Danfoss POV Data sheet
Data Sheet
Compressor overflow valve
Type POV
Designed for protecting compressors against excessive pressure
The POV compressor overow valve is used in
conjunction with the BSV safety relief valve and
is specically designed for protecting
compressors against excessive pressure.
Features
• Applicable for the refrigerants HCFC, HFC,
• The Pilot Operated Internal compressor
• POV + BSV is an internal compressor overow
• The system renders full protection of the
• The POV compressor overow valve (main
• Small dimensions mean easy handling and
• Classication: DNV, CRN, BV, EAC etc. To get
R717 (Ammonia), R744 (CO2).
overow valve System POV + BSV is available
in sizes from DN 40 to DN 80.
system thus eliminating the risk of refrigerant
leakage to the atmosphere.
compressor even on increasing back pressure.
valve) has a very large capacity even with
high back pressure when compared to direct
operating back pressure independent
pressure relief valves.
installation.
an updated list of certication on the
products please contact your local Danfoss
Sales Company.
AI183186419402en-001101
g. 1, Inactive system (closed valve)
g. 2, Active system (open valve)
Pilot valve
BSV 8
Main valve
POV
From
evaporator
To oil separator
condenser
Condensing
pressure
Evaporating
pressure
Danfoss
80Z816
Pilot valve
BSV 8
Main valve
POV
From
evaporator
To oil separator
condenser
Condensing
pressure
Evaporating
pressure
Danfoss
80Z817
Compressor overow valve, Type POV
Function
Pilot valve BSV 8
The pilot valve is actuated by the high pressure P1 and the back pressure P2”. The reference pressure in the stainless
steel bellow (1) P0 is the atmospheric pressure. The eective area of the bellows is equivalent to the area of the valve
seating, so the back pressure P2” does not aect the opening pressure of the valve.
Main valve POV
The main valve is of the normally closed (N.C.) type. The high pressure P1 acts on the valve inlet side of the valve
cone (2). P1 pressure also passes through the piston rod (3) to the upper chamber (4) of the valve, acting on the top
of the piston (5). The area of the piston is larger than the area of the valve seat and this together with the spring
pressure keeps the valve closed.
System BSV 8 + POV
When the pressure P1 reaches the set pressure of the pilot valve, it starts opening. The pressure of the pilot line P2”
and of the lower chamber (6) of the main valve increases. The pressure of the lower chamber is limited by ow
through the nozzle (7). When the ow through the pilot valve exceeds the capacity of the nozzle, the pressure of the
chamber (6) increases, providing the opening of the main valve. When the pressure P1 is reduced, the pilot valve
closes, and the pressure P2” is equalized through the nozzle (7). The spring then closes the main valve. The closing
time is ≤30 seconds.
Table 1: Function
Installation of compressor overow valve POV + BSV
Set pressure
The BSV 8 set pressure is factory set in the range 15 ‑ 25 bar(g) (145 ‑ 363 psig), where 15 bar(g) is the minimum
value for this application Figure 6: Capacity - POV 600.
Standard set pressures
18.0, 21.0, or 25.0 bar(g) (261, 305 or 363 psig). The operational pressure of the plant should be at least 15% below
the set pressure of the pilot valve, and the opening pressure of the pilot valve (pset + 10%) must be below the
reseating pressure of the safety valve protecting the plant. This implies a perfect operation of the plant.
Back pressure
P
is the eective back pressure of the POV main valve P
2-0
outlet line of POV (2).
P
Is normally equal to the evaporating pressure.
2-1
P
must not exceed the limits in Figure 6: Capacity - POV 600.
2-0
Pressure loss in inlet line
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= P
2-0
2-1
+ ∆P
where ∆Poutlet is the pressure loss in the
outlet
POV + BSV system
Flow diagram
Plant Pressure
Compressor
safe system
Set pressure of
pilot valve BSV
Operating
pressure on
plant
Set pressure
on safety
valves (SFV) on
refrigerant plant
e.g. oil separator
Max. opening
pressure of
POV + BSV
system
High pressure
Low pressure
Figure 1: 3
P
2-1
P
2-0
P
1-1
P
1-0
Pilot valve
BSV 8
Main valve
POV 40 - 80
Compressor
Evaporating
pressure
Condensing
pressure
Max. back pressure bar(g)
Set pressure bar(g)
Danfoss
80Z818
Compressor overow valve, Type POV
The pressure loss in the inlet line of the POV (1) will not aect the function of the POV + BSV system, but a high
pressure drop will reduce the capacity. If the pressure drop in the inlet line ΔP
exceed 3% of the opening
inlet
pressure, the capacity reduction must be taken into consideration by calculation.
Pressure drop in the pilot inlet line
In order to ensure a proper function of the POV + BSV system, the pilot valve must be activated by the plant
pressure. It is important that the inlet line of the pilot valve is mounted in a way which ensures that the pilot
pressure is identical with the plant pressure. If the pilot pressure is mounted in the inlet line of the POV valve, it must
be veried that the pressure drop in the pilot inlet line (3) ΔP
Table 2: Installation of compressor
does not exceed 3% of the opening pressure.
inlet
Figure 2: Fig. 4, range of application of BSV 8 ‑ POV
Important: When locating the inlet line to the pilot valve, it is important that the connection is mounted in the gas
phase and not in an oil phase, if any.
• Pressure drop in the pilot outlet line
• The pressure loss in the BSV outlet line (4) ∆P
• Minimum internal diameter of the pilot outlet line 8 mm (0.314 in.)
• Maximum length of pilot outlet line 1 m (3.25 ft)
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is not critical.
P-outlet
Evaporating pressure
Compressor
Condensing
pressure
Oil separator
Danfoss
80Z821
Compressor overow valve, Type POV
Note: The guidelines mentioned above are securing a safe function of the POV + BSV system, but there might be
restrictions from national authorities.
NOTE:
Valve type POV is categorized as a compressor overow accessory (not as a safety accessory). Hence a safety
valve (e.g. SFV) has to be installed to protect the system against excessive pressure.
Fig. 5 shows a typical application of the POV + BSV system. In the example a non return valve has been mounted in
the suction line, as well as a shut-o valve in the pressure line. It is good practise and a demand from the authorities
of most countries to mount a safety valve on the oil separator.
If the shut-o valve in the pressure line is closed, and aIl regulation equipment fails, the pressure after the
compressor will rise, and the BSV + POV system is activated. Provided that the required motor eect is present, there
will be a rise in temperature caused by the compression work, followed by a rise in pressure. Therefore, the safety
relief valve of the oil separator must, besides being dimensioned for “normal” heat input, also be dimensioned for
heat input, corresponding to the eect of the motor.
Figure 3: Installation of compressor overow valve POV + BSV
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Compressor overow valve, Type POV
Media
Refrigerants
Applicable for the refrigerants HCFC, HFC, R717 (Ammonia), R744 (CO2). 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 specic
refrigerants are best checked at store.danfoss.com/en/, or by contacting your local Danfoss representative.
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Features
Description
Pressure setting range
15 - 25 bar(g) (218 ‑ 363 psig)
Strength test
50 bar(g) (725 psig)
Leakage test
25 bar(g) (363 psig)
PB/MWP
40 bar (580 psig)
Temperature range
–50/+150 °C (–58/+302 °F)
ø
Compressor overow valve, Type POV
Product specication
Pressure and temperature data
Table 3: Pressure and temperature data
Design
Control/Identication
All pilot valves (BSV 8 Safety Relief Valves) are adjusted, tested and sealed before leaving Danfoss A/S. For that
reason Danfoss can only guarantee correct operation, as long as the seal remains unbroken.
Transport/Handling
POV and BSV are supplied separately from Danfoss. BSV safety valves are tted with special protection covers and
packed in purpose made cartons. POV valves are provided with protection covers. It is important that the protective
covers remain tted until the valve is installed. To ensure the exact and precise operation of the valve it must be
handled with care.
Re-calibration/servicing
In certain countries the authorities demand that the valves are readjusted at least once a year (see local rules).
Capacity
The design and construction of the compressor overow 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.
Installations
To ensure exact operation of the valve it should be installed with the spring housing upwards (refer to "Installation
of compressor overow valve POV + BSV" on the following pages).
When the valve is mounted, it is important to avoid the inuence of static, dynamic and thermal stress.
Connections
Available with the following connections:
• Welding DIN (2448)
• Welding ANSI (B 36.10):
◦ DN 40, Schedule 80
◦ DN 65 - 80, Schedule 40
Figure 4: DIN
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