Danfoss SFV 20, SFV 25 Data sheet

Data Sheet

Safety relief valve
Type SFV 20-25

Designed for protection of vessels and other components
against excessive pressure

SFV 20 - 25 are standard, back pressure
dependent safety relief valves in angle-way
execution, specially designed for protection of
vessels and other components against
excessive pressure.

The valve is designed to meet the strict quality
demands and safety requirements for
refrigeration installations, specied by the
international classication societies.

The valve is recommended as an external and
internal safety relief valve in refrigeration
plants. The spring housing is closed tightly to
avoid refrigerant leakage.

The inlet ow diameters of the valves are:

• 18 mm (

• 23 mm (1 in.) for SFV 25

The valves can be delivered with set pressures
between 10 and 25 bar (145 and 363 psig).

Standard pressure setting valves having "TÜV
Pressure Setting Certicate" with each valve,
are also available.

Features

• Applicable for the refrigerants HCFC, HFC,
R717 (Ammonia), R744 (CO2) within a

temperature range of –30°C / +100°C (–22°F /
+212°F).

• Classication: DNV, CRN, BV, EAC etc. To get
an updated list of certication on the
products please contact your local Danfoss
Sales Company.

3

⁄4 in.) for SFV 20

AI175286423559en-000701

Safety relief valve, Type SFV 20-25

Media

Refrigerants

Applicable for the refrigerants HCFC, HFC, R717 (Ammonia), R744 (CO2) within a temperature range of -30 °C/+100
°C (-22 °F/+212 °F)

• Flammable hydrocarbons are not recommended.

• For further information please contact your local Danfoss Sales Company.

New refrigerants

Danfoss products are continually evaluated for use with new refrigerants depending on market requirements.

When a refrigerant is approved for use by Danfoss, it is added to the relevant portfolio, and the R number of the
refrigerant (e.g. R513A) will be added to the technical data of the code number. Therefore, products for specic
refrigerants are best checked at store.danfoss.com/en/, or by contacting your local Danfoss representative.

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The SFV-valves are approved in accordance with the European standard

specied in the Pressure Equipment Directive and are CE

marked. For further details / restrictions - see Installation Instruction.

SFV valves

Nominal bore

18 mm (0.709 in.)

23 mm (0.906 in.)

Classied

for

Fluid group I

Category

IV

Safety relief valve, Type SFV 20-25

Product specication

Pressure and temperature data

• Pressure
Pressure setting range: 10 - 25 bar (145 - 363 psig). For further information please contact your local Danfoss Sales
Company.
The valves are designed for: Strength test:

◦ 43 bar (624 psig)

• Leakage safety
Same as set pressure.

IMPORTANT:



The SFV safety relief valve is dependent on the back pressure (if the back pressure is higher than the atmospheric
pressure, the opening pressure will be higher than stated set pressure).
Special circumstances such as vibrations (which should be avoided) and oscillating pressure may require an
increased dierence between the operational pressure and the closing pressure.

• Pressure setting
The operating pressure of the plant should be at least 15% below the set pressure. This allows a perfect re-seating
of the safety relief valve after having been activated.

• Temperature range : –30 °C/+100 °C (–22/+212 °F)

Design

Housing

Made of special steel approved for low temperature operation. Spindle and seat are made of stainless steel, to
ensure precise operation even during extraordinary conditions. The gasket of the valve cone is made of a special
chloroprene (neoprene) rubber.

Re-calibration/servicing

In certain countries the authorities demand that the valves are checked at least once a year (see local rules).

Control/Identication

After adjustment of the set pressure at Danfoss, the valves are sealed. For that reason Danfoss can only guarantee
correct operation, as long as the seal remains unbroken.

All valves are provided with a metal plate with the following information:

• Flow diameter

• Set pressure

• Date of production

• Production number

• Type approved code

Transport/Handling

The valves are tted with special protection covers and packed into purpose made transportation cartons.
It is important the cover remains tted around the valve until it is installed.
To ensure the exact and precise operation of the valve it must be handled with care.

Pressure Equipment Directive (PED)

Table 1: Pressure Equipment Directive (PED)

Table 2: SFV

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Working pressure

Reseating pressure

Set pressure p

Opening pressure

p + 10%

p – 10%

0 100% Opening degree

Size (mm)

Size (in.)

Inlet

Outlet

L (mm)

L (in.)

2025¾1G 1¼

G 1¼

G 1½
G 1½2020

0.79

0.79

ø

Size (mm)

Size (in)

Inlet (mm)

Inlet (in.)

Outlet (mm)

Outlet (in.)

øDTøDTøDTøD

T

20
25

3

⁄4

1

26.9

2.6

2.3251.059

1.327

0.091

0.102

33.7

42.4

2.6

2.6

1.337

1.669

0.102

0.102

Safety relief valve, Type SFV 20-25

Figure 1: SFV Graph

SFV is designed as a standard safety relief valve (DIN 3320), which are recommended for refrigeration plants. On a
rise in pressure above the set pressure, the safety relief valve will initially start opening slightly, to minimise the
outlet of refrigerant. If the pressure continues to increase, the valve will open fully. The safety relief valve will be fully
open before the pressure is 10% higher than set pressure, and fully closed before the pressure is 10% below set
pressure.

Connections

Available with the following connections:

• Outside pipe thread T (ISO 228/1)

• Welding ttings (DIN 2448)

Figure 2: T

Table 3: T outside pipe thread, (ISO 228/1)

Figure 3: DIN

Table 4: Welding ttings DIN (2448)

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q

m

C

A0K

dr

K

b

V

pset

p

atm

p

Valve

Nominal size

Flow diameter

Flow area

De-rated, certied coecient of discharge

Inlet

Outlet

doA

0

K

dr

SFV 20

20 mm

25 mm

18 mm

254 mm

2

0.54

¾ in.

1 in.

0.709 in.

0.394 in

2

SFV 25

25 mm

32 mm

23 mm

415 mm

2

0.48

1 in.1¼0.906 in.

0.643 in

2

Discharge capacity (kg/h)

Discharge function depending of the actual refrigerant (κ) see table 2 (‑)

Flow area of the safety relief valve (mm2).

De-rated coecient of discharge (Kdr = Kd × 0.9), (the Kdr is certied by TÜV) see table 1 (‑)

Correction factor for sub‑critical ow. (-) Kb = 1.0 when the back pressure is lower than approx. 0.5 × relieving
pressure (Pb < 0.5 × p) For all SFV safety valves Kb = 1.0

Specic volume of the vapour at the releiving pressure p. (m3/kg)

Set pressure, the predetermined pressure at which a pressure relief valve under operation starts to open (p

set

is indicated on the metal plate on the safety relief valve). (bar gauge)

Atmospheric pressure. (1 bar)

Relieving pressure, p = pset × 1.1 + Patm (bar absolute)

Refrigerant

Isentropic exponent κ

Discharge function C

R22

1.17

2.54

R134a

1.12

2.5

R404A

1.12

2.49

Safety relief valve, Type SFV 20-25

Installation

To ensure exact operation of the safety relief valve it should be installed with the spring housing upwards. If the
valve is mounted as an internal safety relief valve without any demand for exact opening pressure, the valve may be
tted with the spring housing in other positions. When the valve is mounted, it is important to avoid the inuence
of static, dynamic and thermal stress.

A very precise technique has been applied for the production of the seal. However, this seal can still be damaged, if
dirt is blown from the pipe system into the valve.

It is recommended that safety relief valves exhaust into the open air with a U‑pipe lled with oil on the discharge
branch, to prevent dirt from penetrating into the valve. It is also recommended that the valves be installed in pairs
in conjunction with the double stop valve type DSV. For further information please see the DSV data sheet.

Capacity

The design and construction of the safety relief valve has been tested and approved by TÜV. This test comprises
control of the function of the valve as well as measuring of the capacity, which is the basis of the curves and tables
on the following pages. The values in the table are based on saturated gas.

If e.g. back pressure or superheated gas have to be taken into consideration, the formulas or the Danfoss
computation program (DIRcalc) can be used.

Table 5: Capacity Values

The discharge capacity of the safety relief valves are based on (IS0 4126‑1 / prEN 1313 6 (1998)).

qm= 0.2883 × C × A0× Kdr× K

p

b

v

For further details see the above-mentioned ISO or EN standards.

Table 6: Table 2. Properties of Refrigerants

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