Design Features And Principles Of Sanitary Stainless Steel Joint-type Sight Glass With Scraper

A sanitary sight glass with a wiper uses a dual-seal shaft structure that places two independent seals in series along the rotating shaft. A buffer zone sits between the seals. Any fluid that passes the first seal stays in that gap instead of reaching the atmosphere. This physical arrangement blocks media leakage through the shaft path. The body uses 304 (1.4301) or 316L (1.4404), welded connection, vacuum to 10 bar, and -10°C to 150°C. The union plus lighting version covers -10°C to 80°C.

Dual-Seal Shaft Design for Leak Prevention

The wiper shaft passes through the cover. A primary seal sits at the wetted side and a secondary seal sits behind it. Fluid must cross both barriers to escape. The gap between them acts as a buffer zone.

• Primary seal at the wetted face

• Secondary seal behind the first

• Buffer zone holds any fluid that passes the first seal

• No direct path from process to atmosphere

Seal compounds include PTFE, EPDM, and silicone. PTFE covers broad chemical resistance. EPDM handles steam and CIP cycles. Silicone suits higher temperatures.

Wiper Function and Cleaning

The wiper blade sweeps the inner glass surface. The external handle turns the shaft to move the blade across the glass. This clears product film without opening the line.

Operators restore visibility during a batch. The line stays closed and sterile. A 2 sanitary sight glass unit with a wiper fits small observation ports. Larger bodies use the same shaft design.

Body, Glass, and Connection Options

The body uses 304 (1.4301) or 316L (1.4404). The glass is tempered borosilicate. The welding connection joins the body to the line without a clamp joint.

A 4 sanitary sight glass covers mid-size lines, while a 6 tri clamp sight glass fits larger transfer pipes. Each size keeps the same dual-seal shaft layout.

Material and Surface Requirements

Wetted parts use 304 (1.4301) or 316L (1.4404). 316L resists corrosive products and repeated SIP cycles. Internal surfaces reach Ra ≤ 0.8 μm. Electropolishing lowers roughness toward Ra ≤ 0.4 μm and reduces attachment sites for microbes.

The glass-to-body joint uses a gasket seated in a machined groove. The groove holds the gasket in place and keeps the seal centered under compression.

Installation and Maintenance

Correct mounting keeps the glass visible and the seals seated. The sight glass fits any orientation, though the wiper handle should face the operator.

1. Confirm the weld end matches the line size and schedule.

2. Seat the gasket in the body groove before assembly.

3. Weld the body to the line and grind the seam flush.

4. Test the wiper through its full travel before pressurizing.

5. Inspect both shaft seals at scheduled intervals.

A worn primary seal lets fluid into the buffer zone. Replace both seals when leakage or stiffness appears. Check the glass for scratches that obscure view.

Common Applications

Sanitary sight glass units serve lines that need visual flow checks. The wiper keeps the glass clear without breaking sterility.

• Dairy and beverage flow monitoring

• Pharmaceutical transfer observation

• Brewery tank outlet checks

• Food processing pipeline inspection

• CIP return line verification

A hygienic sight glass with a wiper reduces downtime during batches. Operators clear the glass in place instead of stopping the line for cleaning.

Frequently Asked Questions

How does the dual-seal shaft stop leakage?
Two seals sit in series along the shaft. Fluid must cross both to escape. A buffer zone between them holds any fluid that passes the first seal.

Can the wiper be used under pressure?
Yes. The shaft seals hold against the working pressure, and the wiper turns without opening the line.

Which seal material suits steam service?
EPDM handles standard steam sterilization. PTFE covers broad chemical resistance. Silicone suits higher temperatures.

What is the temperature limit with lighting?
The union and lighting version covers -10°C to 80°C. The standard body without lighting reaches 150°C.

Can the glass be replaced separately?
Yes. The union connection allows glass replacement without cutting the welded body from the line.

Sanitary Stainless Steel Union Sight Glass With Wiper

• We can supply Sanitary Welded Sight Glass, Hygienic Clamped Sight Glass, Hygienic Thread Sight Glass, Sanitary Four Way Sight Glass, Sanitary Union Type Sight Glass, Hygienic Sight Glass With Light, Sanitary Sight Glass With Net.
• Sanitary sight glass is designed for sanitary applications required in food, dairy, and pharmaceutical industries.
• It is used to provide 360-degree viewing of material flow in a line.The unit is available in sanitary connection from 3/4" to 6" sizes,and can be supplied with a protective tubing of polycarbonate tubing, acrylic tubing,or slotted stainless steel,depending on temperature requirements.

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