Document V3bQpyB24RJk4pQRaQ0eLZw84

{^t^^PAoducS) 5 July 1978 TO: FROM: Norm Brock Enclosed please find a report covering the ICI engineering design practices for equipment handling vinyl chloride monomer. It is excellent general information for the two major divisions [Mond and Plastics) of ICI. Please return when finished. JUL 61978 08*1 /SifGR- DEPT- AP000I50I5 INTEROFFICE MEMORANDUM Subject Date 14 Hay 1975 ICI Equipment Report To DlstrlbutIon From J. T. Barr (Location, OflanUatlon, or Department) Valley Forge__________ (Location, Or8*nif*lln, or Dapartmtnt) Distribution N. H. Brock-^ S. Cordaro J L. Cost V. E. Dunning D. H. Francke* R. E. Jones 0. D. Kramer D. V. Lowe T. 0. Hedovlch E. A. Prlmeau * 6. B. H. Speed W. C. Wilde* No attachment The attached report received from ICI 1$ being distributed separately from the trip report because of Its Interest to a different group of people. (320) AP00015016 XMif'KIAL CIIKH1CA1. INIWOTRIRS I.1MITKD PLASTICS DIVISION - HILI.HOUSK WORKS VCH EQP1TMKNT 1NYK5TIGATION Circulation: R K Hodge Runcorn Kond 0 0 Haffon M " U V Huffield K P Crook Hillhduft* M H [. Stove 11 Welwyn FIabLIcs K H Sec* M * l> Wilson ttaxven " Members of Sub Committee Kor information: ABACI ) ICI Australia } Klectroclor ) Solvay ) Via J H Wilson, Velvyn HD/mr/1 August 1974 ' Author: R Drabble J S Seeker Eillhouse V V Madden W O Jones K J Younfc ' C Wright " T Taylor " V Howarth " A (IS Stalker " V Fothergill D H Cassie " li fiovker M -T,T~T AP00015017 I Cl FUSTICS DIVISION HILLHOUSE WORKS 7U the. request of thu lionrt/Plastice Division Liaison Coiomittou on VCM Investigation tli e fallowing mi b-comm i t tee wa: mi tub I inhod to nx change information on tiia performance of online tiring equipment unod lor handling VCM, with particular reference to potential leakages. Chairman R Drabble S Matthews N S Johnson A S Monk 1 C Taylor C Layland M L Tucker T C Ramsdale Plastics Division It II M n - Mond Division nn *H M The discussions* were based on the premise that a broad range or agreement could be reached on the most suitable equipment, bearing in mind the differing conditions under which Mond and Plastics plants operate and. without cutting across the various Division and Company Standards/Codea of Practice* All the recommendations are aimed at desirable equipment and practices for future plants handling VCM which also can be U3ed to consider improvements to existing plants, or in areas where problems become apparent* -The survey is presented in three parts and covers pipework systems, valves and fittings, pumps, compressors and special equipment. Tart 1 covers nil the equipment discussed, with brief recommendations. Part 2 oovere the general discussion notes and Part 3, leakage data on VCM plants and a visit report to the HCN plant at Cassel Works. It is clear from the general discussion stages that contact between engineering personnel of the various Divisions handling similar products is stimulating, rewording in ideas and information, all of which promote efficient processes, and improved aafety standards* fn the case uf the VCM Equipment Investigation $ub-Cnmtnittee it was soon apparent that there were largo areas of common ground ami the personal. contact brought about understanding of the various equipment problems* This contact must not he lost in the future and VCM equipment development programmes of the two Divisions should not be carried out in isolation* From th<' attached recommendations there am initially two major items, ie improved glanded or glandless pumps and valves, each of which require urgent .development and could form the nucleus of future mutual improved equipment investigations. Finally, and as Chairman of the Jiub-Commi ttee, 1 take the .opportunity of thanking all the above $ub-Uommitlee mombprr. for their interest and contributions to the discuauiorir., the taking of minutes, visit report writing and, on the plant, investigation of VCM ievols* Considering the short time allotted for this tank each of the pernoruirl involved concentrated considerable time and effort into its completion. K Drabble AP00015018 PART 1 VRM K0.U1WKNT 1 NVKJTJ CATION (Brief Kocommendations) P l PJ.VORK i > Although there have been no reports of serious difficulties with flanged joints, it is thought necessary to reduce joints to a minimum wherever possible by the use of continuously welded pipe* b) Pipework should be fabricated to Class 1 standard which include 100% radiography of all butt welds followed by a hydraulic test* c) After erection pipework should be leak tested in accordance with I Cl Specification B60 'Pressure testing of erected metallic pipework'. d) After maintenance and re--assembly pipework should be subjected to a nitrogen or air leak test using soapy water, again in accordance vith7~ Specification B80. `. & /Xi^ /UZJ&L Cls-c^tCi. t) At present tafted pipe ends should not be used with thin wall stainless steel pipes for jointing purposes. Plastice Division Metallurgist is currently reviewing tafted pipe end systems* 0 Pipework branches should not be less than 1" nominal bore, to avoid mechanical damage. k) ftrmelo or other compression joints should be avoided if possible and not used in any circumstances above 2" diameter or involving galvanised pipe* h) Ml small bore instrument lines which use screwed or compression fitting should be attached to an initial 1" flanged branch with a flanged isolating valve upstream* i) Small relief valves venting pipelines subject to liquid expansion must not vent to ataoaphero* J) When relief valves are required to vent pipelines, generally >lb capacity, they should vent to a stack or low pressure storage system and be protected by a suitable bursting disc - ND Risk of freezing* k) 'Slip on' or veld neck raised face flanges with CAP gaskets should be used* l) YCM pipework systems should be self draining as far as is possible. m) Bolted flanges are considered satisfactory to cover electrical conductivity of pipework systems when fixed to earthed plant structures and/or vessels* n) At the design stage of any pipework syB'tem a cost comparison should be made between carbon steel pipe painted and stainless steel pipe unpainted, to combat external corrosion. o) Pipework systems should be? clearly identified by a 'painted on' coding system. 'Stick on' identification tapes are not recommended due to . evidence of corrosion under the tapes* AP00015019 2 2 YAMMW a) Hull valves an1 preferred to lubricated plug valves due to the lubrication problem and stiffness in service of the latter* Plastics division prefer Lop entry Wllnot B^oedon ball valves because of their Division approved anti-static device and ease of maintenance. Mond Division will use Serck Audeo and Worcester ball valves which are on ICI contract and are fitted with Company approved anti-static devices. Measurements of leak concentrations show that most ball and plug valves have good gland sealing performance* and there is little to choose between various manufacturers from this point of view* b) Gear operated 'llindle* ball valves have shown in some respects that they are more complicated for maintenance and the geared drive type does not positively retain the spindle when it is removed and used* albeit temporarily* as a hand valve. c) Stainless steel ball valves should be used for PVC autoclave isolation to prevent boay corrosion* d) Ball valves fitted to all other VC services must have stainless steel balls fitted. e) FTFK lined plug valves are satisfactory for obtaining good gland sealing performance. The preferred type is 'Tunin', plug valves, however* can become stiff to operate in service and work is continuing to eliminate this problem. 'Durco', a similar type of valve* is not acceptable because it does not include approved anti-static device. f) Packed glanded valves such as the mushroom valves and screw down valves used on the older Plastics plants* and the control bonnet spindle type* should be regularly checked and repacked as necessary* because they have been found to exhibit excessive leaks in service. However* they . should eventually be replaced by ball valves where pressure and temperature conditions allow. &) Gate and Globe type valves have proved suitable for use with virgin VCM but are not recommended for general use in PVC plants. Hesults of tests given in Appendix indicate tnere are leak problems with packed glands which iu a feature of this valve type. h) Bellow ecaled valves similar to Newman Bender and Serek Ulocon* fitted with back-up packings, are preferred for instrument control applications and should be considered for all other critical applications. i) All valves should be manufactured from non-brittle materials* ie forged or cast steel* to avoid fracture from physical or thermal shock* Cast iron valves must not be used in any circumstances. 5 BUKUTJNG DISCS a) Bursting discs are not generally a problem if tne material and type of carrier are chosen from ICi Division or Company standards to suit the particular VCM duty* b) Bursting discs fitted to critical VCM containing vessels should be tested cold in their carriers before fitting to a minimum of yjft of tneir lower tolerance bursting pressure, it is suggested that vnerever possible spool pieces should be provided to allow for easy removal and testing of bursting disc assemblies. APOOb15020 1 4 SIGHT GLASSES . These are not recommendod and should be avoided wherever possible. They are prone to leakage and mechanical damage. CLAUFED TYPE VALVES Valves and instruments which are damped between pipe flanges are not reoommended and raised face flanged equipment should be used* 6 NON RETURN VALVES These are very rarely 10016 effective, especially where build-up problems are likely to exist. If used, they should be manufactured in carbon steel or etainlcsa steel materials. Where springs are part of the design, these should in all cases be from stainless steel. The simple flapper or swing check valve gives the beet reliability and is more effective if installed in vertical pipelines. 7 PRESSURE GAUGES a) They should preferably be of the flanged type, eg `Budenberg* with etainle&s steel diaphragm to IC1 Standard IH301. b) Pressure gauges should be installed on 1" flanged branches with- a flanged isolating stop valve immediately below it. c) All pressure gauges should be fitted with orifice plates below the isolating valve to restrict flow in the event of breakage. B FUW METERS A) Flow rooters should be of vho glandless type, Foxboro Target ItiB or Ropp and Reuter oval gear. b) Orifice plate systems with DP cello are not recommended because of the small bore pipes with compression or screwed fittings attached to tnem and which are prone to damage and blockage. LINE BLIND VALVES a) This equipment needs regular maintenance, frequencies of one month minimum are recommended to check seals, lubrication and clamping effectiveness. .. b) One piece body type valves with renewable seats are preferred) the two,, piece body type are not recommended. Current evaluation trials are in progress to select the moot acceptable manufacturer/design. 10 COUPLINGS AND HOSES a) Articulated arum are preferred to flexible hooee for tanker loading/ unloading, Cam-lock or Evertite t^ick Release couplings with Vi ton 'A* weals give good leak-froe cervice. b) Metallic convoluted and braided hones uro not recommended. APOOOt 5021 4 c) Hoses by 'Compoflex' type 951 with wire whipped resin sealed flanged ends are recommended, but care should be taken to minimise mechanical damage. d) All flexible connections should be purged with Kg to a stack or safe area, prior to disconnection* 13 RELIEF VALVES a) These should be protected by an upstream bursting disc with the space between monitored lor pressure* b) Relief valves should be vented to a conmon stack of sul'licient height and diameter, or alternatively individually to a safe area* e) Where relief valves vent Into a common stack system a downstream bursting disc should be fitted to prevent corrosion by back diffusion. d) It is reoousoended that all VCM relief valves are fitted with stainless .steel seats and springs. 11 FILTERS AKI) STRIKERS Filters manufactured from carbon steel castings, and fitted with Viton 'A* Joint rings give reliable and leak-free service. 13 PIPE EXPANSION BELLOWS * Where It is necessary to use expansion bellows, Teddington or parsons type are recommended, but they can cause difficulties if particles ingress behind .the expansion seals. Particular attention should be given to correct installation and to instructions regarding the direction of flow. W SAMPLE POINTS a) It is recommended that the number of sample points be kept to an absolute minimum, also the number of samples taken from any system containing VCH. b) Sample points should be connected to a 1" flanged branch with a 1" flanged isolation valve. Thereafter pipe sices may reduce to that determined by the sampling method, 15 PUMPS a) Pumps should be manufactured from non brittle materials, b) They should not be fitted with packed glands, c) Screwed vents or drain points should not be fitted. If necessary they should be flange jointed, d) Preferred pump seals are product flushed Crane lAt Crane 109 or Flexibox mechanical seals, in that order. Ceramic seats are preferred to tungsten carbide but seals fitted with PTFE wedge rings should be installed on a separately sealed shaft sleeve to prevent fretting. ...... i-jr1 rat 'rf ..." " ' AP00015022 ----------- .if.-,. .. ---------1 . 5 *) All pump enaft scale are prone to leak significantly more Uian any other scaled eauionent nueh an valve stems. Consideration should be given to glandless pumps, or situating mechanical sealed pumps m the open sir. ir this is not possible local extraction systems should be installed, f) All pumps should be fitted with double block and bleed arrangements. both upstream and downstream. Nj purge and vent stack connections should he provided for maintenance purposes. 16 PRESSURE VESSELS a) All vessels used for containing VCli should be constructed to Class 1 specification. b) Flanged branches, minimum sip.e 2" nominal bore are preferred to flush fitting pads with stud or set bolt connections. c) CAP and raised face flange joints are recommended up to 8" diameter, above this si Tie consideration should be given to spigoted connections or spiral wound gaskets. d) when flusn-fitting pads cazmot.be avoided and the joint broken at frequent intervals for process or maintenance reasons, they should be fitted with helicoil thread inserts which must be regularly inspected and replaced as necessary. Detailed training of craftsmen is necessary to ensure correct assembly and fitting of ctuds/set bolts* e) All stainless steel vessels should be regularly checked for stress corrosion cracking of welds in-addition to any ststutory/Company requirements. f) because of corrosion problems, inspection frequencies of carbon steel monomer recovery vessels (Plastics Division) must not be given extended frequencies unless carefully considered. g) Ali instrument fittings attached to vessels should be subject to a formal scrutiny at the design stago to check their pressure rating and design. b) PVC reaction vesoela should preferably be fitted with mechanical seals. 17 GAS HOLDERS a) To prevent overfilling, all VCU gas holders should be fitted with high level alarms, and auction control instruments. b) The peripheral seal of a gas holder should not be allowed to 'blow1, the ball should be fitted with a dip pipe oomplete with flow alamo and discharged to a nfe area. 16 MAINTENANCE PROCEDURES a) It is clear that improved maintenance procedures in general will involve greater effort by both monthly/veekJy paid staff, Thi* work should not be allowed to stagnate becauce of maintenance cum, lack of available effort and adequate training at ail levels. AP000I5023 6 b) Although increased scheduled maintenance on pumps, valves, piping; and vesr.eln can have advantages, the system in /general in inclined to be wasteful in offort. A system of scheduled inspections is therefore recommended on top of a scheduled maintenance base load, involving regular monitoring and gas testing of equipment at frequent intervals* c) A formal testing of VCH containing equipment prior to handing back to production department should be carried out* This to include pressure testing and gas leak testing with soap and water when back in service, d) Widespread provision of N for purging purposes with vent lines to a common stack or safe area should be provided to ensure vapour free equipment before any dismantling is attempted* This, however, 1b not always possible and the wearing of breathing apparatus will be necessary in cases of doubt or from experience of certain equipment types. Plastics Division often have the facility for pipeline and vessel evacuation by means of installed vacuum pumps, this is considered a suitable alternative to coomon stack venting* AP00015024 PART 2 VCU EqUimilT INVESTIGATION (General Discussion) 1 . J'IPPWjRK SYSTEMS 1.1 (fond General tiond use carbon steel piping schedule 60 up to and including 1^'\ schedule 40 stove l", J\K> psi and 20-60C. Originally Table E flanges wore used but on new plants as plant modification ASA 150 flanges are adopted. Slipon flanges with CAP joints (untrappeu) are standard. Small bore instrument piping in quit* common and iwitisluetory, using Eraeto or Brownhalls fittings. Where lioiid Division ueo small bore (V1) instrument piping with Krmelo or Brownhalls fittings then the recommended safe practice is to install a larger flanged valve upstream of any such system to allow isolation should leaks develop In the instrument piping. Liquid expansion within plant boundaries in not specially catered for on the grounds that Sufficient flanges are present which will 'spring and breathe'. Outsic(n riant boundaries but within works boundaries any lino containing wore than IS cu ft between valves is fitted with a bursting disc and relief valveback to storage. Outside works boundaries any size line which could trap VC is fitted with disc and relief valve. Piping fabrication specifications are Clans ?, ie 10$ radiography. No tafted piping is used. It io preferred that branches on process vessels are not less than J?" N/B; on pipe lines not leas than 1M N/J5. Vessels are to Class 1 standards. 1.? Plastics General Plastics, also use schedule 80 and 40 carbon steel piping extensively but also have some stainless steel requirements. Slip-on flanges, tafted ends stub fittings, etc, have all been used in the past depending on the nppliention. CAP (trapped Joints) huve been used; all welded lines where possible with trapped .joints where necessary are to be used on 1 Corvie' 8. faftod ends will not. In future, be used on stainless steel VC lines in view of cracking problems experienced at Runcorn. Small bore piping ir- used extensively on older plants and tend to quickly block due to polymeriGed VC11. No general rules on liquid expansion apply, small relief valves venting to atmosphere have been used but are now not generally favoured. Bursting Disc and Relief vent to low pressure storage is recommended. Enneto couplings should only fee used up to the lA" size on US and stainless piping. Ermeto couplings are not recommended for use with galvanised pipework in any circumstance. Piping standards are Class 1 with 100$ radiography. 1.3 Testing of Pipework Up to the present time both Uond and Plastics arrange for full pressure testing of fabricated pipework including a nitrogen or air leak test after erection* This closely follows the B80 Company standard covering 'Pressure testing of erected metalic pipework'. Questioning the need for more stringent testing in view of VC leakage/ toxicity problems, after some discussion it was agreed that the Company's standard D80 should be followed. Further advice is to be sought from the hytooj'en cyanide and phosgene piantu on thio and other related topics. ACTIONi R C Taylor/;; Jiutthowo/N 5 Jo hintson. 1*4 Earthing of Pipework Monel practice differs in detail from Plaalics. both have ceased uning bonded jiccoho flanges, the consensus being that the flange bolto/otuos give adequate earthing routes. PUalicr. earth the plant structure, AP00015025 8 Uond earth individual vessels in addition to the structure* cabling the earthing path back to an earthing point in the owitch room. Codes of Practice will be consulted before further discussion. 1.!? Painting of Pipemrk External corrosion of carbon steel pipework Is becoming an increasing problem on some of the 22 year plus aged Plastics Plants and leaks have been a direct result. Uond appear to spend a larger proportion of their maintenance budget on routine painting than Plastics* in an attempt to keep tho problem at bay. A oost exeroise on the use of stainleas steel piping in lieu of mild steel piping for all liquid VC lines on `Corvic* No 8 Plant, and so reduce routine painting and attendant corrosion problems, shows an increased capital cost of some 3-4,000* which is a small increase on an approximate total plant cost of 3.5M. The exercise was based on 5/foot for 4" N/B carbon steel against 7.50/foot for 4" N/B schedule 10 stainleas steel pipe. 2 VALVES AND FITTINGS 2.1 Uond General Uond are moving from the use of lubricated Plug valves (typically Audco) to Ball valves and having tried out a number of makes have decided on price' delivery and experience basis to opt forSerckAudco or Worcester Ball Valve. Tho Runcorn VCM Plant have very recently had some problems with the Worcester valve. Froblems with Kindle geared drive ball valves have bven found* in that the spindle is not retained in the easing If the geAred drive bridge piece ie removed during maintenance and the valve used in this stage as a hand operated valve. A serious leak of HC1 occurred on an 8" valve when attempting manual operation after removal of the geared drive. 2.2 Plastics General .Plastics have already installed a large number of ball valves and, unlike liond, are not happy with the Worcester valve, which requires 'tailor-made' seats on re-furbiahing and thia night explain Bond's recent problems. Fire safe and anti-static studies have been extensively carried out and the Wilmot Breedon Ball Valve is now the preferred ball valve; there has been evidence of excessive corrosion on carbon eteel bodies of WB ball valves at Sunoom. This is understood* however, to be a fault in the initial material choice and they are now being replaced in stainless steel. The use of Tuflin PTFE ooated plug valves ia now aeriously under consideration for Corvic* 8, having been in use on trial for approximately one year on VC at the Killbouse PVC plants. 2*3 Valve Gland Leaks .There ia a lade of evidence of whether valve glandB leak and if so by hew much. A survey of valve glands and types including pump seals will be carried out on 'Corvic* and VC plants to provide basic evidence. AP00015026 I I I V \ &>iv.l VC-t plant Instrument Section ptrongly augmented Serck (ILocon bollowu Peeled valve:', with a back up prick in-: for uno on control instrument appllcattonr., Nuwmnn llo.idor uro the ^onoral Company standards and far Je5 expensive bellows sealed v:ilvt? for normal lino valvory. The dosign of thoae vrilvee makop thorn very unlikely to leak VC. Zt wan ouggeutod that the Snundorn diaphragm valve uhould be a good contender against leaks if suitable djaphr/itfn materials could bo round, although these bring problems of flow restriction which is important.with, the build up problems of Plastics, in addition to the low pressure rating of these valvea and normal Cl construction. Mona Division, however, da not support this and would not use these valves on VCM. Plastics Division use them on low pressure VCM lines only. Tuflin valves appeared to havo good design features In re3pect of leakage; there was evidence of stiffness in operation of Tiiflin valves after a period of time and there seemed to be some doubt on the fire safe features of the Tuflin. A suggestion that VC swells PTFE (1-2^) is to be confirmed. ACTION: T C Kamsdale. SuhiuKiuesit information on the special techniques required to fit sleeves in FTPS lined valvea to obtain u good seal included softening by heating or allowing the PTFE to swell after removing initial wrapping. Some liners uhow less creep due to inhibition by fillers such as glass fibre. Jlocauce both Mond and Plastics have experience of valves becoming increasingly stiff to operate in service, Welwyn Research have been asked to organise test rig trials with Tuflin valves, after confirming that VCM swells PT?E/Teflon. The manufacturers are also to be involved. It w?m unanimously agreed that valve bodies should be made from non brittle material - le forged or caut steel and not cant iron. 5*. la Lovcio of Leakage v Valve Typen (Investigation) Part 3A ACTION: H C Tyyior/N S Johnson i;; 2.4 Pipe Piltlngo 2.4a Bursting Discs: Plastics seem to have more difficulties with bursting dines than Mond, probably because of build up problems. Divisional standards appear different in detail and this io to be examined further. Mond generally teat bursting disc assemblies before installation; Plastics only selectively d.o thin. This is a typical example of one of the main differences between the two Divisions; Plastics with butch processes have to change discs, operate valvea, oj>en pipe lines, etc, much more frequently than Mond with their continuous proceeo. 0.4b Sight Glasses: These are universally disliked and Mond are aiming to remove the very few remaining ones on their plants* Similarly, Plastics are aiming to eliminate sight glasses out again the process consideration on the older Plastics plants creates a bigger problem in achieving the goal. 2,4c Clumped Valves: There are some vulvon and fittings (eg the 'Careflex* valve) which clump betweon pipe Clangors using long study. This', type of fitting In seen as undesirable boc*mso of tho difficulty of makinj^/maintaining adequate joints, and the manufacturer13 recanmended use of special etud bolt material typos:, ?.4d Won Return Valve3 The general feeling is that only occasionally are UR valves of any real valuo because of build up problora3 and their installation must be carefully considered. Plastics have had continuous difficulties with Eruieto NH spring devices1 fitted in horizontal lines: the flapper typo favoured by moot people works: bent in a vertical line ana hence the need for caroful eonnideration at the dcuign utage. AP00015027 10 ` ;-*4e Pressure Gauges* It was agreed that the best approach was to install 1*' N/fi stubs with valved and flanged ends to receive flanged gauges (typically Buderberg gauge with S/S diaphragm to DH 301). This would give a very robust and secure type of fitting. In addition an orifice plate insert to restrict flow in the event of a breakage was a desirable feature* unless build up is suspected. 2.4f Flow Meters* In general It was agreed that glandless meters be UBed wherever possible. Typically, Morxi use Forbore Target 183 meters and . Plasties Bopp & Reuter Ov&l gear meters, both of ifcich satisfy the ' glandless requirements. Orifice plates with IP cells are not recommended for VQJ services because of the small bore pipes involved and attendant screwed or Ermeto fittings. 2.4g Line Blind Valves Plastics generally use Triangle type valves with one piece bodies. Recently & similar type of valve has been located, manufactured by Hindle of Leeds which is to be evaluated in the next few months. Hie main problem with line blind valves of the Tringle type is the difficulty in maintaining the `Fluon seats which are not replaceable on site. Factory replacement and overhaul coats are approximately 0# the cost of a new valve. Jiond have no experience of Line Blind valves, because their processes are conveniently covered by conventional replacement spade systems. C.dh Couplings and Hose Connections Both Vond and Plasties Division recommend 'Cam Lode' or *Evertie* types of quick release coupling, but in all cases coupling Jointing materials must be Vi ton `A*. The Evertite coupling has a safety catch which cannot be released when the eoupling is under main pressure. ttomi Division propose to install articulated arms for all VC tanker loading, these to be in lieu of large size (.}** and over) flexible hoses which are prone to mechanical damage and not uo manoeuvreable &o the articulated arms when connecting to inaccessible points (Mond Ref -Hazard and Reliability Study Ho 14, 295/5 dated 6 July 1973). Mond find Compoflex Hose type 951 prone to leaks after very few occasions of use and it has been found necessary to treat the whipped ends with special resins - sea to road tanker connections mainly. Plastics use flexible hoses for all VC tanker off loading and are 3" nom bore Compoflex type 951 with wire whipped flanged ends and incorporating a separate bonding wire within the hose walls. -These hoses have given satisfactory service but are prone to damage if not carefully handled. The venting of articulated arms and flexible tanker hoses between isolation valves is a potential VC leak area. It is therefore important that before breaking any coupling the residual VC between the valves should be swept by nitrogen to a local stack. . wn . V vsnr. T.J. APOOOJ5028 n Plastics Division aino une convoluted stainless steel braided hoses, up to approximately 2" nom bore for connections to weighed tanks. These have b<n 1'ound difficult to inspect and predict pin holing failure. The plant are oonaidering the replacement of this typo hose by Compoi'lex. 951 or; alternatively using metered systems direct from stock tanks whenever possible. J.4i Relief Valves At Mond Division all relief valvec used on VCM services must be protected by a bursting disc manufactured from a suitable material, and all Vessels or systems which because of process reasons are difficult to toko out of service ure fitted with twin relief devices. In addition all spaces between the discs and relief valves are continuously monitored and tested on a regular basis. Nearly all Mond plant vents are piped to a scrubber system and thence to a 200 ft stack. NBr This system covers all vents in a VCM complex, and downstream bursting discs are provided to prevent corrosion by back diffusion from the common vent system. Sphere reliefs are direct to atmosphere and considered safe by position* All new relief valve installations by Mond Division are now subject to approval by a central division authority and registered at that time. In general AGUE valves are preferred in an effort to standardise. Vlasticn Division nl.io protect all VC service relief valves with bursting di*>c, but do not provide twin relief valve3, monitoring of the space between dines and relief valves an covered by sample pressure points. Relief valves are all individually vented to atmosphere at the most convenient highest point outuide the plant. . Heiief vjiJvc.) similarly to Mond are subject to approval by a central division authority basud at Welwyn Carden City. ?,4j Filters and Strainers These are very rarely used but should the occasion arise, cast iron construction must be avoided and synthetic rubber joint rings should be in Viton *A' ?.dk Pipe Expansion Bellows VC3 and VC4 use Parsons or, Teddington bellows which operate well. Problems can occur if grit such as carbon obtains ingress into the sleeves. The ynit9 are sensitive to initial Btraln on installation and particular attention must be paid to 'Flow' direction of the contained product* 2*41 Sample and Drain Points Mond Division use min pine connection:* in stainless'steel with flanged joints and double ball valve isolation. A standard wimple system is aino provided comprising a specially designed cample bomb (dl filling ratio max) which in fitted ns required into the pipework system. Venting is to an * enclosed system or pump suction point. In general, VC sampling is n recognised problem area in connection with leakage and therefore should be kopt to a minimum. AP606T5029 12 VC sampling in Plastics Division is not part of the normal process and therefore doe3 not call for any fixed systems. On older plants, vent connections are bore mild steel plate reinforced. It is proposed, however, that all future connections of this type should be 1M minimum with orifice plates fitted if considered necessary. 2.4m Valves (General) Wedgegate and screw-down Globe valves are not recommended for use with VCM, because of leaking packings, jamming and passing. Plastics Division have a special flush fitting mushroom type run off valve fitted to the outlet of autoclaves on the older plants which is prone to leaks through the valve seat and the packings. These are being changed to short pattern ball valves, and piston valves (Yarway) are to be evaluated. 3 PUMPS All screwed vent connections and drains from pipes and pump bodies have been eliminated on new shipment in Uond Division due to the possibility of oorroeion and erosion wear on the plugs and tapped holes. Flanged welded on drainyVents are now used. Atmosphere vents are not reooamended and should be Btack vented. Mord make extensive use of double block and bleed arrangement on the upstream and downstream sides of each pump, mainly for safe isolation to oover individual leaking valves. However, this arrangement is also ideal for pump purging when appropriate supplies of Ng and vent facility to a stack are also provided, either permanent systems or the flexible fplug in' *ype. Mond do not use cast iron pumps and all VOi pumps are fitted with mechanical seals. Crane type 1A single mechanical used (product flushed) for operating temperatures of up to 100C and these have replaced the Crane type 109 whenever possible. Generally the 1A seal has seats in Ceramic, Monel or Hi-ReeiBt, PTFE bellows and 17 m/m piping for product flushing. These assemblies have achieved a working life of one year. Above 100C the type 109 eeal has remained in service and must be fitted with & replaceable Bh&ft sleeve to prevent wedge ring fretting and it also requires a backing seal. Mond Division are investigating the use of glandless pumps for VCM duties. Hie mechanical seal leakage data in part 3 shows the advantages to be gained* Plastics Division ('Corvic* 7) use Duroo pumps on VCM with a single, product flushed, John Crane (American) type 9 mechanical seal running on ceramic stationary .Beats. Plasties (Hillhouee) use two types of pumps, Haywood Tyler fitted with Flexibox type RKCPQ4^-14L product flushed mechanical seal and I/de Howl fitted with Crane type 109 seals,- also product flushed. Serious leaks are now apparent from various types of seals fitted to both Mond and Plastics pumps. It is therefore clear that whenever pumps are necessary to any VCU process they must he fitted in the open air. ''S'- ' " I'll AP000I5030 13 plastics VQi compressors on the older plants are fitted with packed glands and at 'Corvic' 7 with 1A mechanical seals which have been found to have definite improvements. Similarly to pumps, compressors should be fitted in outside locations* PRESSURE VESSELS konri treat YCM containing vessels as Class 1 duty and are all of carbon otoel construction. They nre subject to the usual pressure tests and regainr Inspections, Typical duties are distillation columns, drums, filters, storage vessels etc. No corrosion problems have been experienced nnd as n result some inspection periods have been increased to aix years. Uond prefer.welcied-on branches, minimum siae , ratber than pads. Joints to such branches are CAE such as Klinger 100. It is preferred that all VC storage vessel connections, should have motaflex jointing to cover minor leaks And the fire aspects. Similarly Plastics Division use Class 1 vessels both s/s and carbon steel construction. Raised faced joints are recommended up to 8" diameter; above this size consideration should be given to the use of spiral wound gaskets or spigoted connections. For storage vessels, such as on recovery plants, and other general VCM vessels. Plastics Division prefer welded-on branches of a sufficiently largo r.ize to resist mechanical damage. It is easier to ensure tight Joints with bolted through flanges. Some corrosion of branches and vessels hno been encountered on recovered monomer tanka where water and acids cnn be present. because of these corrosion problems inspection frequencies of monomer recovery vessels (Plastics Division) should not be given extended inspection frequencies unless carefully considered. On autoclave reaction vessels (particularly where problems of build-up nect't'sitnte flush mounted bursting discs, run off valves and instruments etc), nasties Division's practice has been to une welded-in pads with heliooil thread inserts. Extra vigilance is required by maintenance to eneure that only studs of the correct material and length are used and that they are sufficiently inserted into the helicoils. Set bolts are not recommended but if unavoidable must be of the correct length to ensure sufficient thread penetration on the one' hand, and to prevent ungripped joints arising from complete penetration of the bolts on the other hand. Helicoil inserts must be inspected every tiro years and replaced as nece'88aty Following several minor incidents where leaks of VCU occurred, all instruments and fittings mounted on pressure vessels such as thermocouple pockets; pressure transducers, gauges etc, and their associated joints, pipes and systems are now formally subjected to scrutiny at the design stage for their Ability to withstand pressure. Plastics use process operated manhole lids on autoclaves of the breech block type which are sealed using Viton rubber '0* rings. AP00015031 H Thorough inspections are regularly carried out on threads, .joints, studs etc, as well as the vessel. Stainless steel branches, pads and cladding are examined for cracks following past experience of stress corrosion cracking. Agitators on reaction vessels have, on the older plants, packed glands or, on newer plants, the preferred balanced double mechanical seals lubricated using a substance which is compatible with the chemical reaction carried out in the vessel. The apace between the seal and the abrasive slurry is continuously flushed with water which passes through a labyrinth into the vessels. If bearings fall on the seal cartridge then shut off rings are provided on the agitator shaft to prevent major, leaks of VCH. 4.1 Gas Holders Hond do not use gas holders to oontain VCU. Plastics use them as buffer* . capacity on the recovery sections. The main cause of leakage is overfilling which can blow the peripheral water seal. One technique to prevent such leaks from affecting personnel is to vent via a dip pipe positioned in the centre of the moving bell which releases gas to a vent stack. In addition instrument interlocks and alarms should be provided as an early warning. In emergencies this will not always be possible because rapid venting of an autoclave into a gas holder can prevent larger quantities of VCH being released directly from the autoclave to atmosphere, 5 KAISTDJANCE PBOCEDURE Some procedures relating to specific equipment have, where appropriate, been described in the earlier sections of these notes. This section refers to general matters. The main problems were thought to be the'following* Practices for Dismantling Equipment that haB previously contained VCU Despite the advantages of providing nitrogen purges and vent lines to stacks or vente to gasholders, those present realised the practical uncertainty of ensuring always that all traces of VCU have been removed from equipment prior to maintenance especially where trapping can occur. In such circumstances, although it is essential to thoroughly purge vessels, pipes, pumps, valves, etc, prior to maintenance and in many cases to carry out accurate gas tests, there is still a significant advantage to be gained by erring on the aide of safety and using breathing apparatus for such work. At minimum it was thougit advantageous to have a specified list of jobs where it is oompuleory fbr breathing apparatus to be worn with options left open for additional jobs based on a judgment of circumstances at the time. t Polyperoxides can fours in all VCU containing vessels and equipment, therefore, before ODening up, all vessels should be decontaminated with 10$ HC1 in water and boiled for a minimum period of one hour. Ho vessel, pump, pipe or other equipment should bo left containing polymerised VC for longer than one week without dismantling and cleaning or decontaminated as above. AP0bbl5032 15 Maintaining Equipment Leak Free on a Scheduled or other Baals Neither Mond nor Plastics carry out a high level of scheduled maintenance on VCM oquipment. Mond rely on main shutdowns at appropriate intervals for most maintenance on their continuous plant but have regular schedules at-shorter intervals for repacking filters, lubricating plug valves etc. This is supplemented by &s-needed maintenance of equipment that is provided with stand-by duplication* Plastics adopt approximately the same procedure for their continuous recovery sections but, on the batch autoclave sections, tend to carry out opportunity maintenance and some schedules between batches usually combined with breakdown jobs* Bather than increase the level of schedules, it wus generally thought to be an advantage to add onto the above existing . procedures, regular monitoring and inspection of equipment, including gas tests chuck for leaks before they become significant, thus Identifying which equipment is renuired to be repaired (ie scheduled innpections). Any scheduled inspections would need to identify leaks before they reach a defined unacceptable level otherwise this technique would result in some leaks being repaired only after they had become serious. However, the method of scheduled inspections is though to have real practical and cost advantages over extra scheduled maintenance mainly .because, for such items as pump seals and valve stem leaks, such large scatter is experienced in their sealing performance that it is not practical to regularly maintain all equipment at intervals prescribed by the worst performers. Effective ebecking/testing after maintenance, prior to hand-over, can eliminate some of the latter difficulty and a formal procedure for handing back was thought necessary. Because of the recent VC in air problem the implications of the above means increased maintenance costs and equipment outage on existing plants and Increnned capital cool of new plants* MKASURJ-MEfiT OK VC 1.KAK3 ON VARlQlJ? EQUIPMENT Leakage concentration icvelst of VCM adjacent to various equipment wero . measured at both tone! and mastics Division plants. The results and conclusions given uopnrately in Part $A* VISIT TO HCN PLANT AT DILLINGHAM J * The conclusion obtained from this visit was that the main method of preventing personnel from being exposed to HCN is to enclose equipment in well ventilated cubicles from which air is continuously extracted and discharged high into the atmosphere. Strict procedures are adhered to for entry into the cubicles which, after obtaining clearance, is always done wearing full protective clothing and a fresh air mask with a second man in attendance* , AP00015033 16 PART 3A VALVE MECHANICAL SEAL AND FLANGE LEAKAGE DATA In an effort to quantify what Leakage rates are being achieved with different types of equipment, readings were taken on several sites producing the data as tabulated below. In the time available it was not possible to standardize exactly on the method of sampling and analysis and It Is recognised that further work In this field Is necessary. The preliminary results give the following Indications. A. Valves Ball valves are suitable for most applications although their leakage rates vary from site to site. Ball valves that are used Infrequently perform better than those used several times dally. Worcester valves have given trouble on the Mlllhouse 'Corvlc' plants and this problem Is being Investigated Independently. Although the Audco lubricated plug valves show little leakage they are usually difficult to move due to poor lubrication and are being superseded by ball valves. Wedge gate valves, globe valves and control valves appear to have much higher leakage rates than ball valves and the conclusions reached were that more attention must be paid to maintenance of the gland area. The use of glandless bellows seal valves should be considered for critical Installations. Mechanical Seals The leakage rates were very much greater than expected especially since In all cases except one there was no visible leakage. It Is recognized . that the design of such seals depends on a fluid or vapour film to lubricate and cool but the levels had not been previously known. One thing Is obvious and that Is that the actual rate Is very small APOOOI5034 17 And localized since Its effect soon disappeared within the velocity of the unit. Obviously ventlllcatlon Is of prime Importance and special consideration should be given to siting pumping units. As a result of these findings and from previous work It was agreed that the Investigation Into the use of glandless pumps being carried out by Mond Division (VC3 and DED) should proceed as quickly as possible and the results be made available for discussion. Consideration should also be given to providing an external back up gland and quench with EDC if available to dilute high concentrations with otherwise satisfactory seals. C. Flanges The readings indicate that leakage from flanges Is very low. So long as flanges are correctly made and pipe lines tested prior to use they do not present a problem. It Is good practice to use continuously welded mains both from economic and leakage considerations. This practice Is used on other difficult duties such as HCN at Cassel and should be extended where possible. APOOOI5035 90SJ000dV it 4'. i* ):: t `l .1 1.v ` V* *r . * * * I,- ,f,;v . yL. &fey:.- i - . i 1 'v$>-.' *1 ioj 04 6. J. M It 4,0T*4O0, 9-ViT*0 S.21 9-l!TOi ns 9301--03 i/t 4 I ' ' 4-' 4 Vi- 4 4 4 .4 4 4 ...A -ift 4 VI vt VI VI i- VSs 002 000`ou Of CO>: c . oov of o <*" 9*0 " OSl - . on , . - 9 - 29 V 21' ! ** ! mS i "* pI:- K-ii\ * . 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