Document 55zZebOXBxvrB1VZQ98E28xD

Interoffice Aleniornndnm to (Nam* and Location) As Listed* FROM (Nam and vocation) A. D. Willbem *C. F. Hall E. D. Reed J. R. Hanna T. L. Markham E. E. Brown L. A. Thiele J. A. Smith Ray Twist GEN 55 (REV.6/74) DATE August 12, 1980 REFERENCE NO. 'm80'-793-mf ' \ SUBJECT: ENGINEERING SPECIFICATIONS, GASKETS AND PACKING Enclosed is a draft of the proposed re-issue of this portion of our general Chemcel Engineering Standard which will replace the "Gasket Material Specifi cations" of 2-25-69. Many of you have provided input into this standard already, which I appreciate. No radical changes are proposed; we are up grading where needed, eliminating obsolete services, and providing some guid ance for possible new services. We would appreciate your review and any comment you would make by August 29, 1980, so that it may be revised as required and issued soon. ADW:ds cc: J. F. Harper J. C. Susil J. Chervenka Willbem 002448 GASKETS AND PACKING FOR PIPING AND RELATED EQUIPMENT I. SCOPE, GASKETS This section is to describe specific Chemcel gasket practice for flanges in piping and in associated equipment and to provide general design con sideration: for gasket usage. Adhesives, sealants, and/or caulking compounds are not included in this category although they may sometimes be used advantageously to seal flanges with or without the use of a gasket. II. CHEMCEL PRACTICES - GASKETS A. Toxic and/or Highly Corrosive Services - Streams containing these fluids such as formaldehyde, -Formic acid or sulfuric acid, and operating at-temperature of 450 F or less -to use Teflon Envelope Gaskets with Garlock 8748, or equal, insert. (1) For higher temperatures (MO reactors) use 1/4" copper clad asbestos millboard. (2) Use 304 S/S spiral wound asbestos filled gasket as per API 601, Flexitallic GC on MO reactor outlet piping. B. Steam over 100 PSI 5 Other Fluids at 450 F to 800 F. (1) Piping Flanges - Use 304 stainless steel spiral wound asbestos filled gaskets per API 601, with self centering external C/S compression ring, Flexitallic Style GC. Note (1): This standard stock gasket is suitable for existing Chemcel services. A similar gasket is available in other materials for special situations, i. e. different metals for higher temperatures, to avoid stress corrosion cracking, or severe corrosion. Teflon, carbon or ceramic fill are available for services where asbestos is unsuitable. 1- - 002449 (2) Similar first quality gaskets of other manu facturers may also be suitable, but should not be used without further testing. Relatively poor service has resulted from use of other similar gaskets. (3) Gasket surfaces, including orifice plates, for spiral wound gaskets to have approximately 125 micro inch concentric or phonographic groove finish Very smooth plates may permit creep of gasket. (2) Process Equipment - Use metal jacketed asbestos gaskets with type of metal specified by design engineer or special spiral wound type gaskets. C. Fluids Above 800 F Use solid metal gaskets with metal and design specified by design engineer. D. General Service Most process fluids including air, water, condensate, boiler feed water, and steam less than 100 PSIG, are to use Garlock #8748 gasket. This is a compressed asbestos material with Buna-N (nitrile) binder. It was formerly manufactured as "Belmont 585". Alternate materials are Crane 888, or Anchor 451. Notes: (1) ASA Code for Pressure Piping B31.1 Par. 617 prohibits use of this type of gasket on oil or other fluids above their spontaneous combustion temperature. (2) The manufacturer states, confirmed by our experience, that this gasket will harden at about 250 F or higher 2- - 002450 temperatures. While this hardening is undesirable, the gasket remains serviceable and is the preferred material for hot boiler feed water and condensate. (3) Generally, a 1/16" thickness is used. On larger flanges at moderate pressures and/or a poor gasket surface, a 1/8" thickness may be preferred. E. Mild Services For temperatures of 250 F or less and moderate pressures, vegetable fiber, rubber, or neoprene gaskets may be used with standard or light weight flanges. Use neoprene for oil and sun light resistance. Rubber for water and dilute acids. F. Ducting Elevators For very light flanges and to seal rough surfaces at very low (< 6 inches of water) pressure, use closed cell neoprene sponge. III. BASIC FLANGE AND GASKET DESIGN Criteria for gasketed flange design is established in Section VIII of the ASME Boiler and Pressure Vessel Code. Mandatory Appendix II of the Code requires that complete calculations shall be made for two separate and independent conditions. These are: (1) Operating Condition "Miniitum bolt loading shall be determined in accordance with the following equation: (1) Wm. = ---4C2 P + 2 b 3.14 GmP This equation states that the minimum required bolt loading for operating condition is the sum of the hydrostatic end force plus a residual gasket load on the contact area of the gasket times a gasket factor, "m". 3- - 002451 The gasket factor "m" is suggested in Table UA 49.1 (see Attachment A) for various general gasket materials, but it is not mandatory. (2) Gasket Seating - "Minimum bolt loading required to seal the gasket regardless of internal pressure is determined by the equation: (2) Wm2 = 3.14 b G y This equation states that the minimum reguired bolt loading for gasket seating equals the gasket effective seating area times the gasket minimum seating stress "y". Suggested valves of "y" are also given in Table UA 49.1 while "Effective Gasket Width" and effective dimensions are given in Table UA 49.2 (see Attachment B). Wm^ = bolt loading condition 1 (operating) Wm2 = bolt loading condition 2 (gasket seating) 3.14 = Pi G * gasket effective diameter P = operating or design pressure b = effective gasket width m = gasket factor y = gasket seating factor The joint must compress the gasket to fill all voids in the flange surface and stress the gasket so that fluid will not enter it. Adequate stress must be retained in the gasket when there is maximum internal fluid pressure which tends to open the flange and relieve gasket compression. A soft gasket fills 4- - 002452 the voids readily, but may be squeezed out of the joint or crushed by bolting, or be blown out by high pressure. A hard thin gasket requires very smooth sealing surfaces, and heavy flanges and bolting to provide the very high seating force to seal the joint. An efficient joint is usually a compromise between these extremes. It may be noted that when using a relatively soft gasket at high pressure the gasket resilience will add to the bolt loading when pressure testing so that bolt overload could occur during test while the joint is satisfactory for gasket seating and normal service. A harder gasket would contribute less load during the test and may be replaced later with the preferred gasket to avoid otherwise redesigning the joint for the test condition. Flange dimensions for most situations are well covered in ASA Standards. Gasket diameters are covered in ANSI Standard B16.21 for the various standard flanges. The standard is not very helpful with material or thickness selection, however, since Section 4.2 states, "Selection of the proper material for a given service is the responsibility of the user___ and any applicable code or governmental regulation. The material selected shall be suitable for the fluid and temperature condition of service". Section 5.1 states "Selection of gasket thickness is the responsibility of the user, considering properties of gasket material as well as the intended service application----- " 002453 IV. CHEMCHL PRACTICE, PACKING A. General Soft packings are used in glands or stuffing boxes of pumps and other equipment, control valves, and regular valves. While all use packing to seal by squeezing it between the box ID and a shaft Q.D., the packing needs of the three categories are some what different. Pumps require sealing against relatively fast rotary motion, the control valve stem has generally slow or in frequent reciprocating motion, while most other valves have an infrequent combined or helical motion. Packing friction is very important in the pump since it robs horsepower and creates heat. Friction is less important for valves, but must not be high enough to overload operators or cause valve stem wear. In all cases the packing mist provide effective sealing over an extended period of time with minimal adjustment. It must resist the corrosive and solvent action of the fluids involved at the service temperature. While there are many manufacturers of packings, most with similar types of materials, the following usage has evolved over the years at Chemcel. Please advise the Engineering Department and Purchasing when additional field testing proves that alternate and/or better materials should be used. B. Pumps While most of our process pumps use mechanical seals (see Pumps, in Rotating Equipment Section), packing is preferred for water, effluent, and similar streams where moderate leakage is acceptable, and for high concentration formaldehyde where solification is a 6- - 002454 severe problem for seals. (1) Boiler feed pumps use formed rings of John Crane Superseal #1. (2) Other water and effluent services use John Crane #810. This is a square braided lubricated asbestos material. (3) Corrosive services at moderate temperature use John Crane C-1050 which is a braided Teflon yam with TFE dispersion. (4) High concentration formaldehyde and other corrosive or high temperature packed pumps use John Crane #1625 GF. This is a braided graphite filament yam which is very corrosive and heat resistant, self lubricating, and a good conductor to discipate frictional heat. Control Valves Control valves are usually supplied with die pressed or formed packing rings made into sets for the valves. (1) General Service: The preferred packing is die formed John Crane Superseal #5D. (2) Corrosive Service: John Crane style C-60, Teflon impregnated asbestos, style C-1050, a braided Teflon yam with TFE dispersion, and solid Teflon rings. Rings of pressed graphite foil are frequently furnished for corrosive and general high temperature service by control valve manufacturers. While highly regarded in literature, our experience with graphite foil has been relatively poor and other materials, particularily Superseal #5D, are pre ferred where applicable. Replacement graphite foil rings could be made by winding on and field forming Garlock Ribbon Grafoil in the box. A ring of braided graphite filament packing (John Crane 1625 GF) on each side of the graphite foil should provide improved service. Valve Packing (1) General Service: John Crane 1871, a wire inserted asbestos packing lubricated with graphite is to be used for water, air, and steam at tenperatures up to 1200 F. (2) Corrosive Service: Use John Crane style C-60, a Teflon coated braided asbestos or style C-1050, a braided Teflon yam with TFE dispersion for temperatures up to 450 F. 8- - 002456 ATTACHMENT II ( APPENDIX II -- MANDATORY TABLE UA-49.1 GASKET MATERIALS AND CONTACT FACINGS' Gasket Factors (m) for Operating Conditions and Minimum Design Seating Stress (y> Table fA-49.1 W77 Gasket Material Self-Energizing Type* 0 Rinas, Metallic, Elastomer other gasket types considered as self-sealing Gasket Factor m - Min. Design Seating Stress Y '0 0' Elastomers without fabric or n high percentage of asbestos fiber: Below 73A Shore Durometer 73A or higher Shore Durometrr Asbestos with a suitable binder for the operating conditions % thick thick V,, thick Elastomers with cotton fabric insertion . . o.so 1.00 2.00 2.7S 3.50 1.25 0 200 1600 3700 6500 400 Elastomers with asbestos fabric inser tion, with or without wire reinforce* meat 3-ply 2-ply 2.25 2.50 2200 2900 Sketches and Notes ... Use Feeing Sketch Use Column Refer to Tabio UA-49.2 ... "N (laUlb). (IrUldl. (4U5) 1-ply 2.75 3700 Vegetable fiber - . , 1.7S 1100 Spiral-wound metal, asbestos filled Carbon Stainless or Monel Corrugated metal, as bestos inserted or Corrugsted metal, jack eted asbestos filled " Soft alnminum Soft copper or brass froa or soft steel Monel or 4--6% chrome Stainless steels Corrugated metal Soft aluminum Soft copper or brass Iron or soft steel Monel or 4--6% chrome Stainless steels Flat metal jacketed as bestos filled .Soft aluminum ____ Soft copper or brass Iron or soft steel Monel _y_ 4--6% chrome Stainless Metis Grooved metal Soft aluminum Soft copper or brass Iron or soft steel Monel or 4-45 chrome Stainless steels Solid flat metal Soft aluminum Soft copper or brass Iron or soft steel Monel or 4--6% chrome Stainless steels 230 3.00 230 2.75 3.00 3.25 330 2.75 3.00 3.25 3.50 3.75 3.25 330 3.75 330 3.75 3.75 3.25 3.50 3.73 3.75 4.25 4.00 4.75 5.50 6.00 6.50 Ring joint Iron or soft steel Monel or 4--65 chrome Stainless Aieels 5.50 6.00 6.50 10.000 10.000 2900 3700 4500 5500 6500 3700 4500 5500 6500 7600 5500 6500 7600 8000 9000 9000 5500 6500 7600 9000 10100 8800 13000 18000 21800 26000 18000 21800 26000 Corn OaUlb) >11 (laMlb). (lr)j( Id) (lamb). (lc).`( Id).' (J)` sr (leMlb). (I< ).( Id). (2:) km (laUlb). (lfUld). C!).f31. {.(*) lb) ) NOTES: (1) This table gives a liM of many commonly us**d gasket rnairrul> and c:onta I fjrino * ith suggested design \alues of m and y that have grnrraik pruw-d wti'i'artory in ai tuai yr\n r when using effective casket mating width 6 given m Table L \-49.2. The dMgn wiuo.s and other details given in this table are suggested only and an* not inamialorv. (2) The surface ot* a casket having a lap should not b** against (tic nubbin. 317 002457 Table UA-49.2 ATTACHMENT I SECTION VIII -- DIVISION I Kacing Sketch (Kxacseraled) ~ TABLE UA-49.2 EFFECTIVE GASKET WIDTH H4.MC Column 1 (lb,' rrCT". IWS.1.YI LWWVI ITO1 ; n bating Width. hn Column il 2 <-> (id,* (2) 2Z^ ............... ESSSJ^r . < ,Y " cssa; - u- J A' ^VZT7---------------------------- JL. mf titt * KTO! u. <A (3) ^^ 1/64 in. Nubbin < ^ ESS1 u` < ~rr~ ,T"`WBK*2f"~ ' -- (4c (-">' ""'mw''* ES3 ' L-A-J - a4JM -- t ru* fir * & \ -T \-\-maxj u- - .V 4 V 4 3/V . 8 ,V 4 u- - T (u- - A' \ maX)1-;\-- u . 3.Y 8 3Y 8 7.Y 16 3N 8 ..... i -- w 8 Kffrclivp Sailing Width. "h" b,,. when ba in. ^2*. when b,, > ' in. I .oration of (iokrl I .usd Reaction NOTE: The gasket factors listed only apply to flanged joints in which the gasket is contained entirely within the inner edges of the bolt holes Ml I K: t t t Where -erralinn- do not rccri*d I ,'64 in. drpth and 1/32 in. *idth -patin'i. -hrichr.( 16) and (Id) -halt U* used. 318 002458