# US 5,348,456 A · Helical dry screw expander with sealing gas to the shaft seal system

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- Number: US 5,348,456 A
- Document ID: US5348456A
- Status: Granted
- Kind: A
- Application number: 08/051,923
- Filed: 1993-04-26
- Granted: 1994-09-20
- Earliest claimed: 1992-04-16
- Assignees: Praxair Technology, Inc.
- Inventors: Leslie C. Kun; Neno T. Nenov
- Web page: https://patentgrep.com/patent/US5348456A

## CPC

- F25J 3/044: {using a single pressure main column system only (F25J3/0446, F25J3/04624, F25J3/04636 take precedence)}
- F01C 1/16: with helical teeth, e.g. chevron-shaped, screw type {(for non-parallel axes of movement F01C3/00)}
- F01C 19/125: {Shaft sealings specially adapted for rotary or oscillating-piston machines or engines}
- F25J 3/04284: {using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams (F25J3/04333 takes precedence)}
- F25J 3/04296: {Claude expansion, i.e. expanded into the main or high pressure column}
- F25J 3/04866: {Construction and layout of air fractionation equipments, e.g. valves, machines (F25J5/00 takes precedence)}
- F04C 2220/12: Dry running
- F25J 2240/02: Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
- F25J 2290/10: Mathematical formulae, modeling, plot or curves; Design methods
- Y10S 62/91: Expander
- F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)}
- F01C: ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES (internal-combustion aspects F02B53/00, F02B55/00)
- F04C: ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS (engines F03C); ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An improved helical dry screw expander particularly suited for cryogenic service and its use in a cryogenic rectification system. The improved helical dry screw expander is particularly advantageous in a cryogenic waste expansion cycle particularly for nitrogen production.

## Claims

### Claim 1

A helical dry screw expander comprising:
(A) a pair of helical screw rotors, each of said rotors mounted on a shaft, both of said rotors housed in a casing having a process fluid inlet and a process fluid outlet, each said shaft extending through the casing and outside the casing;
(B) a bearing on each shaft spaced from and outside of the casing and means for providing lubricant to the bearing and from the bearing;
(C) a seal system around each shaft between the bearing and the casing;
(D) means for providing sealing gas to each seal system proximate the casing, said seal gas provision means not communicating with said process fluid outlet, and means for withdrawing sealing gas from each seal system proximate the bearing, thereby keeping process fluid from migrating out of the casing along the shafts and keeping lubricant from migrating into the casing along the shafts; and
(E) a regulator for sensing the pressure near the casing regulating the sealing gas flow to the seal systems.