CONSTRUCTION METHODS

CONSTRUCTION METHODS FOR ETCHED SCREENS

Lee Etched Safety Screens are constructed from photochemically etched stainless steel stock that is formed and brazed to a base washer (flange) or insert locking end.

Etched Safety Screens can be formed in two ways; "radial pleated" and "circular pleated". Radial pleated screens are found on the etched flange and boss mount safety screens, and screened inserts. Circular pleated screens are a patented method of increasing screen open area for a given size and are used on the etched flange, boss mount, TWIS and L-4 safety screens.

All standard Lee Etched Screens are made from 304L or 17-7PH stainless steel stock. Discs with the etched hole pattern are formed into cups with convoluted sides, to provide the optimum amount of protection with the least possible volume. With strict attention to cleanliness throughout the process, these cups are then brazed without flux to a base washer in a reducing atmosphere of dry hydrogen. Rigorous process control and regular microstructural examinations ensure the integrity of Lee Etched Safety Screens. The silver or gold braze material used conforms with the SAE Aerospace Material Specification 4774 or 4786. Its major characteristics are as follows:

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SILVER BRAZE / AMS 4774
CompositionNominal Values
Silver63.0%
Copper28.5%
Tin6.0%
Nickel2.5%
Recommendations
Maximum Service Temp
Short Term Service 700°F (371°C)
Long Term Service 400°F (204°C)
GOLD BRAZE / AMS 4786
CompositionNominal Values
Gold 70%
Palladium 8%
Nickel 22%

CONSTRUCTION METHODS FOR DRILLED SCREENS

Lee Drilled Safety Screens are machined from solid bar stock, typically 15-5 precipitation hardening stainless steel, although other materials such as 300 series stainless steels or aluminum alloys may be used for special applications. Individually drilled and deburred by proprietary manufacturing processes, these Safety Screens feature an extremely robust, one-piece design without joints or seams.

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TYPICAL MATERIALS
Material Heat Treat Maximum Service Temp
15-5PH Cres H1025 900°F (482°C)
303 Cres N/A 400°F (204°C)
2024 Alum T651 300°F (149°C)

PRECISION CLEANING OF LEE SAFETY SCREENS

Contamination control is a necessity in today's high performance fluid systems. As safety screens are meant to improve system performance by providing additional protection beyond the system filter, special precautions need to be taken to ensure that the screens themselves are not a source of built-in contamination. While The Lee Company has always manufactured our components in a clean work environment, we have added an additional safeguard by implementing Lee Process Specification H1025 (PS H1025), Precision Cleaning and Packaging of Lee Safety Screens. This specification outlines the procedures and controls for a final cleaning step just prior to packaging. It also specifies standard and cleanroom packaging requirements for Lee Safety Screens, and is available upon request.

LEE Safety Screens
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