A Liquid Helium (LHe) Dewar is a critical component of any helium liquefaction system. LHe Dewar is a double walled vessel & LHe is stored in the inner vessel. Because of very low latent heat of LHe, control of heat in-leak into LHe is very critical, for example in a 1000L LHe Dewar with 1 % per day net evaporation rate (NER), allowable heat in-leak to LHe by all means (Conduction, Convection and Radiation) is just 0.3 watts. High leak tightness and special arrangements are required for long term vacuum retention of the Dewar. LHe Dewar is used in various helium liquefaction systems for storage and distribution of LHe

Sr. No.	Parameter	Values
1	Gross/ net capacity	1068/ 1000 Litres
2	Weight (Empty)	Approx. 684 Kg
3	Material of construction	SS 304L
4	Normal evaporation rate	≈ 1% per day
5	Operating pressure	Shell side (1.0 bara), Jacket side (full vacuum)
6	Design pressure	Shell side (2 bar g), Jacket side (full vacuum)
7	Outside overall height	Approx. 1890 mm
8	Vent connection	DN 15 with DN15 ball valve
9	Level sensor	3/8" and 1000 mm sensing length superconducting liquid level sensor
10	Heaters	1kW heater
11	Ball valves	Cryogenic ball valves: for vent port (1/2"), for flow measurement (1/4")
12	Flow meter	Rotameter0-10 LPM
13	Pressure gauge	-30 to 15in Hg
14	Pressure building	Electric pressure builder (220V, 1 Phase)
15	Safety relief valves	One in G10 tube (15 psi) and two between G10 tube and neck (20 and 25 psi)

INTRODUCTION

A Liquid Helium (LHe) Dewar is a critical component of any helium liquefaction system. LHe Dewar is a double walled vessel & LHe is stored in the inner vessel. Because of very low latent heat of LHe, control of heat in-leak into LHe is very critical, for example in a 1000L LHe Dewar with 1 % per day net evaporation rate (NER), allowable heat in-leak to LHe by all means (Conduction, Convection and Radiation) is just 0.3 watts. High leak tightness and special arrangements are required for long term vacuum retention of the Dewar. LHe Dewar is used in various helium liquefaction systems for storage and distribution of LHe.

1. Liquid Helium (LHe) Dewar is used in various helium liquefaction systems for storage and distribution of LHe. LHe is required to cool superconducting magnets, super conducting RF cavities, etc.

1. Liquid Helium (LHe) Dewar having low net evaporation rate (NER) ≈ 1% per day.

A liquid helium (LHe) receiver vessel is a double walled vessel. LHe is stored in the inner vessel. Annular space between the outer and inner vessels is maintained under high vacuum due to initial evacuation and cryo-pumping at cold conditions. Multilayer super insulation and thermal shields are used between the inner and outer vessels. It is used in helium liquefaction systems for storage and distribution of LHe.

SPECIFICATIONS

Sr. No.	Parameter	Values
1	Gross/ net capacity	1068/ 1000 Litres
2	Weight (Empty)	Approx. 684 Kg
3	Material of construction	SS 304L
4	Normal evaporation rate	≈ 1% per day
5	Operating pressure	Shell side (1.0 bara), Jacket side (full vacuum)
6	Design pressure	Shell side (2 bar g), Jacket side (full vacuum)
7	Outside overall height	Approx. 1890 mm
8	Vent connection	DN 15 with DN15 ball valve
9	Level sensor	3/8" and 1000 mm sensing length superconducting liquid level sensor
10	Heaters	1kW heater
11	Ball valves	Cryogenic ball valves: for vent port (1/2"), for flow measurement (1/4")
12	Flow meter	Rotameter0-10 LPM
13	Pressure gauge	-30 to 15in Hg
14	Pressure building	Electric pressure builder (220V, 1 Phase)
15	Safety relief valves	One in G10 tube (15 psi) and two between G10 tube and neck (20 and 25 psi)

INFRASTRUCTURE REQUIRED

1. SS pressure vessel manufacturing facilities with high bay area and overhead crane.
2. TIG welding and SS-Cu brazing facilities.
3. MSLD facility.
4. Super-insulation wrapping facility inside a moisture free clean room, expertise of manufacturing cryogenic pressure vessels/ pipings.
5. 1000 square feet space is required for assembly, testing & installation of the LHe Dewar.

MATERIAL AVAILABILITY

1. Most of the components are available within the country and some components need to be imported through local agents.

MANPOWER

1. A mechanical engineer & 2 trained technicians will be required for the development of this Liquid Helium (LHe) Dewar.