baber/WOPTO huggingface dataset:
Patent GB-1073819-A (GB)
Title: Production of polyamides
Inventor: MULLER GERHARD
IPC: C09D5/25
Filed: 1965-12-01
Abstract: A red coloured compound of formula <FORM:1073819/C4-C5/1> is derived from hexamethylene diamine and azobenzene tetracarboxylic acid anhydride in dimethylformamide, the product of this reaction being treated with acetic anhydride.ALSO:Polyamides containing azo-groups are prepared by reacting an azo-benzene tetracarboxylic acid dianhydride with a diprimary at 0-350 DEG  C.  Diamines specified are of formula NH2-R-NH2 where R is an aliphatic, araliphatic, alicyclic, or heterocyclic group, e.g. a C1- 6 alkylene, C5- 7 arylene, cycloalkylene, a ,o -diarylene alkane, diarylene ether, diarylene sulphone, diarylene urea or a divalent radical derived from an aryl carboxylic ester or an N-arylamide of an aryl carboxylic acid. The acid anhydride may be added portionwise to a solution of the diamine with cooling.  The molar ratio of reactants may be between 2:1 and 1:2.  Solvents specified include dimethyl formamide, dimethylsulphoxide, N - methyl pyrrolidone, dimethyl acetamide, hydrocarbons and halohydrocarbons.  A Friedel-Crafts catalyst may be present.  The reactant mixture may be coated on to metals, e.g. wires, and then heated to 150-300 DEG  C.  The products may contain 10-1000 repeating units.  They may also be used to make films and foils.  In examples the dianhydride of azobenzene-3,31,4,41-tetracarboxyli acid is reacted with bis(4-aminophenyl) ether (1), bis(aminocyclohexyl) methane (2), N,N1-dimethyl-N,N1-bis(aminophenyl) urea (3), N-methyl-N-p-aminophenyl carbamic acid p-aminophenyl ester (4), and bis(4-aminophenyl) methane (5).ALSO:Polyimides of formula:-<FORM:1073819/B1-B2/1> where R is alkylene, cycloalkylene, arylene, an a , o -diarylene alkyl radical, a diarylene ether radical, a diarylene sulphone radical, a diarylene urea radical, an aryl carboxylic acid ester radical or an aryl carboxylic acid N-aryl-amide and n is 10 to 1000 may be used as coatings.  The coatings may be formed by reacting the corresponding azobenzene tetracarboxylic acid anhydride and diamine together in a solvent to produce a polyamideacid, applying this to the surface and stoving it at 150 - 300 DEG C.  In Example 3 a polyamideacid derived from 3, 3\sv, 4, 4\sv-tetracarboxylic acid of azobenzene and N, N\sv-dimethyl-N, N\sv-bis (4-aminophenyl) urea in dimethyl sulphoxide is applied to metal sheet and stoved.  In Example 5 a polyamideacid derived from azobenzene 3, 3\sv, 4, 4\sv-tetracarboxylic acid anhydride and bis(4-aminophenyl) methane in dimethylacetamide is applied to glass plate and heated.
Patent GB-1215638-A (GB)
Title: A thiophene thiophosphonic acid derivative
IPC: C08G69/02
Filed: 1968-10-28
Abstract: 1,215,638. Thiophene thio phosphonic acid derivative. SUMITOMO CHEMICAL CO. Ltd. 28 Oct., 1968 [31 Oct., 1967], No. 50999/68. Heading C2C. [Also in Division A5] A novel compound of the formula is obtained by reacting thiophene with phosphorus pentasulphide, the reaction being preferably effected at between 80 to 150 C., e.g. under reflux conditions. It is preferred to use from 10 to 20 mols. of thiophene per mol. of the pentasulphide. The product has insecticidal and fungicidal properties and is also useful as an intermediate for the production of the insecticide: O-ethyl-O<SP>1</SP>-p-nitrophenyl-2-thienyl phosphonothioate by the following reaction scheme
Patent GB-1535327-A (GB)
Title: Pressure control valve
IPC: F16K17/04
Filed: 1975-12-15
Abstract: 1535327 Valves SOC GENERALE DE CONSTRUCTIONS ELECTRIQUES ET MECHANIQUES ALSTHOM 15 Dec 1975 [19 Dec 1974] 51332/75 Heading F2V A valve has a co-operating closure member 8 and seat 1, the seat being slidably sealed in a recess 13 by a seal ring 15 and in use being biased towards a shoulder 16 of the recess by fluid pressure. As shown a spring 9 holds the closure in contact with the seat through a cupshaped part 10 engaging a boss 11. The seat may be enclosed by a collar 12 of two or more parts to enable the seat and closure member to be removed without disturbance of the spring, an intermediate part 3 being held by screws 6 between a body 2 and a pipe flange 4.
Patent GB-1121998-A (GB)
Title: Improvements in or relating to lamp holders
IPC: F21S4/00
Filed: 1965-12-06
Abstract: 1,121,998. Lampholders. LUMALAMPAN AB. 6 Dec., 1965 [11 Dec., 1964], No. 51584/65. Heading H2E. [Also in Division F4] In a lampholder for a Christmas tree light, a plastics holding member is divided longitudinally into two parts 3 and 3<SP>1</SP> which are fitted together to carry contacts 5 and 5<SP>1</SP> in slots 17 and are positioned in the upper end of a resilient insulating sleeve 1, simulating a candle stem, preferably by co-operating projections and recesses 18, 19 and ribs and grooves 20, 21. The members 3, 3<SP>1</SP> are provided with screw threads 4, or alternatively with bayonet or sliding-type fittings, for receiving a lamp. A plastics mounting unit is formed in two parts 7, 7<SP>1</SP> secured together and to the sleeve by a rivet 8-8<SP>1</SP>, recesses 22 engaging projections 23 on the sleeve, and is attached to a crocodile clip 9 by a ball and socket joint 10, 11. Apertures 15 in the mounting unit grip conducting leads 6, 6<SP>1</SP>, the bared ends of which are welded to the contacts 5, 5<SP>1</SP>. In a modification, the mounting member 7-7<SP>1</SP> is integral with the holding member 3-3<SP>1</SP>.
Patent GB-1158585-A (GB)
Title: Gate Controlled Switches
Inventor: STACEY MICHAEL ALBRT
IPC: H01L21/308
Filed: 1965-12-06
Abstract: 1,158,585. Thyristors. JOSEPH LUCAS (INDUSTRIES) Ltd. 8 Nov., 1966 [6 Dec., 1965], No. 51621/65. Heading H1K. An NPNP thyristor with P-type gate region adjacent the N-type cathode has the gate region formed by diffusion in a reducing atmosphere. In the embodiment, a 30-50 ohms cm N-type silicon wafer 11 is etched and subjected to aluminium vapour in an argon-hydrogen atmosphere at 1200 C. for 5 hours to produce P-type regions 12 (gate region) and 13 (anode region). The wafer is then subjected to phosphorus pentoxide in an open furnace to produce glass covered N-type layers over the P-regions and one N-type layer and part of the other is removed to leave N-type mesa 16 (cathode) with glass layer 18; the cathode/gate PN junction may have a tortuous perimeter. Boron is diffused in to produce P+ regions 19, 20 and glass layers 21, 22; glass layer 21 is removed and gold diffused into the anode region 13, to reduce turn off time. The upper and lower surfaces are plated with nickel, the mesa junction then wax masked and exposed nickel plated with gold. The wax is then removed and the exposed junction etched with a mixture of nitric, acetic and hydrofluoric acids the gold acting as a mask to produce the device as shown in Fig. 8.
Patent GB-1503144-A (GB)
Title: Mattresses
IPC: A47D15/00
Filed: 1973-11-09
Abstract: 1503144 Mattresses NATIONAL RESEARCH DEVELOPMENT CORP 10 Feb 1975 [9 Nov 1973] 52035/73 Heading A4M A mattress is provided with straps 3 for retaining an occupant 5, each strap 3 being permanently secured at one end to a side of the mattress and being tied at its opposite end to a handle carried at the opposite side when used to retain the occupant. In its out of use position each strap 3 is releasably secured around the side edge of the mattress e.g. by snap fasteners or by "Velcro" (Registered Trade Mark) tape. One or both ends of the mattress may be further provided with a handle 4 or other strap or harness to facilitate dragging of the mattress.
Patent GB-1126195-A (GB)
Title: Improvements in or relating to diazotype photoprinting materials
Inventor: WELCH WALTER JAMES
IPC: G03C1/61
Filed: 1965-12-08
Abstract: 1,126,195. Heat developable diazotype materials. GENERAL ANILINE & FILM CORP. Dec. 8, 1965 [Dec.9, 1964], No. 52169/65. Heading G2C. A sensitizing composition for a heat-developable two-component diazotype printing material comprises guanidine sulphate, an azo coupling component, a light sensitive diazonium compound and a neutral or acid reagent which yields an alkaline reacting compound on heating to 100-200‹ C. The composition may be coated on paper or film e. g. regenerated cellulose or cellulose acetate. The neutral or acid reagent may be an alkali metal or ammonium salt of a strong organic acid e. g. of maleic, oxalic, malonic, benzene sulphinic, or of a carboxylic acid having 1-3 C atoms which may be α- or #- substituted by halogen, -CN or -NO 2  e.g. trichloroacetic acid. The diazonium compounds are preferably the diazotization products of N-mono- or N-disubstituted phenylene diamines. Azo coupling agents specified are 2-(m-hydroxyphenoxy)-ethanol, 2, 3- and 1, 8- dihydroxynaphthalenes, 2, 3 dihydroxynaphthalene- 6-sulphonic acid, sodium-6, 7 -dihydroxy-napthalene-2-sulphonate, phloroglucinol, resorcinol, 2-octyl and 2-methyl resorcinol, α -resocrcylamide, 3 -methyl- 1 -phenyl pyrazolone, acetoacetanilide, H-acid, and 2, 5-xylenol. Other additives include (NH 4 ) 2  SO 4 , ZnCl 2 , NiSO 4 , MgCl 2 , acid stabilizers, wetting agents, thiosinamine, 1-allyl-3-#- hydroxylethyl thiourea, 1-alkyl-thiourea, glycol, glycerine, sodium-1, 3, 6-naphthalene trisulphonate, SiO 2  and polyvinyl alcohol and acetate. The components may be applied to the base in a single step or, applied as separate layers. After imagewise exposure, the image is developed by heating to 100-200‹ C.
Patent GB-1452934-A (GB)
Title: Magnetic bubble multiplying circuit
IPC: G06F13/00
Filed: 1973-11-29
Abstract: 1452934 Magnetic storage arrangements MONSANTO CO 29 Nov 1973 [1 Dec 1972] 52323/75 Heading H3B A magnetic bubble replicator includes means to provide simultaneously a number of replica bubbles corresponding to an input bubble, and means to provide the replica bubbles in serial form on an output path. Replica bubbles on paths 120, 124 pass to annihilators 136, 138 unless there is a bubble on input path 122. In the latter case the replica bubbles are transferred via fields 132, 143 to paths 126, 130. Delays 140, 142 cause the replica bubbles and the bubble from path 122 to appear in sequence on output path 144.
Patent GB-1077807-A (GB)
Title: Amides of olefin-maleic anhydride copolymers and their use as diesel fuel additives
IPC: C08F10/00
Filed: 1965-12-08
Abstract: A fuel for compression ignition engines contains in an amount sufficient to provide detergency and dispersency an alternating copolymer of a C8- 30 aliphatic 1-olefine and a N-substituted maleimide which contains as the N-substituent a C3- 30 organic radical free of aromatic unsaturation, and having one amine nitrogen, the copolymer having 4-20 repeating units.  The base fuel may be a straight run or cracked petroleum distillate, a residual fuel, a fuel derived from shale or produced by the Fischer-Tropsch synthesis, and may have a b.p. of 325-750 DEG  F.ALSO:An alternating copolymer of a C8- 30 aliphatic 1-olefine and a N-substituted maleimide which contains as the N-substituent a C3- 30 organic radical free of aromatic unsaturation and having one amine nitrogen, the copolymer having 4-20 repeating units, is claimed.  The co-polymer may have the repeating structure <FORM:1077807/C3/1> where R is a C6- 28 alkyl, T is a C5- 26 aminohydrocarbyl free of aromatic unsaturation and having one amine N, e.g. -(CH2)2 or 3-NH-Cx where Cx is a C8- 20 aliphatic hydrocarbon and n is 4-20.  The copolymer may be produced by polymerizing a mixture of C15- 20 cracked wax 1-olefines and maleic anhydride in benzene using benzoyl peroxide as catalyst, and then reacting the copolymer with N-octadecenyl propylenediamine.
Patent GB-1275119-A (GB)
Title: Combustion equipment
Inventor: WILLIAMS DAVID EYRE
IPC: F23R7/00
Filed: 1969-10-27
Abstract: 1275119 Gas turbine plant and combustion chambers ROLLS-ROYCE Ltd 27 Oct 1969 52557/69 Headings F1G and F1L In a gas turbine engine having a combustion chamber 22 operating at substantially constant volume the exhaust outlet 23 of the chamber is permanently open but the combustion gases are periodically prevented from escaping by an opposing gas flow 43 directed towards the outlet 23. The engine includes a compressor 11 which supplies air to a rotary valve 19 which causes an intermittent flow to branches 16, 17 leading respectively to combustion chamber 22 and to an auxiliary combustion chamber 35. Fuel is supplied to both chambers 22, 35 and ignited by spark-plugs 32, 37 simultaneously. The fuel/air ratio in chamber 35 is arranged to be higher than that in chamber 22 so that the combustion gases leaving chamber 35 through pipe 41 are at sufficiently high-pressure that the flow 43 thereof when directed through nozzle 42 into pipe 26 prevents for a predetermined short period of time in each cycle the flow of combustion gases through outlet 23 of chamber 22. Thus combustion in the latter takes place at substantially constant volume and the gases cannot escape through outlet 23 until their pressure exceeds that of the opposing flow 43, e.g. about 0-03 secs. after firing. The discharging gases drive a turbine 25 which may drive the compressor 11. The engine may drive a land vehicle.
Patent GB-1348013-A (GB)
Title: Freewheel clutch
IPC: F16D41/00
Filed: 1971-11-17
Abstract: 1348013 Ratchet clutches RELHOR SA 17 Nov 1971 [9 Dec 1970] 53271/71 Heading F2C A freewheel clutch has a spiral spring 10 disposed in a drum 2 rigidly secured to a shaft 1, the spring enclosing a collar 5 affixed to the shaft 1 and the drum having a slot 3 through which a straight portion 11 of the spring passes, and bears against ratchet teeth 9 of a wheel 7 loosely mounted on the shaft 1. For one direction of rotation of wheel 7 the part 11 of the spring (and hence the drum 2 and shaft 1) is driven round by the teeth 9 which abut it, and for the opposite direction of rotation the part 11 of the spring rides over the teeth 9 due to their ratchet shape (Fig. 2, not shown).
Patent GB-1107659-A (GB)
Title: Method of producing dispersion strengthened metals
IPC: C22C1/02
Filed: 1966-11-30
Abstract: A dispersion-strengthened metal is formed by substantially saturating a melt of the metal with the anion of the refractory particles to be dispersed and then adding the particles to the melt.  The refractory particles may be oxides in which case the melt is saturated with the anion by (1) supplying oxygen to the surface at a partial pressure at least as great as the equilibrium partial pressure at the solubility limit, (2) adding high-oxygen feed stock to the melt, (3) using an oxide flux or (4) melting in an oxide crucible.
Patent GB-1117979-A (GB)
Title: Improvements in and relating to heat exchangers
IPC: F28F1/36
Filed: 1966-12-02
Abstract: 1,117,979. Tubular heat exchangers. SULZER BROS. Ltd. 2 Dec., 1966 [31 Dec., 1965], No. 54022/66. Heading F4S. A heat exchanger comprises an outer casing 1 encircling a bundle of finned tubes 2 in contiguous side-by-side relationship, the space 6 between the easing and the tube bundle being filled with a mouldable material which ultimately hardens. In one example the mouldable material is cast in position and consists of a synthetic resin e.g. foamed polyurethane with an admixture of granular or pulverized solid such as quartz or graphite. In another example, the mouldable material is a putty-like or claylike substance which is shapable when in a plastic state and which is injected into the space 6 under pressure. Methods of applying the filler are described. The tube assembly may be encased by metal foil 7 before applying the filler. The tube fins each comprise a corrugated tape 3 wound helically on the tube, the corrugations of consecutive helix convolutions being offset from one another. The fin outline may be hexagonal (as shown), square, or triangular.
Patent GB-1533300-A (GB)
Title: Puncture-sealing pneumatic tyre and a method of producing the same
IPC: B29C73/20
Filed: 1976-12-24
Abstract: 1533300 Tyre puncture sealants BRIDGESTONE TIRE KK 24 Dec 1976 [29 Dec 1975] 54117/76 Headings C3M and C3V [Also in Division B2] A pneumatic tyre has a puncture-sealant on its inner peripheral surface comprising (1) 5-35 p.b.w. of a rubber selected from (a) ethylene-propylene copolymers (b) ethylenepropylene-diene terpolymers (c) polyisobutylene and (d) isobutylene-isoprene copolymers, (2) 95-65 p.b.w. of polybutene and (3) 5-35 p.b.w. of "white carbon" (SiO 2 ) particles of size #50 Ám., wherein components (1) and (2) total 100 p.b.w.; the puncture sealant has a visocity of 1À6 x 10<SP>4</SP> to 2À0 Î 10<SP>6</SP> poises under a shear rate of 100 sec<SP>-1</SP> at room temperature. The diene used in (b) may be dicyclopentadiene, cyclooctadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 1,4-hexadiene or a 2-alkylnorbornadiene.
Patent GB-1317517-A (GB)
Title: Method for rectifying oxygen-containing tetrafluoroethylene
IPC: C07C17/386
Filed: 1971-11-24
Abstract: 1317517 Purification of tetrafluoroethylene DAIKIN KOGYO KK 24 Nov 1971 [26 Nov 1970] 54506/71 Heading C2C Oxygen is removed from tetrafluoroethylene by continuously feeding oxygen-containing tetrafluoroethylene to a rectification tower, contacting effluent tetrafluoroethylene vapour from said tower with a liquid terpene to produce condensed tetrafluoroethylene saturated with the terpene, removing the oxygen as non- condensable gas, recycling the terpene-saturated tetrafluoroethylene to the top of the rectification tower to produce a reflux ratio of at least 50 and recovering oxygen-free tetrafluoroethylene from the bottom of the rectification tower.
Patent GB-1204753-A (GB)
Title: Sealed beverage drinking cup
IPC: B65D81/00
Filed: 1968-11-18
Abstract: 1,204,753. Drinking cups and containers. FRIGEO-WERK BELTLE & CO. 18 Nov., 1968 [18 Nov., 1967], No. 54515/68. Heading B8K. A conical cup of plastics or waterproof paper or cardboard is folded along diametrically opposite lines to form a substantially flat bag. The bag is then filled with a desired amount of powdered or granular material, from which beverage may subsequently be prepared, and the bag sealed by a tape or string 7 coated with a heat-sealing adhesive with the addition of wax. The sealing member 7 extends chordally from an edge 8 of the bag to an edge 9 and projects from the edge 9 to facilitate gripping when opening.
Patent GB-1262693-A (GB)
Title: Fibrillated yarns and films consisting of mixtures of linear thermoplastic polymers
Inventor: LAMB GEORGE EDWIN ROBERT
IPC: D01D5/42
Filed: 1969-11-10
Abstract: 1,262,693. Fibrillated yarns. ALLIED CHEMICAL CORP. 10 Nov., 1969 [20 Nov., 1968], No. 54989/69. Addition to 1,260,957. Heading B5B. [Also in Divisions C3 and D1] A fibrillated shaped extrudate is produced by extruding a unitary shaped body of an intimate mixture consisting essentially of (I) 50-95% by weight of at least one of (a) fibre-forming polyamides, (b) fibre-forming polyesters, and (c) fibre-forming olefine polymers, and (II) 5-50% by weight of a polyester of molecular weight too low for it to be effectively fibre-forming, orienting the extrudate by stretching at a temperature between the extrusion temperature and ambient temperature, and then fibrillating the oriented extrudate so as to impart to it a relatively high bulk fibrillar structure, the degree of stretching being sufficient to permit fibrillation of the extrudate without disintegrating it. The mixture may contain nylon 6 or 66, fibre-forming polyethylene terephthalate or fibre-forming polypropylene. The non-fibre-forming polyester may have a reduced viscosity, measured in m-cresol, of 0À1-0À35, preferably 0À15-0À25, decilitres/gram. The extrudate may be stretched in two or more steps prior to fibrillation. The extrudate may be annealed after orientation. The fibrillation may be effected by mechanical means, or by the use of an air jet or by mechanical means followed by the use of an air jet. In an example, a blend of 70 parts by weight of nylon 6 having a reduced viscosity (in m-cresol) of 2À3 dl./g. and 30 parts of low molecular weight polyethylene terephthalate (reduced viscosity 0À18) is extruded through a 0À020 inch diameter orifice at a melt temperature of 288‹ C., the monofilament thereby formed quenched in water at 20‹ C. and taken up as an 8 mil filament. The filament is drawn at a stretch ratio of 3 over a metal block maintained at 190‹ C. and thereby molecularly oriented and reduced to 150 denier. The drawn filament is flattened to a width of about 0À002 inch by passing through the nip of a set of rollers and fibrillated by an air jet operating at a gauge pressure of 80 p.s.i. The cross-section of the resulting fibrillated yarn contains about 177 fibrils.
Patent GB-1298606-A (GB)
Title: Abrasive cutting element
IPC: B24D5/12
Filed: 1970-11-19
Abstract: 1298606 Abrasive tools KAYEX CORP 19 Nov 1970 [28 Nov 1969] 55012/70 Heading B3D An abrasive sawblade comprises a thin metal support 10 having generally parallel side surfaces 15, 16 and surfaces 17, 18 which converge towards each other along an edge 11, a deposit 12 of abrasive grit bonded to at least the converging surfaces to form a cutting portion having an extremity 20 terminating beyond the edge 11 and a thickness that is greater than that of the support at the junction of the side surfaces and converging surfaces and increases generally uniformly from the junction to the extremity. The deposits may be on the inner or outer periphery of an annular support or along one edge of a straight support and consist of an abrasive, such as diamond particles, secured to the support by a nickel bond, the support being of metal, such as steel or phosphor bronze, and having a thickness of, for example, 0À004 inch. The blade may be used for cutting wafers of quartz, germanium, silicon and the like.
Patent GB-1330898-A (GB)
Title: Master-slave manipulator
IPC: B25J3/00
Filed: 1970-11-20
Abstract: 1330898 Manipulators PROGRAMMED & REMOTE SYSTEMS CORP 20 Nov 1970 [25 Nov 1969] 55283/70 Heading B8H In a master-slave manipulator, the master arm 16, 36 and the slave arm 17, 37 are pivotally mounted about axes 22, 23 in a rotatable housing 14 and are secured to pairs of sprockets 25, 27 interconnected by chains 30, 31 whereby upward movement of the master arm produces upward movement of the slave arm. Guides are provided in the housing 14 for maintaining all the control cables at a substantially constant tension, and for maintaining the relative orientation of other components of the arms when the arms are moved about axes 22, 23. The master and slave forearm portions 36, 37 are pivotally mounted on the upper arm portions 16, 17 and are provided with sprockets 43, 44 which are interconnected by chains 47, 53 and cables 45, 46. The cables extend through the upper arm portions 16, 17 and, in the housing 14, pass between rollers 50, on the axis 22, 23 of sprockets 25, 27, and rollers 51, 52 on axes 54 extending between each of the pairs of sprockets 25, 27. The master arm has a gripper and actuator mechanism 60 which controls tongs 61 on the slave arm, the mechanism 60 and tongs 61 being rotatable about the axes of the respective forearm portions. The control cables for these movements pass through the housing 14 wherein they pass between pulleys, mounted on the axes 22, 23 of sprockets 25, 27, and mating pulleys mounted on the axes 54 between the pulleys 51, Figs. 3, 6, 7 (not shown). When the upper arm portions are pivoted about the axes 22, 23, the mating pulleys shift with the sprockets 25, 27 to guide the control cables and compensate for changes in the positions of the arms. The arms are counterbalanced with a constant force spring 70 on a reel 72.
Patent GB-1357209-A (GB)
Title: Testing underwater pipelines for leaks
IPC: G01M3/24
Filed: 1971-11-30
Abstract: 1357209 Acoustic detection of pipe-line leaks BRITISH PETROLEUM CO Ltd 30 Oct 1972 [30 Nov 1971] 55553/71 Heading H4D [Also in Divisions G1 and F2] A method of detecting a leak in an underwater pipe-line comprises filling the pipe with water under pressure, allowing the pressurized water to remain undisturbed for a given period, measuring the pressure drop if any at the end of the period and if a pressure drop confirms a leak, discharging water from the pipe-line and charging the pipe with air, then by towing a narrow beam side-scan sonar parallel to the axis of the pipe, detecting the pulses reflected by the escaping air bubbles.