Hello gentleman! Here is the Spec and please do comment.Thanks

Dejan

1 Scope

This Specification covers the hydraulic bolt tension and bolting-up requirements for piping and pipeline flange joints as specified in ANSI-B16.5 and or API-6A for Class 600 raised flat face type flange.

2 Purpose

To provide inspection, assembly and torque values for Piping and Pipeline flanges. So that this flanged connections are not damaged during assembly and maintain their tight seal during service.

3 Standards and References

Table 1: Code and Standards Table

4 Requirements

This Section specifies the minimum requirements for the installation of gaskets and bolting in flanged joints.

4.1 Bolting-up Requirements

The method of tightening of bolts in flange connections shall be done with the application of hydraulic bolt-tension equipment. Use of Hydraulic bolt tensioners requires that the threaded portion of the bolt extend at least one bolt diameter beyond the outside nut face on the tensioner side of the joint.

4.2 Selection of Tools

Tightening of bolts in flange connections is normally done by means of spanners and torque wrenches. This may result in uneven stress distribution in bolting and uneven gasket seating pressure that may lead to flange leakage. When flange joints are leaking additional force is often applied to the bolts in the area where the leak occurs. This may result in more deformation of the flange and its facing, thus increasing the tendency to leak.

An improved method of tightening is the application of hydraulic equipment.

The torque bolt tensioning device, including adapters, shall be suitable for matching boltsize. Each Torque Wrench Device shall be accompanied with a clear manual in language of personnel involved indicating clearly the relationship between read-out hydraulic pressure and moment applied on nut.

All tools used for tightening shall fit the hexagon of bolts and nuts without damaging the width across flats and be suitable for matching nuts in accordance with ANSI B 18.2.2.

5 Inspection

5.1 FLANGE INSPECTION AND PREPARATION

Check the condition of the flange faces for smoothness, scratches, dirt, scale, and weld spatter protrusions. Wire brush clean as necessary. Deep scratches, dent or combinations of defects will require re-facing with a flange facing machine.

All threads and bearing surfaces shall be free from sand, chips or any other foreign material which may influence the torque during tightening.

Check coating on flanges, including inside bolt holes shall be coated to specification.

Examine the gasket contact surfaces of both joint flanges for appropriate surface finish. Raised face flanges shall have concentric or phonographic finish in the range of 125 to 250 microinches Ra as per ASME B16.5.

5.2 gASKET INSPECTION AND PREPARATION

Only new gaskets shall be used. Damaged gaskets including loose spiral windings shall be rejected. Gasket dimensions, gasket material and type, shall be checked to be per specification DEDSNG M-301 and DEDSNG M-401. Extra care shall be taken not to damage the face of the Spiral Wound Gasket

When installing the gasket ensure the flange and gasket faces are completely clean and dry. Check gasket contact surface of both joint flanges for flatness, both radially and circumferentially.

5.3 STUD AND NUT INSPECTION AND PREPARATION

Check thread on stud and nut for damage such as rust, corrosion, and burrs. Nut to flange contact surface shall be clean and smooth. Studs area for nuts to be lubricated with approved lubricant. The same lubricant shall be used consistently on all joints. See Table 3 in Appendix 1.

5.4 INSPECTION OF FLANGE JOINT FIT-UP

Prior to installation of the flange gaskets, fit-up of the flange joint shall be visually inspected for proper alignment and fit-up. The requirements for the flange joint fit-up shall be as specified below.

5.4.1 Flange Face Alignment

All flange faces at rest prior to bolt-up shall be parallel to within 1/16 of an inch per foot across any diameter.

5.4.2 Flange Bolt Hole Alignment

The maximum allowable offset of the bolt holes in flanges at rest prior to bolt-up shall be of 1/16 an inch.

5.4.3 Gap Between Flange Faces

Flange faces at rest shall be practically matching without bolting. In no case shall the gap between flanges at rest exceed 1/16 of inch over the minimum dimension required to allow proper insertion without damaging the gasket installation of the flange gaskets.

6 Installation Procedure

Install gasket and all bolts and nuts before any tensioning. Controlled torque wrenching shall be carried out using Hydraulic Bolt Tensioners.

The Bolt Tensioners operate by hydraulically "stretching" the bolt to a pre-defined limit after which the operator is then able to hand-tighten the nuts. The hydraulic load is then released and the bolt remains tensioned. The advantage of tensioning (stretching) against torquing is that the process is not dependant on the type of lubrication used and eliminates the effect of friction under the nut and between threads. Accurate bolt tensions are therefore obtained.

To pull down the flange evenly, several bolts can be tensioned at the same time. All the bolts will eventually be tensioned at the same time. All bolts will eventually be tensioned after successive "passes" of the bolt tensioning equipment.

Note that the use of the bolt tensioning equipment usually requires the studbolts to protrude past the nut by an additional bolt diameter. Obstructions such as pipe supports and instrument tappings may prevent the bolt tensioning equipment from being fitted over the studbolt. In such cases, hydraulic torque wrenches will then be used to tension the bolts.

6.1 INSTALATION OF FLANGE GASKETS

The following steps shall be used when installing flange gaskets:

Step 1: Align the boltholes in the flanges by the use of a drift punch or other suitable means. The alignment of the bolt-holes shall allow the stud bolts to pass freely through the bolt-holes.

Step 2: Insert two bolts in bottom flange holes in vertical flanges. Align the flanges to have a gap sufficient for installation of the gasket.

Step 3: Place the Spiral Wound Gasket centrally within the flange assembly and clamp in place. Use of grease, pastes, adhesives or gasket compounds to hold the flange gasket in place is not allowed.

6.2 BOLT TORQUING PROCEDURE

Check and ensure that the general requirements of Section 4 have been satisfied.

To achieve uniform joint tightness and stress distribution the bolts shall be tightened in three stages as follows; 30%, 60% and 100% of the torque values stated in Table 3, Appendix 1. At each stage of the tightening, bolts shall be tightened in a controlled sequence as follows:

Table 2: Bolt Tightening Sequence

Note: Bolts numbered clockwise around the flange

Finally the bolts shall be chased round using the 100% torque value stated in Appendix 1, Table 3 until no movement occurs.

NOTE: Bolts must be tightened in the cross-pattern tightening sequence and employing the incremental rounds of tightening as prescribed in Section 6.2 of this procedure. If this is not done, the flanges may become cocked relative to each other, an indicator of non-uniform gasket loading and potential joint leakage. This is particularly true the smaller the flange bolt circle and the fewer the number of bolts.

DIAGRAM 1: BOLT TIGHTENING SEQUENCE EXAMPLE

Bolt Tightening Sequence: 1-7-4-10 2-8-5-11 3-9-6-12

The bolt-up sequence indicated in Diagram 1 is as an example applicable for all types of fastening tools, orientation can be changed to suit very minor differences in distance between flange facings resulting from fabrication tolerances, not out-of angle welded flanges.

6.3 BOLT TENSIONING REQUIREMENTS

The torque bolt tensioning device stretches the bolt shanks by means of hydraulic oil pressure. While the bolts are elongated, the nuts shall be run down the thread by hand, until they bear against the flange. When the hydraulic pressure is released all of the bolt extension is retained over its active length between the nuts, and the required load is obtained assuring high integrity of Flanged Joints.

A Hydraulic Bolt Tensioner or Jacking Tool screws onto one end of the bolt, therefore the bolt needs an additional length of thread protruding out of the hexagonal nut at one end by about 1 to 1.5 times the bolt diameter. After the tightening procedure is complete the extended thread lengths shall be protected against corrosion and damage to allow the nuts to be subsequently unscrewed. Grease filled rubber or plastic caps are recommended for this purpose. The hydraulic pressure is supplied by a high-pressure oil pump via a distribution ring main to a number of jacking tools. The number of tools used depends on the application or the total number of bolts to be tightened, refer to Section 6.4.

6.4 hydraulic BOLT TENSIONING PROCEDURE

Check and ensure that the general requirements of Section 4 have been satisfied.

Before starting work check that the tensioning tool is not too large to fit on the nuts and flange.

The application of hydraulic jack bolt tensioning equipment shall be in strict accordance with the manufacturer's instructions and safety procedures.

Personnel using the equipment shall be properly trained in its application.

6.4.1 Installation of Service Flange Bolts

Installation of the flange bolts shall be performed just following completion of the visual inspection requirements specified herein. Installation of the flange bolts shall be performed in accordance with the following steps:

Step 1: Just following installation of the flange Spiral Wound Gasket, select the required flange bolt components in accordance with the appropriate pipe material specification in DEDSNG G-301 "Pipeline Components Data Sheets" and DEDSNG G-401 "Piping and Piping Components Data Sheets"

Step 2: Install the bolts in the flange assembly so they have an equal length of threads exposed on each end. Bolt holes in the flange assembly shall be aligned so that the studs will pass freely through all of the flange holes.

Step 3: Apply the specified bolt lubricant shown in Appendix 1 to the bolt threads over the length of the thread engagement, and the face of the nut that will contact the flange.

Step 5: Install all studs and nuts finger tight so that the studs are centered between the nuts and have an equal number of thread projection at each end of the studs.

Step 6: Number each bolt according to its position in the flange as shown in Diagram 1, Section 6.2

Step 7: Tighten bolts with a calibrated non-impact type torque wrench in accordance with the stud bolt tightening sequence shown on in Diagram 1 and Table 2.

Note:

The hydraulic Pressures "1^st Pass" and "2^nd Pass" listed in the tables were given by Hedley Purvis Limited in Appendix 2 and by Hydratight Limited in Appendix 3 and by Hydratight Limited in Appendix 3 and Appendix 4. The following procedures explain how these values should be applied depending on the number of hydraulic tools employed:

6.4.2 Procedure "A"- 100% Tensioning:

Set up hydraulic tools on all flange bolts simultaneously.

Apply "2^nd Pass" Pressure and tighten nuts with tommy-bar. Release pressure.

Repeat step (ii). Tightening completed.

6.4.3 Procedure "B"- 50% Tensioning: (i) Set up hydraulic tools on first half of alternate flange bolts, which shall be positioned equi-spaced around the flange. (ii) Apply "1^st Pass" Pressure and tighten nuts with tommy-bar. Release pressure. (iii) Repeat step (ii) (iv) Transfer hydraulic tools to second set of alternate flange bolts (v) Apply "2^nd Pass" Pressure and tighten nuts with a tommy-bar. Release pressure (vi) Repeat step (v) (vii) Transfer four hydraulic tools back to the first half set of flange bolts. (viii) Conduct a "Break Loose" check.

Apply pressure and increase slowly whilst holding the tommy-bar in the "sockets" and applying pressure in the loosening direction.

At the moment the nut becomes loose, stop the pump and note the pressure. This is termed the "Break Loose Pressure".

If this is equal to or greater than the "2^nd Pass" Pressure then the tightening is complete.

If this pressure is less than the "2^nd Pass" Pressure then repeat steps (i) thru' (viii).

6.4.4 Procedure "C"- 25% Tensioning (i) Set up hydraulic tools on the first set of bolts, equi-spaced around the flange. (ii) Apply "1^st Pass" Pressure and tighten nuts with tommy-bar. Release pressure. (iii) Repeat step (ii) (iv) Repeat steps (i), (ii) and (iii) on each successive set of bolts around the flange until all bolts have been tightened, using the "1^st Pass" Pressure on each set. (v) Transfer the hydraulic tools back to the first set of bolts. (vi) Conduct a "Break Loose" check (see procedure B, (vii))

If the "Break Loose" pressure is equal to or greater then the "2^nd Pass" Pressure then tightening is complete.

If the "Break Loose" pressure is less than the "2^nd Pass" Pressure then repeat steps (i) thru' (iii) (vii) Continue to transfer the hydraulic tools to each successive set of bolts around the flange, repeating step (vi) on each set of turn.

To summarize, the hydraulic tools must be continually transferred to each successive set of bolts in turn and tightened to the "1^st Pass" Pressure until a "Break Loose" pressure equal to or greater than "2^nd Pass" pressure is achieved.

It is important that the "1^st Pass" Pressure should not be simultaneously applied to all bolts as this may cause overstressing of the flange.

When alternative manufacturer's equipment is proposed, it is the alternative manufacturer's responsibility to determine the 1^st and 2^nd Pass Pressures that will achieve the recommended bolt stresses listed in the tables without overstressing the bolt and the flanges, taking cognizance of the aforementioned procedures.

NOTE:

Hedley Purvis Ltd "1^st Pass" Pressure equates to "Pressure A" supplied by Hydratight Ltd and Hedley Purvis Ltd "2^nd Pass" Pressure equates to "Pressure B" supplied by Hydratight Ltd.

6.5 THREAD LUBRICANTS AND PRESERVATION FLUIDS

All bolts shall be treated with a preservative lubricant using only the approved grade below:

Molykote 1000 (combined friction coefficient for application nut face and threads=0.11)

The use of lubricants with a lower coefficient of friction than that shown (i.e.< 0.11) can lead to excessive bolt stress being applied by wrenches or torque wrenches, and yielding or failure of flanges or bolting may result. Molybdenum Disulphide greases shall not be used under any circumstances as this can result in stress corrosion cracking.

Note that Molykote 1000 does not contain molybdenum disulphide.

When the bolt tightening procedure is completed, to prevent corrosion a liberal coating of grease should be applied to the nuts up to the back of the flange, and to the stud ends protruding from the nuts. This is particularly important where low alloy bolts are used on unpainted stainless steel flanges.

6.6 CLAMP CONNECTORS

This standard does not contain bolt torques for clamp connector bolting. Using Dow Molykote 1000 bolt thread lubricant with a coefficient of friction of 0.11, the bolt torques required to achieve the required residual bolt stress shall be obtained from the particular clamp connector manufacturer.

6.6.1 Clamp Connector Tightening Procedure (i) Note that clamp connectors are particularly sensitive to cleanliness. Check that the sealing surfaces of the hubs and seal ring are perfectly clean and completely free from scratches, corrosion or any other damage. Superficial marks or superficial corrosion on the hub sealing surface may be removed by light application of emery cloth. (ii) A light lubricant may be applied to the sealing surfaces immediately before assembly to assist the correct location and alignment of the seal ring. (iii) Apply Dow Molykote 1000 to the bolt threads, nut threads and the domed surface of the nuts. (iv) Assemble the joint fitting with the nuts with the domed surface of the nuts facing the domed seating on the clamps. On horizontal piping the clamps should be orientated with the bolts at the top and bottom of the joint to allow water to drain from the clamp to hub interface. (v) To ensure even tightening of the two clamps, the bolts should be tightened diagonally in a criss cross pattern. Apply the clamp manufacture's recommended bolt torque in 3 stages, setting the torque setting to 30%, 60% and 100% of the recommended torque at each stage. Finally apply the 100% bolt torque value to each bolt in a clockwise direction. The gap between the clamp lugs should be the same at each set of bolts.

7 Hydraulic Torque Wrench Requirements

7.1 Torqu wrench requirements

All torque loads shall be applied by the use of a suitable calibrated non-impact type torque wrench. All wrenches torque shall be calibrated at the start of each work shift. Use the final torque values shown in Appendix 1, Table3. Note: do not exceed the specified final torque values shown in torque Table 3, Appendix 1, this could over stress the flange gasket or flange bolting.