RU2230090C1 - Labricant for pressure seal of threaded connections - Google Patents

Abstract

FIELD: production of lubricant for pressure seal of threaded connections of pipes in petroleum industry and others. SUBSTANCE: the invention presents a lubricant for pressure seal of threaded connections and is dealt with production of technological and operational lubricants, that may be used for pressure sealing of threaded connections of pipes predominantly in petroleum equipment. The invention provides for development of composition of lubricant for pressure seal of the threaded connections, providing a reliable heavy-duty coating on a thread, multiple reuse of the lubricant at a screwing up and unscrewing a threaded connection, and also decrease of a drying time of the lubricant. The task achieved by creation of a composition of the lubricant for pressure seal of the threaded connections, that includes a powdered graphite, liquid glass - sodium silicate, and also a powder of thermoexpanded blacklead produced by thermoexpansion of the blacklead powder in the furnace at the temperature of 800-1000^o. EFFECT: the invention allows to produce a lubricant for pressure seal of threaded connections providing a reliable coating on a thread, multiple reuse of the lubricant and decreased drying time. 1 tbl, 3 ex

Description

Technical field

The invention relates to technological and operational lubricants and can be used to seal threaded pipe joints, mainly oil equipment - casing, tubing, etc.

State of the art

Known sealing (threaded) grease R-402 and R-416, commercially available according to TU 101708-78, for the assembly and disassembly of drilling equipment with large threads, to ensure the tightness of the joints. Lubricants are prepared on the basis of petroleum oils by thickening with lithium, aluminum, zinc stearates, and contain powders of lead, copper, and graphite. The disadvantages of such lubricants are leaching them from a threaded connection, the oxidation of metal powders, which leads to an increase in the efforts of screwing threads, incomplete sealing, one-time use.

Also known is a lubricant for sealing threaded joints (USSR AS No. 1413123, 1986), containing, wt.%: Graphite powder - 4, aluminum powder - 4, liquid glass - 92. The disadvantages of this lubricant are insufficient adhesion to metal and runoff with thread, high coefficient of friction (up to 0.35). Such a lubricant after unscrewing the thread is completely destroyed and before screwing it must be applied again to the cleaned surface and dried for 12-18 hours.

Closest to the claimed technical solution for the totality of features, i.e. the prototype is a lubricant for threaded connections (ed. St. No. 1505963. Lubricant for sealing threaded connections. Bull. No. 33 from 09/07/89).

Lubricant for sealing threaded connections contains components, wt.%:

Graphite Powder 15-65

Liquid glass 35-85

After stirring, the grease is applied to the thread with a brush or brush and dried under natural conditions for 16-24 hours.

The lack of lubrication is the insufficient strength of the coating (about 0.1 N / mm ² ), which leads to the destruction of the lubricant layer on the thread during transportation and screwing, uneven coating and the formation of sagging. Long drying times make it difficult to use the grease directly under operating conditions. When screwing up again, the grease must be applied again.

SUMMARY OF THE INVENTION

The inventive task was to develop a lubricant composition for sealing threaded joints, providing a durable coating on the thread, uniform (without sagging and draining) coating, repeated use of the lubricant when screwing and unscrewing the threaded joint, and also reducing the drying time of the lubricant.

The task is achieved by creating a lubricant composition for sealing threaded joints, including graphite powder, liquid glass - sodium silicate, as well as thermally expanded graphite powder obtained by thermal expansion of graphite powder in an oven at 800-1000 ° С, with the following ratio of components, wt.%:

Graphite Powder 25-35

The above thermally expanded graphite powder is 0.2-0.5

Water glass - sodium silicate Up to 100.

EUT-II graphite powder is produced according to GOST 4404-78 and is used in powder metallurgy as a constituent element of iron-graphite and bronze-graphite parts of friction units.

Thermally expanded graphite powder is obtained by thermal expansion in a furnace at a temperature of 800-1000 ° С of various graphite powders (GAK, GSM, EUT-II, pencil, etc.). Thermally expanded graphite has a special structure and properties and is used as a sorbent, heat insulator, cushioning material.

Liquid glass (sodium silicate) is commercially available according to TU 6-15-433-92 and is used mainly as an adhesive for paper and cardboard.

Using the claimed combination of essential features allows to obtain the achieved technical result, namely: to reduce the drying time of the lubricant applied to the thread by 3-4 times, increase the strength of the coating (dried layer of lubricant) by 2-3 times, to ensure multiple loosening and wrapping of threads to 3 times (at 100% sealing of the threaded connection).

Information confirming the possibility of carrying out the invention

Example 1. 25 g (25 wt.%) Of graphite powder EUT-II and 0.2 g (0.2 wt.%) Of thermally expanded graphite powder obtained by thermal expansion of graphite powder in an oven at 800-1000 ° C, was placed in a glass or enameled dishes, added 74.8 g (74.8 wt.%) water glass and mixed until a homogeneous paste.

Example 2. 30 g (30 wt.%) Of graphite powder EUT and 0.35 g (0.35 wt.%) Of thermally expanded graphite powder obtained by thermal expansion of graphite powder in an oven at 800-1000 ° C, was placed in a bowl and added 69 65 g (69.65% by weight) of water glass. The mixture was stirred until a homogeneous paste.

Example 3. 35 g (35 wt.%) Of graphite powder EUT and 0.5 g (0.5 wt.%) Of thermally expanded graphite powder obtained by thermal expansion of graphite powder in an oven at 800-1000 ° C, was placed in a glass dish, was added 64.5 g (64.5 wt.%) Of water glass and mixed until a homogeneous paste.

The resulting pastes are ready for use as a lubricant for sealing threaded joints.

The resulting lubricant compositions (in the form of a paste) do not exfoliate and are stable in properties (in closed containers) for 180-200 days.

Evaluation of the quality of lubricants was carried out according to the following indicators: drying time of the lubricant applied to the thread - visually until the lubricant hardens; the strength of the dry layer of lubricant deposited on a smooth steel plate, compression test to break the layer on a tensile testing machine RM-3; the number of screwdrivers (loosening) of the thread with a single application of grease - visually during hydraulic testing of the threaded connection.

The test results are shown in the table.

The table shows that the drying time of the lubricant on the thread decreased by 3-4 times, the strength of the dry lubricant layer increased by 2–3 times, and the number of thread wraps (turns) increased by a factor of 2–3 with a single application of grease.

The advantages of the proposed lubricant composition for sealing a threaded connection include a low coefficient of friction (up to 0.1); uniform (without sag) coating; stronger connection with metal pipes; filling of all microdroughs due to the presence of thermally expanded graphite in the composition; 100% sealing of a threaded joint due to the elastic aftereffect of thermally expanded graphite powder particles; the ability of the lubricant to work in a threaded connection from -50 ° С to + 400 ° С due to the presence of thermally expanded graphite (lubricant - prototype works from -50 ° С to + 250 ° С).

Claims (1)

A lubricant for sealing threaded connections, including graphite powder and liquid glass - sodium silicate, characterized in that it additionally contains thermally expanded graphite powder obtained by thermal expansion of graphite powder in an oven at 800-1000 ° C, in the following ratio, wt.%: Graphite Powder 25-35 The above thermally expanded powder graphite 0.2-0.5 Water Glass - Sodium Silicate Up to 100