Hygienic Sight Glass Types: Tubular, Union Type, Wiper and LED
A sight glass lets you see the product inside a closed tank or pipeline without opening it. Operators can visually check whether the product is flowing, its colour, foaming, the filling level or the progress of CIP cleaning. In this article we explain the types of hygienic sight glasses and which one is preferred for which application.
Features of a Hygienic Sight Glass
- Stainless steel body: Bodies are made of AISI 304 or AISI 316L stainless steel with a mechanically polished finish.
- Cleanable design: Smooth surfaces allow sight glasses to be used together with CIP (clean-in-place) systems.
- Welded installation: Sight glasses are welded into the pipeline or onto the tank or equipment surface for a permanent, leak-tight fit.
Sight Glass Types
Tubular Sight Glass
In the hygienic sight glass, a glass tube is clamped between two stainless steel end pieces and surrounded by a protective cage. Because the section the product passes through is made entirely of glass, the flow can be observed from every side. Sizes from DN15 to DN100 are listed on the product page.
Union Type Sight Glass
The union type sight glass consists of a stainless steel body welded onto the surface and a flat glass held in place by a union nut. The glass can be cleaned or replaced by removing the nut. It is used to monitor the contents of tank shells and equipment. Sizes from DN25 to DN100 are listed on the product page.
Wiper Sight Glass
The wiper sight glass cleans product stuck to the inside of the glass with a wiper operated by an external lever. Viscous products such as yoghurt, chocolate, sauces and jams can form a film on the glass and block the view; the wiper keeps the inside of the tank clearly visible at all times.
LED Wiper Sight Glass
The LED wiper sight glass adds LED lighting to the wiper mechanism. It makes it easier to see the product surface and level when the inside of the tank is dark. Its low-heat lighting is safe to use in food, beverage and pharmaceutical processes. Sizes from DN50 to DN150 are listed on the product page.
| Type | Key feature | Typical use |
|---|---|---|
| Tubular sight glass | Flow visible from all sides | Process pipelines |
| Union type sight glass | Flat glass removable via the nut | Tank and equipment shells |
| Wiper sight glass | Wiper that cleans the glass | Tanks processing viscous products |
| LED wiper sight glass | Wiper and LED lighting | Dark tank interiors, level checks |
Choosing the Right Sight Glass
- What will you monitor? A tubular sight glass suits monitoring flow in a pipeline; union type sight glasses suit viewing the inside of a tank or equipment.
- Nature of the product: For dense or viscous products that stick to the glass, wiper models keep the view clear.
- Lighting: If the inside of the tank is not bright enough, choose the LED model.
- Size and material: The size of the sight glass must match the line or port it is fitted to. AISI 316L offers higher corrosion resistance than AISI 304 in chloride-containing and aggressive environments.
Technical Information and Quotes
The dimension tables and technical drawings of the sight glasses are available on the related product pages. You can find other tank equipment in the Hygienic Products category and information on CIP systems in our CIP equipment article. To request a quote, get in touch with us.