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Sight GlassLighting

Understandingand Specifying

ApplicationHandbook


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Table of Contents

Introduction 1

Light echnologies 1

Light Output 3

Determining Wattage orYour Application 8

Mounting Lights 9

Light Accessories 11

Environmental Considerations 11

L.J. Star Incorporated provides an extensive line o process observation equipmentsightglasses, lights, sanitary ttings, and level gage indication. Product lines include Metaglas

Saety Sight Windows, Lumiglas Explosion Proo Lights and Cameras, Visual FlowIndicators, Sight Ports, Sanitary Clamps, Magnetic Level Gages and Gage Glass. Metaglas isthe #1 selling used sight glass, proven in thousands o installations around the world. Unlikesome other sight glasses, it meets stringent DIN 7079 and DIN 7080 quality standards, andhas been tested and proven to meet the USP ype I standard.

Copyright 2011 L.J. Star, Inc.


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1

Introduction

How to Spec Lighting for Sight Glass ApplicationsChances are the interior o vessels and pipelines are too dark or operators toview important stages o their process through a sight glass. Flashlights cannotsupply sucient lighting, and may cause a glare on the sight glass, making

visual inspection virtually impossible. Tereore, illumination must besupplied by mounting lights (also called luminaires) onto sight glasses.

When deciding upon a proper light or an application, be sure to consider all

o the properties o the light. Te type o technology, size, weight, voltage,wattage, materials o construction, mounting conguration, and lightpattern are all very important actors. So are energy consumption, locationrequirements (i.e. hazardous), heat output, ambient conditions, and vibration.Tis handbook covers all these considerations so that speciers can choose theideal lighting solution or the application.

Light TechnologiesTere are several technologies used to generate light. Te types o lightsinclude incandescent, halogen, LED, metal halide (HID), compact uorescent(CFL), and ber optic. Halogen lights are the most common types used insight glass applications, but LED lights are growing in popularity.

Halogen and Incandescent Lights

85% o energy is consumed by heat generation not energy ecient

2800 K temperature approximates dusk and causes eye atigue

Emit a spherical light source that is dicult to capture and apply tothe operational eld

Filament can be damaged by shock, vibration and over-voltage,shortening bulb lie

Limited bulb lie rating requires routine maintenance or

bulb replacement Inexpensive and readily available


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Sight Glass Lighting

Applications Handbook

LED Lights

Long service lie (ve years and improving) reduces needor maintenance

Shock and vibration resistant because there is no lament

Smaller size compared to halogen and incandescent lights osame brightness

Cold light output

Energy ecient (low operating costs green technology)

Generate directional light Easy-to-control color output or greater denition and less eye atigue

Can remove potentially harmul or unwanted radiation, such asultraviolet and inra-red light

Metal Halide (HID) Lights

Cool burning

Consume less power than halogen lights Produce more light at higher color temperature

Require a ballast

Oen the best choice where long continuous use and high intensityoutput are required

Compact Fluorescent Lights (CFL)

Require proper disposal (mercury)

Last around 10,000 hours

2025% o energy cost compared to halogen

Dicult to reect; not good or process vessel lighting

Most commonly used or residential area lighting

Fiber Optic Lights

A specially designed halogen bulb generates the light into a bundle o

ber optic strands which transmits the light to the sight glass Te light housing can be mounted several eet away rom vibrating

equipment to preserve bulb lie

LED technology can also be used as the light source

Can easily be designed or cold light output


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Comparison of LED and Halogen/Incandescent Lighting

LED LightHalogen andIncandescent Lights

Heat Generation 5% o energy consumed is lost toheat generation

85% o energy consumed is lostto heat generation

Eciency 55.6 lumens per watt 10 lumens per watt

ColorTemperature

4800 - 6300 K temperature,approximates daylight, providesgreater ground defnition andless eye atigue

2800 K temperatureapproximates dusk and causeseye atigue

Usable Pattern Emits a directional lightsource that can eciently becaptured and translated into theoperational feld

Emits a spherical light sourcethat is very dicult to captureto the operational feld

Lie Filament ree design Filament design that whensubjected to shock and vibrationcauses damage and shortensbulb lie (instant expiration)

Value Lower maintenance costs, betterwarranty coverage, lower powerconsumption, and longer lie

Routine maintenance,standard warranty, high powerconsumption, and shorter lie

Light Output

Terms of Light Measurement: Lumens and Foot-Candles

Lumens is a measurement o light in all directions. Tis unit o measurement

is best used or incandescent bulbs. When a reector is used, the light isreected in one direction. As a result, lumens is not an efective measuremento reective light. Tereore, the unit o measurement that measures light at adistance rom the bulb is called candela, which is more commonly reerred toas oot-candles.

Another efective unit o measurement o reective light is called lux. Foot-candles can be converted to lux by the ollowing ormula:

Foot-Candles 0.0929 = Lux

Generally speaking, oot-candles and lux are inversely proportional to thedistance squared. For example, a lux o 200 at a distance o 5 eet rom a bulb


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is 50 lux at a distance o 10 eet. In other words, i the distance is doubled thenthe lux is reduced to o the original lux.

Relationship of Voltage to Light Output

A bulb with lower voltage (say 24V) will produce light more eciently than abulb with higher voltage, such as 120V. Here is the basic power ormula:

Voltage Amperage = Wattage

As the voltage increases and the wattage remains the same, the amperage must

be reduced. In other words, the amperage is inversely proportional to thevoltage, assuming the wattage remains constant. As a result, the higher thevoltage the more resistance is needed. Tereore, a longer, thinner lamentis required.

A shorter, thicker lament has two benets: First, a thicker lamentcan burn hotter and produces a brighter, whiter light. Second, a shorterlament produces more light at the reectors ocal point, resulting in moreecient reections.

Reector

In order to maximize the light output using a reector, the center o the bulbslament must be placed at the ocal point o the reector. Te intention isto have all the light directed in a parallel manner (see Figure A). Tere willalways be some angle o light since some light will be direct (see Figure B). Atypical angle o reection or a spot conguration is 10. Te shape o the

reector and its position in relationship to the bulb afects how wide ornarrow the beam will be.

Figure A Figure B


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Flood Light

It is not always desirable to have a narrow light beam or a spot light. Tere arethree ways to accomplish this, but keep in mind that light eciency will becompromised. Te rst way is to position the center o the lament near theends o the reector (see Figure C). In addition, this allows or more directlight to be generated.

Figure C Figure D

A second method is to design the reector at a slightly diferent parabolicshape so as to reect the light at angles (see Figure D). A third way can beaccomplished by a dimpled glass lens which is usually incorporated into thebulb and reector, known as an encapsulated bulb. A common example othis is an outdoor oodlight. A typical angle o reection or a oodlight isapproximately 3035.

Light Intensity (Output)

Te light required or a given task depends on the nature o the task. Te tablebelow shows that tasks or close inspection require more light than other tasks.Unortunately, this table is not as helpul or speciying lighting or processobservation. For this, the specier must trust experience or seek the advice oa lighting supplier.


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Typical Tasks

Lighting

ReQuirements

Suggested

Foot-Candles

Dicult tasks, reading, general oce work,inspection, complex assembly, color coding,adding fnishes to products, repair involvingsmall parts

Bright 100-200

Moderate assembly, sorting, checking,complex bench work, viewing instrumentpanels, automotive repair, oce hallways

Moderate 50-100

Casual tasks, simple assembly, grinding,

simple inspection, packing, labeling, generalindustrial work

General 20-50

Washrooms, rough active storage,mechanical rooms

Adequate 10-20

Inactive storage, stairs Dim 5-10

When determining how much illumination is needed or a particular viewingtask, the actors to consider are the depth o the vessel, its characteristics, the

required viewing area, and the nature o the material under view. What is theview distance, and does it change signicantly i the vessel must be observedat both ull and empty levels. I the vessel interior is polished and ofers areection, then lower wattage light may be used compared to a glass-lined

vessel with a dark surace that absorbs light. Is a wide view o the processessential, or will a narrow view suce? A larger view will require higher lightoutput. Finally, the material under view plays a role. Light colors need lesslight; dark colors need more. I the goal is simply to observe level, then this

task may be accomplished with little light. I the goal is to observe residue,then more light may be needed. I the goal is to inspect or the presence ooam, then a wide view may be needed that may require more light.

Light Distribution Chart

Te ollowing is a typical light chart that illustrates the intensity o light atvarious distances rom the bulb. In addition, the chart shows the diameter othe area illuminated at the various distances. Te design o the reector to thebulb will determine the distribution pattern, or angle o light.


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3.3 ft.

6.5 ft.

9.8 ft.

13 ft.

223

56

24

147.2 ft.

diameter

5.4 ft.

3.6 ft.

1.8 ft.

Distance

From Source

Foot-Candles

(at center)

Reducing Heat Output

A typical halogen bulb produces 15% light and 85% heat. Heat comes romthe inrared light o a bulb, which cannot be seen by the naked eye. Tere arethree ways to reduce the IR light (or heat) rom a light source. First is the useo a cool beam bulb. Tis type o bulb incorporates a reector that allows IRlight to pass through while reecting only the white or visible light. However,

this is not 100% ecient in eliminating IR light rom exiting the luminairesince some light is direct and does not pass through the reector.

A second method o reducing IR light rom a halogen bulb is to incorporatean IR mirror. Tis device, placed opposite the reector, reects the IR light


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back into the luminaire while allowing the visible light to pass through. Athird solution, similar to the IR mirror, is an IR lter. However, insteado reecting the IR light, the lter absorbs it while allowing the visiblelight to pass through. An IR lter is oen used in the pharmaceutical andbiotech applications when the product under process is heat sensitive. Tecombination o a cool beam bulb and an IR mirror or lter is very ecient.

It should be noted that LED lights are available that do not add heat to theprocess. Tese lights have the additional advantage o extremely long lieand are shock and vibration resistant, which reduces maintenance costs. In

addition, metal halide, or high intensity discharge (HID), lights producemuch less heat since they operate at much lower wattage compared to halogenlamps o equal intensity.

Filtering Light Output

Filter glass is available that will block light o a certain color. Te lter may beadded in lighting applications in which the process uid is light sensitive, such

as a photo process uid. A light o higher intensity may be needed to providesucient illumination or viewing.

Determining Wattage for Your Application

Te wattage o the bulb you select should be based on the distance o the bulbrom the target. Te ollowing gure shows the maximum recommendeddistance or bulbs o diferent wattages. Tis chart is or halogen bulbs only.

For LED and metal halide (HID) lights, convert the wattages to the halogenequivalent, and then apply to the ollowing gure. Most manuacturers othese special lights will provide the halogen equivalent.


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3 ft.

6 ft.

9 ft.

12 ft.

15 ft.

20 ft.

30 ft.100 Watt Spot

100 Watt Flood

50 Watt Spot

20 Watt Spot

35 Watt Flood

20 Watt Spot

35 Watt Flood

5 Watt

Recommended

Maximum

Distance

Mounting Lights

Lights use diferent mounting congurations ranging rom a hal-moontype that ts a weld-on sight port to a light that ts directly into a sanitarytting or one-piece mounting onto a sanitary errule. o add lights to existingsight glasses, mounting brackets are oen an option to mount directly to theretaining ange. Brackets are also the most common means o mountinglights on sight ow indicators.

In some applications, one sight glass is used or viewing and another isdedicated to lighting. In this case, a light may be equipped with a built-insight glass or it is oen mounted onto a sight glass the same diameter o the


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light. Other designs have the light mounted of-center o a larger sight glass,allowing combined lighting and viewing.

I a sight glass is too small to utilize a standard light and leave room orviewing, then a ber optic light is recommended. Te ber optic bundlemounts to the sight glass and the halogen bulb or other light source may bemounted at a distance. Tis arrangement is good or tight spaces and ormoving the light source away rom vibration that could damage the bulblament and reduce bulb lie.

Oen, standard mounting options will not t to the design o an existing port.Special ports may require special mounting. Special mounting congurationscan be designed to suit specic requirements. Below are some mountingcongurations.

Half-Moon Light &

Sight Port Combination

Sanitary Connection

Light Port Only

Bracket Mount Light &

Sight Port Combination

Light Mounted onto

Visual Flow Indicator


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11

Light Accessories

Special consideration should be given to determine how the light will becontrolled. A simple solution is a pushbutton switch that the operator can

press when he or she needs to see inside the vessel. Alternatively, the lightmay be controlled by an electronic or pneumatic timer that, when manuallyactivated, keeps the light on or a pre-determined length o time. Videocameras are also available that include lighting in their conguration. Ocourse, i the application is in a hazardous location, then these accessoriesmust satisy requirements or explosion-proo rated devices.

Environmental Considerations

Explosion Proof Ratings

Many processes take place in hazardous environments where explosiveconditions may be present. Explosion-proo lights, oen called EX lights, arereadily available or these applications. Te datasheet o the specic light will

state which standards the light meets.Te standards or hazardous locations are dened by the National ElectricCode (NEC) Article 500. For Class I ratings, the level o hazard dependson requency o occurrence. Te longer the material is present, thegreater the risk.

FreQuency Division System Zone System

Continous

Class 1, Division 1

Zone 0

Intermittent Periodically Zone 1

Abnormal Condition Class 1, Division 2 Zone 2

In North America, explosion-proo ratings are classied into our groups,based on Material, Class, and Division. Division is based on requencyo occurrence.


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Class I groups are based on explosive properties o the gas present. Anotherstandards body is CENELEC, the European Committee or ElectrotechnicalStandardization. Cenelec uses three groups.

Gas Class/Division Gas Groups Zone Gas System

Acetylene AII C

Hydrogen B

Ethylene C II B

Propane D II A

Gas Class/Division System Zone System

Gasses or VaporsClass I, Division 1Class I, Division 2

Zone 0 Zone 1Zone 2

Combustible DustsClass II, Division 1Class II, Division 2

Zone 20 Zone 21Zone 22

Fibers or FlyingsClass III, Division 1Class III, Division 2

No equivalent


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Temperature Classes

Ignition temperature is the minimum temperature at which an explosiveatmosphere ignites.

Te maximum temperature o the sight glass light must be lower thanthe ignition temperature in order or it to meet a given explosion-proorating. Te ollowing chart illustrates the maximum temperatures or eachtemperature class.

North AmericanTemperature Code

IEC/CENELEC/NEC 505Temperature Classes

Maximum

TemperatureC F

T1 T1 450 842

T2 T2 300 572

T2A 280 536

T2B 260 500

T2C 230 446

T2D 215 419

T3 T3 200 392

T3A 180 356

T3B 165 329

T3C 160 320

T4 T4 135 275

T4A 120 248

T5 T5 100 212

T6 T6 85 185


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NEMA Requirements for Hazardous Locations

Te National Electrical Manuacturers Association (NEMA) has aclassication system or the enclosures o electrical devices, which indicate thelevel o protection the enclosure ofers. Tis system ollows the NEC hazardclassications.

NEMA 7 enclosures are intended or indoor use in locations classiedas Class I, Groups A, B, C or D as dened in the National ElectricalCode (NEC).

NEMA 8 enclosures are intended or indoor or outdoor use inlocations classied as Class I, Groups A, B, C or D as dened in theNational Electrical Code (NEC).

NEMA 9 enclosures are intended or indoor use in locations classiedas Class II, Groups A, B, C or D as dened in the National ElectricalCode (NEC).

NEMA 10 enclosures are intended or use in areas covered by the

Mine Saety and Health Administration (MSHA).


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NEMA and IP Ratings

Sight glass lights may need to be installed in areas subject to airborne dust orwashdowns, and the light should be enclosed in a housing that will protect thelights internal components against dust and moisture. Speciers can look toNEMA ratings or the IP rating dened in international standard IEC 60529.

NEMA

Rating Description

EQuiv. IP

Rating

1 GENERAL PURPOSE. Intended or use indoors. IP 10

2 GENERAL PURPOSE. Intended or use indoors withadditional drip protection. IP 10

3, 3SGENERAL PURPOSE WEATHER-RESISTANT. Intendedor use outdoors, with protection rom windblown dust, rainand sleet, and undamaged by the ormation o ice.

IP 10

3RGENERAL PURPOSE WEATHER-RESISTANT. Intendedor use outdoors, with protection rom alling rain and sleet,and undamaged by the ormation o ice.

IP 10

4, 4X

GENERAL PURPOSE WEATHER-PROOF. Intended or

use indoors or outdoors, with protection rom wash downenvironment and corrosion resistance.

IP 10

5GENERAL PURPOSE DUST-TIGHT. Intended or useindoors or outdoors, with protection rom dust providedby gaskets.

IP 10

6, 6PGENERAL PURPOSE SUBMERSIBLE. Intended oruse indoors or outdoors, with protection rom occasionalsubmersion.

IP 10

7 HAZARDOUS. Intended or indoor use in Class I, Groups A,B, C and D environments per NFPA rating system. IP 10

8HAZARDOUS. Intended or indoor or outdoor use inClass I, Groups A, B, C and D environments per NFPArating system.

IP 10

9HAZARDOUS. Intended or indoor or outdoor use in ClassII, Groups E, F and G environments per NFPA rating system.

IP 10

12, 12KINDUSTRIAL USE. Intended or use in industrialapplications with protection rom dust and non-corrosive

liquid drip.

IP 10

13INDUSTRIAL USE. Intended or use in industrialapplications with protection rom dust, spraying water, oil,and non-corrosive liquid drip.

IP 10


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Te IP rating classies the degrees o protection provided against the intrusiono solid objects, dust, accidental contact, and water in electrical enclosures.

Te chart on page 15 denes the NEMA ratings and shows their equivalentIP ratings.

Minimum Required Application Information

It is important to know the ollowing inormation at a minimum to speciythe appropriate light or a specic application. Tere may also be unusualactors or conditions to be taken into consideration such as extreme ambient

temperatures, light or heat sensitive process media and equipment vibration toproperly select a light. I there are remote switches/timers required or physicalconstraints, a diagram is very helpul. Te more inormation, the better theselection.

Here is a checklist o the typical inormation needed in order to speciy sightglass lighting:

Area Classication: Non-Explosion Proo

Explosion-Proo (CENELEC)

Explosion-Proo (UL)

Light Housing:

Aluminum

316 Stainless Steel Special: ________________

Mounting Conguration:

Standard Bracket

Sanitary Connection

Special: ________________


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Available Power Supply:

120VAC 24VDC or AC

230VAC

12VDC or AC

Other: ________________

Desired Light Output:

5W 10W

20W

35W

50W

100W

Other: ________________Vessel Dimensions:

___________ diameter ___________ height

Desired Vision Area in Vessel:

___________ diameter ___________ distance rom light source

Light/Sight Port Information:

Separate light and sight ports One port will be used or the light and sight


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L.J. Star Incorporated

P.O. Box 1116

Twinsburg, OH 44087

Telephone: (330) 405-3040

FAX: (330) 405-3070

www.ljstar.com

For general information: [email protected]

For pricing information: [email protected]

For delivery information: [email protected]

For technical information:[email protected]

L.J. Star is a leading expert in the

application of sight glasses and sight glasslighting. The broad product line includes

LED lights

Halogen lights

HID lights

Fiber optic lights

Explosion-proof lights

Non-Ex lights

Cordless lights

Sanitary lights

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