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Viewing Window for Engine Test Cells

Viewing Window for Engine Test Cells

Viewing Window for Engine Test Cells

Dear Experts,

This is quite an unusual question but I was wondering whether there are any particular kind of glass that is normally used for engine test cell windows. The engine test cell at my work place is currently being upgraded and we are looking to use glass window for viewing. I am looking at using bullet proof glass for safety reasons but I think it may be a bit of overkill. I will be doing some calculations on energy from connecting rod or fly wheel falling of the engine and possibly hitting the window. Are there any other calculations I should consider? What would be really useful if you could please provide an idea of which type of glass is normally used and/or any methods used to specify a particular glass for the application?

Thank you.

RE: Viewing Window for Engine Test Cells

It was a lot of years ago that I worked in engine test cells but if I remember correctly there were multiple layers of glass with space between them in two banks set at different angles. Don't know what type of glass it was. We were running heavy duty diesel truck & off highway vehicle engines up to 700 HP and there was a LOT of rotating energy. Very infrequently there were major failures and a flywheel would get loose. They could tear up a cement block wall or climb the wall and walk across the ceiling. I preferred the test cells where the operator and window were not in the plane of any rotating objects.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Viewing Window for Engine Test Cells

I was thinking the same thing; first line of defense is keeping the windows out of the way of rotational planes. A flywheel of connecting rod has so much more mass and kinetic energy than a bullet ...

RE: Viewing Window for Engine Test Cells


....I preferred the test cells where the operator and window were not in the plane of any rotating objects.

All the cells I've seen had viewing windows at the front of the engine for that reason. Usually glass with mesh.

RE: Viewing Window for Engine Test Cells

We had quite a few where the window was parallel to the engine axis, IE in the plane of rotation. Now that you mention it, I think there was wire mesh as well.

I was running a NATO certification test cycle on a 700 HP engine and a visiting dignitary opened the test cell door and stood right next to the engine running full bore. Fortunately nothing happened but I nearly had a heart attack.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Viewing Window for Engine Test Cells

Thank you very much for you help guys. :)

RE: Viewing Window for Engine Test Cells

Like others noted, the single recip engine test cells I have seen had the operator facing the front of the engine. Things can get pretty exciting at the sides and rear (flywheel) end if a rotating/reciprocating component breaks free. The windows were also very short in height, maybe 10-12" or so. Just high enough so the operator could see the engine when sitting at the control station. I guess the smaller windows present less of a target. The level of noise transmitted to the operator can be a significant problem with extended periods of testing, especially with high-performance or large engines. You can wear hearing protection, but simply having your body exposed to high levels of engine noise for long periods of time can be physically fatiguing. I think small multi-pane windows would be helpful in reducing the amount of transmitted noise the operator is exposed to.

I agree with what GregLocock said about fire related hazards, especially with confined test cell spaces. Many years ago I recall doing some dyno work with a large diesel engine that used a prototype 1500bar CR injection system. The engine produced quite a bit of vibration, and the high-pressure fuel line connections occasionally sprang leaks during running. In just the blink of an eye these high-pressure leaks would envelope the engine in a cloud of finely atomized diesel fuel, creating the perfect conditions for an explosion. The spray from the high-pressure leaks was so finely atomized that it was hard to see from the control station. We had to have one operator constantly watching for leaks (thru a small window) during operation, which was not an easy thing to do for a test period lasting several hours. But even if the operator saw the leak the instant it occurred, hitting the E-stop and bringing that large engine to a halt still took a couple seconds. The test cell was sealed except for two large ducts that circulated outside air thru the test cell by fan. Thankfully we never experienced a test cell fire or explosion, but I still wonder if the barrier (window and wall) between the test cell and the operator station would have withstood the pressure from an explosion.

Engine test cells located inside a building structure might need to be fire rated for an extended period of time, possibly an hour or more. Thus a fire rated window material would be required, which means some type of glass such as this.

Hope that helps.

RE: Viewing Window for Engine Test Cells

For normal viewing, why use windows?
Video cameras and monitors are cheap enough, and they can't transmit kinetic energy.
for a few bucks more you can get remote pan and zoom units.
For a full fail-safe window, some basic durable heat resistant glass with some thick steel plate on the inside that can be swung out of the way if something destroys all the cameras.
(if all the cameras were destroyed, would YOU open the shield?)


Jay Maechtlen

RE: Viewing Window for Engine Test Cells

hmm - regardless of the presence/absence of windows, would IR cameras be effective for flames?
Other "color" filters for other kinds of events?

Jay Maechtlen

RE: Viewing Window for Engine Test Cells

i think you best put this question to a knowledgeable glass manufacturer. they can supply many types of glass, be it of the "bulletproof" variety of glass that can act as a soundbarrier. what you need is a combination of both - and the most suitable combination can consist of different layers of glass, glued together or separated. there has been quite a development in the types of glass and glass combinations over the past years so you would be best served by someone from inside the glass industry to advise you.

RE: Viewing Window for Engine Test Cells

Here's an extreme example of an engine test cell window. 4 separate layers of ballistic/explosion resistant glass.

Here's a link to a manufacturer of engine test cells for hazardous applications that has a couple videos discussing how they deal with problems like fire, noise, explosion, etc.

The safest approach would be to eliminate the window, move the operator station to a location away from the test cell, and install a system of sensors and cameras that the operator can use to monitor the test cell. However, this would also likely cost more money than the OP is willing to spend on this test cell upgrade.

Lastly, as romke suggested you can try contacting a manufacturer of ballistic/explosion/fire resistant glass such as this: http://www.fireglass.com/glass/pyrostop/Pyrostop_B... . But due to liability concerns, all they will likely say to you is refer to the data we have published for the material.

RE: Viewing Window for Engine Test Cells

When selecting a window for an engine test cell, you generally need to consider blast, pressure, fire and noise resistance. The properties of the window (and doors) need to be matched to the properties of the wall, else one component may compromise performance of the entire structure.

Windows should be placed out of the plane of rotation of major equipment. If this is not possible, then a ballistic analysis should be performed by a qualified person to determine the necessary impact resistance for the window, and the window designed to suit.

Windows should have internal pressure rating equal to that of the test cell walls and doors. Test cells designed for gaseous or volatile fuels should have pressure limiting features, with (usually) one "weak" wall that vents to a safe outside area. See NFPA 68.

Wire glass windows in fire-rated walls are quite limited in allowable size (100 in^2). Large view windows can be made of fire-resistant glass, but this material is very expensive, and probably the assembly would not be UL rated. Also fire-resistant glass is "one time use", it must be replaced in event of a fire. Therefore it is common to install a non-fire-rated glass window but to protect the window on the test cell side with an automatic closing fire shutter. Usually the shutter has thermal fuses on both sides of the wall. The shutter can be closed by hand for privacy.

Good sound transmission resistance usually requires at least two "lights" (glass panels) separated by an air space. Typical construction for a vehicle engine test cell might be 1-1/4" thick laminated safety glass test cell side, with 1/4" thick LSG operator side. This construction will obtain pressure rating of 100-144 psf depending upon window size.

David P

RE: Viewing Window for Engine Test Cells

With how low electronics prices are I would sooner opt for three of four HD (1080p) video cameras. You would have much better vision through these than through 1" of laminated glass.

I worked with some people recently on a test cell (not engine) where they handle highly flammable fluids at high pressure. They installed a high pressure water fire suppression system. They deliver water and nitrogen to the heads at about 5,000psi and create a fog. I watched them put out test fires, and leave no puddles in the room. They knock the oxygen level back to about 12% and absorb heat with the mist.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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