Valve connection, maintenance, grease and other knowledge knowledge: valve gasket installation method and main matters

Valve connection, maintenance, grease and other knowledge knowledge: valve gasket installation method and main matters

Valve connection mode Valve installation Valve grease maintenance Common problems in the application of matching electric actuator valves

Valve connection mode

1. Flange connection:

This is the most commonly used connection form of the valve. According to the shape of the combined surface, it can be divided into the following types:

1, smooth type: for pressure is not high valve. Processing is more convenient

2, concave and convex type: high working pressure, can use a hard washer

3. Mortise and groove type: gasket with large plastic deformation can be used in erosive medium, and the sealing effect is better.

4, trapezoidal groove type: with oval metal ring gasket, used for working pressure ≥64 kg/cm2 of the valve, or high temperature valve.

5, lens type: the washer is the shape of the lens, made of metal. High pressure valves with working pressure ≥ 100kg/cm2, or high temperature valves.

6, O-ring type: this is a new form of flange connection, it is followed by a variety of rubber O-ring, and developed, it in the sealing effect of the connection form.

Two, clamp connection:

A connection in which the valve and two pipes are threaded together directly by bolts.

Three, butt welding connection:

Install valves welded directly with pipes

1, before the valve installation, should carefully check whether the valve model, specifications and design are consistent;

2, according to the valve model and factory copy check check whether the valve can be applied under the premise of requirements;

3. When hoisting the valve, the rope should be tied to the flange connection of the valve body and the valve cover, and not tied to the handwheel or valve stem, so as not to damage the valve stem and handwheel;

4. When installing the valve on the horizontal pipe, the valve stem should be vertically upward, and the valve stem should not be installed downward;

5. When installing the valve, it is not allowed to use the forced pair connection mode, so as not to cause damage due to uneven force;

6, open rod gate valve should not be installed in the underground wet place, so as to avoid valve rod rust.

Supporting electric actuator

Electric actuator and valve matching, used in automatic control system. There are many kinds of electric actuators, and they are different in the way of action. For example, the angular travel electric actuator is the output corner torque, and the direct travel electric actuator is the output displacement thrust. The type of electric actuator in the system application should be selected according to the work needs of the valve.

Four, threaded connection:

This is a simple connection method, often used for small valves. There are two more cases:

1, direct sealing: internal and external threads directly play a sealing role. In order to ensure that the joint does not leak, often filled with lead oil, thread and polytetrafluoroethylene raw material belt; The polytetrafluoroethylene raw material belt, the use of daily; This material erosion resistance function is very good, sealing effect is good, use and retain convenience, disassembly, can be completely removed, because it is a layer of non-viscous film, than lead oil, thread linen much better.

2. Indirect sealing: The strength of screw tightening is transferred to the washer between the two planes, so that the washer plays a sealing role.

Five, sleeve connection:

Sleeve connection, its connection and sealing principle is, when tightening the nut, the sleeve under pressure, so that the edge bite into the outer wall of the pipe, the outer cone of the sleeve and the joint body cone close under pressure, so that can reliably prevent leakage.

The advantages of this form of connection are:

1. Small size, light weight, simple structure, easy disassembly and assembly;

2, even relay strong, wide range of use, can withstand high pressure (1000 kg/cm2), high temperature (650℃) and impact vibration

3, can choose a variety of materials, suitable for erosion prevention;

4, processing accuracy requirements are not high; Easy to install at high altitude.

The sleeve connection form has been used in some small diameter valve products in China.

Six, clamp connection:

This is a quick connection method that requires only two bolts and is suitable for low pressure valves that are often removed.

Seven, internal self-tightening connection:

The above connection forms, are the use of external force to offset the medium pressure, to achieve sealing. A self-tightening connection using medium pressure is described below. Its sealing ring is installed in the inner cone, with the medium opposite side into a certain Angle, medium pressure to the inner cone, and transfer to the sealing ring, at a certain Angle of the cone, produce two components, one and the valve body Central Line parallel outward, the other pressure to the inner wall of the valve body. The latter component is the self-tightening force. The greater the medium pressure, the greater the self – tightening force. So this type of connection is suitable for high pressure valves. It is more than the flange connection, to save a lot of materials and manpower, but also needs a certain preload, so that in the valve pressure is not high, reliable use. Valves made of self – sealing principle are generally high – pressure valves. There are many forms of valve connection, such as small valves that do not need to be removed, welded together with pipes; Some non-metallic valves, the use of socket connection, and so on. Valve users should be treated in detail according to the condition.

Related accessories

There are valves and fittings, which are used in the connection or control system of pipes. Valves and fittings can not exist, complement each other. Valve fittings are carbon steel and stainless steel, and PVC, or other materials, commonly used is the first two, in recent years with the progress of people’s living level, the demand for food also followed by a large. So it drives the rapid development of food machinery, so stainless steel sanitary valve fittings out of the industrial boom, people usually say that valve fittings, mostly still stainless steel sanitary grade.

Grease injection maintenance

The professional maintenance work of the valve before and after production before welding plays a vital role in the service of the valve in the production and operation. Accurate and orderly and effective maintenance will protect the valve, make the valve function normally and extend the service life of the valve. Valve maintenance may seem simple, but it is not. There are often overlooked aspects of work.

When valve grease is injected, the quantity of grease is often ignored. After the grease is added, the operator chooses the valve and the grease connection mode and carries out the grease work. There are two situations: on the one hand, the amount of fat injection is less, and the sealing surface is accelerated by the lack of lubricant. On the other hand, fat injection is excessive, resulting in extravagance. Is not according to the valve type type, the different valve sealing capacity for accurate calculation. Can be calculated by valve size and type sealing capacity, and then a reasonable amount of grease injection.

Second, valve grease, often ignore the pressure problem. During the operation of grease injection, the pressure of grease injection regularly changes in peaks and valleys. If the pressure is too low, the seal leaks or fails. If the pressure is too high, the grease filling port is blocked, the grease in the seal is hardened, or the sealing ring is locked with the valve ball or valve plate. Usually when the grease injection pressure is too low, more grease is injected into the bottom of the valve chamber, which generally occurs in small gate valves. If the injection pressure is too high, on the one hand, check the injection nozzle, and replace it if the obstruction of the fat pore is determined; On the other hand is lipid hardening, to use cleaning fluid, repeatedly soften the failure of the seal grease, and inject new grease replacement. In addition, sealing type and sealing material, also affect the fat injection pressure, different seal forms have different fat injection pressure, in general, hard seal fat injection pressure is higher than soft seal.

Third, when the valve grease, pay attention to the valve in the switch position. Ball valve maintenance is generally in the open state, special circumstances choose closed maintenance. Other valves can not be treated in open position. Gate valve must be in a closed state when maintenance, to ensure that the grease along the sealing ring is covered with sealing groove, if open, sealing grease will directly fall into the flow channel or valve chamber, resulting in extravagance.

Fourth, valve grease, often ignore the problem of grease effect. The pressure, the amount of grease and the switch position in the grease injection operation are normal. However, in order to ensure the valve grease effect, sometimes it is necessary to open or close the valve, check the lubrication effect, and confirm the average lubrication of the valve ball or ram surface.

Fifth, grease, should pay attention to valve body blowdown and wire plugging pressure relief problems. After the valve pressure test, the gas and water in the valve chamber of the sealing chamber will increase the pressure due to the increase of the ambient temperature. During the grease injection, the pressure relief should be improved to facilitate the smooth grease injection. After grease injection, the air and water in the sealing cavity are fully replaced. Timely release of valve chamber pressure, but also to ensure the safety of valve use. After the grease injection, be sure to tighten the blowdown and pressure relief wire plug to prevent accidents.

Sixth, fat injection, we should pay attention to the problem of fat average. During normal fat injection, the fat hole near the interval fat injection mouth is the first to produce fat, and then to the low point, the *** is the high point, and the fat is produced successively. If not according to the rule or not fat, it is confirmed that there is blockage, timely clearance treatment.

Seventh, grease should also observe the valve diameter and sealing ring seat flush problem. For example, ball valve, if there is open interference, can be adjusted to the open limiter, confirm the straight diameter after locking. Adjust the limit not only the pursuit of open or close side position, to consider the whole. If the opening position is flush and not closed in place, it will cause the valve to close loosely. Similarly, adjust the close in place, but also consider the corresponding adjustment of the open position. Make sure the valve has a right Angle stroke.

Eighth, after fat injection, be sure to seal the fat injection mouth. Avoid the entry of impurities or lipid oxidation at the grease injection mouth. The cover should be coated with anti-rust grease to avoid rust. For the next manipulation.

Ninth, fat injection, but also to consider in the future oil sequential transmission of detailed topics in detail. Given the different qualities of diesel and gasoline, the flushing and decomposition capacity of gasoline should be considered. In the future, when the valve is operated and the gasoline section is met, grease should be added in time to prevent wear and tear.

Tenth, when fat injection, do not ignore the fat injection of the valve stem. The valve shaft part has a sliding shaft sleeve or packing, also need to maintain lubrication, in order to reduce the friction resistance during the operation, if can not ensure lubrication, the electric control torque increase wear parts, manual control switch effort.

Eleven, some ball valve body marked with arrows, if there is no English FIOW handwriting, for the sealing seat direction, not as a medium flow reference, the direction of the valve self-discharge. Normally, two-seat sealed ball valves have two-way flow.

Twelfth, valve maintenance, but also pay attention to the electric head and its transmission of water problems. Rain that penetrates especially during the rainy season. One is to rust the motor structure or the transmission shaft sleeve, and the other is to freeze in winter. Cause the electric valve operation torque is too large, damage the transmission parts will make the motor no-load or super torque protection jump can not achieve electric control. The transmission unit is damaged and manual control is not possible. After the super torque protection action, manual control is also unable to switch, such as forced control, will damage the internal alloy parts.

The friction torque is small and the return difference is small.

Why the use of rubber lined butterfly valve, fluorine lined diaphragm valve for desalting water medium short service life /p>

The desalted water medium contains low concentration of acid or base, which has greater erodibility to rubber. Rubber erosion performance is expansion, aging, low strength, with rubber lined butterfly valve, diaphragm valve use effect is poor quality is caused by rubber erosion resistance. After the rubber lined diaphragm valve is improved into a fluorine lined diaphragm valve with good corrosion resistance, but the diaphragm of the fluorine lined diaphragm valve can not withstand up and down folding and is broken, resulting in mechanical damage, and the life of the valve is shorter. Now the better way is to treat the ball valve with water, it can be used to 5 ~ 8 years. The sealing gasket is a sealing spare part often used in machinery, equipment and so on. It is a sealing material. From this definition, it is not difficult for us to know how important the sealing gasket is, so how to install the sealing gasket is worth facing. Accurate installation can ensure the sealing function, so that the equipment runs smoothly, otherwise it will damage the sealing gasket. Now, let’s look at how to do that in more detail. The accurate installation of gaskets should be carried out under the condition that the flange connection structure or thread connection structure, static sealing surface and gasket are inspected without doubt, and other valve parts are intact.

Sealing gasket is a sealing spare part often used in machinery, equipment and so on. It is a sealing material. From this definition, it is not difficult for us to know how important the sealing gasket is, so how to install the sealing gasket is worth facing. Accurate installation can ensure the sealing function, so that the equipment runs smoothly, otherwise it will damage the sealing gasket. Now, let’s look at how to do that in more detail.

The accurate installation of gaskets should be carried out under the condition that the flange connection structure or thread connection structure, static sealing surface and gasket are inspected without doubt, and other valve parts are intact.

1. Before installing gaskets, the sealing surface, gaskets, threads and rotation parts of bolts and nuts are coated with a layer of graphite powder or a sliding agent blended with oil (or water) of graphite powder. Gaskets and graphite should be kept clean.

2, gasket installed on the sealing surface to meet, accurate, can not skew, can not extend into the valve cavity or the shoulder of the table.

3. The installation gasket only agrees to install one piece, and does not agree to install two or more pieces between the sealing surface to eliminate the gap between the two sealing surface.

4. The sealing of the elliptic gasket should make the inner and outer ring of the gasket contact, and the two end faces of the gasket shall not contact with the bottom of the groove.

5, O ring installation, in addition to the ring and groove should meet the design requirements, the amount of compression should be appropriate, under the condition of sealing, compression deformation rate as small as possible, can extend the life of the O ring.

6. Before the gasket is on the top cover, the valve should be in the open position, so as not to affect the installation and damage the valve parts. When the cover should be aligned with the position, do not use the way to push and pull contact with the gasket, so as to avoid the displacement and abrasion of the gasket.

7. The installation of gaskets connected by bolts or threads shall make the gaskets in a horizontal position (the gasket cover connected by threads shall not use pipe pliers if there is a wrench).

8. Before the gasket is pressed, it is necessary to understand clearly the pressure, temperature, nature of the medium and characteristics of the gasket material and determine the preloading force. Preload should be ensured in the case of pressure test without leakage, as far as possible to reduce.

9. After the gasket is tightened, it should be ensured that the connecting parts have a pre-tightening gap, so that there is room for pre-tightening when the gasket leaks.

10. When working at high temperature, the bolt will produce high temperature creep, resulting in stress relaxation and deformation increase, leading to the leakage of the gasket and the need for hot tightening; On the contrary, under the premise of low temperature, bolts will shrink and need to be loosened.

11, sealing surface using liquid sealing gasket, the sealing surface should be cleaned or surface treatment. The plane sealing surface should be ground and matched, the coating adhesive should be average, and the air should be excluded as far as possible. The adhesive layer is generally 0.1-0.2mm.

12. When the thread seal is made of PTFE film tape, the starting point of the film should be pulled thin and glued to the thread surface, and then the excess tape at the starting point is removed, so that the film glued to the thread is wedged.

Through the above introduction, we know how to install the sealing gasket. Installation is not complicated, just need to pay attention to the details, the details are handled well, the installation can be smooth. Accurate installation is related to the sealing and operation of the equipment, so the installation and operation staff should keep the above matters in mind and check them when installing.