The safety valve is a pipeline fitting that protects high-pressure equipment and pipelines from mechanical damage and various kinds destruction as a result of emergencies. This is achieved by venting excess liquid, gas or vapor from the system, as well as vessels in which excessive pressure is formed. In addition, this valve prevents the discharge working environment when the nominal pressure is restored.

A safety valve is a mechanism that operates in direct contact with the working medium, together with other structures that perform the function of protective fittings, including pressure regulators.

The main types of valves and their purpose

All safety products may differ from each other in a number of parameters, depending on design features, namely:

1. Closing valve type:
   • proportional;
   • on-off.
2. According to the lifting height of the closing body:
   • low-lift;
   • medium-lift;
   • full-lift.
3. Depending on the type of load on the spool:
   • spring;
   • lever;
   • lever-spring;
   • magnetic spring.

Also, safety valves may differ in the nature of their operation and be direct or non-direct devices. direct action. The former are considered classic safety mechanisms, while the latter belong to the class of impulse devices. The most commonly used modification in the industry is the spring type angular safety choke.

High pressure (or rather, its excess) can occur in the system for various reasons caused by physical internal processes or other external factors, such as:

equipment malfunctions;

unwanted heat input from the outside;

errors in the collection of thermal-mechanical circuits. The safety valve is often installed in places where there is a possibility of such complications. These devices are compatible with almost any equipment, but they are most in demand when used with domestic or industrial tanks operating under high pressure conditions.

Spring Type Relief Valve

Spring-loaded safety valves protect the equipment, and thereby prevent its destruction, as a result of exceeding the pressure above the norm. They are used on boilers, various tanks, tanks, pipelines and perform the function of dumping the working medium. The surplus can simply be discharged into the atmosphere or into a special discharge pipeline system. After the pressure returns to normal, the valve closes. The main characteristics of the safety spring valve are its throughput, as well as the value of the response pressure. The latter is configured on special equipment at the factory, and to test the operation of the device, or to remove dirt that accumulates during operation, the valves have a device that allows you to manually open this device, although some modifications can do without it. For efficient and reliable operation of the valve in a gaseous medium, a forced airflow device may be present in its design. In spring valves, the pressure of the medium on the gate is opposed by the degree of compression of the spring. It is she who determines the actuation force, and the range of adjustments depends on the elasticity of the spring used. This fitting has gained wide popularity due to its simple design, easy settings and a wide range of these products. All this allows you to choose the most suitable model for use in specific conditions. The safety choke is mounted vertically. The locking element in the spring valve device is a butterfly valve. A special device, along with a spring, sets the clamping force and, in the event of overpressure, the declared downforce is not enough to hold the medium. As a result, the process of removing its excess from the system takes place until the pressure level is normalized to the initial level. You can learn more about the device and design features of a particular spring valve by examining its passport. Its main components are the locking body, consisting of a valve and a seat, as well as a setter. The adjuster allows you to adjust the valve. It is very important that the spool fits snugly against the seat and prevents leakage. These adjustments are made with a screw. The shutter, as a rule, closes when a pressure appears, which is less than the working one by 10%.

Lever Type Safety Valves

A lever valve is a device in which the shut-off element is sealed with a spring or weight. The purpose of such valves is invariably - the discharge of excess volume of the working medium in the event of an excessive increase in pressure. Adjust the lever valve so that at normal pressure readings, the valve always remains in the closed position. The valve spool feels the pressure of two forces at once - it can be a load or a spring, as well as directly the working substance. The load is fixed on the arm of the lever and its weight is transferred to the valve stem. At predetermined pressure parameters, the force of pressing the valve to the seat must be higher than the pressure force of the working medium and, accordingly, the valve is held in the closed position. With increasing pressure, at a certain moment the downforce becomes equivalent to it and it is at this moment that the valve opens. During the period when the valve is open, the excess working medium is taken in, as a result of which the pressure in the system decreases. After that, the valve is again pressed against the seat and the valve closes. The vast majority of lever valves are made in the form of an angular body (the angle of the fittings is 90 degrees). But there are also such designs in which the fittings are located on the same axis. This body is called a passage. The main purpose of lever valves is to protect against all kinds of emergencies. Due to this this species reinforcement is considered a particularly important critical node. Like any other product, lever valves must meet certain requirements:

• operation in the event of excessive pressure should be carried out quickly and without any complications, and when its performance drops to normal, the valve must return to the closed position;
• the flow capacity of a single valve must be sufficient and equivalent to the amount of the supplied working medium.

Each node of the pipeline system plays an important role in ensuring its performance. For example, a safety spring valve is a pipe fitting that is required to protect against destruction when excessive pressure appears in the pipeline. This is possible by releasing the environment from the system.

Another spring valve ensures the termination of the discharge of the medium when the operating pressure is within the normal range.

Features and principle of operation

The spring-type safety valve is a direct-acting valve that operates from the medium. Where can excess pressure appear in the system? As a rule, the reason lies in external and internal factors:

• incorrectly assembled thermal mechanical circuit;
• heat transfer from sources;
• equipment is not functioning properly.

The spring-loaded safety coupling valve is installed wherever there is a risk of excessive maximum pressure. As a rule, these are household or industrial storage vessels operating under pressure.

The great popularity of this fitting provides simple design, easy settings, product range. After all, such a variety and possibilities allow you to choose the optimal model for specific conditions.

The safety choke is mounted vertically. The device of a spring-loaded flanged safety valve implies the use of a disk valve as a locking element, which, when locked, is located between the seats.

Downforce is set using special device and springs for safety valves.

When the pressure is very high, the specified downforce is not enough to contain the medium, so the excess is removed until the pressure equalizes to the working level.

The passport for the safety spring valve allows you to find out about the design of the product. The main components are the setter and the locking body. The latter consists of a saddle and a shutter.

It is adjusted by means of a dial so that the spool is properly pressed against the seat to prevent the passage of medium. Adjustment is done with a screw.

The closing pressure of the gate is usually taken below the working one by 10 percent.

Product classification

Consider what types of safety products exist.

By the nature of the lifting of the closing body:

• two-position action;
• proportional action.

According to the height of the organ:

• full-lift;
• medium-lift;
• low-lift.

By type of load on the spool:

• cargo;
• magnetic spring;
• lever-spring;
• spring-.

According to the principle of action:

• direct - traditional safety products;
• indirect action - impulse devices.

One of the modifications widely used in industry is the angular safety spring choke.

Another principle of classification is according to the conditional diameter. For example, if a DN15 spring check valve is used, it means that the nominal diameter is 15 mm, and the DN50 check spring sleeve throttle is 50 mm.

Product characteristics

Throughput calculation is performed in accordance with GOST 12.2.085. The devices can be used in petroleum, chemical, gaseous and liquid media. Tightness is determined according to GOST 9789-75.

The closing pressure of the valve is more than 0.8 Pn, where Pn is the set pressure, which is the highest at the inlet to the valve, at which it remains in the closed state, while maintaining proper tightness.

Springs for them are most often made of steel 50HFA. spring check valve type 402 is made of cast iron.

In order to check the health of the device in working order, the SPPK spring-loaded safety valve has a solution for manual opening, purge, therefore, products without SPKK do not have the possibility of manual opening.

The dimensions of the sealing surfaces of the flanges are determined in accordance with GOST 12815-80.

As an example of one of the modifications of the device, we give the fuse 17s28nzh, corresponding to TU3742-017-00218118-2002.

The device has the characteristics:

• working pressure - 1.6 MPa;
• working medium - non-aggressive, gas, steam, water;
• body material - steel;
• sealing material – stainless steel;
• connection - flange;
• temperature - from minus 40 to plus 250 degrees;
• weight and length depend on the nominal diameter.

Nuances of choice

To choose the optimal product, it is necessary to take into account the requirements that apply to them:

• timely and trouble-free installation of a safety valve with a specified increase in the level of working pressure in the system;
• in the open position, the necessary throughput must be provided;
• timely closing of the shutter with the desired level of tightness;
• ensuring stable operation.

Cost is important when choosing. For example, let's consider how much you can buy a safety spring valve 17s28nzh: the price of a reverse clutch spring throttle is from $300.

Of course, a lot depends on the manufacturer. So, a similar Danfoss spring check valve will cost more - from $ 400.

Features of the product (video)

Installation nuances

Before installing a safety spring valve, follow these simple steps:

• check labeling;
• inspect the case for external damage;
• remove the protective cap;
• there shouldn't be any inside foreign objects;
• It should be remembered that during installation, the components of the product will heat up.

The installation process is carried out in accordance with the current safety rules and regulatory and technical standards. The choice of location, design and number of valves, as well as the direction of the discharge of the medium, is determined by the project.

The place must be selected so that free access for maintenance and repair is provided. Installation is carried out in a vertical position at the top of the vessel. Also, the installation can be performed near the vessel or pipeline, only there should not be a shut-off device between the products.

The size of the fitting cannot be less than the diameter of the inlet pipe of the valve.

Spring loaded poppet valve with a large number plates can provoke an increase in their resistance, which can change the pressure difference in the upper and bottom parts of the product. Therefore, it should be installed in the last area.

Self-installation of such devices is a complex procedure that requires experience and certain skills. Therefore, it is necessary to turn to professionals.

Faults and repairs

The leakage of the medium through the valve occurs when the pressure is lower than the setting pressure.

• delay on the sealing elements of foreign objects - it is necessary to purge the throttle;
• damage to the sealing elements - turning or grinding is performed, followed by a leak test; if the depth of damage is more than 0.1 mm, it is necessary to perform machining;
• spring deformation - it is being replaced;
• misalignment of the elements due to a large load - the load is eliminated, the discharge and intake lines are checked, it is necessary to re-tighten the studs;
• reduced opening pressure - adjustment, deformation of the spring - it is being replaced;
• poor-quality assembly after repair - eliminate all assembly shortcomings.

Repair of safety spring chokes must be trusted to professionals. The cost of the procedure will cost from $50.

Safety valves- a type of pipeline fittings designed to protect the heating system from excessive pressure. The safety valve is a direct acting valve, i.e. valves operating directly under the control of the working medium itself (as well as direct-acting pressure regulators).

Photo Designation	Name	DN, mm	Operating pressure(kgf/cm2)	Housing material	Workspace	Connection type	Price, rub
		20	16	bronze	water, steam	coupling-cap	3800
	Spring safety valve	25	16	bronze	water, steam, gas	union-coupling	12000
	Safety low lift spring valve	15-25	16	steel	ammonia, freon	tsapkovy	1200-2000
	Safety valve steel	50	16	steel	liquid or gaseous non-aggressive medium, ammonia	flanged	6660-10800
		50-80	25	steel		flanged	6000
	double-lever safety valve	80-125	25	steel	Water, air, steam, ammonia, natural gas, oil products	flanged	9000-19000
	Safety valve full lift spring	25	40	steel	water, air, steam, ammonia, oil, liquid petroleum products	flanged	20000
	Angle safety valve	50-80	16	steel	water, steam, air	flanged	12500-16000
	Single lever safety valve	25-100	16	cast iron	water, steam, gas	flanged	1500-7000
	Double-lever safety valve	80-150	16	cast iron	water, steam, gas	flanged	6000-30000
	Spring safety valve	15-25	25	steel	freon, ammonia	union-coupling	5000-7000
	Low lift safety valve VALTEC	15-50	16	brass	water, water vapor, air	coupling	860-10600
	safety valve	34-52	0,7	steel	water, steam	flanged	15000
	Spring safety valve	50-150	16	steel		flanged	20200-53800
	Spring safety valve	50-150	40	steel	water, air, steam, ammonia, natural gas, oil, oil products	flanged	20000-53800
	Spring safety valve	50-150	16	steel	water, air, steam, ammonia, natural gas, oil, oil products	flanged	20200-53800
	Safety valve spring angular.	50	100	steel	gas, water, steam, condensate	flanged	37900
		80	100	steel	gas, water, steam, condensate	flanged	39450
	Angle safety valve with damper	50	64	steel	steam	flanged	37300
	The safety valve spring with a damper angular.	80	64	steel	gas, water, steam, condensate	flanged	46500

Safety valve classification:

By the nature of the rise of the closing body:

• valves of proportional action (used on incompressible media);
• two-position valves;

According to the lifting height of the closing body:

• low-lift (lifting height of the locking element (spool, plate) does not exceed 1/20 of the saddle diameter);
• medium-lift (plate lifting height from 1/20 to ¼ of the saddle diameter);
• full-lift (lift height is 1/4 of the saddle diameter or more);

By type of load on the spool:

• spring
• cargo or lever-cargo
• lever-spring
• magnetic spring

In low-lift and medium-lift valves, the lift of the spool above the seat depends on the pressure of the medium, therefore they are also called valves. proportional action. These valves are mainly used for liquids where a large capacity is not required. In full-lift valves, the opening occurs in one step, therefore they are also called valves two-position action. These valves are highly efficient and are used for both liquid and gaseous media.

Lever (lever-weight) safety valves, principle of operation:

			Cargo to 17s18nzh, 17h18br

The principle of operation of a lever-weight safety valve is to counteract the force on the spool from the pressure of the working medium - the force from the load transmitted through the lever to the valve stem. The basis of the mechanism of this type valves is a lever and a load suspended from it. The operation of the device depends on the weight of the load and its location on the lever. The more weight and the farther on the lever it is, the more high pressure valve is activated. Lever valves are adjusted to the opening pressure by moving the weight on the lever (possibly changing the weight of the weight). Levers are also used to manually purge the valve. Lever valves must not be used on mobile heating devices.

The internal structure of the lever safety valve:

1.Inlet port; 2. Outlet; 3. valve seat; 4. Spool; 5. Cargo; 6. Lever.

For hermetically sealed saddles large diameters requires heavy weights on long arms, which can cause severe vibration of the device. In these circumstances, valves are used, inside which the medium discharge cross-section is formed by two saddles, which are blocked by two spools using two levers with weights (see for example: , ). The use of these two-lever valves with two gates, which allows to reduce the weight of the load and the length of the levers, ensuring the normal operation of the system.

The adjustment of the lever-load valve, as noted above, is carried out by moving the load along the lever. After required pressure was configured, the load is fixed with bolts, covered with a protective cover and locked. This is done to prevent unauthorized changes to the settings. Flanges are often used as cargo.

Features of lever-weight valves:

Lever valves are pipeline fittings that were developed before the 40th year of the last century. This is an obsolete valve, purchased only to maintain boiler stations and similar objects times of the Soviet public utilities.

A feature of the valve is the need to grind the working surfaces (spool and seat - pressed bronze sealing ring) directly at the valve installation site. Lapping refers to the processing of a bronze seat abrasive materials to achieve tighter contact between the spool and the seat. The spool in the valve body is not fixed and its working surfaces are easily damaged during transportation and loading. A valve without lapping will not seal.

Benefits of Lever Relief Valves:

• Simplicity of design;
• maintainability;
• Manual setting of valve actuation;

Disadvantages of Lever Relief Valves:

• The need to grind working surfaces;
• Small service life of the valve;
• Bulky design;

Spring loaded safety valves, working principle:

		safety valve

The principle of operation of a spring-loaded safety valve is to counteract the force of the spring - the force on the spool from the pressure of the working medium (coolant). The coolant exerts pressure on the spring, which is compressed. When the setting pressure is exceeded, the spool rises and the coolant is discharged through the outlet pipe. After the pressure in the system has decreased to the setting value, the valve closes and the coolant descent stops.

The internal structure of the spring-loaded safety valve:

1 - body; 2 - nozzles; 3 - lower adjusting sleeve; 4, 5 - locking screw; 6, 19, 25, 29 - gasket; 7 - upper adjusting sleeve; 8 - pillow; 9 - spool; 10 - guide sleeve; 11 - special nut; 12 - partition; 13 - cover; 14 - stock; 15 - spring; 16 - support washer; 17 - adjusting screw; 18 - locknut; 20 - cap; 21 - cam; 22 - guide sleeve; 23 - nut; 24 - plug; 25 - cam shaft; 27 - key; 28 - lever; 30 - ball.

The opening pressure of a spring-loaded safety valve is set by fitting the valve with various springs. Many valves are manufactured with a special mechanism (lever, fungus, etc.) for manual blasting for control blowing of the valve. This is done in order to check the operability of the valve, since various problems may arise during operation, for example, sticking, freezing of the spool to the seat. However, in industries using aggressive and toxic media, high temperatures and pressures, control purge can be very dangerous. Therefore, for spring valves used in such industries, the possibility of manual purge is not provided and is even prohibited.

When working with aggressive chemical media, the spring is isolated from the working medium by means of a stem seal with a stuffing box, bellows or an elastic membrane. The bellows seal is also used in cases where leakage of the medium into the atmosphere is not allowed, for example, at nuclear power plants. Maximum medium temperature for safety spring valves up to +450°C, pressure up to 100 bar.

The relief relief valve opens before the set pressure is reached. The valve opens completely when the pressure exceeds the set pressure by 10-15% (depending on the model). The device closes completely only when the pressure is 10-20% less than the setting pressure, because the outgoing coolant creates additional dynamic pressure.

If the heating system functions stably, without failures and excess pressure, the relief safety valve remains without "work" for a long period of time and may become clogged. Therefore, it is recommended to clean it periodically.

Benefits of Spring Valves :

• simple equipment design;
• small size and weight with large passage sections;
• possibility of installation in both vertical and horizontal positions;
• the possibility of obtaining high throughput.

Disadvantages of Spring Valves :

• a sharp increase in the force of the spring when it is compressed in the process of lifting the spool;
• the possibility of obtaining a hydraulic shock when the valve is closed;

Magnetic spring safety valves, working principle:

Magnetic spring safety valves use an electromagnetic actuator. The electromagnet provides additional pressing of the spool to the seat. When the set pressure is reached, the electromagnet is turned off and only the spring counteracts the pressure, and the valve starts to work like a conventional spring valve. Also, the electromagnet can create an opening force, that is, oppose the spring and forcibly open the valve. There are valves in which the electromagnetic drive provides both additional pressing and opening force, in this case the spring serves as a safety net in case of a power outage. Solenoid spring valves are commonly used in complex impulse safety devices as pilot or impulse valves.

All pressure vessels must be fitted with pressure relief devices. For this are used:

lever-cargo PC;

safety devices with collapsing membranes;

Lever-and-cargo PCs are not allowed to be used on mobile vessels.

Schematic diagrams of the main types of PC are shown in Figures 6.1 and 6.2. Weight on lever-load valves (see fig. 6.1,6) must be securely fixed in a predetermined position on the lever after the valve is calibrated. The design of the spring PC (see Fig. 6.1, c) should exclude the possibility of tightening the spring in excess of the set value and provide for a device for

Rice. 6.1. Schematic diagrams of the main types of safety valves:

1 - cargo with direct loading; b - lever-cargo; in - spring with direct loading; 1 - cargo; 2 - lever arm; 3 - outlet pipeline; 4 - spring.

checking the correct operation of the valve in working condition by forcibly opening it during operation. The device of the spring safety valve is shown in fig. 6.3. The number of PCs, their dimensions and throughput should be calculated so that in Fig. 6.2. The rupture safety disc did not exceed more than 0.05 MPa for vessels with pressure up to 0.3 MPa,

15% - for vessels with pressure from 0.3 to 6.0 MPa, 10% - for vessels with pressure over 6.0 MPa. When the PC is in operation, it is allowed to exceed the pressure in the vessel by no more than 25%, provided that this excess is provided for by the project and is reflected in the vessel passport.

The bandwidth of the PC is determined according to GOST 12.2.085.

All safety devices must have passports and operating instructions.

When determining the size of flow sections and the number of safety valves, the calculation of the valve capacity per G (in kg / h) is important. It is performed according to the methodology described in the SSBT. For water vapor, the value is calculated by the formula:

G=10B 1 B 2 α 1 F(P 1 +0.1)

Rice. 6.3. Spring device

safety valve:

1 - body; 2 - spool; 3 - spring;

4 - discharge pipeline;

5 - protected vessel

where bi - coefficient taking into account the physical and chemical properties of water vapor at operating parameters in front of the safety valve; can be determined by expression (6-7); varies from 0.35 to 0.65; the coefficient taking into account the ratio of pressures before and after the safety valve depends on the adiabatic index k and exponent β, for β<β кр =(2-(k+1)) k/(k-1) коэффициент B 2 = 1, показатель β вычисляют по фор муле (6.8); коэффициент B 2 varies from 0.62 to 1.00; α 1 - flow coefficient indicated in the passports of safety valves, for modern designs of low-lift valves α 1 \u003d 0.06-0.07, high-lift valves - α 1 \u003d 0.16-0.17, F- valve passage area, mm 2 ; R 1 - maximum overpressure in front of the valve, MPa;

B 1 \u003d 0.503 (2 / (k + 1) k / (k-1) *

where V\ - specific volume of steam in front of the valve at parameters P 1 and T 1, ) m 3 /kg - medium temperature in front of the valve at pressure Р b °С.

(6.7)

β = (P 2 + 0.1)/(P 1 +0.1), (6.8)

where P2 - maximum overpressure behind the valve, MPa.

Adiabatic exponent k depends on the temperature of the water vapor. At a steam temperature of 100 °C k = 1.324, at 200 "C k = 1.310, at 300 °C k= 1.304, at 400 "C k= 1.301, at 500 ° ck= 1,296.

The total capacity of all installed safety valves must not be less than the maximum possible emergency inflow of medium into the protected vessel or apparatus.

Burst discs (see figures 6.2 and 6.4) are specially loosened devices with a precisely calculated pressure burst threshold. They are simple in design and at the same time provide high reliability of equipment protection. The membranes completely seal the outlet of the protected vessel (before operation), are cheap and easy to manufacture. Their disadvantages include the need to replace after each actuation, the impossibility of accurately determining the actuation pressure of the membrane, which makes it necessary to increase the margin of safety of the protected equipment.

Diaphragm safety devices can be installed instead of lever-load and spring safety valves, if these valves cannot be used in a particular environment due to their inertia or other reasons. They are also installed in front of the PC in cases where the PC cannot work reliably due to the peculiarities of the influence of the working medium in the vessel (corrosion, crystallization, sticking, freezing). The membranes are also installed in parallel with the PC to increase the throughput of pressure relief systems. The membranes are installed in parallel with the PC to increase the throughput of pressure relief systems. Membranes can be bursting (see Fig. 6.2), breaking, tear-off (Fig. 6.4), shear, snapping out. The thickness of bursting discs A (in mm) is calculated by the formula:

PD/(8σ vr K t )((1+(δ/100))/(1+((δ/100)-1)) 1/2

where D - working diameter; R- membrane actuation pressure, σvr - tensile strength of the membrane material (nickel, copper, aluminum, etc.) in tension; TO 1 - temperature coefficient varying from 0.5 to 1.8; δ - relative elongation of the membrane material at break, %.

For tear-off diaphragms, the value that determines the response pressure,

is the diameter D H (see Fig. 6.4), which is calculated as

D n \u003d D (1 + P / σ vr) 1/2

The membranes must be labeled as prescribed by the Rules of Content. Safety devices must be installed on branch pipes or pipelines directly connected to the vessel. When installing several safety devices on one branch pipe (or pipeline), the cross-sectional area of ​​​​the branch pipe (or pipeline) must be at least 1.25 of the total cross-sectional area of ​​the PC installed on it.

It is not allowed to install any shut-off valves between the vessel and the safety device, as well as behind it. In addition, safety devices should be located in places convenient for their maintenance.

Safety devices. Safety devices (valves) should automatically prevent the increase in pressure beyond the allowable by releasing the working medium into the atmosphere or the disposal system. At least two safety devices are required.

On steam boilers with a pressure of 4 MPa, only impulse safety valves should be installed.

Passage diameter (conditional), mounted on boilers lever-,; cargo and spring valves, must be at least 20 mm. Allowance for this passage to be reduced to 15 mm for boilers with a steam capacity of up to 0.2 t / h and a pressure of up to 0.8 MPa when two valves are installed.

The total capacity of the safety devices installed on steam boilers must be at least the rated capacity of the boiler. Calculation of the capacity of the limiting devices of steam and hot water boilers must be carried out according to 14570 “Safety valves for steam and hot water boilers. Technical requirements".

Places of installation of safety devices are determined. In particular, in hot water boilers, they are installed on the outlet manifolds or on the drum.

The method and frequency of regulation of safety valves (PC) on boilers is indicated in the installation instructions and ex. Valves must protect the vessels from exceeding the pressure in them by more than 10% of the calculated (allowed).

Short answer: All pressure vessels must be fitted with pressure relief devices. For this are used:

spring safety valves (PC);

lever-cargo PC;

pulse safety devices, consisting of a main PC and a direct-acting control pulse valve;

safety devices with collapsing membranes;

other safety devices, the use of which is agreed with the Gosgortekhnadzor of Russia.

To relieve excess pressure into the atmosphere, safety spring valves are used, which are special pipeline fittings that provide reliable protection of the pipeline from malfunctions and mechanical damage. The device is responsible for the automatic discharge of excess liquids, steam and gas from vessels and systems until the pressure is normalized.

Purpose of the spring valve

Dangerous overpressure in the system occurs as a result of external and internal factors. Both incorrect collection of thermal and mechanical circuits, which causes malfunctions in the operation of equipment, heat entering the system from extraneous sources, and internal physical processes that are not provided for by standard operating conditions that periodically occur in the system, lead to an increase.

Safety products are an indispensable part of any household or industrial pressure system. Installation of safety mechanisms is carried out on pipelines in compressor stations, on autoclaves, in boiler rooms. Valves perform protective functions on pipelines through which not only gaseous, but also liquid substances are transported.

The device and principle of operation of spring valves

The valve consists of a steel body, the lower fitting of which is used as a connecting element between it and the pipeline. If the pressure in the system rises, the medium is discharged through the side fitting. The spring adjusted depending on the pressure in the system ensures that the spool is pressed against the seat. The spring is adjusted by means of a special sleeve, which is screwed into the top cover located on the device body. The cap located in the upper part is designed to protect the bushing from destruction as a result of mechanical influences. The presence of a special lug for sealing allows you to protect the system from outside interference.

For valves in which a spring acts as a balancing mechanism, the force of the working body is selected. If the parameters are chosen correctly, in the normal state of the system, the spool, which is responsible for releasing excess pressure from the pipeline, should be pressed against the seat. When the performance increases to a critical level, depending on the type of spring device, the spool moves up to a certain height.

The safety spring valve, which provides timely pressure relief, is made of different materials:

• Carbon steel. Such devices are suitable for systems in which the pressure is in the range of 0.1-70 MPa.
• Stainless steel. Valves made of stainless steel are designed for systems, the pressure in which does not exceed 0.25-2.3 MPa.

Classification and characteristics of spring valves

The safety spring valve is available in three versions:

• Low lift devices suitable for gas pipeline and steam pipeline systems, the pressure in which does not exceed 0.6 MPa. The lift height of such a valve does not exceed 1/20 of the seat diameter.
• Medium lifting devices, in which the spool lift height is from 1/6 to 1/10 of the nozzle diameter.
• Full lift devices, in which the valve lift reaches up to ¼ of the seat diameter.

Known classification of valves based on the way they open:

• Check spring valve. To control the check spring valves, an indirect external pressure source is involved. Spring check valves, which are called impulse safety devices, can be operated by the action of electricity.
• Straight valve. In direct type devices, the working pressure of the medium has a direct effect on the spool, which rises with increasing pressure.

Allocate open valves And closed type. In the case of a direct type device, when the valve is opened, the medium is discharged directly to the atmosphere. Closed-type valves remain completely sealed to the environment by relieving pressure in a dedicated piping.

Advantages

There are various types of equipment that provide relief of excess pressure from the system, but spring safety valves are popular due to the presence of important advantages:

• Simplicity and reliability of a design.
• Ease of setting the operating parameters and ease of installation.
• Variety of sizes, types and designs.
• Installation of a safety product is possible both in horizontal, and in vertical position.
• Relatively small overall dimensions.
• Large cross section.

The disadvantages of safety valves include the presence of limitations in the lift height of the spool, increased requirements for the quality of manufacturing of the spring for safety valves, which can fail when operating in an aggressive environment or constant exposure to high temperatures.

How to choose a spring valve?

When choosing a fuse, it is worth relying on several important principles, the consideration of which depends on the uninterrupted operation of the system and the ability of the fuse to perform the necessary functions:

• Spring Relief Valves are smaller than other types of Relief Valves and should therefore be selected where space is not available.
• Features of the use of valves are associated with the presence of increased vibrations, which adversely affect the performance of the device and can quickly render it unusable. For example, lever-type devices are more prone to breakage due to vibration due to the presence of a long lever with weight and hinges in the design. Therefore, for systems in which significant vibration effects are observed, it is worth choosing a safety spring valve.
• Depending on the design features of the device, the spring can change the pressure force over time. This is due to the fact that the constant rise of the spool causes changes in the structure of the metal.

Installation nuances

A spring-type safety valve is installed at any point in the system that is subjected to increased pressure and is at risk of mechanical damage. The device does not require a large free space, which is a significant advantage compared to other types of safety devices.

In order to avoid malfunctions, no shut-off valves should be installed upstream of the safety valve. To discharge the gaseous medium, special devices are installed or the discharge occurs directly into the atmosphere. To alert personnel, along with spring valves, a special whistle is mounted, which is placed on the discharge pipe. When the valve is actuated, a whistle will sound to indicate that the system has been pressurized and the valve has opened to release media.

Possible causes of safety valve failures

Safety valves are robust and reliable devices that provide permanent protection of systems against overpressure. A direct or check spring valve fails for several reasons:

• The presence of increased vibrations;
• Constant exposure to aggressive media on the safety throttle.
• Incorrect installation of the safety spring throttle or valve.

In order to avoid accidents and malfunctions in the functioning of systems, safety valves are periodically checked for malfunctions. Valves are tested for strength and tightness before being put into service. Periodic checks are also carried out to determine the tightness of sealing surfaces and stuffing box connections.

With the right choice of safety devices, taking into account the parameters of the system, carrying out periodic checks and timely troubleshooting, safety spring valves will ensure reliable operation of the system and trouble-free protection against overpressure for a long time.