Danfoss PMFL, PMFH, SV Data sheet
Data Sheet
Liquid level regulating valves
Type PMFL / PMFH and SV
For modulating liquid level control in refrigeration,
freezing and air conditioning plant
For modulating liquid level control in
refrigeration, freezing and air conditioning
plant, a system comprising a liquid level
regulating valve type PMFL or PMFH, controlled
by a pilot oat valve type SV, is used.
PMFL and SV systems are used on the
evaporator side. PMFH and SV systems are used
on the condenser side.
The system is suitable for use with ammonia or
uorinated refrigerants. The PMFL and PMFH
can be used in liquid lines to or from
• evaporators
• separators
• intermediate coolers
• condensers
• receivers
Modulating liquid level regulation provides
liquid injection that is proportional to the
actual capacity. This gives a constant amount of
ashgas, thus ensuring stable regulation and
economic operation because variations in
pressure and temperature are held to a
minimum.
AI242086443737en-001001
Liquid level regulating valves, Type PMFL / PMFH and SV
Features
• Applicable to HCFC, HFC and R717 (Ammonia)
• PMFL / PMFH are based on PM valve family housings
• Same ange programme as for PM valve series
• Valve housing in low temperature cast iron (spherical) - EN GJS 400-18-LT
• Manual operation possible
• Position indicator available
• Pressure gauge connection to monitor inlet pressure
• Simple installation
• Main valve top cover can be located in any position without aecting the function
• Classication: DNV, CRN, BV, EAC etc. To get an updated list of certication on the products please contact your
local Danfoss Sales Company
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to SV float
Subcooling
Pressure
dierence over main valve
bar
psi
bar
psi
K
F
4 – 15
58 – 218
1.2 – 4.0
17 – 58
0 – 8
0 – 14
Normal spring set
Weak spring set
8 – 40
14 – 72
Strong spring set
PMFL
C/w normal (factory mounted) spring set, subcooling 0 – 8 K ~ 0 – 14 F
Pressure
dierence (Dp) over PMFL in bar or psi
< 5 bar
5 – 8 bar
8 – 10 bar
10 – 12 bar
> 12 bar
< 72 psi
72 – 116 psi
116 – 145 psi
145 – 174 psi
> 174 psi
80
No tension
2 – 3
3 – 4.5
4.5 – 6
ca. 7
125
No tension
3 – 5
5 – 7
7 – 9
ca. 10
200
No tension
3 – 5
5 – 7
7 – 9
ca. 10
300
No tension
4 – 6
6 – 9
9 – 12
ca. 14
PMFL
C/w strong spring set, subcooling 8 – 40 K ~ 14 – 72 F
Pressure
dierence (Dp) over PMFL in bar or psi
6 – 9 bar
> 9 bar
87 – 131 psi
> 131 psi
80
4
Max. tension
125
6
Max. tension
Liquid level regulating valves, Type PMFL / PMFH and SV
Functions
PMFL
Figure 1: PMFL
When the liquid level inside the oat drops, the oat orice opens. This relieves the higher pressure, ps, acting on
the servo piston to the low pressure side causing the PMFL to open. Variations in liquid level will result in variations
in pressure over the piston and variation in the amount of liquid injected. It is important to choose the correct
spring set when designing the plant. The spring set should be selected from the table below:
Table 1: Subcooling
The setting spindle, pos. 60, has not been set from factory. It is imperative that the setting spindle is adjusted before
the valve is put into operation. The outer spring, pos. 23, is preset and the inner spring, pos. 43, is adjusted when
turning the spindle. The following tables shows the adjustment of the inner spring in number of turns of the spindle
as a function of valve size, spring type and pressure dierence:
Table 2: PMFL
Table 3: PMFL
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PMFL
C/w stong spring set, subcooling 8 – 40 K ~ 14 – 72 F
Pressure dierence (Dp) over PMFL in bar or psi
6 – 16 bar
87 – 232 psi
300
Spring must always be set to max. tension
PMFL
C/w weak spring set, low pressure plants
Pressure dierence (Dp) over PMFL in bar or psi
1.2 – 1.8 bar
1.8 – 2.5 bar
2.5 – 3 bar
3 – 4 bar
17 – 26 psi
26 – 36 psi
36 – 43 psi
43 – 58 psi
80
No tension
3 – 4
4 – 6
Max. tension
125
No tension
4 – 6
6 – 8
Max. tension
200
No tension
4 – 6
6 – 8
Max. tension
300
No tension
5 – 7
5 – 7
Max. tension
From compressor
To compressor
From evaporator
Condenser
Alarm
Alarm
float switch
Through type receiver
Liquid level
Overflow
valve
Filter
Oil drain
valve
To evaporator
Liquid level regulating valves, Type PMFL / PMFH and SV
Table 4: PMFL
Table 5: PMFL
Figure 2: PMFL function example
The values for spindle turns are an indication for an initial setting only. If a position indicator is used, a more precise
modulation can be achieved when ne tuning the valve setting. If the PMFL is not opening fully, the spring tension
must be reduced. If the PMFL is operating in a ON / OFF function, the spring tension should be increased. The
condenser pressure will have an eect on the ne tuning and large variations in condensing pressure might call for
readjustment. The subcooling is measured just before the PMFL and the pressure dierence is for the valve only
excluding piping and armatures.
The PMFL can be used together with SV 4 as a pilot valve.
The orices determines the Kv (Cv) value of the pilot and the following table can be used as an initial selection guide:
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PMFL
SV 4 – 6
Ø 2.5
Ø 3 (SV 4)
80X125X200X300
X
Inlet to SV 4 from PMFL
Liquid level regulating valves, Type PMFL / PMFH and SV
Table 6: PMFL
The nal choice of orice may vary depending on refrigerant and pressure levels. Smaller pressure levels needs a
bigger orice. Pressure dierence levels below 3 bar (43 psi) need SV 4 – 6 with Ø3 mm orice.
SV oats for PMFL
SV 4 can be used for PMFL low pressure control system. The oat must be connected as shown.
Figure 3: SV oats for PMFL
NOTE:
Only one inlet connection possible for SV 4.
PMFH
Figure 4: PMFH
If the liquid level inside the SV oat rises, the oat orice opens and relieves pressure through the pilot line to the
top of the PMFH, increasing the pressure, ps, moving the pushrod downwards and opening the PMFH. The pilot line
is connected in the topcover at SI. Override of the pilot signal can be made by using an EVM valve at SII. It is
important to choose the correct spring set when designing the plant. The spring set should be selected from the
table below:
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Pressure dierence over main valve
bar
psi
bar
psi
0 – 4.5
0 – 65
> 4.5
> 65
Weak spring set
Normal spring set
SV 3 (1)
From low stage
compressor(s)
Tohigh stage
compressor(s)
From high stage
compressor(s)
To
low stage
separator
Condenser
Alarm
float
switch
Intermediate
pressure
vessel
Liquid trap
receiver
Filter
To
compressor
cooling
Alarm
S-connection
P-connection
Liquid level regulating valves, Type PMFL / PMFH and SV
Table 7: spring set selection
The PMFH can be used together with either SV 1 or 3 with the SV mounted with the bleed valve downwards, refer to
the drawing below. This reverses the opening so that rising oat opens the orice.
Figure 5: PMFH function example
NOTE:
High pressure oat system (for explanatory purposes only)
SV 1 - 3
SV 1 – 3 oat has 2 dierent pilot connections: S-port (series connection with PMFH) or P-port (parallel connection
with the PMFH).
P-port:
When using the P-port, it is possible to force open the PMFH valve to a fully open position. This is practical for
service purposes or to conrm if the oat has sucient capacity for the PMFH and the operating conditions.
However, when P-port connection is used it is possible to overll a system due to constant bleeding or unautorised
tampering. In this case, it is advisable to introduce a shut o when the liquid level reaches a preset point. Shut o
can be done via an electrical switch if an EVM valve is mounted in the SII port in the top of the PMFH. It is only
advisable to use the P-port at low pressure dierence.
S-port:
The S-port oers the advantage of a preorice which divides the pressure drop and any wear possibility due to
cavitation. S-port connection must be used at high pressure dierences, dp > 10 bar (145 psi). The Kv (Cv) value of
the SV is higher using P-port than using S-port. A higher P-band can thus be obtained.
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