal, all components of the flange connection must be optimally mounted, the most common cause of a leak is improper mounting. Before starting to assemble, we must pay attention to the angularity and centering tolerances related to the pair of flanges that make up the set. The use of excessive force will lead to a deterioration of the joint with the proclivity to generate losses.

Assembly sequence

  • Place the gasket on the surface of the flange to be sealed.
  • Position the other flange in contact with the gasket.
  • Clean the studs and lubricate them properly, with a mixture of oil and graphite for example.
  • Place these studs in the holes.
  • Approach the nuts by hand.
  • Follow the adjustment sequence according to the figures.
  • Do not exceed 30% of the recommended torque values ​​for the studs, as it may cause a bad seating of the joint.
  • Once the recommended torque according to the table has been reached, make a pass in hourly sequence for verification.
  • Due to stress relaxation and creep, it is essential to pre-tighten the studs to ensure the correct torque value during system operation.
determinar el torque de apriete

CALCULATION OF TIGHTENING TORQUE IN FLAT JOINTS

To determine the torque necessary to apply, first of all we will determine the required surface pressure that must be applied to the joint to achieve an adequate seal, which will be:

Where:
Ecal: Calculated Surface Pressure in Bar.
Emin: Minimum Surface Pressure in Bar.
R: Radial Pressure where R = m. Pd.
y: Set Pressure in Bar.
H: Force that tends to separate the flanges H = Ai. Pd.
A: Gasket contact area.
Pd: Design Pressure in Bar.
Ai: Internal area of ​​the duct.

El torque estará dado por la siguiente expresión:

Where:

Ejun: Surface pressure of the joint in Bar.-
A: Contact area of ​​the joint.
d: Effective diameter of the Stud.
N: Number of Studs.

The torque to be applied to the studs of the flanges equipped with flat gaskets must be the one with the highest value, comparing the minimum with the calculation.

determinar el torque de apriete

DETERMINATION OF TIGHTENING TORQUE FOR SCREWS

First of all, we will calculate the torques to apply to the flange bolts, which allow obtaining a surface pressure to be exerted on the joint, in such a way that a correct sealing of the joint is ensured, based on the pressure of design corresponding to the classes of pipes, their values ​​being the following:

MINIMUM AND CALCULATED TORQUE FOR FLANGES ANSI S-150#

DNDbDrNdideePamPdAiEcal.TcalTmin
pulg.mm.mm.c/u.mm.mm.mm.Bar-Barcm2BarNm.Nm.
1/212.710.17422.034.91.604004.0019.503.80490.861412
3/412.710.17427.842.91.604004.4019.506.07492.122117
112.710.17434.550.81.604004.4019.509.35494.692722
1 1/212.710.17449.673.01.604004.4019.5019.32494.725746
215.912.88461.992.11.604004.4019.5030.09494.0711694
2 1/215.912.88474.6104.81.604004.4019.5043.71498.03136110
315.912.88490.7127.01.604004.4019.5064.61498.30199160
415.912.888116.1157.21.604004.4019.50105.87501.40142114
619.115.758170.7215.91.604004.4019.50228.85510.52276216
819.115.758221.5269.91.604004.4019.50385.33518.23381294
1022.218.5512270.3323.81.604004.4019.50573.83522.82404309
1222.218.5512327.0381.01.604004.4019.50839.82532.54494371
1425.421.2712350.3412.71.604004.4019.50963.77528.26700530

MINIMUM AND CALCULATED TORQUE FOR FLANGES ANSI S-300#

DNDbDrNdideePamPdAiEcal.TcalTmin
pulg.mm.mm.c/u.mm.mm.mm.Bar-Barcm2BarNm.Nm.
1/212.710.17422.034.91.604004.0049.903.80632.501912
3/415.912.88427.042.91.604004.4049.905.73632.333622
115.912.88434.551.01.604004.4049.909.35641.704629
1 1/219.115.75449.673.01.604004.4049.9019.32642.3911471
215.912.88861.992.11.604004.4049.9030.09640.717547
2 1/219.115.75874.6104.81.604004.4049.9043.71650.8610967
319.115.75890.7127.01.604004.4049.9064.61651.5515998
419.115.758116.1157.21.604004.4049.90105.87659.48229139
619.115.7512170.7215.91.604004.4049.90228.85682.81246144
822.218.5512221.5269.91.604004.4049.90385.33702.54406231
1025.421.2716270.3323.81.604004.4049.90573.83714.30474266
1228.624.4516327.0381.01.604004.4049.90839.82739.16678367
1428.624.4520350.3412.71.604004.4049.90963.77728.21666366
1631.827.6220410.3469.91.604004.4049.901322.19759.73865455
1831.827.6224461.8533.41.604004.4049.901674.94748.94965515