The flanged spring safety valve 17s28nzh is one of the main types that is used to protect pipeline equipment. The spring safety valve 17s28nzh is designed to protect equipment and pipelines from unacceptable excess pressure in the system. Ensuring safe pressure values ​​is carried out by automatically releasing excess working environment into a specially installed outlet pipeline or into the atmosphere, and when the operating pressure is restored, the safety valve 17s28nzh stops discharging the working medium.

The spring safety valve 17s28nzh is mounted with the equipment and using a flange connection. The flanged spring safety valve 17s28nzh has a service life of more than 11 years, and the manufacturer provides a guarantee for it for 18 months from the date the valve is put into operation. Safety valve 17s28nzh is not sealed in relation to the external environment.

Material of the main parts from which the 17s28nzh safety spring valve with flange connection is made:

• Housing, cover - Steel 25L
• Disc, seat - Steel 20Х13
• Rod - Steel 20Х13/Steel 40
• Gasket - AD1M
• Spring - 50HFA

Safety spring valve device 17s28nzh

1 .Cap

2 . Adjustment screw

3 . Spring

4 . Lid

5 . Stock

6 . Manual detonation unit

7 . Spool assembly

8 . Saddle

9 . Frame

Overall and connecting dimensions of safety valve 17s28nzh

DN, mm

Dimensions, mm

4

Technical characteristics of safety valve 17s28nzh

Name	Meaning
Nominal diameter, DN, mm
Seat hole diameter dc, mm
Allowable leakage in the valve, cm 3 /min	5-for air 1-for water		10-for air 2-for water
Seat cross-sectional area Fс, mm 2, not less
Nominal inlet pressure РN, MPa (kgf/cm2)
Nominal outlet pressure РN, MPa (kgf/cm2)
Full opening pressure Рп.о. MPa (kgf/cm 2), no more	For gaseous media: pH+0.05 (0.5) for pH<0,3 МПа; 1,15 Рн для Рн>0.3 MPa For liquid media: pH+0.05 (0.5) for pH<0,2 МПа; 1,25 Рн для Рн>0.2 MPa
Closing pressure Рз	not less than 0.8 pH
Spring setting pressure limits, pH MPa (kgf/cm2), not less	0,05-0,15 (0,5-1,5); 0,15-0,35 (1,5-3,5); 0,35-0,7 (3,5-7,0); 0,7-1,0 (7-10); 1,0-1,6 (10-16)
Temperature environment, РС		from minus 40 to 40
Working environment temperature, °С		from minus 40 to 450
Characteristics of the working environment	Water, steam
Flow rate?	0.8 for gaseous; 0.5 for liquid media
Connecting dimensions and dimensions of housing sealing surfaces	according to GOST 12815-80 version 1 row 2
Weight without flanges (kg)

Safety valves are used in industrial scale and are installed on the main line in order to discharge excess flow of the working medium from the pipeline to reduce the pressure level (a type of household safety valve is the Mayevsky valve, which bleeds air from heating systems).

Design and types of safety valves

The main element of a safety valve is a valve, a rod, adjusting elements, and adjustment springs. By design, safety valves can be lever-load (the working medium presses on the spool, and this pressure is counteracted by the force of the load) and magnetic-spring (actuated by an electromagnetic drive).

Types of safety valves:

• direct action. Triggers when the pressure exceeds the norm;
• indirect action. They are triggered when exposed to an extraneous impulse (for example, from an electric one, used for remote control);
• proportional action. Used in incompressible media;
• two-position action.

Video of safety valve operation

Safety valves can also be low-lift (the lift of the locking part is 1/20 of the diameter of the seat), full-lift (1/4 of the seat, intended for large highways). bandwidth), medium lift. Check valves are a type of safety valve. Safety valves are also divided into shut-off and control valves. The limit pressure is adjusted at the time of installation by changing the position of the adjusting screw that compresses the pressure spring.

• We recommend spring safety valves! Unlike membrane ones, they are equipped additional devices, preventing the spool from freezing to the seat.

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With pressure exceeding the established one. The valve must also ensure that the release of the medium ceases when the operating pressure is restored. The safety valve is a fitting direct action, operating directly from the working medium, along with most designs of protective fittings and direct-acting pressure regulators.

Dangerous overpressure can arise in the system both as a result of third-party factors (improper operation of equipment, heat transfer from third-party sources, incorrectly assembled thermo-mechanical circuit, etc.), and as a result of internal physical processes caused by some initial event not provided for by normal operation. PC are installed wherever this can happen, that is, on almost any equipment, but they are especially important in the field of operation of industrial and household pressure vessels.

Encyclopedic YouTube

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Why a safety valve in a hot water supply system?

Safety valve design (in stereo anaglyph format)

Subtitles

Operating principle

When the safety valve is closed, a force from working pressure in the protected system, tending to open the valve and the force from the set pointer, preventing the opening. With the occurrence of disturbances in the system, causing an increase in pressure above the operating pressure, the magnitude of the force pressing the spool against the seat decreases. At the moment when this force becomes equal to zero, an equilibrium occurs between the active forces from the influence of pressure in the system and the setpoint on the sensitive element of the valve. The shut-off element begins to open, if the pressure in the system does not stop increasing, the working medium is discharged through the valve.

With a decrease in pressure in the protected system caused by the release of the medium, disturbing influences disappear. The shut-off element of the valve closes under the force of the adjuster.

The closing pressure in some cases turns out to be 10-15% lower than the operating pressure, this is due to the fact that to create a tightness of the shut-off valve after operation, a force is required that is significantly greater than that which was sufficient to maintain the tightness of the valve before opening. This is explained by the need to overcome, during landing, the adhesion force of the molecules of the medium passing through the gap between the sealing surfaces of the spool and the seat, to displace this medium. Also, the decrease in pressure is facilitated by the delay in closing the shut-off organ, associated with the impact on it of dynamic forces from the passing flow of the medium, and the presence of friction forces, requiring additional force for its complete closure.

Classification of safety valves

According to the operating principle

• direct acting valves - usually these are the devices that are meant when the phrase is used safety valve, they open directly under the influence of pressure from the working environment;
• indirect-acting valves - valves controlled by using an external source of pressure or electricity, the generally accepted name for such devices is pulsed safety devices;

According to the nature of the elevation of the closing organ

• proportional action valves (used on incompressible media)
• on/off valves

According to the height of the lift of the closing organ

• low-lift
• mid-lift
• full lift

By type of load on the spool

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

Design Differences

Safety valves usually have an angular body, but they can also have a straight body; regardless of this, the valves are installed vertically so that the stem goes down when closing.

Most safety valves are manufactured with one seat in the body, but designs with two seats installed in parallel are also available.

Low-lift safety valves are those in which the lifting height of the locking element (spool, plate) does not exceed 1/20 of the seat diameter; full-lift are valves in which the lifting height is 1/4 of the seat diameter or more. There are also valves with a poppet lift from 1/20 to 1/4, these are usually called mid-lift. 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 conventionally called valves proportional action, although the rise is not proportional to the pressure of the working medium. Such valves are used, as a rule, for liquids when large throughput is not required. In full lift valves, opening occurs immediately at full speed plates, that's why they are called valves on/off action. Such valves are high-performance and are used for both liquid and gaseous media.

The greatest differences in safety valve designs lie in the type of load on the spool.

Spring valves

In them, the pressure of the medium on the spool is counteracted by the compression force of the spring. The same spring valve can be used for different response pressure settings by equipping it with different springs. Many valves are manufactured with a special mechanism (lever, fungus, etc.) for manual detonation for control purging of the valve. This is done to check the functionality of the valve, since during operation there may be problems various problems, for example, sticking, freezing, sticking of the spool to the seat. However, in some industries under conditions of aggressive and toxic environments, high temperatures and pressures, control blowing can be very dangerous, therefore, for such valves, the possibility of manual blowing is not provided and is even prohibited.

Most often, springs are exposed to the working environment, which is discharged from a pipeline or container when triggered; special spring coatings are used to protect them from mildly aggressive environments. There is no stem seal in such valves. In cases of working with aggressive media in chemical and some other installations, the spring is isolated from the working environment using a seal along the rod with a stuffing box, bellows or elastic membrane. Bellows seals are also used in cases where leakage of the medium into the atmosphere is not allowed, for example at nuclear power plants.

Lever-weight valves

In such valves, the force on the spool from the pressure of the working medium is counteracted by the force from the load, transmitted through the lever to the valve stem. Setting such valves to the opening pressure is done by fixing a load of a certain mass on the lever arm. Levers are also used to manually purge the valve. Such devices are prohibited from being used on mobile vessels.

For sealing seats large diameters significant masses of weights on long levers are required, which can cause strong vibration of the device; in these cases, housings are used, inside of which the medium discharge cross-section is formed by two parallel seats, which are overlapped by two spools using two levers with weights. Thus, two parallel operating valves are mounted in one body, which makes it possible to reduce the mass of the load and the length of the levers, ensuring normal operation of the valve.

Magnetic spring valves

These devices use an electromagnetic drive, that is, they are not direct-acting valves. The electromagnets in them can provide additional pressing of the spool to the seat, in this case, when the response pressure is reached based on a signal from the sensors, the electromagnet is turned off and only the spring counteracts the pressure, the valve begins to operate like a regular spring one. Also, the electromagnet can create an opening force, that is, counteract the spring and force the valve to open. 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 interruption

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

Photo Designation	Name	Du, mm	Working pressure (kgf/cm2)	Housing material	Working environment	Connection type	Price, rub
		20	16	bronze	water, steam	coupling-pin	3800
	Spring safety valve	25	16	bronze	water, steam, gas	union-fitting	12000
	Low-lift spring safety valve	15-25	16	steel	ammonia, freon	pin-type	1200-2000
	Steel safety valve	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, petroleum products	flanged	9000-19000
	Full-lift spring safety valve	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-fitting	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, petroleum products	flanged	20000-53800
	Spring safety valve	50-150	16	steel	water, air, steam, ammonia, natural gas, oil, petroleum products	flanged	20200-53800
	Angle spring safety valve.	50	100	steel	gas, water, steam, condensate	flanged	37900
		80	100	steel	gas, water, steam, condensate	flanged	39450
	Spring safety valve with angular damper	50	64	steel	steam	flanged	37300
	Spring safety valve with angular damper.	80	64	steel	gas, water, steam, condensate	flanged	46500

Classification of safety valves:

According to the nature of the elevation of the closing organ:

• proportional action valves (used on incompressible media);
• on/off valves;

According to the height of the lift of the closing organ:

• low-lift (the lifting height of the locking element (spool, plate) does not exceed 1/20 of the seat 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-load
• 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, which is why they are also called valves proportional action. Such valves are mainly used for liquids when large throughput is not required. In full-lift valves, the opening occurs simultaneously, which is why they are also called valves on/off action. Such valves are high-performance and are used for both liquid and gaseous media.

Lever (lever-weight) safety valves, operating principle:

			Load to 17s18nzh, 17h18br

The principle of operation of a lever-load 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 on it. The operation of the device depends on the weight of the load and its location on the lever. The greater the weight and the further it is on the lever, the more high blood pressure the valve is activated. Lever valves are adjusted to the opening pressure by moving a weight along the lever (the weight of the load may change). Levers are also used to manually purge the valve. Lever valves are prohibited for use on mobile heating devices.

Internal structure of lever safety valve:

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

Sealing of large diameter seats requires heavy weights on long arms, which can cause severe vibration of the device. In these circumstances, valves are used, inside of which the medium discharge cross-section is formed by two seats, which are closed by two spools using two levers with weights (see for example:,). The use of these two-lever valves with two gates, which reduces the weight of the load and the length of the levers, ensuring normal operation of the system.

Adjustment of the lever-weight valve, as noted above, is carried out by moving the weight along the lever. After the required pressure has been adjusted, the load is secured with bolts, covered with a protective casing and locked. This is done to prevent unauthorized changes to the settings. Flanges are often used as weights.

Features of lever-weight valves:

Lever valves are pipeline fittings that were developed before the 40s of the last century. This is an obsolete valve, purchased only to maintain boiler points and similar facilities from the Soviet public utilities era.

A special feature of the valve is the need to grind in the working surfaces (spool and seat - pressed bronze sealing ring) directly at the valve installation site. Lapping means treating the bronze seat with abrasive materials to achieve tighter contact between the spool and the seat. The spool in the valve body is not secured and during transportation and loading its working surfaces are easily damaged. A valve without lapping will not be sealed.

Advantages of lever safety valves:

• Simplicity of design;
• Maintainability;
• Manual adjustment of valve actuation;

Disadvantages of lever safety valves:

• The need to grind in working surfaces;
• Short valve life;
• Bulky design;

Spring safety valves, operating principle:

		Safety valve

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

Internal structure of spring 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 - rod; 15 - spring; 16 - support washer; 17 - adjusting screw; 18 - lock nut; 20 - cap; 21 - cam; 22 - guide sleeve; 23 - nut; 24 - plug; 25 - cam shaft; 27 - key; 28 - lever; 30 - ball.

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

When working with aggressive chemical media, the spring is isolated from the working environment using a seal along the rod with a stuffing box, bellows or elastic membrane. Bellows seals are also used in cases where leakage of the medium into the atmosphere is not allowed, for example at nuclear power plants. The maximum operating temperature for safety spring valves is up to +450°C, pressure up to 100 bar.

The relief safety 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 reaches 10-20% less than the set pressure, because the escaping coolant creates additional dynamic pressure.

If the heating system is functioning stably, without failures or overpressure, the relief safety valve remains without “working” for a long period of time and may become clogged. Therefore, it is recommended to clean it periodically.

Advantages of spring valves :

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

Disadvantages of spring valves :

• a sharp increase in the spring force when it is compressed during the process of lifting the spool;
• the possibility of receiving a water hammer when closing the valve;

Magnetic spring safety valves, operating principle:

Magnetic spring safety valves use an electromagnetic actuator. The electromagnet provides additional pressing of the spool to the seat. When the response pressure is reached, the electromagnet turns off and only the spring counteracts the pressure, and the valve begins to operate like a regular spring valve. Also, the electromagnet can create an opening force, that is, counteract the spring and force the valve to open. 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 power failure. Magnetic spring valves Typically used in complex impulse safety devices as control or impulse valves.

Spring safety valve (PPV)– a type of pipeline fittings designed to automatically protect equipment and pipelines from excess pressure above a predetermined value by releasing excess working fluid and ensuring that the discharge stops when the closing pressure is restored and the operating pressure is restored.

Basic assembly units and valve parts:

1 - body, 2 - seat, 3 - spool, 4 - cover, 5 - rod, 6 - nut, 7 - pin, 8 - spring, 9 - bellows (installed in bellows valves), 10 - locking screw, 11 - adjusting bushing, 12 - guide bushing, 13 - partition, 14 - adjusting screw, 15 - cap, 16 - threaded flange.

Operating principle. At normal operating pressure, the force of the compressed spring presses the spool against the seat (the passage for relieving the working medium is closed). When the pressure increases above the set value, an oppositely directed force begins to act on the spool, which compresses the spring, and the spool rises, opening a passage for discharging the working medium. After the pressure in front of the valve decreases to the closing pressure, the spool under the action of the spring is again pressed against the seat, stopping the discharge of the medium.

Installation position – vertical, cap up.

Shutter tightness– class “B” GOST R 54808. At the customer’s request, it is possible to manufacture with other classes of tightness.

Possible valve designs:

• A sealed cap with a forced opening unit, and without one.
• Balancing bellows.
• Thermal barrier.
• "Open" lid.
• A locking element that prevents the valve from operating.

Pipeline connection:

• flanged;
• for lens gasket (flange according to GOST 9399);
• fitting;
• tsapkovoe.

Valves with bellows.

The bellows is a mechanism that compensates for the effect of back pressure at the outlet of the valve. The bellows is designed to protect the valve spring from harmful effects aggressive working environment at high or low temperatures. Bellows valves are made of steel grades 12Х18Н9ТЛ and 12Х18Н12МЗТЛ and are intended for working environments with temperatures from minus 60 °С and below. Designation of bellows valves: KPP4S, KPPS.

The design of the sealing surfaces and the connecting dimensions of the valve flanges are in accordance with GOST 12815-80, row 2, face-to-face lengths are in accordance with GOST 16587-71.

Valves DN 25 PN 100 kgf/cm2 can be manufactured with union ends for connection to a pipeline in accordance with GOST 2822-78, as well as with a flange connection in accordance with GOST 12815-80, row 2.

Safety valves with nominal pressure PN 250 kgf/cm2 and PN 320 kgf/cm2, like other models, are designed to protect equipment from unacceptable excess pressure by automatically releasing excess working fluid. Used on equipment with liquid and gaseous working media that do not cause corrosion of body parts of more than 0.1 mm.

Safety valves with a stamped-welded body can be manufactured with individual face-to-face length (L and L1), height (H) and flange mounting dimensions, which allows them to be used as substitutes for imported valves without changing already installed equipment and pipelines.

Calculation of valve capacity - according to GOST 12.2.085-2002.

Setting pressure, pH– the highest excess pressure at the inlet to the safety valve, at which the valve is closed and the specified tightness of the valve is ensured.

Opening start pressure, Рн.о.(starting pressure; set pressure) – excess pressure at the inlet to the safety valve, at which the force tending to open the valve is balanced by the forces holding the locking element on the seat. When the opening pressure begins, the specified tightness in the valve shutter is broken and the locking element begins to rise.

Full opening pressure, Рп.о.– excess pressure at the inlet to the safety valve, at which the valve moves and maximum throughput is achieved.

Closing pressure, Рз(reseating pressure) – excess pressure at the inlet to the safety valve, at which, after the working medium is discharged, the locking element is seated on the seat, ensuring the specified tightness of the valve. Valve closing pressure, Рз – not less than 0.8 Рн.

Back pressure– excess pressure at the outlet of the fittings (in particular, from the safety valve).

Back pressure is the sum of the static pressure in the exhaust system (if closed system) and the pressure arising from its resistance during the flow of the working medium.

Mandatory minimum order information.

When ordering valves, you must fill in questionnaire(Appendix B):

• product type, designation, type designation (according to the table of figures);
• nominal diameter of the inlet pipe, DN, mm;
• nominal pressure, PN, kgf/cm2;
• setting pressure (Рн, kgf/cm2) or spring number (when only the spring number is specified, the valve is adjusted to the minimum value from the range of the specified spring);
• body material;
• the presence of a manual detonation unit in the valve design;
• the presence of a bellows in the valve design.

Example of designation when ordering a spring safety valve:

An example of designation when ordering a spring safety valve DN 50 PN 16 kgf/cm2 made of steel 12Х18Н9ТЛ with a manual detonation unit, setting pressure – Рн=16 kgf/cm2, model KPP4R according to TU 3742-005-64164940-2013:

Safety valve KPP4R 50-16 DN 50 PN 16 kgf/cm2, pH=16 kgf/cm2, 17nzh17nzh. When placing an order, the need to complete the valves with matching parts (matching flanges, gaskets, studs, nuts; for valves DN 25 PN 100 – nipples with union nuts and gaskets).