Oil Sight Glasses

Oil Sight Glasses

Save your equipment by monitoring the oil!

Product line-up

Hex-Duty oil sight glass

Hex-Duty OSG

High temperature oil sight glass

High Temperature OSG

High volume oil sight glass

Large Volume OSG

►Hex-Duty Oil Sight Glass (OSG)

The Hex-Duty Sight Glass is stronger and more durable, with double the pressure rating at 400 psi.  The new hexagonal design allows for easier installation, draining and disassembly. Available in 1-ounce and 3-ounce bottle sizes, with either a ¼”, 3/8”, ½” or ¾” NPT.

Water wreaks havoc on lubrication systems, causing premature wear. With the Hex-Duty OSG, you have immediate visual inspection of the oil and the ability to drain and accumulate water. The OSG is installed directly to a drain port located at the bottom of a reservoir or with an elbow for drain ports located on the sides of equipment. The spring-loaded drain valve is utilized to purge any accumulated water. Any sediment or particles in the lubrication fluid will matriculate to the OSG where, upon inspection, you can determine appropriate action. The OSG is perfect on 


  • Cast acrylic
  • Brass nipple
  • Brass drain valve

Recommended Temperature Range

  • -40° F to 200° F
  • -40° C to 93° C
  • Up to 400 psi

Available Options

  • 1 oz and 3 oz bottle sizes
  • 1 oz model has a ½” NPT installation port (adaptors available for other sizes)
  • 3 oz model has a ¾” NPT installation port (adaptors available for other sizes)
  • Stainless steel hardware
  • Magnetic drain valve for ferrous particles


  • pumps, 
  • gearboxes, 
  • storage tanks
  • fluid-lubricated machinery
Hex-Duty oil sight glass
Hex-Duty oil sight glass

Esco sight glasses

►High Temperature Oil Sight Glass (OSG)

High Temperature Oil Sight Glass is a solution when radiant heat is a factor. Offered in 1 ounce or 3 ounce vertical mount, it attaches to the drain valve of equipment and provides immediate oil inspection and ability to see and drain water contamination for high heat applications up to 232°C (450°F). Available in Vertical Style.

Even under extreme temperature conditions, you will still be able to visually monitor the oil qualities and expel water contamination.


    • Heavy-walled Pyrex glass
    • Teflon™ end plates
    • Stainless steel nuts & bolts
    • Viton O-rings
    • 1/4”, 3/8” or 1/2” NPT brass nipple included
    • Brass drain valve (1/4” NPT)
    • Stainless steel hardware or magnetic drain valve options available
    • See FAQs for more information

Operating Range

  • 232°C (450°F) at 200 PSI
High temperature oil sight glass
High temperature oil sight glass features

Esco sight glasses

►Large Volume Oil Sight Glass (OSG)

The Large Volume Oil Sight Glass vertical models of 16 oz and 32 oz capacity are used in situations where water contamination is severe or the operators want to observe larger volumes of oil.

When reservoirs or equipment produce so much water such that other products cannot hold it all between maintenance checks, the Large Volume Oil Sight Glass provides the extra storage to keep water out of the oil until it can be drained.

Commonly used on large oil reservoirs, or on equipment operated in environments with regular high pressure wash downs or high condensation problems, where water contamination cannot be avoided or minimized.

The added volumes of this line of products provide continuous fluid monitoring of the clarity, colour, sediment and water contamination. 

Added advantage: storage of more water accumulations between service or monitoring intervals.


  • Commercial grade cast acrylic
  • Brass spring-loaded drain valve included (1/4” NPT)
  • Offered in both 16 oz and 32 oz vertical bottles
  • ½” NPT brass nipple included for connection
  • Stainless steel hardware available
  • See FAQs for more information on installation & cleaning

Operating Range

  • 82°C (180°F) to 265 PSI
  • 95°C (203°F) to 66 PSI
  • 110°C (230°F) at atmospheric pressure
  • -40°C (-40°F) minimum low temperature

High volume oil sight glass

Large volume osg

Esco sight glasses

For more technical- and price-info please visit our webshop


FAQ Oil Sight Glasses

When is a High Temperature Oil sight Glass required?

When oil operating temperatures or radiant heat from adjacent equipment exceeds or is continually at or near the operating range upper limits, you should consider utilizing the High Temperature Oil Sight Glass.

How do I clean the Oil Sight Glasses?

The best way to clean is with soap and warm water. Commercial cleaning products containing alcohol or ammonia (including Windex) should be avoided, as they may cause crazing that can expedite staining and/or compromise the bond strength.

How often should the Visual Oil Analysis Products be replaced?

Under normal operating conditions, the life spans of the 3-D BullsEye, Oil Sight Glass, and Oil Level Indicator are not limited. Repeated exposure to caustic chemicals can cause staining and small surface cracks called crazes, which can lead to larger cracks and bonding failure. Environmental factors such as long periods of direct sunlight and radical swings in temperature can expedite staining or crazing. Designed to withstand normal industrial lubrication applications, the visual oil analysis product line can work for years without failure or degradation, but operators should watch for staining, crazing or microscopic oil seepage that may arise and replace the unit immediately to insure safe and effective oil management.


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