RU2214449C2 - Plastic grease - Google Patents

Abstract

FIELD: lubricants. SUBSTANCE: grease suitable for greasing stop valves of trunk and gas- distributing stations contains, wt %: stearic acid 12.0-18.0, lithium hydroxide 2.0-3.0, polymer 0.4-8.0, graphite 0.5- 5.0, multifunctional additive: boron-modified zinc dialkyl dithiophosphate 0.1-1.0, cellulose 0.5-5.0, and distillate oil with congelation temperature below -45 C - to 100. As polymer, polyisobutylene or butadiene/styrene thermal elastomeric plastic, or synthetic rubber, or atactic polypropylene. EFFECT: enhanced sealing ability and improved lubricating properties of grease due to extended working capacity temperature range from -60 to +120 C, and ensured environmental safety. 2 cl, 2 tbl

Description

 The invention is used for lubrication and sealing of stop valves of gas pipelines and gas distribution stations.

 For the lubrication and sealing of stop valves of gas pipelines and gas distribution stations, “Grease for gas valves” (TU 38-101316-78), “Grease SGP” (TU 38-101733-78), and “Plastic sealing grease LZ-162” were developed and produced. (TU 38-101315-77), "Grease plastic Armatol-238" (TU 38-101812-80) (see. "Fuel, lubricants, technical fluids. Assortment and application". Reference. / Edited by V. M. Shkolnikov, 2nd ed., Revised and supplemented. - M., Tekhinform Publishing Center, p.353).

"Plastic grease Armatol-238" is operable at ambient temperatures from minus 50 ^o C to plus 100 ^o C.

 This grease does not ensure the elimination of gas leaks through leaks of shut-off valves that occur during their operation. In addition, this grease and other sealing greases and pastes have a significant drawback, namely, due to the high content of mineral fillers after repeated use, these greases and pastes clog the packing channels of the valves (fillers in the form of a solid fraction are deposited on the walls of the channels, reducing the diameter of the latter). Therefore, subsequent gaskets require a significant increase in discharge pressure, which in most cases is unacceptable by the operating instructions for shut-off valves. That is, if there is a gas leak and it is impossible to eliminate it, valve replacement is required.

 The closest technical solution in terms of technical nature and the achieved result to the proposed one is grease (see Sinitsyn V.V. Grease in the USSR. Handbook. - Moscow: Chemistry, 1984, p.57) Tsiatim-201 (GOST 6267-74 )

Grease Tsiatim-201 consists of components, wt.%:
Stearic acid - 12.0-15.0
Lithium hydroxide - 1.2-2
Diphenylamine - 0.5
Mineral oil - up to 100
Its disadvantages when used in shut-off valves include the lack of sealing properties due to low dynamic viscosity (gas pressure is squeezed out of the channels), insufficient lubricating properties at high contact loads.

The technical result achieved by using the proposed technical solution is to increase the sealing properties and improve the lubricating properties of grease by expanding the temperature range of operability from minus 60 ^o C to plus 120 ^o C, ensuring environmental safety.

 Environmental safety is ensured by reliable sealing of cranes, which prevents the release of hydrocarbon gas into the atmosphere during its production, processing and transportation.

The proposed grease is operable in the temperature range from minus 60 ^o C to plus 120 ^o C and ensures the elimination of gas leaks through valve leaks arising during the operation of shut-off and control valves of gas lines.

 The technical result is achieved as follows.

A grease containing stearic acid, lithium hydroxide and petroleum distillate oil with a pour point below 45 ^o C, additionally contains cellulose, graphite, a polymer and a multifunctional additive - boron-modified zinc diacyldithiophosphate, in the following ratio, wt.%:
Stearic acid - 12.0-18.0
Lithium hydroxide - 2.0-3.0
Polymer - 0.4-8.0
Graphite - 0.05-3.0
Multifunctional additive:
Zinc dialkyldithiophosphate modified with boron - 0.1-1.0
Cellulose - 0.5-5.0
Mineral oil - up to 100
The polymer contains polyisobutylene or thermoplastic elastomer butanediene styrene or synthetic rubber ethylene propylene or atactic polypropylene.

The proposed grease is mobile (i.e. efficient) at an ambient temperature of minus 60 ^o C. Its dropping point is above 175 ^o C, which allows its intended use at temperatures up to 140 ^o C. The combination of organic filler, graphite with multifunctional additive provides high lubricating properties of the lubricant. The additional introduction of cellulose with a wide dispersed composition provides such sealing properties of the lubricant that it allows to eliminate gas leaks at gas pressures up to 7.5 MPa. This fact is especially important due to the fact that the elimination of gas leaks into the atmosphere in addition to the economic effect ensures environmental safety and also reduces the likelihood of emergencies during the production, processing, transportation and use of natural gas.

 Stearic acid (technical stearin).

The lower limit of the content of stearic acid in the proposed lubricant is limited to 12%, because with a lower content, the required heat resistance is not achieved - the dropping point of the lubricant is below 175 ^o C, the upper limit of 18% is limited by the loss of plasticity of the lubricant (penetration decreases to below 150 points) and its mobility.

 Technical stearin is made according to GOST 6484-64 or use imported antique.

Lithium hydroxide:
The lower 2.0% and upper 3.0% limits correspond to the stoichiometric amounts necessary to neutralize stearic acid.

As the polymer in the proposed lubricant use:
- polyisobutylene P-20 (TU 38-10-2257-80);
- thermoplastic elastomer butadiene styrene (TU 38.103267-80);
- synthetic ethylene-propylene rubber (SKEPTOL TU2243-002-48896943-99);
- atactic polypropylene (TU 6-05-19-02-81).

The lower 0.4% and upper 8.0% of the polymer limits are limited by the required level of viscosity properties and adhesion at high and low temperatures. The polymer content in the lubricant below 0.4% does not allow to reach a sliding temperature of 120 ^o C, the polymer content of more than 8.0% leads to an increase in the viscosity of the lubricant at a temperature of minus 40 ^o C to a value that impedes the possibility of its pumping through the supply channels to the seal cranes.

 Graphite.

 The introduction of graphite into the lubricant provides an increase in lubricating properties at high loads, prevents sticking of rubbing surfaces and provides a grease color from gray to black.

 A graphite content below 0.05% does not prevent sticking of rubbing surfaces, an excess of graphite content in excess of 5.0% is not economically feasible.

 Dry graphite colloidal graphite preparations are used as graphite: C-0, C-1, C-2 (TU 113-08-48-63-90).

 As a multifunctional additive, additive A-22 (zinc dialkyldithiophosphate modified with boron), TU 0257-006-40065454-97, is used.

 The lower 0.1% and upper 1% limits of the content of additive A-22 are limited by recommendations for its use. The lower limit of the additive content allows to provide the required level of antioxidant, anti-wear and anti-corrosion properties of the proposed lubricant, the upper limit is limited by the ability of the additive to destroy the structural structure of the lubricant at high concentrations (the limit of the density of the lubricant drops sharply and the penetration rate increases).

 As a filler in the proposed grease using a mixture of particles of cellulose and graphite.

As cellulose use:
- filler DON STP 5313-001-17432726-01), which is a polydisperse mixture of particles;
- carboxymethyl cellulose (TU 6-15-1077-92, TU 6-55-40-90, TU 2385-001-42245052-99).

 The lower limit of 0.5% of the content is limited by the sealing ability of the lubricant (reliable sealing is not ensured below 0.5%), the upper limit of 5% is limited by the ability of the lubricant to pump to the seal through the supply channels and check valves.

As mineral oil use low-viscosity petroleum oils:
- the basis of washing oil "Volna" (TU 38-301-29-40-92);
- spindle oil AU (TU 38.1011232-89 with amendment 1 or TU 38.301-29-71-97).

 Grease for gas valves (code name SAG type 2) is prepared as follows.

30-50% of the calculated amount of oil is loaded into a heated stirrer. The oil is heated to 65-70 ^o C with stirring and the required amount of stearic acid is charged. After the stearic acid is melted, the calculated amount of an aqueous lithium hydroxide solution is loaded into the mixer. At a temperature of 85 to 95 ^{° C.} , stearic acid is neutralized with lithium hydroxide. The mixture of oil and lithium soap of stearic acid is heated to the temperature of complete evaporation of water. Then, the remaining calculated amount of oil and polymer is loaded into the mixer. The oily base of the grease, thickened with polymer, is mixed in a mixer until a homogeneous mixture is obtained and poured into a container. Heat treatment and cooling of the lubricant base is carried out by pumping the mixture through an electric heater (heating to 240 ^o C), followed by cooling the melt in a thin layer on a refrigeration drum. Cooled to a temperature of 40-80 ^o With the grease base is cut off from the surface of the rotating drum and enters the drive agitator. The cooled lubricant base is pumped to another mixer mixer as it accumulates. Then, the calculated amount of additive and filler particles of cellulose and graphite are loaded into the mixer-mixer. Mixing and dispersion is carried out in the last mixer with the simultaneous operation of the mixing device and the circulation pump for 15-30 minutes. Ready grease is packaged using a pump in a container.

SAG grease type 2 is used in shutoff valves of gas pipelines, where it is supplied with special stuffing devices under pressure up to 15 MPa at an ambient temperature from plus 40 ^o С to minus 50 ^o С.

 Examples of grease.

Example 1
20.0 kg of Volna oil are placed in a heated stirrer and heated to 75 ^° C with stirring. Then 15.0 kg of stearic acid are charged and the temperature in the mixer is brought to 85 ^° C. After this, 2.5 are added to the stirrer kg of lithium hydroxide in the form of an aqueous solution and stirring is continued at a temperature of 95 ^o C for 30 minutes to neutralize stearic acid. Then, a mixture of oil and lithium soap of stearic acid is dehydrated with stirring and heating from 95 to 140 ^o C. After that, 5.0 kg of polyisobutylene of grade P-20, 50.0 kg of Wave oil are loaded into the mixer. The oily base of the lubricant with polyisobutylene is mixed in the mixer for 10 minutes and discharged into a container, from where it is continuously pumped through the flow-type electric heater, where it is heated to a temperature of 225 ^o C, onto a rotating drum for cooling in a thin layer to a temperature of 60 ^o C. Cooled grease cut off from the surface of the drum and enters the mixer-drive. After heat treatment and cooling of the entire mass of the grease base, it is pumped to the mixer mixer and A-22 additive (0.5 kg), graphite (1.5 kg) and cellulose-filler DON (2.5 kg) are fed there. A mixture of a grease base with an additive and fillers is mixed while the mixing device and the circulation pump are operating at a temperature of 40-60 ^o C for 15 minutes After mixing, a lubricant sample is beaten off for physicochemical analyzes. Upon receipt of positive test results, the lubricant is packaged with pumps in a container.

 Thus, lubricant samples 2, 3 and 4 were obtained (see table 1). The tests were carried out by standard and research methods.

The ability of a lubricant to eliminate gas leaks through leaks of ball and plug valves (sealing ability) was evaluated on a laboratory bench, which is a capsule with a volume of ~ 4 cm ³ with holes with a diameter of 0.8 and 1.2 mm, which is hermetically connected through a reducer to a gas cylinder with nitrogen under a pressure of 8.0 MPa. The capsule is pre-filled with grease, connected to the gearbox. Gas is supplied to the lubricated capsule at a pressure of 7.5 MPa. Lubrication passes the test if it prevents gas leakage through the hole in the capsule. In addition, tests of lubricant samples were carried out on plug and ball valves in real conditions of their operation on gas pipelines. In this case, cranes having gas leaks were selected.

 The test results of the SAG grease type 2 and control samples are presented in table 2.

 The test results presented in table 2 indicate that samples 1-4 of the SAG type 2 grease are superior to Tsiatim-201 grease, as well as Armatol-238 grease (similar in purpose) in terms of heat resistance and colloid stability, and most importantly, they have effective sealing ability, manifested both in laboratory bench-top and in real-life operating conditions of shut-off valves in main gas pipelines.

Comparing the effectiveness of the proposed technical solution with the known, we can conclude that the proposed technical solution:
- increases the sealing ability by selecting the optimal component composition of the lubricant (mineral oil, polymer, cellulose and graphite), which reduces gas losses, improves environmental conditions in the zone of gas pipelines and their fire and explosion safety;
- has non-deficient lubricant components and its cost is not high;
- the proposed lubricant is non-toxic and explosion proof.

 When using application materials, you must contact the authors of the proposed technical solution.

Claims (1)

1. A grease containing stearic acid, lithium hydroxide and petroleum distillate oil with a pour point below minus 45 ^o C, characterized in that it additionally contains cellulose, graphite, polymer and a multifunctional additive - zinc dialkyldithiophosphate, modified with boron, in the following ratio of components , in wt.%:
Stearic acid - 12.0-18.0
Lithium hydroxide - 2.0-3.0
Polymer - 0.4-8.0
Graphite - 0.5-5.0
Multifunctional additive - 0.1-1.0
Cellulose - 0.5-5.0
Mineral oil - Up to 100
2. Grease according to claim 1, characterized in that the polymer used is polyisobutylene or thermoplastic elastomer butadiene-styrene or synthetic rubber ethylene-propylene or atactic polypropylene.

Images