RU238696U1 - Gate valve with wear-resistant coating of drive friction elements - Google Patents

Abstract

This utility model relates to shut-off devices and can be used in the oil refining industry, particularly in catalytic cracking units. A gate valve with a wear-resistant coating on its drive friction elements comprises a housing with inlet and outlet zones, a support cone, a support plate, guides, a gate disc, an actuator with a stem, and a sealing gland with a tip. The stem and gland tip have a wear-resistant coating for high temperatures. The wear-resistant coating has a hardness of at least 50 HRC and is resistant to temperatures up to 800°C. The use of the wear-resistant coating improves the protective properties of the gate valve's structural components. 4 clauses, 2 figs.

Description

This utility model relates to shutoff devices and can be used in the oil refining industry, particularly in catalytic cracking units. Gate valves are used to regulate the flow of feedstock, catalyst, and other process fluids during the cracking process.

During operation of gate valves in catalytic cracking units, some structural elements are subject to abrasion and wear, which leads to frequent repairs and replacement of particularly important structural elements.

A gate valve is known (patent RU 91611 U1), which contains a locking element in the form of a plate with parallel sealing surfaces and sealing seats located on the valve body, which contact the sealing surfaces of the locking element, in which the sealing surfaces of the locking element and the surface of the seats on the side of contact with the sealing surfaces of the locking element are made in the form of a layer of coating sprayed by a gas-thermal method based on tungsten carbides, chromium, titanium, silicon on a binder of nickel or cobalt alloys, including nickel-chromium, cobalt-chromium, nickel-tungsten, nickel-titanium, self-fluxing alloys, including nickel-chromium-boron-silicon, with inclusions at the grain boundary of the sprayed coating of nanoparticles, including oxides of aluminum and / or titanium, wherein the content of nanosized oxides lies in the range from 0.05 up to 5 wt.%.

The disadvantages of the well-known analogue are:

- Lack of protection of moving parts;

- The presence of nanoparticles in the coating can lead to uneven wear, especially under high loads.

A "Gate Regulating Device" (Patent RU 57409 U1) is known. The gate regulating device comprises a housing with a bypass channel, guides, which are made in the form of plates rigidly fixed in the housing, made of a material resistant to corrosion and/or abrasive wear and equipped with windows corresponding to the bypass channel in shape and cross-sectional area, a gate plate made of a material resistant to corrosion and/or abrasive wear, placed between the guide plates in a sliding fit, and a drive for reciprocating movement of the gate plate between the "closed" and "open" positions. To increase reliability, the bypass channel of the housing is lined with sleeves, which are at least partially made of a material resistant to corrosion and/or abrasive wear, serve as stops for the guide plates and are fixed in the housing from axial displacement by thrust threaded bushings, and the gate plate has a window in the upper part for the passage of fluid.

Disadvantages of the device:

- The technological complexity of precise assembly of the structure leads to the risk of uneven distribution of loads and the formation of microcracks.

- Lack of protection of moving parts.

The closest analogue (prototype) was chosen to be the spool valve disclosed in patent US 5,301,712 A. The spool valve comprises a body having an outer metal shell and a refractory lining forming a through channel having an inlet and an outlet, as well as a side opening intersecting the flow channel, intermediate between the inlet and the outlet, a groove located on each side of the lining, extending transversely from the side opening outside and on opposite sides of the flow channel, forming an opposite guide on each side of the flow channel, a diaphragm with an opening that can be shifted through the side opening in the grooves. The refractory lining, which was preferably cast in place and thus fixed to the inner surface of the metal shell to form a through channel. The metal mesh is attached to the inner surface of the metal shell, for example, by welding, and the refractory material is cast in place and then shaped, for example, using molds, trawls, etc., to form the flow channel. The cast refractory lining, which forms the inlet, has a conical surface that extends downward and inward from its upper end to the opening at its intersection with the side opening, and a conical surface.

Disadvantages of the prototype (US 5301712 A):

- Lack of protection for moving parts: the rod and seal in the analogue do not have a wear-resistant coating, which leads to rapid abrasion and wear due to the movement of the rod while the seal is immobile.

- Low thermal stability: the refractory lining is prone to cracking due to temperature changes.

- Complex sealing: sealing by pressing the plate requires perfect guide geometry, which is disrupted by wear.

The technical problems that the claimed technical solution is aimed at solving are:

1. Reduction of wear of drive friction elements.

2. Increasing the service life of the gate valve structural elements and the interval between repairs by increasing the durability of key components.

3. Increasing the reliability of the device in conditions of high temperatures and abrasive environments.

The technical result of the claimed utility model: improving the protective characteristics of the structural elements of a gate valve through the use of a wear-resistant coating.

The technical result is achieved due to the fact that the gate valve with a wear-resistant coating of the friction elements of the drive contains a housing with an input and output zone, a support cone, a support plate, guides, a gate disk, a drive device with a stem and a sealing gland with a tip, wherein the stem and the tip of the gland have a wear-resistant coating made of a material with a hardness of at least 50 HRC and resistant to temperatures up to 800°C, for example, from Tribaloy T-800 material and applied by surfacing.

The device is illustrated by the following figures:

Fig. 1 - gate valve in section.

Fig. 2 - view of the connection of the rod and the gate disk.

The gate valve consists of a housing (1) made of heat-resistant metal, with clearly defined inlet and outlet zones. Inside the housing are a support cone (2), a support plate (3), guides (4), a gate disc (5), and an actuator (6) including a stem (7) and a sealing gland with a tip (8). The actuator mechanism, located inside the actuator (6), can operate with both a manual and a hydraulic drive. The actuator mechanism actuates the stem (7) - a cylindrical connecting rod installed in a groove of the gate disc (5) to transmit reciprocating motion from the actuator (6) between the "open" and "closed" positions. A sealing gland with a tip (8) is used to fix the stem (7) and ensure a tight seal.

The rod (7) and the inner surface of the tip (8) of the seal are subject to the greatest wear and tear due to the mobility of the rod while the seal is stationary.

The main innovation of this technical solution is the application of a wear-resistant, high-temperature coating to the stem (7) and tip (8) of the gland. This solution is also suitable for components located in areas where lubrication is impossible. The coating must be made of a material with high wear and corrosion resistance, which significantly reduces wear on these components during operation. The material must have a hardness of at least 50 HRC and be able to withstand temperatures up to 800°C. This coating increases the durability of the device and extends the interval between repairs. The requirement for a hardness of at least 50 HRC is due to the need to ensure high operational reliability under significant mechanical, abrasive, and corrosive loads. Gate valves operate in environments with high pressures, abrasive particles, and aggressive substances, which places increased demands on the wear resistance and strength of the structural components.

Justification for hardness requirements:

- a hardness of 50 HRC provides increased resistance to abrasive wear that occurs when the gate comes into contact with the guides during operation;

- materials with a hardness of at least 50 HRC have high resistance to plastic deformation and crack formation under cyclic and impact loads;

- high hardness prevents changes in the geometric parameters of parts (e.g. gaps and profiles of sealing surfaces), which is critical for ensuring the tightness and functionality of the valve.

Consequences of reduced hardness:

- a decrease in hardness leads to accelerated wear of the working surfaces, an increase in gaps and a loss of the valve's tightness;

- under mechanical loads, plastic deformations may occur, which disrupts the functionality of the valve and can lead to jamming of the gate;

- a decrease in hardness reduces the service life of parts, increasing the frequency of maintenance and replacement of components;

- wear and deformation of sealing surfaces lead to leaks of the working medium, which is unacceptable in systems with high pressures or hazardous substances.

Using components with a hardness below 50 HRC will result in the valve becoming less reliable, more likely to fail, and requiring repair. In critical oil and gas systems, this can lead to serious accidents and financial losses. Therefore, a hardness of 50 HRC is the minimum threshold that ensures the longevity and safe operation of a gate valve.

Examples of materials that are suitable for high temperature conditions and can be applied using methods similar to cladding, such as thermal spraying or laser machining:

- Stellite 6, Stellite 21: cobalt-containing alloys with high wear resistance;

- Colmonoy 88, Colmonoy 6: nickel-containing alloys, resistant to wear;

- WC-Co, Cr3C2-NiCr: carbide coatings applied by thermal spraying;

- Tribaloy T-400, T-700, T-800: other Tribaloy grades with similar properties.

Carbide coatings, such as WC-Co, can provide even greater hardness, but their brittleness requires caution when used under thermal cycling conditions. Therefore, Tribaloy T-800, with the following characteristics, was chosen as the primary and optimal coating material:

- base material - Co (cobalt); Cr (chromium) content: 17.5%; Mo (molybdenum): 28.5%; C (carbon): <0.08%; Si (silicon): 3.4% and others: Ni (nickel), Fe (iron);

- density: 8.5 g/ ^cm3 ;

- hardness HRC: 54-62;

- tensile strength: 1105 MPa;

- yield strength: 815 MPa;

- impact strength: 181 J/cm ³ ;

- coefficient of thermal expansion: 12.9×10-6°C;

- thermal conductivity: 17.3 W/(m×K).

Due to its hardness, Tribaloy T-800 alloy is wear-resistant and highly resistant to abrasive wear and erosion. It is also resistant to pitting, crevice corrosion, total corrosion, and stress corrosion cracking. The material does not require heat treatment to develop its mechanical properties and has excellent weldability.

The material is applied using a surfacing method, which includes the following main stages:

1. Surface preparation:

- the surface of the part must be cleaned of dirt, oxides and grease.

- mechanical processing (e.g. grinding) to ensure good adhesion of the welded material.

2. Selecting the surfacing method:

- Gas surfacing (gas flame): uses an acetylene-oxygen flame. Suitable for small parts or repair work.

- Arc surfacing: includes methods such as manual arc welding (MMA), argon arc welding (TIG) and plasma surfacing.

- laser cladding: A high-precision method that minimizes thermal impact on the base.

- surfacing with flux-cored wire: a special wire with Tribaloy T-800 powder is used.

3. Surfacing:

- the surfacing material (powder, wire or rod) is applied to the surface of the part using the selected method.

- It is important to control the heating temperature to avoid deformation or cracks.

- surfacing can be performed in several layers to achieve the required coating thickness.

When welding, the recommended coating thickness is 0.5-2 mm (preferably 1.8 mm). This coating thickness provides wear protection, corrosion resistance, and heat resistance.

Reducing the coating thickness to less than 0.5 mm results in a reduced service life and a risk of corrosion.

Increasing the coating thickness by more than 2 mm increases the risk of cracks, insufficient adhesion and defects.

4. Cooling:

- After surfacing, the part must be cooled slowly to minimize internal stresses and prevent cracking.

5. Mechanical processing:

- After surfacing, grinding or machining may be required to achieve the desired geometry and surface finish.

Operating principle:

When the actuator is activated, the stem transmits reciprocating motion to the gate disc, which moves along guides, regulating the flow of fluid between the "open" and "closed" positions. A wear-resistant coating on the stem and gland tip reduces friction and wear when these elements meet, ensuring reliable and stable operation even under intensive use.

Claims (5)

1. A gate valve with a wear-resistant coating on the friction elements of the drive, comprising a housing with an input and output zone, a support cone, a support plate, guides, a gate disc, a drive device with a stem and a sealing gland with a tip, characterized in that the stem and the tip of the gland have a wear-resistant coating made of a material having a hardness of at least 50 HRC and resistant to temperatures up to 800°C. 2. A gate valve according to paragraph 1, characterized in that the wear-resistant coating is applied by surfacing. 3. A gate valve according to item 1, characterized in that the wear-resistant coating is made of Tribaloy T-800 material. 4. A gate valve according to paragraph 1, characterized in that the thickness of the wear-resistant coating is 0.5-2 mm. 5. A gate valve according to paragraph 1, characterized in that the thickness of the wear-resistant coating is 1.8 mm.