RU2163917C2 - Sealing material for threaded joints - Google Patents

Abstract

FIELD: sealing materials. SUBSTANCE: invention, in particular, relates to sealing threaded joints subjected to unscrewing forces. Material in the form of tape is manufactured from polyethylene film 0.02-0.1 mm thick, showing tensile strength 10 to 20 MPa and having sticky glue layer with thickness no more than half thickness if film and stickiness within a range of 30 to 300 sec. In a preferred embodiment of invention, glue layer employs composition prepared by dissolving synthetic rubber in rubber solvent followed by addition of colophony and mineral oil. EFFECT: reduced cost of material.

Description

 The invention relates to sealing materials for threaded joints, in particular for tapered threaded joints undergoing unscrewing.

 Sealing materials are known in the form of non-hardening lubricants obtained by displacing mineral and synthetic oils with a thickener, anti-friction, anti-seize and sealing additives (see AS USSR N 1505965, class C 10 M 159/18, N 1664816, class C 10 M 105/16, N 1796648 and N 1812205, class C 09 K 3/10, application for a patent of the Russian Federation N 96123774/04 (030378), as well as the book Sinitsyna V. V. "Plastic greases in the USSR", ed. 2, M.: Chemistry, 1984, pp. 163-171). Their disadvantage is the inconvenience of transportation, storage and use. In winter, they thicken, making it difficult to evenly apply them to threads and creating the risk of leaving some threads without a lubricant layer. In the summer, they liquefy and create the danger of the deposition of powdered additives on the bottom of the container.

 Sealing materials are known in the form of hardening compositions obtained by mixing an acrylic oligomer, phenolic or epoxy resin, water glass and other substances with fillers and hardener (see RF patent N 2036946, class C 09 K 3/10, USSR AS N 1413119, class C 10 M 103/06; N 1413123 and N 1546470, class C 10 M 169/04, N 1595887, class C 10 M 165/00). They have a high cost, low adhesive ability and make it difficult to unscrew the threaded connection after long-term operation of the pipes.

 Known sealing devices in the form of an elastic thin-walled tubular cover or ring installed between male and female threaded parts (see AS USSR N 1555587 and N 1689699, CL F 16 L 15/04 and F 16 T 15/02). Their disadvantages are the high cost, unsuitability of devices of one size for threaded connections of other sizes and the need to change the design of the threaded connection, for example, grooves.

 A sleeve seal in the form of a ring of an elastoplastic film material is also known (see the description of the invention according to the application of the Russian Federation 94040312/06, class F 16 L 17/00, Bull. N 23, 08/20/96). Its disadvantage is unsuitability for use in threaded connections at high pressure drops.

 The closest to the claimed technical essence and the achieved result is a sealing material in the form of a tape made of an elastoplastic plastic polymer - fluoroplastic, produced under the name FUM tape according to TU 6-05-1388-86 by the Kirov-Chepetsk Chemical Combine (see the nomenclature list "Products from Teflon - 4D ", 1992, AOI" Kirov-Chepetsk Chemical Plant "). The FUM tape, depending on the brand, has a thickness of 0.035 - 0.200 mm and a width of 3 - 60 mm. It is widely used in the oil and gas industry for sealing threaded joints of casing and tubing, operated at high pressure drops. The disadvantages of the FUM tape are the high cost and inconvenience of use in the field. Due to the absence of a sticky adhesive layer, the FUM tape is weakly held on the thread and is often blown away by the wind until the pipe-wound nipple end of the pipe is inserted into the threaded socket end or sleeve of the previous pipe. Another disadvantage of the FUM tape is that, having the lowest coefficient of friction, it is easily squeezed out of the threaded connection when it is screwed up and therefore sometimes the threaded connection remains unsealed. The manufacture of FUM tape with an adhesive layer is difficult due to the lack of adhesive compositions suitable for this purpose.

 The problem to which this invention is directed, is the creation of a cheap sealing material that is convenient for application to a threaded surface in the field and provides reliable sealing of threaded pipe joints at high pressure drops.

 The problem is solved in that the sealing material in the form of a tape is made of plastic film with a thickness ranging from 0.02 - 0.1 mm and tensile strength within 10 - 20 MPa, has a sticky adhesive layer with a thickness of not more than half the film thickness and stickiness within 30 - 300 s.

 In an advantageous embodiment, the tape can be made of a film of high pressure polyethylene (low density) or a composition of high and low pressure polyethylene with a thickness of 0.05 mm and a tensile strength of 15 MPa. Tensile strength is determined according to GOST 10354-82 and GOST 14236-81.

 In an advantageous embodiment, the sticky adhesive layer has a thickness of 0.010-0.025 mm and an adhesiveness of 50-150 s. Stickiness is determined according to GOST 20477-86.

 The material is made by applying the adhesive composition onto a polyethylene film by the roll method, cutting it into tapes with roller knives and reeling it into rolls into polyethylene or cardboard sleeves. The adhesive composition should not harden during storage and transportation. In a preferred embodiment, it is made by dissolving synthetic rubber in galosh gasoline, followed by the addition of rosin and mineral oil.

 The proposed material is suitable for sealing threaded connections of tubing in accordance with GOST 633-80 (diameters 33 - 114 mm) and casing in accordance with GOST 632-80 (diameters 114 - 508 mm). On the thread of the nipple part of the pipe, the tape is wound in 1.5-2.5 turns (layer) depending on the diameter of the pipe. For convenience and economy of material, the tape is made with a width of 20 - 100 mm. On the thread, the tape is held in the form of a ring, regardless of the adhesion to the metal and the presence of oil contaminants, moisture, ice crust on the metal surface (in winter). The stickiness values are assumed to be optimal, since with stickiness less than 30 s there is a danger of the tape sticking off, and with stickiness more than 300 s it is difficult to peel the tape from the reel, especially in cold weather when you have to work outdoors with gloves on. The thickness of the adhesive layer of the tape affects the sealing ability of the material. The smaller the thickness of this layer, the more polyethylene remains in the threaded connection after it is screwed up and the connection is sealed at higher pressure drops. The best result occurs when the thickness of the adhesive layer is less than half the thickness of the plastic film.

 The main factors affecting the sealing ability of a material are the thickness and strength of the film at break. The best filling of the gaps in the threaded connection is provided when the total thickness of the film layers is 10-20% higher than the transverse size of the gap. In threaded connections of tubing and casing, this gap is 0.07-0.08 mm and the optimal total film layer thickness is 0.08-0.10 mm. Therefore, when winding in two layers, the optimal thickness of one film layer is 0.04-0.05 mm, which is confirmed by the results of bench tests (see table). Tests also showed that the optimal film strength at break is 10-20 MPa. With such strength, the tightness of the threaded joint under pressure up to 50 MPa is ensured. With greater film strength, it is difficult to make pipes with couplings until the main planes of the threads coincide and unscrew them with existing tools. In addition, there is a danger of under-rotation of the threaded connection and the possibility of stragging it under the action of axial forces reaching 100 tons and above.

 Bench tests of 7 samples of the material, differing from each other by the film thickness, its tensile strength, the thickness of the adhesive layer and its stickiness, were carried out. The tests were carried out with nozzles and couplings of a tubing pipe with a diameter of 73 mm according to GOST 633-80. Tightening of threaded joints was carried out with a torque of 75 kgm. The compounds were subjected to hydraulic pressure testing at room temperature with a slow build-up of pressure up to 50 MPa and holding under this pressure for 1 h. The pressure values for a leak in the form of droplets or jets are shown in the table.

 An experimental batch of the proposed material was made with a film thickness of 0.05 and an adhesive layer thickness of up to 0.02 mm. It was tested at the pipe bases and wells of JSC Tatneft.

 The bench test results confirmed the properties of the sealing material according to the invention and the effectiveness of its use.

Claims (1)

 Sealing material for threaded joints in the form of a tape of an elastic plastic polymer, characterized in that the tape is made of a polyethylene film with a thickness in the range of 0.02 - 0.1 mm and tensile strength in the range of 10 - 20 MPa, has a sticky adhesive layer with a thickness no more than half the film thickness and tack within 30 - 300 s.

Images