Data Sheet
Sight glass
Type LLG 185 - 1550
For industrial and marine refrigeration installations.
LLG are sight glasses in ductile steel which meets the strictest requirements on industrial and marine refrigeration installations.
The sight glasses are o€ered in 3 di€erent versions:
• with welding nipples (LLG)
• with stop valves equipped with caps (LLG S)
• with stop valves and sight adapter in acrylic glass ready for insulation on site (LLG SF)
The range of sight glasses is based on 3 basic sight glasses: LLG 185, LLG 335 and LLG 740. The other standard lengths are combined by using variations of basic glass lengths.
LLG produce sufficient flow areas to secure the highest possible degree of synchronous operation, and have a specially hardened reflection glass for quick reading. The front and the base frame are mounted together from the front with countersunk allen screws. This ensures easy insulation on site as well as easy inspection and service, if any.
All sight glasses are equipped as standard with a built-in safety system (non return device). If a glass is damaged, the pressure of the refrigerant will activate the safety system and refrigerant loss will be limited to an absolute minimum.
AI176286432251en-000701
Sight glass, Type LLG 185 - 1550
Features
•Refrigerants
◦Applicable to HCFC, HFC and R717 (Ammonia).
•Temperature range:
◦–10/+100 °C (–14/+212 °F) or
◦–50/+30°C (–58/+86°F)
•Maximum operating pressure
◦25 bar g (363 psi g)
•Equipped with boron silicate glass, hardened by an accurately controlled heat treatment process
•Classi†cation: CRN, EAC etc.
To get an updated list of certi†cation on the products please contact your local Danfoss Sales Company.
Product speci€cation
Technical data
Refrigerants
Applicable to HCFC, HFC and R717 (Ammonia). For further information please see installation instruction for LLG. Flammable hydrocarbons are not recommended. For further information please contact your local Danfoss Sales Company.
Temperature range
The sight glasses are applicable to the above mentioned refrigerants within the temperature range of:
•–10/+100°C (+14/+212°F) for the LLG types with safety system with welding nipples and the LLG S types with safety system with stop valves.
•–50/+30°C (–58/+86°F) for the LLG SF types with safety system with stop valves and sight adapter (acrylic glass) and the LLG F types with safety system and sight adapter (acrylic glass).
Pressure range
All LLG types are designed for:
Max. operating pressure 25 bar g (363 psi g)
Strength test: 50 bar g (725 psi g)
Leakage test: at 25 bar g (363 psi g)
Design
Glass
LLG's are equipped with a boronsilicate glass, hardened by an accurately controlled heat treatment process. All glasses are according to DIN 7081.
Gaskets
The glasses are equipped with a special nonasbestos carbon compound gasket which provides superior mechanical characteristics and a long time guarantee against service leakage.
Connectors
LLG 590, LLG 995, LLG 1145 and LLG 1550 are joined together by 2 basic LLG’s by means of a connector. The connector holds the two basic glasses together by means of screws and guiding pins, which ensures a rigid construction.
Stop Valves/Nipples
The glasses are connected to the refrigeration system by means of welding nipples or stop valves. Which ever system is used, the nipples or stop valves are screwed into a flange, which is located in the correct position and subsequently tightened with a seal gasket and 4 screws.
Installation
Install the glasses on a bracket using the 4 screws supplied with the glass.
© Danfoss | Climate Solutions | 2021.02 |
AI176286432251en-000701 | 2 |
Sight glass, Type LLG 185 - 1550
Use the threaded holes on the back of the frame to mount the glass on a bracket (not of Danfoss supply). Always connect the piping after mounting on the bracket. Please note the importance of a minimum of stress in the sight glasses from the connected pipes. Please also make sure that there is sufficient space behind the the sight glasses to ensure proper insulation, service and inspection, etc.
For installations below –10 °C (+14 °F) it is recommended to add the sight adapter to enable reading after insulation has been applied. For installations below –10 °C (+14 °F) in R717 plants it is recommended to use an oil column as described in the following pages. There will be no formation of bubbles or ice build-up in oil†lled sight glasses, which may be the case in the refrigerant-†lled glasses.
The sight glasses are designed to withstand high internal pressures. However, the piping system in general should be designed to avoid liquid traps and reduce the risk of hydraulic pressure caused by thermal expansion.
NOTE:
The LLG sight glass can only be placed in CE approved applications with the stop valves in front.
Frostproof sight glasses
Example 1
Refrigerant: R717 (ammonia)
Temperature: Recommended for temperatures below –10 °C (+14 °F).
The principle shown in Figure 1 can be used in connection with low temperature liquid separators or intermediate coolers when the refrigerant is R717 (ammonia). As the liquid level in the R717 separator varies the oil level will change simultaneously.
Figure 1: Working principle of sight glass
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LLG |
1 |
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2 |
3 |
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4 |
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1Separator/ Intermediate cooler
2Purge valve
3Oil charging valve
4Oil vessel
Oil changing
The system is charged with synthetic oil type SHC 226 with a speci†c weight, di€ering from that of R717, and (h) must be multiplied by approximately 1.35 (the ratio of density oil to density R717) to calculate H.
Charge the oil vessel (volume approximate 10 litres) to a level just below the lower balancing pipe (A) through the oil charging valve. Close the oil charging valve.
The oil will show in the sight glass at a level equal to the level in the oil vessel. When R717 is †lled into the separator or intermediate cooler it will enter the oil vessel and press down the oil surface.
The R717 will also rise into the upper balance pipe (B) to a level equal to the level in the separator or intermediate cooler. As the oil surface in the oil vessel is pressed down, the oil will rise into the sight glass.
NOTE:
It is important to use an oil which is not likely to mix with R717. The oil must have a high viscosity index to ensure easy flowing at low temperatures. Mobil SHC 226 of the synthetic polyalphaole†n type has proven suitable for this purpose.
© Danfoss | Climate Solutions | 2021.02 |
AI176286432251en-000701 | 3 |
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