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August 2004 / Bulletin 60-15 for Valve Types
P-H-M-V-W-D-A
®
FOR USE ON REFRIGERATION and/or AIR CONDITIONING SYSTEMS ONLY Bulletin 60-15 August 2004 Superdes Bulletin 60-15 August 1996 and all prior publications.
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© Copyright 2004 By Sporlan Valve Company, Washington, Missouri
The SPORLAN Level-Master Control is a positive liquid level con-trol device suitable for application to all flooded evaporators.
DESCRIPTION and OPERATION The LMC is a standard thermostatic expansion valve equipped with
a Level-Master Element. T he combination pro-vides a simple, economical and highly effective liquid level
control. The bulb of the conventional thermostatic element has been modified to an inrt type of bulb which incorpo-rates a low wattage heater. A 15 watt heater is supplied as standard. For applications below -60°F evaporating
temperature specify a special 25 watt heater.
The inrt bulb is installed in the accumulator or surge drum at the point of the desired liquid level. As the level at the inrt bulb drops, the electrically added heat increas
the pressure within the thermostatic element and opens the valve. As the liquid level at the bulb ris, the electrical input is balanced by the heat transfer from the bulb to the liquid refrigerant and the LMC either modulates or eventu-ally shuts off. The evaporator pressure and spring assist in providing a positive closure.General
The Level-Master control can be applied on any system that has been specifically designed for flooded operation.
Sporlan is not responsible for system design and, therefore is not liable for any damage arising from faulty design or im-proper piping, or for misapplication of its products. Figures 2 through 8 are piping schematics only to illustrate possible methods of applying the LMC valves.
If the valves are applied in any manner other than as de-scribed in this bulletin, the Sporlan warranty is void. The system piping should be designed to protect the compres-sor at all times. T his includes protection against overheating,
slugging with liquid refrigerant, and trapping oil in various
system locations. Sporlan recommends that recognized pip-ing references, such as equipment manufacturers’ literature and the ASHRAE Handbooks be consulted for assistance.The valve is usually connected to feed into the surge drum above the liquid level. It can also feed into the liquid leg or coil header.The inrt bulb can be installed directly in the shell, surge drum or liquid leg on new or existing installations. Existing
float systems can be easily converted by installing the LMC inrt bulb in the float chamber.The Level-Master Control may be installed at any ambient temperature. A thermostatic switch in the heater asmbly protects the element from the excessive temperature cre-ated by the heater.Inrt
Bulb The inrt bulb should be installed at the point where the
liquid level is to be maintained. The bulb must be in contact
with the refrigerant, i.e., NOT installed in a well. If the inrt
bulb is projected directly into the surge drum, it should be shielded from possible splash from either the valve feed or
the return from the coil. While generally installed in a hori-zontal position, e Figure 1, it will operate effectively at any angle or vertical position.Modulated flow蚂蚁斗大象
The Level-Master Control provides a modulated flow and maintains practically a static liquid level in the low side.
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No moving parts
The inrt bulb controlling the liquid level has no moving parts. Control does not operate through u of a mechanical float device of any kind.
qifuSimplified and economical installation
The inrt bulb can be placed directly in the shell, accumulator or liquid leg for direct contact with refrigerant. Existing float
control systems can be easily and economically converted.
Not affected by turbulence
When agitation occurs in the low side, the effect on the Level-Master is merely that of striking a mean level and holding that level constant.
Tight closing
is assured by the spring action in the thermostatic expansion valve during
shut down periods when the heater element is off and liquid refrigerant is in contact with the bulb.
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Minor adjustments in liquid level can be made with the ex-pansion valve adjustment stem. The inrt
bulb asmbly is provided with a lock ring and gasket joint so the bulb can be removed without breaking the pipe joint.
Electrical Connections
The heater comes with a two wire neoprene covered cord two feet in length. It runs through a moisture-proof grom-met and a 1/2” male conduit connection affixed to the in-
rt bulb asmbly, e Figure 2.
ommend using an externally equalized valve. (See ordering
instructions.)
Oil Return
General - All reciprocating compressors allow some oil to pass into the discharge line along with the discharge gas. Mechanical oil parators are ud extensively; howev-er, they are never completely
effective. The untrapped oil pass through the condenr, liquid line, expansion device and finally into the evaporator. In a properly designed direct expansion system, the re-frigerant velocity in the evaporator tubes, and in the suction
line, is high enough to insure a continuous return of oil to the compressor crankca. But, this is not characteristic of flooded systems. Here we purpoly design the surge drum
for a relatively low vapor velocity to prevent entrainment of
liquid refrigerant droplets and conquent carry over into
the suction line. This design prevents oil from returning to the low side in the normal manner. If oil is allowed to concentrate at the inrt bulb location of
the Sporlan Level-Master Control, overfeeding with possible floodback can occur. The tendency to overfeed is caud by the fact that oil does not convey the heat from the low
wattage heater element away from the bulb as rapidly as does pure liquid refrigerant. The bulb pressure is higher节日顺序
than normal and the valve remains in the open or partially
open position. Oil and Ammonia Systems - Liquid ammonia
and oil are immiscible for all practical purpos. Since the density of oil is greater than that of ammonia it will fall to the bottom of any vesl containing such a mixture, if the mix-ture is relatively placid. T herefore, the removal of oil from an ammonia system is a comparatively simple task. Generally, on systems equipped with a surge drum, the liquid leg is ex-tended downward below the point where the liquid is fed off to the evaporator, and a drain valve is provided to allow periodic manual draining as shown in Figure 3.For flooded chillers that do not u a surge drum, a sump
with a drain valve is usually provided at the bottom of the chiller shell.
The above methods are quite satisfactory, except on some
low temperature systems, where the drain leg or sump gen-erally has to be warmed prior to attempting to draw off the oil since the trapped oil becomes quite viscous at lower temperatures.
Bulletin 60-15 / Page 3
If oil is not drained from a flooded ammonia system a reduction in the evaporator heat transfer rate can occur due to an increa in the refrigerant film resistance. Difficulty in maintaining the proper liqu
id level with any type of flood-ed control can also be expected.
With a float valve you can expect the liquid level in the evaporator to increa with high concentration of oil in a remote float chamber.
If a Sporlan Level-Master Control is ud with the int bulb installed in a remote chamber, oil concentration at the bulb can cau overfeeding with possible floodback. The lower or liquid balance line must be free of traps and must be free draining into the surge drum or chiller as shown in Figure 4. The oil drain leg or sump must be located at the lowest point in the low side.
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Oil and HFC/HCFC Systems- With HFC and HCFC systems- Refrigerants 134a, 22, 507, etc, the oil and re-frigerant are miscible under certain conditions. Mineral oil is partially miscible in liquid R-22 and POE lubricant tends to be more miscible in R-134a and R-507 and other HFC refrigerants. In R-22 systems, a 5% (by weight) of napthenic mineral oil in liquid refrigerant will remain in solution to approximately 0°F. But at temperatures below 0°F a liquid pha paration occurs. An oil rich solution will appear at the top and a refrigerant rich solution will lie at the bottom of any relatively placid remote bulb chamber. Keep in mind
miscibility data for systems using R-22 and HFC refrigerants depends on the oil ud and the percentage of oil prent in the refrigerant.
In HFC systems, the miscibility of the POE oil depends on the oil approved for the system. Different POE oils will yield different results. POE oils formulated with lower molecular weight alcohols tend to be more miscible than tho with higher molecular weights. Depending on the system,the POE lubricant and refrigerant can be completely miscible at all temperatures normally encountered, or some
liquid pha paration could exist for a particular POE oil/ refrig-erant combination. Oil in flooded evaporator applications can produce many effects.Oil as a contaminant will rai the boiling point of the liquid refrigerant if it exists in significant quantity in the evaporator. Oil can change the heat transfer properties with a conquent loss in system capacity. In addition, oil can affect the liquid level control and produce “foaming”, potentially carrying liquid into the suction line.
With a float valve you can normally expect the liquid level in the evaporator to decrea with increasing concentra-tion of oil in the float chamber. This is due to the differ-ence in density between the lighter oil in the chamber and lower balance leg, and the heavier refrigerant/oil mixture in the evaporator. A lower column of den mixture in the evaporator will balance a higher column of oil in
the re-mote chamber and piping, in a manner similar to a “U” tube manometer with a different liquid in each leg.
With the Sporlan level Master Control the heat transfer rate at the bulb is decread producing overfeeding and possi-ble flood back. In order to minimize that, we must keep the oil concentration as low as possible in the evaporator, surge drum, and remote inrt bulb chamber- if one is ud. With HFC/POE oil systems,the oil/refrigerant mixture is likely homogenous (but not necessarily) and you can drain from almost any location in the chiller,surge drum,or remote chamber that is below the liquid level. With R-22 or a pos-sible HCFC/POE oil mixture that is not homogenous,the drain must be located at, or slightly below the surface of the liquid since the oil rich layer is at the top. There are many types of oil return devices:
1. Direct drain into the suction line.
2. Drain through a high pressure liquid warmed heat exchanger.
3. Drain through a heat exchanger with the heat supplied by an electric heater.
The following Figures 5,6,7,and 8 are reprentative of the three methods.
Draining directly into the suction line, as shown in Figure 5, is the simplest method but the hazard of possible floodback to the compressor remains.
Page 4 / Bulletin 60-15
Typical Installation
DIRECT DRAIN - of oil to the suction line is one of three ways to recover oil in flooded systems. Heat from the environment or a liquid-suction heat exchanger is required to vaporize the liquid refrigerant so drained. Vapor velocity carries oil back to the compressor.
Draining through a heat exchanger as indicated in Figure 6, is a popular method since liquid refrigerant floodback prob-lems are minimized by using the warm liquid to vaporize the liquid refrigerant in the oil/refrigerant mixture.The u of a heat exchanger with an inrt electric heater, as shown in Figure 7, is a variation of the preceding method.
In all of the oil return arrangement discusd a solenoid valve should be installed in the drain line and arranged to clo when the compressor is not in operation. Otherwi liquid refrigerant could drain from the low side into the compressor crankca during the off cycle.
If the inrt bulb is installed directly into the surge drum or chiller, then oil return from this point only is necessary. However, if the inrt bulb is located in a remote chamber
which is tied to the surge drum or chiller with liquid and gas balance lines then oil return should be made from both locations as shown in Figures 5, 6, and 8.
OIL RETURN - by draining oil-refrigerant mixture through a heat exchanger is illustrated here. Heat in in-coming liquid vaporizes refrigerant to prevent return of liquid to compressor. Liquid feed is controlled by a hand expansion valve.
Manual Crankca
ELECTRIC HEATER - may also be ud to parate
oil and refrigerant. This system is similar to that of Fig-ure 6 except that heat required for vaporization is added electrically.
Conclusions - The problem of returning oil from
a flooded system is not highly complex and there are un-doubtedly other methods in u today that are comparable to tho outlined above. Regardless of how it is accom-plished, oil return must be provided , for proper oper-ation of any flooded system – not only with the Sporlan Level-Master Control but with a float or other type of level control device.
Bulletin 60-15 / Page 5
Figure 6
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Figure 7
新生儿可以喝白开水吗For Refrigerants
134 , 22, 507, 717 (Ammonia) - The rat-ings are bad on vapor free (subcooled) liquid refrigerant
entering the expansion valve (100°F for Refrigerants – 134a, 22, and 507, and 86°F for Refrigerant 717) and standard fac-tory tting. Becau of the artificial superheat provided
by the electric heater, the Level-Master will have a greater
capacity than a conventional thermostatic expansion valve. For lections for other refrigerants contact Sporlan Valve Company, Washington, MO 63090.
