DURAN®

DURAN® is a borosilicate glass invented by Otto Schott, and Schott still makes DURAN glass tubing for laboratory and industrial use. Duran gauge glass is that tubing cut to length for a boiler or tank water gauge: the tube sits between two gauge valves and shows the liquid level inside it. The product pages on BoilerSupplies.com list it as Schott Duran.

Four Duran types are on BoilerSupplies.com: Redline High Pressure Gage Glass (RLHP), Redline Heavy Wall Gage Glass (RLHW), Clear High Pressure Gauge Glass (CLHP) and Clear Heavy Wall Gauge Glass (CLHW). Redline or clear is the way the level shows in the tube: a Redline tube has a red stripe fused into the glass, a clear tube has none. High pressure or heavy wall is the wall grade, and a replacement takes the same grade as the tube coming out. Each is sold as a single tube or as a multi-pack. Gauge glass washers, gauge glass nuts, protection rods and cleaning brushes are on the site with them.

Key facts

• DURAN borosilicate glass was invented by Otto Schott, and Schott makes DURAN glass tubing for laboratory and industrial use.

• BoilerSupplies.com lists four Duran gauge glass types: Redline High Pressure (RLHP), Redline Heavy Wall (RLHW), Clear High Pressure (CLHP) and Clear Heavy Wall (CLHW).

• Redline gauge glass has a red stripe fused into the tube; clear gauge glass has no stripe.

• High pressure and heavy wall are the two wall grades of Duran gauge glass on BoilerSupplies.com.

• Each Duran gauge glass type is sold as a single tube or as a multi-pack.

• In-stock small-pack orders placed before 2:00 PM EST, Monday through Friday, ship the same day.

Gage glass, sight glass, water glass, boiler glass: is that all the same Duran tube?

In the boiler room, mostly yes. Gauge glass, gage glass, water glass and boiler glass are what buyers call the Duran tubular gauge glass on BoilerSupplies.com. That is the tube between two gauge valves that shows the level. Sight glass is wider and covers other level glass too. Some product names keep the older spelling, Gage Glass. A flat glass level gauge is a different part.

What do you need from me to size Duran gauge glass?

Measure the old tube before it goes in the trash: outside diameter and overall length. Then say which one it is, Redline or clear, high pressure or heavy wall, and how many you need. With the old tube already gone, send the gauge valve size and the distance between the two valves instead. Note the service, steam or water.

What is the red stripe on a Redline gauge glass for?

The red stripe is fused into the tube so the water level reads at a glance. The stripe shows through liquid and not through vapor, so the wet part of the tube looks dark and the dry part looks light. Clear Duran glass has no stripe and shows the water itself. Both are on BoilerSupplies.com in high pressure and heavy wall.

How do I tell whether my gauge takes high pressure or heavy wall Duran glass?

Match the tube coming out. High pressure and heavy wall are the two wall grades of Duran gauge glass, and a gauge takes one or the other. The old tube or the gauge paperwork tells you which one is in there now. When neither is at hand, send the tube markings and the boiler pressure with the quote request.

How often should a boiler gauge glass be replaced?

A tubular gauge glass comes out when it clouds, etches or gets scored and the level is hard to read. Some plants change it at a scheduled outage rather than wait. Keep a spare Duran tube and a set of gauge glass washers from BoilerSupplies.com on the shelf, so a cracked glass does not take the boiler down.

Order Duran gauge glass on BoilerSupplies.com by type, outside diameter and length, or call 1-770-957-9599 or toll free 1-800-780-3776 with those three details.