Process Machinery Piping 165 (Text continued from page 157) All bolt torque values are based on the use of new nuts (ASTM A194, GR 2H) and new bolts (ASTM A193, GR 87) 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 Only torque wrenches that have been calibrated should be used The proper bolt tightening pattern must be followed (see Figure 4.6 for proper bolting pattern) 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 The contact dimensions listed are taken from the inside diameter (ID) and outside diameter (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 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 Gasket Installation In a flanged connection, all components must be correct to achieve a seal The most common cause of leaky gasketed joints is improper installation procedures Figure 4-6 Installation sequence for 4-, 8-, and 16-bolt flanges 166 Machinery Component Maintenance and Repair 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, not tighten any bolts more than 30 percent 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, 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 pre-stress the bolts to ensure adequate stress load during operation Hydrostatic Testing Precautions If hydrostatic tests are to be performed at pressures higher than those for which the flange was rated, higher bolt pressures must be applied in order to get a satisfactory seal under the test conditions Use high-strength alloy bolts (ASTM B193 grade B7 is suggested) during the tests They may be removed upon completion Higher stress values required to seat the gasket during hydrostatic tests at higher than flange-rated pressures may cause the standard bolts to be stressed beyond their yield points Upon completion of hydrostatic testing, relieve all bolt stress by 50 percent of the allowable stress Begin replacing the high-strength alloy bolts (suggested for test conditions) one by one with the standard bolts while maintaining stress on the gasket After replacing all the bolts, follow the tightening procedure recommended in the bolting sequence diagrams (Figure 4-6) Pre-Stressing Bolts for Thermal Expansion Bolts should be pre-stressed to compensate for thermal expansion as well as for relaxation, creep, hydrostatic end pressure, and residual gasket loads Process Machinery Piping 167 A difference in the coefficient of thermal expansion between the materials of the flange and the bolts may change loads In cases of serious thermal expansion, it may be necessary to apply a minimum of stress to the bolts and allow the pipe expansion to complete the compression of the gasket A gasket with a centering guide ring should be compressed to the guide ring A gasket without a centering guide ring must be installed with precautions taken to prevent thermal expansion from crushing the gasket beyond its elastic limit Calculating Load Requirements The load requirements can be calculated from two formulas that define the minimum load required to effect a seal on a particular gasket The two formulas are Wml and Wm2 When these formulas have been calculated, the larger load of the two is the load necessary to effect a seal Let: p = 3.14 p = Maximum internal pressure M = Gasket factor “M” defined in Figure 4-7 (M = for spiral woud gaskets) Y = Seating stress “Y” defined in Figure 4-7 (Y = 10,000 psi for spiral wound gaskets) N = Basic width of a gasket per chart in Figure 4-8 (For raised face flanges see diagram 1a) B0 = Basic seating width of a gasket per chart, Figure 4-8 (For raised face flanges, B0 = N/2) B1 = Effective seating width of a gasket; must be determined ID = Inside diameter of gasket OD = Outside diameter of gasket For gaskets where the raised face is smaller than the OD of the gasket face, the OD is equal to the outer diameter of the raised face Find: ID = OD = 168 Machinery Component Maintenance and Repair Figure 4-7 Gasket factors “M” and “Y.” Process Machinery Piping Figure 4-8 Effective gasket sealing width 169 170 Machinery Component Maintenance and Repair Given the ID and OD, find the value of N Then define B0 in terms of N (see Figure 4-8): N = B0 = Determine if B0 is greater or less than 1/4≤, then find B1: If B0 £ 1/4≤, then B1 = B0; If B0 > 1/4≤, then B1 = (÷B0)/2; B1 = Using B1, determine G: G = OD - [(B1)(2)] Now, insert these values in the final equations to determine minimum required load: Wm1 = [p(P)(G2)/4] + [2(B1)(p)(G)(M)(P)] Wm2 = p(B1)(G)(Y) When Wm1 and Wm2 have been calculated, the larger of the two numbers is the minimum load required to seat a gasket In most cases the available bolt load in a connection is greater than the minimum load on the gasket If not, higher bolt stresses or changes in the gasket design are required for an effective seal NOTE: Flange design code suggestions for low-pressure applications calling for minimum seating stress (Y value) are sometimes inadequate to seat the gasket because the bolting and flange rigidity are insufficient to effect a proper seal Care should be taken to ensure that flange conditions provide a suitable seating surface For internal pressure to be contained, flange rotation and sufficient residual loads must also be considered in the flange design General Installation and Inspection Procedure This segment covers recommended procedures relating to the preparation and inspection of a joint prior to the actual bolt-up Obviously, high temperature piping joints in hydrogen-containing streams are less forgiving than those in more moderate service Critical flanges are defined as joints in services in excess of 500°F and in sizes above six in in diameter: (Text continued on page 175) Process Machinery Piping 171 Figure 4-9 Typical flanged joint record form 172 The torque required to produce a certain stress in bolting is dependent on several conditions, including: • • • Diameter and number of threads on bolt Condition of nut bearing surfaces Lubrication of bolt threads and nut bearing surfaces The tables below reflect the results of many tests to determine the relation between torque and bolt stress Values are based on steel bolts that have been well-lubricated with a heavy graphite and oil mixture A nonlubricated bolt has an efficiency of about 50 percent of a well-lubricated bolt Also, different lubricants produce results that vary from 50 to 100 percent of the tabulated stress figures For Alloy Steel Stud Bolts (Load in pounds on stud bolts when torque load is applied) Nominal Diameter of Bolt (inches) /4 /16 /8 /16 Stress Number of Threads (per inch) Diameter at Root of Thread (inches) Area at Root of Thread (sq inch) 20 18 16 14 0.185 0.240 0.294 0.345 0.027 0.045 0.068 0.093 30,000 psi Torque Compression (ft lbs) (lbs) 12 20 810 1,350 2,040 2,790 Torque (ft lbs) 12 18 30 45,000 psi Compression (lbs) 1,215 2,025 3,060 4,185 Torque (ft lbs) 16 24 40 60,000 psi Compression (lbs) 1,620 2,700 4,080 5,580 Machinery Component Maintenance and Repair Table 4-5 Torque to Stress Bolts /2 /16 /8 /3 /8 0.400 0.454 0.507 0.620 0.731 0.838 0.963 1.088 1.213 1.338 1.463 1.588 1.713 1.838 2.088 2.338 2.588 2.838 0.126 0.162 0.202 0.302 0.419 0.551 0.728 0.929 1.155 1.405 1.680 1.980 2.304 2.652 3.423 4.292 5.259 6.324 30 45 60 100 160 245 355 500 680 800 1,100 1,500 2,000 2,200 3,180 4,400 5,920 7,720 3,780 4,860 6,060 9,060 12,570 16,530 21,840 27,870 34,650 42,150 50,400 59,400 69,120 79,560 102,690 128,760 157,770 189,720 45 68 90 150 240 368 533 750 1,020 1,200 1,650 2,250 3,000 3,300 4,770 6,600 8,880 11,580 5,670 7,290 9,090 13,590 18,855 24,795 32,760 41,805 51,975 63,225 75,600 89,100 103,680 119,340 154,035 193,140 236,655 264,580 60 90 120 200 320 490 710 1,000 1,360 1,600 2,200 3,000 4,000 4,400 6,360 8,800 11,840 15,440 7,560 9,720 12,120 18,120 25,140 33,060 43,680 55,740 69,300 84,300 100,800 118,800 138,240 159,120 205,380 257,520 315,540 379,440 Table continued on next page Process Machinery Piping 11/8 11/4 13/8 11/2 15/8 13/4 17/8 21/4 21/2 23/4 13 12 11 10 8 8 8 8 8 8 173 174 For Machine Bolts and Cold Rolled Steel Stud Bolts (Load in pounds on stud bolts when torque load is applied) Nominal Diameter of Bolt (inches) /4 /16 /8 /16 /2 /16 /8 /4 /8 11/8 11/4 13/8 11/2 15/8 13/4 17/8 Number of Threads (per inch) 20 18 16 14 13 12 11 10 7 6 51/2 5 41/2 Stress Diameter at Root of Thread (inches) Area at Root of Thread (sq inch) 0.185 0.240 0.294 0.345 0.400 0.454 0.507 0.620 0.731 0.838 0.939 1.064 1.158 1.283 1.389 1.490 1.615 1.711 0.027 0.045 0.068 0.093 0.126 0.162 0.202 0.302 0.419 0.551 0.693 0.890 1.054 1.294 1.515 1.744 2.049 2.300 7,500 psi Torque Compression (ft lbs) (lbs) 12 15 25 40 62 98 137 183 219 300 390 525 563 203 338 510 698 945 1,215 1,515 2,265 3,143 4,133 5,190 6,675 7,905 9,705 11,363 13,080 15,368 17,250 15,000 psi Torque Compression (ft lbs) (lbs) 10 15 23 30 50 80 123 195 273 365 437 600 775 1,050 1,125 405 675 1,020 1,395 1,890 2,340 3,030 4,530 6,285 8,265 10,380 13,350 15,810 19,410 22,725 26,160 30,735 34,500 Torque (ft lbs) 12 20 30 45 60 100 160 245 390 545 730 875 1,200 1,550 2,100 2,250 30,000 psi Compression (lbs) 810 1,350 2,040 2,790 3,780 4,860 6,060 9,060 12,570 16,530 20,760 26,700 31,620 38,820 45,450 52,320 61,470 69,000 Machinery Component Maintenance and Repair Table 4-5—cont’d Torque to Stress Bolts Process Machinery Piping 175 (Text continued from page 170) • Indentify critical flanges and maintain records A suitable record form is attached in Figure 4-9 A suggested identification procedure is to use the line identification number and proceed in the flow direction with joints #1, #2, etc Prior to Gasket Insertion • • • • • Check condition of flange faces for scratches, dirt, scale, and protrusions Wire brush clean as necessary Deep scratches or dents will require refacing with a flange facing machine Check that flange facing gasket dimension, gasket material and type, and bolting are per specification Reject nonspecification situations Improper gasket size is a common error Check gasket condition Only new gaskets should be used Damaged gaskets (including loose spiral windings) should be rejected The ID windings on spiral-wound gaskets should have at least three evenly spaced spot welds or approximately one spot weld every six in of circumference (see API 601) Use a straightedge and check facing flatness Reject warped flanges Check alignment of mating flanges Avoid use of force to achieve alignment Verify that: The two flange faces are parallel to each other within 1/32 in at the extremity of the raised face Flange centerlines coincide within 1/8 in Joints not meeting these criteria should be rejected Controlled Torque Bolt-Up of Flanged Connections Experience shows that controlled torque bolt-up is warranted for certain flanged connections These would typically include: • • • • • All flanges (all ratings and sizes) with a design temperaure >900°F All flanges (all ratings) 12 in diameter and larger with a design temperature >650°F All in diameter and larger 1,500 pound class flanges with a design temperature >650°F All in diameter and larger 900 pound class flanges with a design temperature >650°F All flanges not accessible from a maintenance platform and >50 ft above grade Table 4-6 Flange and Bolt Dimensions for Standard Flanges 150 psi NPS (inches) /4 /2 /4 1 11/4 11/2 21/2 31/2 10 12 14 16 18 20 24 Dia of Flange (inches) No of Bolts 33/8 31/2 37/8 41/4 45/8 71/2 81/2 10 11 131/2 16 19 21 231/2 25 271/2 32 4 4 4 4 8 8 12 12 12 16 16 20 20 300 psi Dia of Bolts (inches) Bolt Circle (inches) Dia of Flange (inches) No of Bolts /2 /2 /2 /2 /2 /2 /8 /8 /8 /8 /8 /4 /4 /4 /8 /8 21/4 23/8 23/4 31/8 31/2 37/8 43/4 51/2 71/2 81/2 91/2 113/4 141/4 17 183/4 211/4 223/4 25 291/2 33/8 33/4 45/8 47/8 51/4 61/8 61/2 71/2 81/4 10 11 121/2 15 171/2 201/2 23 251/2 28 301/2 36 4 4 4 8 8 8 12 12 16 16 20 20 24 24 24 1 1 11/8 11/8 11/4 400 psi Dia of Flange (inches) No of Bolts 33/8 33/4 45/8 47/8 51/4 61/8 61/2 71/2 81/4 10 11 121/2 15 171/2 201/2 23 251/2 28 301/2 36 4 4 4 8 8 8 12 12 16 16 20 20 24 24 24 Dia of Bolts (inches) Bolt Circle (inches) /2 /2 /8 /8 /8 /4 /8 /4 /4 /4 /4 /4 /4 /8 21/4 25/8 31/4 31/2 37/8 41/2 57/8 65/8 71/4 77/8 91/4 105/8 13 151/4 173/4 201/4 221/2 243/4 27 32 1 11/8 11/8 11/4 11/4 11/4 11/2 600 psi Dia of Bolts (inches) Bolt Circle (inches) Dia of Flange (inches) No of Bolts /2 /2 /8 /8 /8 /4 /8 /4 /4 /8 /8 /8 /8 21/4 25/8 31/4 31/2 37/8 41/2 57/8 65/8 71/4 77/8 91/4 105/8 13 151/4 173/4 201/4 221/2 243/4 27 32 33/8 33/4 45/8 47/8 51/4 61/8 61/2 71/2 81/4 103/4 13 14 161/2 20 22 233/4 27 291/4 32 37 4 4 4 8 8 8 12 12 16 20 20 20 20 24 24 1 11/8 11/4 11/4 13/8 13/8 11/2 13/4 Dia of Bolts (inches) Bolt Circle (inches) /2 /2 /8 /8 /8 /4 /8 /4 /4 /8 /8 21/4 25/8 31/4 31/2 37/8 41/2 57/8 65/8 71/4 81/2 101/2 111/2 133/4 17 191/4 203/4 233/4 253/4 281/2 33 1 1 11/8 11/4 11/4 13/8 11/2 15/8 15/8 17/8 900 psi NPS (inches) /2 /4 11/4 11/2 21/2 10 12 14 16 18 20 24 Dia of Flange (inches) No of Bolts 43/4 51/8 57/8 61/4 81/2 95/8 91/2 111/2 133/4 15 181/2 211/2 24 251/4 273/4 31 333/4 41 4 4 8 8 12 12 16 20 20 20 20 20 20 1500 psi Dia of Bolts (inches) Bolt Circle (inches) Dia of Flange (inches) No of Bolts /4 /4 /8 /8 31/4 31/2 43/8 47/8 61/2 71/2 71/2 91/4 11 121/2 151/2 181/2 21 22 241/2 27 291/2 351/2 43/4 51/8 57/8 61/4 81/2 95/8 101/2 121/4 143/4 151/2 19 23 261/2 291/2 321/2 36 383/4 46 4 4 8 8 12 12 12 16 16 16 16 16 16 3 /8 /8 11/8 11/4 11/8 13/8 13/8 13/8 11/2 15/8 17/8 21/2 Dia of Bolts (inches) Bolt Circle (inches) /4 /4 /8 /8 31/4 31/2 43/8 47/8 61/2 71/2 91/2 111/2 121/2 151/2 19 221/2 25 273/4 301/2 323/4 39 3 /8 11/8 11/4 11/2 13/8 15/8 17/8 21/4 21/2 23/4 31/2 2500 psi Dia of Flange (inches) No of Bolts 51/4 51/2 61/4 71/4 91/4 101/2 12 14 161/2 19 213/4 261/2 30 4 4 8 8 8 12 12 12 Dia of Bolts (inches) Bolt Circle (inches) /4 /4 /8 31/2 33/4 41/4 51/8 53/4 63/4 73/4 103/4 123/4 141/2 171/4 211/4 243/8 3 11/8 11/8 11/4 11/2 13/4 2 21/2 23/4 WARNING: Properties/applications shown throughout this table are typical Your specific application should not be undertaken without independent study and evaluation for suitability For specific application recommendations consult the manufacturer Failure to select the proper sealing products could result in property damage and/or serious personal injury Performance data published in this table have been developed from field testing, customer field reports and/or in-house testing While the utmost care has been used in compiling this material, we assume no responsibility for errors 178 Machinery Component Maintenance and Repair In addition, it is generally appropriate to apply the above criteria to flanged connections on equipment and other components such as: • • • Valve bonnets, where the valve is positioned to include the above referenced design temperature/size/flange rating category Flanged equipment closures where they qualify for inclusion in the above categories All flanged connections which will eventually be covered with low temperature insulation within the above reference criteria Adherence to the following procedure is recommended for controlled torquing of line flanges, bonnet joints, ect., when specified Preparation • Thoroughly clean the flange faces and check for scars Defects exceeding the permissible limits given in Table 4-7 should be repaired Table 4-7 Flange Face Damage/Acceptance Criteria Type Gasket Type Used Ring Joint Damage Scratch-like Critical Defect Across seating surface Smooth depression Permissible Limits 1–2 mils deep-one seating surface only mils deep-one seating surface only Spiral wound in tongue and groove joint Scratch-like >1/2 of tongue/ groove width mil maximum Spiral wound in raised face joint Scratches, Smooth depressions & gen’l metal loss due to rusting >1/2 of seated width (min of 1/4≤ intact surface left) Up to 1/2 of serrated finish depth Asbestos ≤ >1/2 of seated width Up to 1/2 of serrated finish depth For gasket types and refacing required if more than 3–5 (permissible) defects found Seating surface taken as center 50 percent of groove face Process Machinery Piping • • • • • 179 Check studs and nuts for proper size, conformance with piping material specifications, cleanliness, and absence of burrs Gaskets should be checked for size and conformance to specifications Metal gaskets should have grease, rust, and burrs completely removed Check flange alignment Out-of-alignment of parallelism should be limited to the tolerance given in Figure 4-2 Number the studs and nuts to aid in identification and to facilitate applying crisscross bolt-up procedure Coat stud and nut thread, and nut and flange bearing surfaces with a liberal amount of bolt thread compound Equipment For studs larger than 11/2 in in diameter, use “Select-A-Torq” hydraulic wrench (Model 5000 A) supplied by N-S-W Corp of Houston, Texas, the “Hydra-Tork” wrench system (Model HT-6) supplied by Torque System, Inc., the “Hytorc” (Figure 4-10), tensioners by Hydratight-Sweeney (Figure 4-11), or one of many available Furmanite “Plarad” devices (Figure 4-12) Torque wrenches can be used on small flanges, with stud diameters less than 11/2 in The torque wrenches should be calibrated at least once per week Figure 4-10 “Hytorc” stud tensioner 180 Machinery Component Maintenance and Repair Figure 4-11 Tensioners by Hydrotight-Sweeney Hot Bolting and Leakage Control Hot bolting during startup and during process runs has been found to be an important factor in minimizing flange leakage During heat-up and because of temperature changes, the bolts and gaskets deform permanently This causes a loss of bolt stress after the temperature changes have smoothed out Hot bolting helps correct this Process Machinery Piping 181 Figure 4-12 Furmanite “Plarad” hydraulic tensioning devices in action Hot Bolting Procedure The objective of hot bolting is to restore the original bolt stress which has dropped due to yielding and/or creep of the flange joint components If possible, this should be done with a bolt tensioning device Hot bolting should start at the point of leakage and proceed in a crisscross pattern as described previously Seized bolts sometimes present a problem when hot bolting In such cases, it is necessary to use a wrench on both nuts Using Bolt Tensioners There exists considerable experience with the use of various bolt tensioners for hot bolting These procedures typically involve first running a die over the stud projections to facilitate subsequent installation of the tensioner heads Mechanics are instructed to leave the heads in place for the minimum time necessary so as to prevent leakage of hydraulic fluid at the seals Past procedures called for immersion of heads in water between applications; however, this is no longer necessary 182 Machinery Component Maintenance and Repair Using Hammer and Wrench or Torque Wrench If leaks occur, it may be necessary to employ a lb or heavier hammer to stop the leak Tightening should first be done where the leakage has originated and the crisscross pattern should be used from there Joints with spiral-wound gaskets can be tightened only to the limit of the steel centering ring thickness Further tightening is fruitless if a spiral-wound gasket has already been tightened to this point If Hot Bolting Does Not Stop Leak If leakage cannot be stopped by tightening, the line must be isolated and the joint broken to determine the cause: • • • • • • • • Examine flange facings for damage, distortion (warping), or foreign matter Check flange alignment, cut and realign piping if necessary Check gasket for proper material, dimensions, and type Use a new gasket for reassembly of the joint Check gasket deformation to determine if it was centered This is best done by noting the position of the gasket before it is withdrawn and examining it immediately after withdrawal Reassemble the joint If leakage persists, piping support and flexibility must be examined It may be necessary to revise the support system or install spring hangers to lower bending moments If leakage occurs during rainstorms, it will be necessary to install sheet metal rain shields, which may cover the top 180° of the flange, to prevent such leakage These should be located about four inches away from the flange surface and should have sufficient width to cover the bolts plus two inches on each side If leakage occurs during sudden changes in process temperatures, examine the process sequence to determine if steps can be taken to minimize rapid heat-up or cooling of lines It may only be necessary to open a valve more slowly Recommendations for the Installation, Fabrication, Testing, and Cleaning of Air, Gas or Steam Piping* The importance of starting any compressor with clean piping, particularly on the intake to any cylinder, cannot be over-emphasized This is particularly important with multi-stage high-pressure compressors where * Refer to appendices at the end of this chapter for typical checklists Process Machinery Piping 183 special metallic packing is required and parts are much more expensive than in a low-pressure compressor Any dirt, rust, welding beads or scale carried into the compressor will cause scored packing rings, piston rods, cylinder bores, and pitted, Leaky valves It is important that the piping be fabricated with sufficient flange joints so that it can be dismantled easily for cleaning and testing It is far better to clean and test piping in sections before actual erection than after it is in place If it is necessary to conduct the final test when the piping is in position, care should be taken to provide vents at the high spots so that air or gas will not be trapped in the piping Make provision for complete drainage after the test is completed These connections should be planned in advance When piping is cleaned in sections before erection, it is possible to a thorough job of eliminating all acid This is difficult to with piping erected and in position, because carry-over of acid into the cylinders is almost certain to occur when the machine is started This can cause extensive damage The use of chill-rings for butt welds in piping is recommended This prevents welding beads from getting into the pipe to carry through, not only on the original starting, but later on during operation After hydrostatic tests have been made and the pipe sections have been cleaned as thoroughly as possible on the inside, the piping should be pickled by this procedure: Pickle for 14 hours with hydrochloric acid Circulate the acid continuously by means of a small pump Use a five to 12 percent solution of hydrochloric acid, depending upon the condition of the pipe Neutralize the caustic Blow hot air through for several hours Fill with mineral seal oil and drain Blow out with hot air Pipe is now ready to use If the pipe section is not to be assembled immediately, seal the ends tightly until ready for use Then, before installation, pull through a swab saturated with carbon tetrachloride Even though this procedure has been carefully followed; on reciprocating compressor piping, a temporary filter (such as Type PT American Filter, Type PS Air-Maze, or equal) should be installed in the suction line to the suction bottle to remove particles 230 microns* (0.009 in diameter) or larger Provision must be made in the piping to check the pressure drop across the filter and to remove the filter cell for cleaning Filter cell should be removed and left out only when the inlet line is free of welding beads, pipe scale, and other extraneous matter * 140 microns (0.0055 in diameter) for nonlubricated cylinders 184 Machinery Component Maintenance and Repair On large piping (where a man can work inside), the pickling procedure can be omitted if the piping is cleaned mechanically with a wire brush, vacuumed and then thoroughly inspected for cleanliness Time and trouble taken in the beginning to ensure that the piping is clean will shorten the break-in period, and may save a number of expensive shutdowns Pickling Procedure for Reciprocating Compressor Suction Piping: Method I General Recommendations The job should be executed by experienced people Operators must wear adequate safety equipment (gloves and glasses) Accomplish entire pickling operation in as short a time as possible Preliminary Work Install an acid-resistant pump connected to a circulating tank Provide 11/2 in (or greater) acid resistant hoses for the connections (prepare suitable assembly sketch) For ensuring the filling of the system, flow must go upward and vents must be installed Provide method for heating the solutions (e.g., a steam coil) Pretreatment Pretreatment is required only when traces of grease are present Fill the system with water at 90°C (194°F) Add percent sodium hydroxide and 0.5 percent sodium metasilicate (or sodium orthosilicate if cheaper) If these compounds are not available and only a small amount of grease is present percent of NaOH and percent of Na2CO3 may be used Circulate for 20–30 minutes at 90°C (194°F) Dump the solution and wash with water until pH = Acid Treatment Fill the system with water at 50°C (122°F) Add percent of Polinon 6A® and circulate to ensure its complete distribution Process Machinery Piping 185 Add hydrochloric acid to reach the concentration of percent Circulate intermittently for about 45 minutes or more until the pickling has been accomplished Notes: In order to avoid corrosion: (a) Keep the flow rate lower than m/sec (b) Take samples of the solution and check for the Fe+++ content: if [Fe+++] > 0.4 percent dump solution In order to determine when the system has been adequately pickled, put a piece of oxidized steel in the circulation tank and inspect it frequently Neutralization Add sodium hydroxide for neutralizing the acid, and water to avoid a temperature rise Circulate for 15–30 minutes Dump the solution and wash with water until pH = Note: The concentration must be calculated on the overall volume of the solution Passivation Fill the system with water at 40°C (104°F) Add 0.5 percent of citric acid and circulate to ensure complete mixing Check the pH of the solution: if pH < 3.5, slowly add ammonia to raise pH to 3.5 Circulate for 15–20 minutes Slowly add ammonia to raise pH to in 10 minutes Add 0.5 percent sodium nitrite (or ammonium persulfate) Circulate for 10 minutes Add ammonia to raise pH to 9 Circulate for 45 minutes 186 Machinery Component Maintenance and Repair 10 Stop the pump and hold the solution in the system for at least three hours 11 Dump the solution Cleaning of Large Compressor Piping: Method II Cleaning of the piping may be done by commercial companies with mobile cleaning equipment or by the following recommended cleaning procedure After hydrostatic tests have been made and the pipe sections have been cleaned as thoroughly as possible on the inside, the piping should be pickled by the following (or equivalent) procedure: Remove all grease, dirt, oil, or paint by immersing in a hot, caustic bath The bath may be a solution of eight ounces of sodium hydroxide to one gallon of water with the solution temperature 180°–200°F The time of immersion is at least thirty minutes, depending on the condition of the material Remove pipe from caustic and immediately rinse with cold water Place pipe in an acid pickling bath Use a to 12 percent solution of hydrochloric (muriatic) acid, depending upon the condition of the pipe Rodine inhibitor should be added to the solution to prevent the piping from rusting quickly after removal from the acid bath The temperature of the bath should be 140°–165°F The time required in the acid bath to remove scale and rust will vary, depending on the solution strength and condition of piping; however, six hours should be a minimum The normal time required is about 12 to 14 hours Remove pipe from acid bath and immediately wash with cold water to remove all traces of acid Without allowing piping to dry, immerse in a hot neutral solution A one to two ounce soda ash per gallon of water solution may be used to maintain a pH of or above The temperature of the solution should be 160°–170°F Litmus paper may be used to check the wet piping surface to determine that an acidic condition does not exist If acidic, then repeat neutral solution treatment Rinse pipe with cold water, drain thoroughly and blow out with hot air until dry Immediate steps must be taken to prevent rusting, even if piping will be placed in service shortly Generally, a dip or spray coating of light water displacement mineral oil will suffice; however, if piping is to be placed in outdoor storage for more than several weeks, a hard-coating water displacement type rust preventative should be applied Process Machinery Piping 187 Unless piping is going to be placed in service immediately, suitable gasketed closures must be placed on the ends of the piping and all openings to prevent entrance of moisture or dirt Use of steel plate discs and thick gaskets is recommended for all flanges Before applying closures, the flange surfaces should be coated with grease Before installation, check that no dirt or foreign matter has entered piping and that rusting has not occurred If in good condition, then pull through a swab saturated with carbon tetrachloride 10 For nonlubricated (NL) units where oil coating inside piping is not permissible (due to process contamination), even for the starting period, consideration should be given to one of the following alternatives: (a) Use of nonferrous piping materials, such as aluminum (b) Application of a plastic composition or other suitable coating after pickling to prevent rusting (c) After rinsing with water in step six, immerse piping in a hot phosphoric bath The suggested concentration is three to six ounces of iron phosphate per gallon of water, heated to 160°–170°F, with pH range of 4.2 to 4.8 The immersion time is three to five minutes or longer, depending on density of coating required Remove and dry thoroughly, blowing out with hot air CAUTION: Hydrochloric acid in contact with the skin can cause burns If contacted, acid should be washed off immediately with water Also, if indoors, adequate ventilation, including a vent hood, should be used When mixing the solution, always add the acid to the water, never the water to the acid On large piping (where a man can work inside), the pickling procedure can be omitted if the piping is cleaned mechanically with a wire brush, vacuumed and then thoroughly inspected for cleanliness Time and trouble taken in the beginning to insure that the piping is clean will shorten the break-in period, and may save a number of expensive shut downs Temporary Line Filters When first starting, it is advisable to use a temporary line filter in the intake line near the compressor to catch any dirt, chips, or other foreign 188 Machinery Component Maintenance and Repair material that may have been left in the pipe But clean the pipe first Do not depend on a temporary line filter If the gas or air being compressed may, at times, contain dust, sand, or other abrasive particles, a gas scrubber or air cleaner must be installed permanently and serviced regularly Even though the previous cleaning procedure has been carefully followed on the compressor piping, a temporary filter (such as Type PT American Filter or equal) should be installed in the suction line to the suction bottle to remove particles 230 microns (0.009 in.) in diameter or larger If the compressor is an “NL” (nonlubricated) design, the filter should be designed to remove particles 140 microns (0.0055 in.) in diameter or larger Provision must be made in the piping to check the pressure drop across the filter and to remove the filter cell for cleaning If the pressure drop across the filter exceeds percent of the upstream line pressure, remove the filter, clean thoroughly and reinstall The filter cell should be removed and left out only when the inlet line is free of welding beads, pipe scale, and other extraneous matter Appendix 4-A Detailed Checklist for Rotating Equipment: Machinery Piping* 189 ... 25 /8 31/ 4 31/ 2 37 /8 41/ 2 57 /8 65 /8 71/ 4 81 / 2 10 1/2 11 1/2 13 3/4 17 19 1/4 203/4 233/4 253/4 2 81 / 2 33 1 1 11 /8 11 /4 11 /4 13 /8 11 /2 15 /8 15 /8 17 /8 900 psi NPS (inches) /2 /4 11 /4 11 /2 21/ 2 10 12 14 ... 8 12 12 12 16 16 16 16 16 16 3 /8 /8 11 /8 11 /4 11 /8 13 /8 13 /8 13 /8 11 /2 15 /8 17 /8 21/ 2 Dia of Bolts (inches) Bolt Circle (inches) /4 /4 /8 /8 31/ 4 31/ 2 43 /8 47 /8 61/ 2 71/ 2 91/ 2 11 1/2 12 1/2 15 1/2... /8 /8 31/ 4 31/ 2 43 /8 47 /8 61/ 2 71/ 2 71/ 2 91/ 4 11 12 1/2 15 1/2 18 1/2 21 22 2 41/ 2 27 2 91/ 2 3 51/ 2 43/4 51/ 8 57 /8 61/ 4 81 / 2 95 /8 10 1/2 12 1/4 14 3/4 15 1/2 19 23 2 61/ 2 2 91/ 2 3 21/ 2 36 383 /4 46 4 4 8 8