GLASS FILAMENT WINDING IN EUROPE FRANCIS
F. J A R A Y
hen comparing the state of glass filament-wound
W production in Europe with American production, one is struck more by the differences than by the similarities. Just as Europe is not a federal state but a continent of states with widely different languages and habits, so the achievements in fiber winding in Europe differ widely from country to different country. The pattern of development has been patchy-large sales of tanks in one country have not been accompanied by increased interest in a neighboring country. Also apparent is the lack of government-sponsored research and the largely empirical approach. Huge safety margins are relied upon to avoid failures. I n short, the approach (with some important exceptions) is largely pragmatical, dictated more by results obtained and tolerated than by theoretical considerations. I t therefore becomes necessary to report country by country on the achievements in Europe. This article is restricted to fiber winding, excluding the winding of cloth and tape. T h e latter is a very much easier process, but it does not lend itself to the high quality articles which make use of new developments in fiber winding. Belgium and Holland
The market in these two countries has been satisfied by the products of Atgliers Belges Reunis of Familleureux. Some four or five years ago this company, advised by the writer, installed a winding machine capable of handling vessels up to 10 feet in diameter and 35 feet (more than 10 meters) in length. T h e machine is capable of applying 150 rovings simultaneously. T h e angle of application can be infinitely varied. Normally, winding is circumferential. Allowance is made for the axial stresses by the insertion of a completely unidirectional, crimpless cloth. For all structures which are subject to any considerable chemical or mechanical stress, the following technique is invariably used. First, a layer of bonded cloth is applied on the mandrel. This is approximately 6 inches wide and is applied spirally with a suitable overlap. I t is impregnated with a resin, the composition of which depends on the service of the tank or pipe. I n the case of foodstuffs the resin is very often an epoxy; in the case of solvents or alkalies, a furan; and in the case of fuels or oxidizing liquids, a bisphenol A polyester. 52
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In England-a
72-inch diameter pifieline
The main load-bearing layer of glass fibers and general purpose polyester (or heat-resistant polyester) is applied onto this inner layer, either when it is still wet or immediately after cure. Bonding of the two resins generally is excellent and does not often require special precautions. The thickness of the inner protecting layer varies from 0.5 to 1.5 mm. The range of products of A.B.R. is quite extensive; a pipeline of 8-inch diameter and more than a mile long has been produced for the transport of hydrochloric and sulfuric acids from barges to storage vessels. Storage vessels for wine, fuel oil, and many chemicals-including highly concentrated caustic soda a t temperatures of 115" to 120" C. (245" F.)-are standard products. One interesting application is a road tanker of about 3600 gallons capacity (13,500 liters), divided into three compartments and drawing an identical trailer. This unit leaves Brussels once a week loaded with phthalates, to go to Italy and to return with wine. These tanks have now been in continuous use for three years without maintenance. France
Astonishingly enough, there is no company in France engaged in fiber winding of pipes and vessels. There is, however, one company, Plastrex in Mulhouse, which produces winding equipment for pipes up to approximately one foot in diameter. Plastrex also sells a small AUTHOR Efrancis F. Jaray is a Consulting Engineer in
Worcester, England. H e acted as consultant for one of the installations described here. He wishes to acknowledge the advice and assistance of G. Tolley in preparing this article.
In Germany-a
storage tank for hydrochloric acid
amount of these pipes for electrical purposes, but it has not entered the fluid-carrying or fluid-holding market. Germany
German activities combine a lack of research and development with the greatest turnover of any country in Europe. German companies have been active in employing ideas and techniques and are aggressive in their development of markets. With only one exception, the achievements of their various manufacturers are rather similar. The most important firms making glass fiber-wound reinforced tanks in Germany are Burger Eisenwerke, Schwelmer Eisenwerke, Koenig & Go., Phoenix Rhein Rohr and Deutsche Steinzeugfabrik, Mannheim Friedrichsfeld, and Dr. Otto Saurebau. As good twenty-end rovings are as yet unobtainable in Germany, all work is done with sixty-end rovings. As a consequence, wetting of the fibers is on the whole not very good. The laminates are translucent with every fiber clearly visible from the outside. Wherever chemical resistance beyond the basic minimum is required, the tanks are made from a bisphenol A polyester resin. This material, aided by the great wall
thicknesses and low mechanical stresses, has on the whole given good results. In order to prevent emergence of glass fibers on the inside of the vessels, the technique pioneered by A.B.R. is customary-that is, a layer of bonded cloth is wound on the inside to suppress the top fiber layers. (This idea was obtained by the manufacturers of the bonded cloth who sell it now in 5-inch strips from A.B.R. in Belgium.) Burger Eisenwerke, well aware of the limitations of this system, has advertised tanks with a layer of poly(viny1 chloride) or polythene on the inside (and has even issued pamphlets and prices), but it is not yet in production. Usually the ends of vessels are made by pressing in plastic molds in a rubber bag, or alternatively using plastic or even concrete molds in presses. The exothermal heat developed raises the temperature of the molds sufficiently to produce quite reasonable cycles. The ends are then inserted into the shells and the joint is filled by running resin into it. If the inside of the tank has to be flush, the shell is “toggled” by the thickness of the ends. The ends then sit comfortably in the bell thus produced. Fittings are normally produced by dough molding and are cemented to the tank shell or ends. Manholes are customary both on shell and ends. The overwhelming majority of tanks in Germany have been used for storage of wine, beer, and fruit juice. A very few tanks were built for transport purposes. At least one tank has been taken out of commission because the owner, one of the large oil companies, was concerned about the effects of static charges-a problem which has been overcome in other countries. Much more progressive is the firm of Dr. Otto Saurebau in Bendorf/Rhein. It has built what must rank among the biggest storage vessels: a vertical tank of 10 feet diameter and 33 feet height for the storage of concentrated hydrochloric acid. This firm has recognized the importance of fully wetted rovings, with the result that the laminates have a very much higher first point of discontinuity than have most other laminates. As a consequence, the laminates may be stressed to higher levels and economical use is made of sandwich structures. This latter system (used in America by the Triangle Corporation of Toronto and its subsidiaries, Tank Linings Ltd. of Toronto, Ont., and Wilmington, Del.) consists of using only the minimum thickness of rovings-not more than is required by pure tensile stresses. The stiffness is obtained by applying, again by winding, a number of layers of a coarse, openmesh cloth onto the layers of wetted rovings on the mandrel, and then finishing off with a second layer of wetted rovings. The cloth can be made from sisal, asbestos, glass, or an expanded material such as aluminum, poly(viny1 chloride), or polyethylene. I n this way it is possible to stress the glass rovings to much higher levels while attaining the necessary stiffness with a cheap sandwich core. Weight and price saving can reach 50%) as compared with a nonsandwich structure. Like all other German manufacturers, Otto is at present winding circumferentially and relying on unidirectional cloth for axial strength. A new machine VOL. 5 5
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now being built will make it possible to wind even large containers at any angle up to 45' with the axis. This will eliminate dependence on the slightly varying properties of the unidirectional cloth. Dr. Otto Saurebau has found it possible to bond polyester resin via an intermediate layer to practically any thermoplastic, including poly(viny1 chloride), polypropylene, polyethylene, chlorinated polyethers, and fluorocarbons. As all these materials are weldable, Dr. Otto Saurebau offers tanks and pipes with a homogeneous inner layer of any thermoplastic backed with a standard fiber-wound polyester layer in sandwich construction. I n these designs the glass fiber cannot be wetted by the tank contents; therefore it has become possible to design for very much higher permanent stresses than was possible hitherto, with a concomitant reduction of weight and cost. Such vessels can be used for practically any purpose and temperature ; even red fuming nitric acid should not offer any problems. Again Triangle and Tank Linings Ltd. offer the same developments on the American market.
has been fundamental. Bristol Aeroplanes Ltd. (now Bristol Aeroplane Plastics Ltd.) was a leader in original research on fiber-winding patterns and has been producing fiber-reinforced pipes up to 24-inch diameter for a number of bears. I t is using 15- or 20-end rovings and various types of epoxy resins. The inner layer of its pipes is reinforced with a fine cloth of synthetic fibers, applied using a hard, chromium-plated steel mandrel. This produces a mirrorlike inner surface and also gives to the slightly reinforced gel-coat particularly good reverse impact resistance. Bristol Aeroplane has recently installed a completely automatic pipe-Minding machine. T h e creel is so great and the number of rovings applied simultaneousl)
In Belgium-a
transport tank divided into three compartments COURTESY A T ~ L I E R S BELOES RE'UNIS
Switzerland
Buchser Eisenwerke has recently begun production of fiber-wound vessels. The methods and systems employed and the sizes offered are very similar to those on the neighboring and larger German market. United Kingdom
A very considerable amount of research connected with fiber winding has been carried on, under the impulse of military requirements. The work emanating from the Royal Aircraft Establishment in Farnborough
FI LAMENT-WOUND PROCESS EQUIPMENT
Hercules' Explosives Dept. has its commercial Spiralloy
I N T H E UNITED STATES
products, too, but most of them up to n o w have been electrical components. Hercules has licensed its patented filament-winding techniques t o t w o other companies who are active in the chemical equipment field. Black, Sivalls & Bryson i s licensed to make tanks, while Amercoat Corp. has a license t o produce filament-wound pipe. B., S. & B. markets a complete line o f its Poxyglas tanks-made of filament-wound glass, bonded with epoxy resin. Usual make-up o f filament-wound structures is from 50 per cent to 80 per cent glass fiber by weight, with the balance bonding resin. B., S & 6. says its tanks are about 60 per cent glass filaments by weight. It offers vertical tanks from 1885 gallons to 16,800 gallons capacity, and horizontal tanks from 300 to 1100 gallons in pressure and nonpressure designs. Amercoat Corp. has been making Bondstrand pipe for several years. It is an epoxy-bonded glass fiber product also and includes pipe sizes and fittings from 2-in. through 12-in. diameters.
The development o f filament-winding techniques in the
U. S. has followed a pattern which is not uncommon in recent years.
The first developments have come as a
result o f defense projects, with their ample financial backing and the pressure o f urgency. The principal practical applications of filament-wound structures are still in the weapons field, particularly in rockets and missiles, where their high strength-to-weight ratio is of prime importance. Applications include radomes, aircraft components, electrical components, buoys, pontoons, and missile parts such as solid fuel motor casings and liquid fuel pressure tanks. Once the manufacturers g o t info the filament-winding field through the defense products, many of them began to look for other markets in commercial and industrial products. Hercules Powder Co., one of the leaders in solid fuel rocket work, does a l o t of filament winding o f motor cases.
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so numerous that a whole pipe surface can be covered with fibers in only one pass. The number of passes and the inclination of the fibers is preset on a computer which controls the operation of the machine, and the angle is kept constant automatically in spite of increasing diameter of the built-up laminate. For civil uses Bristol Aeroplane are restricting themselves to the manufacture of pipelines of a few predetermined diameters, intended for chemical and oil field work. Tredigan Limited of Glasgow, which has taken over the production of James Mitchell & Son (Greenock) Ltd., is producing fiber-wound pipes. Normal production goes up to 12 inches, using 20-end rovings and epoxy resins. The pipes are normally connected with loose flanges, whereas Bristol Aeroplane has developed their own soluble and permanent connecting systems. For special chemical jobs, isophthalic and bisphenol polyester resins are used. If required, this firm can make pipes up to 48 inches in diameter. I t does not make vessels. Whessoe Ltd. of Darlington, which more than 100 years ago built locomotives and is now the biggest tank producer in Britain, has opened a plastics department where tanks are made by the fiber-winding process. The present limit is 7 feet in diameter by 2 5 feet in length, but tanks of larger diameter will soon be produced in a new factory now under construction. Filament Wound Reinforced Plastics Ltd., a subsidiary of W. B. Bawn Ltd. of London, have recently opened their new factory in Billericay. Pipes and tanks up to 10 feet in diameter and up to 30 feet in length are produced there; longer tanks can be produced if required. This company's winding machine is probably the most modern universal machine. I t can deposit fibers by
winding from an angle of 90" to the axis right down to 0" and is arranged for automatic multistart winding. Twenty-end, evenly tensioned and conditioned rovings are being used, usually with a general purpose or heat resistant polyester for the main load bearing' structure. Sandwich structures are normally used for all products of more than 4-foot diameter, as this increases stiffness and greatly reduces weight and price. T o make the load bearing polyester-glass laminate resistant to the service conditions, an inner layer based on bonded cloth and impregnated with various resins or a suitable thermoplastic foil is being used; the procedure is similar to methods used by Otto and Triangle. Methods have been developed to apply an outer layer which is antistatic ; that is, slightly electrically conductive so that no static charges can build up. Ends are pressed, normally using a unidirectional cloth. The inner surface receives a covering which is identical to that of the cylindrical shell. The shells are normally belled out so as to give a flush inside surface. Personnel have to enter the tank only once while it is being made; the adjoining parts of end and shell have to be connected with a chemically identical material. This is either a thermoplastic material in the form of a strip which is welded over both adjoining edges, or a suitable cement (furan, epoxy, and so forth). The joint is completed by injecting a suitable bonding resin. These tanks are used as static storage containers for practically any liquid or in the form of elliptical or coffer shaped tanks for transport purposes. It is the new method of sandwich structure which has made possible at an economical price the tremendous stiffness demanded of rather flat transport containers.
Haveg Industries (Wilmington, Del.) offers F.R.P. armored pipe, another epoxy-glass filament product. Sizes up t o 12 inches are available, with fittings t o match. Haveg i s also building filament-wound pressure vessels. Justin Enterprises (Fairfield, Ohio1 has a line o f filamentwound tanks, including spherical tanks. Tank capacities in the standard line range from 102 gallons t o 5400 gallons, and the company has just completed its initial venture in vessel 28 feet in on-site filament winding of a tank-a diameter made on the customer's tank pad. DowSmith Inc., a joint effort of D o w Chemical and A. 0. Smith, sells Red Thread pipe, designed for petroleum, gas distribution, and chemical industry applications. Glass and epoxy are the materials o f construction again. Pipe is available in 2 inches t o 10 inches in diameter. Several other manufacturers, mostly firms which g o t into the filament winding business through defense contracts, are developing commercial filament-wound products for chemical industry use. Some o f them are close t o production.
Lamtex Industries (Farmingdale, N. Y.) has done filament winding of rocket motor casings on a production basis and has made some custom-built tanks for chemical applications, but is not yet on a production basis for industrial filamentwound products. Brunswick Corp.'s plant a t Muskegon, Mich., has produced such things as missile components and radomes, and the Industrial Products Division is capable o f winding structures up t o 6 feet in diameter and 10 feet long. Brunswick i s doing development work and has wound some experimental vessels, but has no production contracts presently. The company hopes t o develop such contracts in the future. Spiral-Glas Pipe Co. ( O l d Bridge, N. J.) has developed a fiber-wound pipe, working closely with Eniay Chemical Co. Spiral-Glas i s still working on fittings t o g o with the pipe and will not get into the market until it can offer the complete line o f pipes and fittings. In general, any company which i s engaged in filamentwinding projects under defense contracts has the capability t o develop industrial products, too, and many are doing it.
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FEBRUARY 1963
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