The Norgren guide to effective air preparation

NT-12

CLE

AN

CO

MP

RES

SED

AIR

The air leaving a

compressor is hot, dirty, wet and

generally at a higher pressure than

the downstream equipment requires.

A typical 100 scfm compressor will

push 1,189 gallons of water and 2

gallons of degraded compressor oil

into the system in a year along with

considerable amounts of dirt

particles. Before this air can be

used it needs to be treated to

remove the contaminants, have its

pressure reduced to the right level,

and in many cases have oil added

to lubricate downstream equipment.

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Figure 1.Compressed air installation, showing examplesof air prepration applications. See details onpages 4 and 5.

APPLICATIONS4 -5

REMOVING CONTAMINANTS6 - 10

PRESSURE CONTROL11 - 13

LUBRICATION14 - 15

PROTECTING SYSTEMS, PERSONNEL AND THE ENVIRONMENT

16 - 17

SAFE SYSTEMS18

NORGREN AIR PREPARATIONPRODUCT OVERVIEW

19 - 21

GLOSSARY22

REFERENCE TABLES23

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Compressed air is often wronglyassumed to be a cheap or even ‘free’source of power. In fact it can be 10times as expensive as electricity bythe time all generation,transmission, treatment and systemcosts are taken into account. Goodair preparation must thereforeconsider the energy consumption ofthe system and air treatmentequipment.

The process of airpreparation has been at the core ofNorgren’s business for over 70years. The aim of this booklet is tooffer guidance on the correct,economic and safe treatment ofcompressed air in industrialapplications. Here we can onlyprovide a brief summary of theextensive experience Norgren has asa world leader in FRL technology.

For more detailed advicecontact your local NorgrenTechnical Sales Center.

APPLICATIONS

The following section shows several typicalsystems of a generic type and the equipmentnormally used for the application. Rememberevery system should be treated on its merits andbroken down into several elements to ensureoptimum installation, running and maintenancecosts are achieved.

The applications below are typicallybranches taken off a large works distributionmains and isolating valves are usually placed infront of all branches to permit isolation from themains to allow for maintenance to take placewithout recourse to complete plant shut-down.

For expert advice on the rightequipment for your application contact yourlocal Norgren Technical Sales Center.

General Pneumatic Circuits:eg: directional control valves and cylinders, inmulti-valve circuits, machine cleaning, airmotors and high speed tools.

A Micro-Fog lubricator is required forthe several varying flow paths to ensure fulllubrication. (Figure 2)

Multiple Simple Applications:eg: OEM machines.

It is often a case that with fairly simplemachines, lubricated air is require for valvingand pneumatic circuitry and oil-free air for airbearings. To keep costs low two separate linesare unnecessary and a typical arrangement fromone air supply only can be arranged as shown.

Other elements such as pressureswitches and check valves may be madeavailable within modular systems. (Figure 3).

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Figure 2.

Shut-off valve, filter/reg, Micro-Fog lubricator,soft start/dump, relief valve.

Figure 3.

Shut-off valve, filter/regulator, oil removal filter,porting block, Micro-Fog lubricator.

Breathing Air:eg: face masks and hoods, air agitation.

The typical application assumes that airintakes are of a reasonable quality with no C0 orC02 contamination. It may in some instances bea consideration to remove water vapor. (Figure4)

Oil-Free Applications:eg paint spraying, foodstuffs, film processing,powders.

These applications need to be free fromany water deposits in the downstream system.For many installations this will require airdrying. The drying medium (for desiccant ordeliquescent dryers) will need protecting fromoil to allow it to work efficiently and the down-stream system will also need protection fromaccidental migration of the material into it. Atypical arrangement would be as figure 5 and insome instances it might be worth considering

an oil vapor removal filter too.Heavy Duty Lubrication:eg: large slow moving cylinders.

In such applications large amounts oflubricant are required for effective lubrication.Again a soft start/dump valve is shown but isdependent upon the application. (Figure 6).

Critical Pressure Control (Instrumentation):eg: precision regulation, fluidic systems, airgauging, process control.

A typical arrangement is shown, whereoil aerosols which can prevent fast response ofdownstream devices, need to be removed.Dependant upon air quality drying may not berequired. (Figure 7)

Direct Injection Lubrication:eg: conveyor chains.

The application does not allow for‘fog’ type lubrication because of the surroundingenvironment and absence of a lubricationchamber. (Figure 8).

Continuous Processes

Another facet of Norgren’s Olympian Plus is theability to make duplex systems. This is invalu-able for systems which cannot be shut-down,such as continuous process plant. Two identicalair sets are joined together and one may beisolated (and serviced) whilst the other set is in

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Figure 4.

Shut-off valve, general purpose filter, Ultrairefilter, regulator.

Figure 5.

Shut-off valve, general purpose filter, oilremoval filter, drier, oil removal filter,regulator, relief valve.

Figure 6.

Shut-off valve, filter/reg, Oil-Fog lubricator, soft start/dump valve, relief valve.

Figure 7.

Shut-off valve, general purpose filter, oilremoval filter, drier, oil removal filter, precisionregulator.

Figure 8.

Shut-off valve, filter/reg + direct injectionlubricator.

Figure 9.

Duplex system: shut-off valve, filter/reg,lubricator, porting block, oil removal filter andshut-off valve x 2 with manifold block connectors.

operation. (Figure 9).REMOVING CONTAMINANTS

The air produced by a compressor is hot, wetand dirty. The first step in good air preparationis to filter out these contaminants. This sectionconsiders the removal of liquid water, watervapor, solid particles and finally oil.

LIQUID WATER

In compressed air systems water vapor exists asa contaminant originating at the compressoroutlet in vapor form, but as the air cools, it willexist as both liquid and vapor.

The amount of water vapor that canexist in any given volume of compressed air isdirectly proportional to the air temperature andinversely proportional to the pressure.

Most liquid water will be present whenthe temperature is lowest and the pressure ishighest and removal at this point will achievethe highest efficiency.

In order to achieve this an essentialelement of any system following the compressoris an efficient after cooler of sufficient capacityto reduce the temperature of the outgoing air towithin 8°C of the temperature of the waterentering the after cooler.

The outgoing air should then be pipedto a receiver of adequate capacity located in thecoolest location available, definitely not withinthe compressor house itself. This will permitfurther cooling of the air to occur and thereforemore condensation.

Generally the capacity of the receiver isabout 30 times greater than the rated free airdelivery of the compressor when operating inthe 7 bar g region, typical of most industrial airsupplies. See figure 10 for a typical compressorinstallation.

Further cooling may occur in thedistribution mains themselves. These should belaid out with a pitch in the direction of air flowso that gravity and air flow will carry water todrain legs located at appropriate sites. Downloops in distribution mains should be avoided,if not locate a drain leg at the down loop. Withthe exception of drain legs all air take-off pointsfrom the distribution mains should be takenfrom the top of the main to prevent water from

entering the take-off lines. See figure 1 for atypical good distribution main arrangement.

As stated earlier most efficient waterremoval will take place at high pressure, soanything which will produce a pressure dropwithin the distribution system should beavoided. This will also be a loss of energy to thesystem and increase the the cost of compressedair generation. Areas to avoid here are complexflow paths with undue bends and inadequatelysized piping. See page 23 Reference Data forfriction losses in pipe and for recommendedpipe flows.

The action of water removal can beachieved by drip leg drains, automatic drainvalves and as discussed later, filters. Thesedevices should be located in positions whereliquid water is present in amounts large enoughto be removed. (See figure 11). Because of thepossibility of cooling occurring during thepassage of the air through distribution mainsand branch lines it is preferable to installsmaller individual filters as near to the actualpoint of air usage as possible, rather than relyon one large filter adjacent to the air receiver. Apoint to remember is that since most water willbe present at higher pressures, always locatefilters upstream of any pressure reducing valves.

Filters which have the ability to removewater are designed for efficient water removaland low pressure drop in accordance with therecommended pipe flows (see page 23) andNorgren filters will have high efficiencies up to200% of this recommended figure.

WATER VAPOR

A properly designed air line filter of the correctsize, in the correct location will effectively andefficiently remove liquid water, but will notreduce the water vapor content of the air. Furtherair cooling may result in more water condensingout. If complete freedom from water contamina-tion is essential then the water vapor content ofthe air must be lowered such that the ‘DewPoint’ of the air is lower than any temperaturethat the air can be exposed to in the system.

Once all liquid water is removed fromcompressed air, then normally the air will becompletely saturated with water vapor. Theparticular temperature and pressure at which thecompressed air exists at that moment is knownas the ‘Pressure Dew Point’.

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Figure 10TYPICAL COMPRESSOR INSTALLATION

Figure 11. DRIP LEG DRAIN

Dew Points are normally measured atatmospheric pressure and can be related toPressure Dew Points through appropriate charts.

In order to remove water vapor from acompressed air system Air Dryers must beemployed. The efficiency of these devices ismuch increased by ensuring that they are notcontaminated by liquid water or oil (or combina-tions - emulsions) and are supplied with air atthe lowest possible temperature. So they areadditions to the system and not alternatives tofilters and after coolers.There are 3 principle types of Air Dryer;

Refrigerant, Regenerative Adsorbent Desiccant andDeliquescent Absorbent Dryers(The general comparative abilities and

comparative costs are tabled in the ReferenceData on page 23)

In order to keep the costs of air dryingto a minimum consider the following:-

a) Does the particular process require airdrying or will efficient after coolers,receivers and filters suffice?

b) Do not specify extremely low DewPoints if the process does not warrantthem.

c) Limit the volume of air being dried tothat actually needed for the particularprocess with an adequate margin forfuture expansion. This may indicateonly one area of a process plant needemploy a dryer.

d) The major requirement for air dryers ingeneral industrial applications is wherehigh ambient temperatures exist.

SOLID PARTICLES

Like water, solid particles exist in anycompressed air system regardless of the type ofcompressor. These can arise from four principlesources:-

a) Atmospheric dirt inhaled at thecompressor inlet port.

b) Corrosion products due to the action ofwater and weak acids, formed by theinteraction of water and gases such assulphur dioxide inhaled by thecompressor.

c) Carbon products formed by the actionof the heat of compression on thelubricating oil or the normal wear ofthe carbon piston rings used in sometypes of oil free compressors.

d) Particles originating from the mechan-ical fixing of the metal pipe work andcomponents into the air distributionsystem.The size of dirt particles covers a very

wide range from several hundred to below onemicron (see figure 12) and the level of filtrationdepends upon the degree of cleanliness neededfor the particular process involved. Generally itis inadvisable to provide finer filtration than isabsolutely necessary because the finer thefiltration, the greater the quantity of dirt trappedby the filter element and the more rapidly it willbecome blocked.

Particles can be broken broadly intotwo groups, coarse (40 microns and above) orfine. Most normal air line filters will satisfacto-rily remove particles down to 40 microns.

Fine filtration in the region 10 - 25µmis normally required for high speed pneumatictools or process control instrumentation.Filtration of 10µm and below is essential for airbearings and miniature pneumatic motors.Norgren general purpose filters are availablewith different grades of element to offer thesevarious filtration levels. Some applications mayneed filtration better than this and indeed forpaint spraying, breathing air and food relatedapplications particle removal below 1µm is alsoessential. Standard air line filters cannot be

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Figure 13. GENERAL PURPOSE FILTER

Figure 12. PARTICLE SIZES

Particle Diameter, Microns0.01 0.1 1.0 10.0 100

Aerosols llll ll l l l l l l l l l lSprayTobacco SmokeHuman HairVirusesBacteriaSiltFine SandCarbon BlackCoal DustPollens

used and high efficiency filters (oilremoval/coalescing filters) must be employed.Standard air line filters should still be employedas pre-filters to these high efficiency filters.High efficiency filters will remove theseextremely fine particles and if exposed also tothe coarser particles they will simply clog andbecome congested with dirt extremely quickly.

All elements will become blocked inuse. The level to which the blocking is accept-able is dependent upon the application and theenergy consciousness of the plant operation.Standard filters can be cleaned and reused butin today’s environment with labor costs high andspare parts inexpensive it is normally better toreplace elements. This will also ensureminimum pressure drop on reinstallation ascleaning at very best will only remove 70% ofaccumulated particles. High efficiency filterelements cannot be cleaned and must bereplaced before they become blocked with dirt.

Under normal usage conditions generalpurpose filter elements are usually changedbefore their pressure drop is greater than 0.5bar, or in routine annual maintenance. Theperiod can always be adjusted by monitoring forcritical applications using a service indicator(figure 15).

High efficiency filters should have theirelements replaced when a pressure drop of 10psi is achieved. Again a low cost serviceindicator is often employed. This device has ascale of two colors, usually green/red. Theelements should be changed when or before allred is achieved. Electrical service indicators arealso available from Norgren, to provide remotesignalling. Maintenance schedules can beproduced to ensure this ‘last chance’ situation isnot achieved, indeed some applications cannottolerate even this much pressure drop, espe-cially if this is at the generation point of a largecompressed air distribution main as the cost ofextra energy alone would be very large.

OIL

The principle source of oil contamination withina compressed air system is from thecompressor. An oil lubricated compressor of105 scfm capacity may introduce as much as0.17 quarts of oil per week into the system.

Oil is used for lubrication of thecompressor but when it emerges with thecompressed air prior to distribution the oil isnow in a totally unusable state. Having beensubjected to high temperatures during aircompression it becomes oxidized and acidicand can be considered as an aggressivecontaminant rather than a lubricant and so mustbe removed.

Normal air line filters will removesufficient liquid oil (along with water) to leavethe air in a suitable condition to supply mostpneumatic tools and cylinders, but certainprocesses demand completely oil-free air.

One solution is to use oil-freecompressors. These will still produce aircontaminated with dirt and water and it is oftenmore economical to use lubricated compressorsin conjunction with after coolers and standardair line filters, only fitting high efficiency oilremoval filters at the points in the system whichdemand oil-free air. This ensures that theamount of air needing special treatment is keptto a minimum by allowing a smaller specializedfilter in the affected area and not a large special-ized filter for the whole plant.

Oil in a compressed air system canexist in three forms, oil/water emulsions,aerosols (small particles suspended in the air)and oil vapors.

Emulsions can be removed by standardair line filters but the aerosols are our nextconcern.

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Figure 14. ‘PURAIRE’ COALESCING FILTER

Figure 15.FILTER SERVICE INDICATOR

OIL AEROSOLS

These particulate oil droplets exist in theairstream and the most troublesome are in thesize range 0.01 to 1 micron (approx 90%), therest may be slightly larger (see figure 12 particlesize chart).

Most standard air line filters achievewater removal by centrifugal action but due totheir small particle size these aerosols areunaffected and require special coalescing filters.

In addition to removing the oil dropletsthese filters will also remove minute waterdroplets, but they must be protected againstgross dirt or water contamination by means ofstandard air line filters mounted immediatelyupstream (figure 16). It is normally advisablethat these filters are capable of removingparticles down to 5 microns or less otherwisethe coalescing filter may quickly become chokedand blocked with dirt, requiring a filter elementreplacement.

Coalescing filters are normally rated bythe amount of air which they can ‘process’ toachieve a given oil removal performance,normally a maximum remaining oil content inthe exit air of 0.01 ppm. To try to overflow theseunits will not only result in a greater pressuredrop across the unit and therefore extra energycost but more importantly the remaining oilcontent will increase. This may be acceptable forsome applications where oil removal down tothe order of 0.5 ppm is quite adequate to give adegree of protection to a system particularlyprone to gross oil contamination.

Figure 19 shows Norgren coalescingfilters flow capacities to achieve their givenperformance.

OIL VAPOR

For most processes the removal of oil vapor isunnecessary since unlike water vapor, oil vaporexists only in minute quantities and is notobjectionable except in circumstances where itsodour is unacceptable eg. in food processing,pharmaceutical and beverage industries andbreathing air applications.

The most common method of removalis to pass the air through an adsorbing bed,usually of activated carbon, although othermaterials can be used.

Such vapor removal filters willnormally reduce the total remaining oil contentwhen used in conjunction with a pre-filter(general purpose filter) and a coalescing filter to0.003 ppm.

A common misconception of thesefilters is that they will remove carbon monoxideor carbon dioxide - they will not.

As with oil removal (coalescing) filtersthe vapor removal filters should only beemployed where their function is needed, themaximum flow rating is not exceeded and theyare preceded by a general purpose and acoalescing filter. This will minimize the size ofthe filters required and therefore the cost of theinstallation.

Norgren offers an integrated coalescingand vapor removal filter in the Olympian Plusrange. (See figure 17). This includes a colorchange service indicator as standard.

The location of the compressor intakemay also have an effect on the level of filtrationrequired, if for example the intake is situated bya source of hydrocarbon vapors etc. Clean airintake will reduce the cost of producing cleancompressed air.

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Figure 16.OIL REMOVAL FILTER WITH GENERALPURPOSE PRE-FILTER

Figure 17.‘ULTRAIRE’ OIL VAPOR REMOVAL FILTER

FILTER SELECTION

Once all of the contaminants have been consid-ered the degree of cleanliness of air for eachpart of an industrial plant or process can bedetermined. By only employing the correctfilters in the right location energy and mainte-nance costs can be kept to a minimum. Thevolume of air involved in each stage mustalways be considered as undersized, inappro-priate filters are a prime cause of high energy costs.

A very general guide to the typicallevels of cleanliness required for commonprocesses is given in figure 21. Each applicationshould however be considered on its ownmerits.

Recommendations on air drying areparticularly difficult since this is dependantupon the temperature of the compressed airmain adjacent to the application/machine thelevel of pressure reduction and air flow rate.

For well laid out generation anddistribution systems drying is seldom requiredin countries of typically low to moderate relativehumidities and ambient temperatures.

When choosing a filter to cleancompressed air ensure:-

● The correct type of filter and elementrating is selected for particle removal.

● The liquid removal efficiency is highand that re-entrainment is not possible.

● Ease of maintenance and liquidcondensate collection is possible.

● Easy visibility of condensate and/orelement ensures that function isachieved or shows if maintenance isrequired. This may be a pressure drop device,

liquid level indicator or transparent bowl. In order to aid determining the type of

water and particle removal, figure 20 showsISO 8573 Air Quality Classification.

Figure 18. GENERAL PURPOSE FILTER FLOWS

Pipe Unit Flow (scfm)*Size

1/8" F07 32

1/4" F72G 63

1/2" F64G 147

F74G 175

1" F15 368

*Flow at 91 psi and 7.3 psi pressure drop.

Figure 19. HIGH EFFICIENCY FILTER FLOWS

Pipe Unit Flow (scfm)* OilSize Removal

Class**

1/8" F39 5.9 2

1/4" F72C 9.5 2

3/8" F64C 34 2

F64B 15 1

F74C 34 2

1/2" F64H 59 2

F64L 5.2 1

F74H 59 2

1" F53 126 2

F52 126 1

1 1/2" F47 179 2

F47 253 3

2" F47 421 2

F47 602 3l l l l

0 10 100 1 000

*Flow with 91 psi inlet to achieve ‘class’requirements.**See figure 20.

Figure 21.RECOMMENDED FILTRATION LEVELS.

Application Typical Quality Classes

Oil Dirt

Air agitation 1 3

Air bearings 2 2

Air gauging 2 2

Air motors 4 4

Brick and glass machines 5 4

Cleaning of machine parts 3 4

Construction 4 5

Conveying, granular products 2 4

Conveying, powder products 1 3

Fluidics, power circuits 2 5

Fluidics, sensors 2 3

Foundry machines 4 5

Food and beverages 1 1

Hand operated air tools 5 5

Machine tools 5 4

Mining 5 5

Micro-electronics manufacture 1 1

Packaging and textile machines 5 3

Photographic film processing 1 2

Pneumatic cylinders 3 5

Pneumatic tools 5 4

Pneumatic tools (high speed) 4 3

Process control instruments 2 3

Paint spraying 1 1

Sand Blasting 4 5

Welding macines 5 5

General Workshop air 5 4

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Figure 20.

AIR QUALITY CLASSIFICATIONS ISO 8573Quality Class Dirt Water Pressure Dew-point Oil

Particle Size in Microns °F (ppm vol.) at 102 psig (including vapor) ppm

1 0.1 -94 (0.3) 0.01

2 1 -40 (16) 0.1

3 5 -4 (128) 1

4 40 +37 (940) 5

5 — +45 (1 240) 25

6 — +50 (1 500) —

PRESSURE CONTROL

In order to use compressed air most effectivelyand efficiently it is necessary to reduce thepressure to precisely the level required for itsapplication.

All pneumatic equipment has anoptimum operating pressure. Using it at ahigher pressure causes excessive wear, with nosignificant increase in output, whilst wasting thecompressed air itself and the cost expended ingenerating it. If the compressed air is stored atthis higher pressure and only used at exactly thelower level required for the application thestorage vessel or receiver need only be toppedup from some intermediate figure to the fullcapacity, which is more efficient. In order toachieve this optimum usage the compressorusually operates between two pressure levels,that is the receiver normally has a pressureswitch set to give compressor cut-off at therequired storage pressure (usually the highestachievable for filtration efficiency) and a lowerlevel usually about 10 - 20% lower. This figurecan be adjusted for the optimum when thereceiver size, system flow demand andcompressor output rating are considered. Theoutcome of this arrangement is that thecompressor is not continually running, using upexcess energy, producing more heat whichproduces more water, which must be removed(extra cost) to supply a system requirement attoo high a pressure which causes excessivewear (extra cost) for no increase in output.

A pressure reducing valve can thereforegenerate cost savings greater than its purchaseprice in a short time period. Also it is mandatoryin such applications as blow guns and coolingnozzles where the use of compressed air at highpressure is potentially hazardous.

Pressure reducing valves or regulatorshave two principle characteristics which must beconsidered in establishing which to select, theirability to keep the outlet pressure constantirrespective of the inlet pressure (called theregulation characteristic) and irrespective of theoutlet flow (flow characteristic). Standarddesigns are manufactured which achieve certainlevels of the ideal performance on each charac-teristic. A simple application with loosedemands of the two principle requirementscould employ a standard and therefore low cost

reducing valve. The correct selection anddeployment in the relevant part of the air systemwill achieve the lowest cost most energyefficient system.

The penalty for poor regulationcharacteristics is that the outlet pressure willvary but in the bulk of compressed air applica-tions, inlet pressures are fairly constant so thisposes few problems.

The penalty for poor flow characteris-tics is pressure drop which directly reflects inenergy costs. Every regulator suffers from someamount of pressure drop so for good systemdesign this is the more important property toexamine.

An important cost saving can beachieved by employing a reducing valve inconjunction with double acting cylinders wherea reduced pressure can often be used advanta-geously on the non-working return stroke andcost savings as high as 30% can be achieved.This can be very important on multi-cylinderinstallations.

A point common to all pressureregulators is that in order to work constantly andrepeatability within their design limits they willrequire a supply pressure at least 14.5 psihigher than the required outlet pressure. Theywill work with a lower differential but perform-ance can be impaired.

TYPES OF REGULATOR

Although Norgren produces a vast array ofregulators they can be broadly broken into 4types:-

General PurposePilot OperatedPrecisionSpecial PurposeMost general purpose regulators are of

the diaphragm type (figure 22). In general theseare more sensitive than piston type regulatorswhich tend to have better flow capacity for agiven size. In the majority of compressed airsystems response, rather than compactness fora given pipe size is the major requirement,hence diaphragm type regulators are mostcommon.

Regulators can be relieving or non-relieving. The relieving feature allows for thesystem (outlet) pressure to adjust from a higherlevel to a lower one without actuating down-stream equipment (this is done by having a venthole through the diaphragm to atmosphere).Generally this relief hole is very small in relationto the regulator main ports so no more than ableed flow can be achieved and this should notbe considered a full relief or even safety reliefdevice.

Non-relieving versions do not have aconnection from the downstream system toatmosphere and so can only be adjusted from ahigher desired or achieved outlet pressure to alower one by cycling downstream equipment orusing a 3/2 shut-off valve to expel excess airfrom the downstream system.

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Figure 22. GENERAL PURPOSE REGULATOR

Pilot operated regulators are thosewhich do not have a direct mechanical means ofadjusting the outlet pressure. This eliminatesleverage problems in achieving high 232 psipressures in large pipe size units. The outletpressure is controlled by means of an airpressure signal (Figure 23) which is normallyproduced by a precision regulator. This allowsfor example a pilot operated regulator to beremotely situated in the large distribution mainsnormally in a building’s roof, but be adjusted togive the desired output pressure from shop floorlevel. For the majority of pilot operated applica-tions it is best to take the system or outletpressure reading from the pilot operated (oftencalled a slave or main) regulator itself or thedistribution system as the pilot regulator’s outletpressure is generally not the same.

Pilot operated regulators also givebetter performance by eliminating the controlspring and usually have a large diaphragm areacompared to valve area which also improves theaccuracy of pressure control in response tosmall pressure changes.

Another level of control accuracy canbe achieved by employing a feedback pilotregulator. This device senses the outlet pressurein the system and a piped connection feeds this

signal back to the pilot regulator whichcompares it to the desired outlet signal and‘compensates’ by increasing the outlet pressureif the feedback signal is too low, or decreases ifthe signal is too high. This type of control isusually employed where a large steady air flowto a continuous process is required.

Precision regulators (or controllers) arenormally used for instrumentation applicationswhere exact repeatability and freedom fromoutlet pressure setting drift over short or longterm operation is necessary. These regulatorsnormally have a small outlet flow range, butexhibit superior flow and regulation characteris-tics. Their ability to achieve the ideal of thesecharacteristics over flow and pressure ranges isreflected in their size and price.

Generally most precision regulatorsemploy a special arrangement to allow aconstant bleed of air to escape to atmosphere.Although this is a cost to system as a whole,being a loss of air, it is the price which must bepaid in order to achieve the very fast responseto the applications demands needed to keep thesystem pressure as constant as possible. Thebest types of precision regulators also employan integral pilot operation, producing effectivelytwo diaphragms and valves, one small and

sensitive the other a slave to ensure that theoverall performance meets the requirements ofthe particular application.

Another feature of precision regulatorsis their relief capacity and some have the abilityto relieve up to 80/90% of their recommendedregulated flow for specialist application such astensioning belts, paper rolling and balancing.(Figure 24).

Special purpose regulators can cover awhole range of specific demands includingmeeting exact environmental requirements withspecial materials, having high relief flows,plunger operation in place of handwheels etc.They can be derivatives of any of the other typesof regulators with application specific additions.

REGULATOR SELECTION

Ensure the regulator chosen exactly fitsthe performance requirements of the application.A regulator which controls the pressure to adistribution main is usually of the generalpurpose type or for large volume/flow applica-tions pilot operated.

Decide if the performance requirementsneed a standard or precision regulator. Thendecide if the flow capacity of the regulator issuitable for the pipe size needs (see figure 38)and check with the regulators flow characteris-tics. Figure 25 shows flow ratings of NorgrenGeneral Purpose Regulators . If there is novariation in the inlet pressure to an applicationthen the regulation characteristic of the regulatoris unimportant but the flow characteristic willbe. If the inlet pressure is exposed to variations

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Figure 24.NORGREN MICRO-TROL PRECISIONREGULATOR

SUPPLYAIR

SUPPLYAIR

OUTLETAIR

PILOT OPERATEDREGULATOR

PILOT OUTPUTLINE

CONVENTIONALPILOTREGULATOR

Figure 23.

then the regulation characteristics of the chosenregulator must also be considered.

A variety of spring ranges are offeredwith most regulators. Ideally the regulatorsshould be operated inside the middle third oftheir range, since at the lower end of their rangethe spring loses some sensitivity and at thehigher end may suffer in linearity. Also low ratesprings can help reduce pressure droop, sosprings can be selected to best fit the systemsrequirements.

If a precision regulator is requireddecide on the level of sensitivity, flow andregulation characteristics and if required reliefcapacity and temperature sensitivity. Select onlya regulator suitable for its application. Correctselection could see a general purpose regulatorwith ordinary performance characteristicsfulfilling what may be considered a precisionregulators function without system degradationat a lower installed cost and more cost effi-ciently.

Figure 25.GENERAL PURPOSE REGULATOR FLOWS

Pipe Unit Flow (scfm)*Size1/8" R07 131/4" R72G 691/2" R64G 253

R74G 2211" R15 379

*Flow with 145 psi inlet, 91 psi outlet and 15psi pressure drop.

FILTER/REGULATORS

Filter/regulators both clean the air to theapplication and control the pressure in onecompact unit. For general purpose applicationsfilter/regulators are usually lower cost than twoseparate units.

Some specialist filter/regulators areavailable for instrument applications with fineparticle removal or even oil removal propertieswith precision regulator characteristics, as areothers with special material compatibility.

Figure 26.NORGREN FILTER/REGULATOR FLOWCAPABILITIES.

Pipe Unit Flow (scfm)*Size1/8" B07 131/4" B72G 801/2" B64G 2321/2" B74G 2111" B15 484

*Flow with 145 psi inlet, 91 psi outlet and 15psi pressure drop.

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Figure 27.GENERAL PURPOSE FILTER/REGULATOR

Figure 28.ALUMINUM INSTRUMENT FILTER/REGULATOR

LUBRICATION

The next important step in processingcompressed air is that of introducing into the aira suitable amount of lubricant, usually oil toenable the operating equipment to perform to itsrequirements efficiently without excessiveresistance or wear. Excessive resistance tomotion will result in extra power consumptionand excessive wear will result in shortenedequipment life. Both result in extra cost.

There are two basic types of lubricatorin general use, aerosol and injection pump.

The most widely used is the aerosol,which was the first type of dependable automaticair line lubrication device, invented by Norgrenin 1927.

Aerosol lubricators are available in twomain types, Oil-Fog and Micro-Fog. In an Oil-Fog lubricator the fog produced generally hasrelatively large oil particles and so will onlyremain airborne for relatively short distances. Asa general rule of thumb the maximum distancean Oil-Fog lubricator should be placed from thepneumatic device which it is to service is 9meters. Large particles are more stronglyaffected by gravity and so Oil-Fog lubricatorsshould not be used in attempting to lubricate adevice at a higher level than the lubricator.

The Micro-Fog lubricator uses aspecial fog generator to atomise only a fractionof the oil.

Because the airborne fog is now madeup of only light particles, less than about 2microns in size, gravity does not have the sameeffect upon it and so this fog can travel not only“up-hill” but also for long distances andthrough more complex feed lines withoutwetting out in the pipe. Micro-Fog can alsoensure proportionate distribution throughmultiple lubrication outlets, ideal for multiplevalve control circuits.

A comparison of these two types oflubricators can lead to a simple division of themas being high delivery (Oil-Fog) or low deliverytypes (Micro-Fog). All of the droplets of oilshown in the Oil-Fog sight dome will bedelivered into the system and for the Micro-Fogonly about 5 to 10% of the droplets witnessedwill be delivered. The Micro-Fog can thereforebe used in applications where only very smallamounts of lubricant are required, possibly over

large areas. By adjustment of the drip ratehigher oil delivery can be achieved to match thatof an Oil-Fog lubricator at normal usage rates.

The Micro-Fog principle has madepossible the application of aerosol lubrication togeneral machine lubrication such as bearings,gears, chains etc.

Both Oil-Fog and Micro-Fog lubrica-tors include a non-return valve in the syphontube to ensure immediate lubrication as soon asthe air is turned on. However for some rapidlycycling duties or systems with small strokecylinders it is sometimes not possible tolubricate correctly with conventional lubricators.For such applications system modificationssuch as quick exhaust valves must be employedor a bi-directional lubricator suitably locatedcan overcome such problems.

The second type of lubricator, theinjection oil-pump is a positive displacementdevice. Because of its nature it cannot continu-ously deliver lubricant but has particularapplications in multi-spindle nut runners whereconventional lubricators will split air flowsaccording to passageway geometry. Theinjection pump will deliver the same amount oflubricant to the application point every time it iscycled. This type of lubricator is often used onconveyor chains where their application willovercome problems of incorrectly located oradjusted conventional lubricators.

Several such injectors can be mani-folded together to lubricate at several differentpoints, but at the same frequency.

Whichever type of lubricator isemployed it is important to remember that alllubricators are total loss systems in that thedispensed lubricant will reach its ‘bearing’surface and be broken down into smallerparticles and ‘lost’ as the system is cycled.

The amount of oil which should bedelivered to a pneumatic system to providesufficient lubrication is difficult to determine asall systems will be different. Pneumatic devicesin a system may require different amounts oflubricant and so equipment manufacturersrecommendations should always be followed,where they exist.

For a general guide for most pneumaticsystems an oil output density of 60mg/m3 is agood basic starting point. From regular inspec-tion and servicing the optimum setting may be

found by increasing or decreasing the amountdelivered.

FILLING LUBRICATOR BOWLS

With all lubricators eventually the bowlor reservoir will need filling. Most Oil-Foglubricators have a check valve fitted to allowthem to be refilled whilst in use. Most Micro-Fog lubricators can be fitted with a quick fillnipple and so be topped up with lubricant,supplied at a pressure of approximately 1 barabove that within the bowl.

Remote fill devices also exist whichcan do this automatically. Such devices can beused to supply several bowls or reservoirs fromone central position.

Another way to reduce the scheduledtask of refilling lubricators or to ensure criticaloperations never ‘run dry’ is to employ a liquidlevel switch. Such devices are normally floatoperated switches which can give an electricalsignal on low or high liquid level. Such signalscan then be built into a control system to fill orstop filling or give warning alarms.

14

Figure 29. OIL-FOG LUBRICATOR

Although a high level signal may atfirst seem strange remember that overfilling willnot only prevent the lubricator from performingits function of producing an air/oil mix of fog,but will distribute bulk lubricant into thepneumatic system, flooding it.

LUBRICATOR SELECTION

Determine which parts of the systemrequire lubrication (some distribution lines willbe to oil free areas such as paint spraying orbreathing air applications).

Determine what type of lubrication isrequired for each part of the system. Slowmoving heavy cylinders need high delivery sochose an Oil-Fog type lubricator. Long runs ofpipe in multi-valve circuits require a Micro-Fog(or several Oil-Fog) lubricators to lubricateeffectively. High speed tools are better served bya Micro-Fog, as are tips of cutting tools.

All lubricators are a source of pressuredrop and therefore energy loss, so althoughMicro-Fogs may be positioned almost anywherein a system select and place them as conve-niently close to the application as possible.

Always select lubricators and locate them wheredifferent levels of lubrication are required, neverattempt to fit one lubricator to supply a wholedistribution system as differing parts will thenbe over lubricated, whilst others are underlubricated.

Ensure that only special purposeMicro-Fog lubricators are used for bearinglubrication as other types are not suitable.

Check that the lubricator chosen hassufficient flow capacity without excessivepressure drop for the pipe line size being used(see figure 37 and individual lubricator perform-ance graphs).

Figure 31. LUBRICATOR FLOW RATES

Pipe Unit Flow (scfm)*Size1/8" L07 111/4" L72 511/2" L64/L74 1521" L15 368

*Flow at 91 psi and 7 psi pressure drop.

Since lubricators require a minimumpressure drop to operate which is normallyrelated to a flow, ensure that this minimum flowcondition is met or there will be no oil output. Itis important to note that leaks from compressedair systems are a source of energy loss and alsosuch leaks are effectively a constant flowthrough the system. If a lubricator with a verylow start point is used then even a smallleakage, if in excess of the start point will causeit to drip and supply oil to the system. This isoften the cause of oil flooding during periods ofshut-down, especially over weekends.

Where continual usage exists select alubricator with sufficient reservoir capacity. Forunits in 1/2" pipe size and above, severalreservoir capacities are usually available. Wherethis is not possible because of space or usagerate utilise remote fill devices or liquid levelswitches to auxiliary systems.

Where very high flows are encountereduse a fixed venturi type lubricator. Unlikestandard types this does not automaticallyadjust to give a constant air/oil density, so theflow requirement needs to be essentiallyconstant. This type of device will then notproduce excessive pressure drops associatedwith high flows and so be more energy efficient.

For exceptionally high flow rates smallamounts of lubricant (especially for anti-freezeusage) can be injected by small lubricators intolarge distribution mains of 1 to 2” and above,where a full bore lubricator would be expensivein both cost and pressure drop.

15

Figure 30. MICRO-FOG LUBRICATOR

PROTECTING SYSTEMS, PERSONNEL AND THE ENVIRONMENT

Safety in the workplace is essential and isemphasised via the Machinery Directive, thePressure Systems legislation and the Provisionand Use of Work Equipment Regulations(PUWER).

The following section can helpmachine designers and others using pneumaticsby illustrating those air line products which,when correctly applied, can be used to ensuresafe pneumatic systems.

In it we have cross referenced relevantdocuments. Norgren strongly recommend thatall who are involved with machine and systemdesign should become familiar with these andother relevant safety documents.

OVERPRESSURE PROTECTION

The components in pneumatic systems willoften have a pressure rating lower than thatgenerated at the compressor and pressureregulators are used to reduce this pressure tosafe efficient levels. In the event of a fault thecomponents can be exposed to excess pres-sures leading to mis-function or in extremesfailure of the pressure containing envelope.

To protect against this excessive overpressure situation several solutions can beemployed the most common being a relief valve.Selecting a relief valve is not a simple process,and detailed consideration of the system orelement of the system is required.

In general all pneumatic componentsand equipment will have a Safe WorkingPressure (SWP) and over pressure limit of 10%.The designer of the pneumatic system can useregulators to run the system at pressures belowthe SWP and use the 10% safety factor to be thelimit of over pressure that the system canexperience with the relief valve in operation.

A relief valve is defined as a devicewith its outlet so connected to a pressuresystem to enable the system pressure to be heldat a constant level. This constant level wouldthen be at or below the stated SWP + 10% overpressure allowance.

Relief valves need to be set to onlyoperate when the regulated pressure is exceeded

and so need to be set higher than the regulator.There will be a tolerance on the relief valvesetting and on the regulators outlet setting,depending on its flow and regulation character-istics. A common problem is a relief setting tooclose to the system operating pressure. Theconsequence of this is to have the relief valveoperating and venting air during normal systemoperation, which is an expensive waste of air.(See figure 22).

Once the relief valve setting pressureand acceptable level of over pressure arechecked the flow capacity of the relief deviceand that of the system can be considered. Therelief device must be able to match or exceedthe amount of flow through the part of thesystem being protected without the systempressure rising above the acceptable overpressure level.

Several methods can be used toachieve this:-

The relief device has a flow capacity inexcess of the compressors free air deliverycapacity - in systems where no receiver exists -i.e. flow out of system is greater than flow in.

The relief device has a capacity inexcess of the flow through the smallest flowpassageway upstream of the equipment beingprotected. Tables of orifice flow exist todetermine the flow at different pressures throughdiffering sizes of orifice. The smallest bore isacting as a restriction to the flow into thedownstream system and unless the upstreampressure can be increased the flow will bechoked through this area and therefore limited.This is important since a mains distributionsystem can be of very large volume with pipesof large bore and compressors of high capacity,but the device being protected could be fed by1/8" nominal bore tubing. So a small low costdevice only is required and not one largeenough to cope with the full system capacity.

In areas where no such flow restrictionexists, one should be created in order to reducethe cost of the relief valve to be employed,ensuring of course that the restriction does notcause excessive pressure drop in the course ofnormal operation.

Legislation Reference: BS EN 983 5.1.2

TYPES OF RELIEF VALVES

Several types of relief valves exist to achievedifferent levels of performance with respect tothe flow capacity and over pressure limitations.The most common is the ‘pop’ type, followed bythe diaphragm type. For better performance usepilot operated valves with the integral pilotoperated type being the most compact and costeffective (figure 32).

An “in-line” type of relief device hasrelief port at 90° to the direction of flow and innormal operation flow passes through the bodyof the device, without interfering with normalupstream operation. A common use of this typeof device is with machine builders, where all thecontrol equipment/protection devices are in onediscrete position, aiding both installation andscheduled servicing.

The in-line device differs from the popor diaphragm type of relief valves which areconnected into the system on a tee-piece. Flowthrough these devices only occurs when inoperation and air vents to atmosphere.

In both cases the exhaust flow can bepiped away to an area where the noise and flowwill not cause disruption or harm to the environ-ment or the operators. Exhaust silencers maybe required to reduce noise levels in high flowexhaust applications where piping away to lesssensitive areas is not possible.

16

SOFT START/DUMP VALVES

The next form of protection is that associatedwith the moving parts of the system, where theparts themselves can need protection againstexcessive wear due to loading on start up orthere is danger to personnel from suddenmovement of the parts.

Here the use of “soft start” (“slowstart”) valves is desirable. The normal operationis to allow air to pass to a pneumatic system ordevice in a gradual manner, where the rate ofpressure build-up can be controlled by adjust-ment of the valve. The valve design is generallyan internal poppet valve which is springoperated and when the gradual pressure build-up produces a force in excess of that holdingthe poppet closed, the poppet moves to theopen position allowing flow to proceed throughthe normal flow passageways. The level atwhich the poppet operates is called the snappoint and for most devices this snap point willbe in the range of 40 to 70% of full linepressure.

Because pressure build up in anysystem is dependant upon the system volume itis important to locate these devices close to thepiece of equipment they are to protect. Fittingof a larger valve to a complete distributionsystem will generally mean the system will takemany minutes to fully pressurise.

It is extremely common to couple theslow start valve with a dump or exhaust functionvalve within one body, for compactness.

The function of the ‘dump’ valve is toquickly exhaust the pressure from the down-stream system. The valve can have solenoid orair pilot operators and often a manual overrideor emergency dump function.

Legislation Reference: BS EN 983 5.1.4

EXHAUST AIR

Exhaust air needs to be treated correctly toreduce the effects of noise, oil mist and tominimise danger to personnel.

Where a dump valve is employed, largevolumes of air can be released at high speedwhich will produce high noise levels. Simplesilencers made of porous materials are oftenable to deal with this. In more demanding highvelocity cycling applications a heavy dutysilencer may be needed.

Silencers are normally rated for theirnoise reduction and associated back pressureso the choice should be dependent upon theduty required of the device to ensure the mostcost efficient silencer is utilised.

The next major pollutant is oil. Allpneumatic lubrication systems are total losssystems, the lubricant goes into the system,gets degraded in its function and is carriedalong with impurities and dirt to the atmos-pheric exhaust.

In well maintained and correctlylubricated systems of a general engineeringnature the amount of exhausting oil is verysmall and will disperse without generallyaffecting the working environment adversely.However incorrectly lubricated systems or thosewhich require high levels of lubrication forheavy duty applications can expel high levels ofoil into the atmosphere on their exhaust cycle.In such instances use of a coalescing exhaustsilencer should be considered. The action ofthis device is exactly as those for oil removal

17

Figure 34. COALESCING SILENCERFigure 33. SOFT START/DUMP VALVE

Figure 32. INTERNAL PILOT RELIEF VALVE

filters which cause the small oil droplets tomerge together into large droplets which fallinto a container for removal. (See figure 34.) Inthe course of this process the porous materialemployed also reduces the noise level of theexhaust air.

Since these devices are on the exhaustside of the pneumatic system they are exposedto sudden shock loading, which means their oilremoval capabilities are not as good as thoseemployed in coalescing filters. A good exhaustcoalescing silencer will however give figures oftypically 2ppm under average usage conditions.

PROTECTION DEVICESELECTION

(i) Decide which parts of the system cannotwithstand the maximum pressure which can bedeveloped in the distribution system (orcompressor).

Determine which type of relief valve isrequired to control this air pressure mosteffectively with consideration of failure flowthrough that part of the system. Consider usinga restrictor (orifice) without producing excessivepressure losses in the normal operation of thatpart of the system.

For very large flows consider a pilotoperated regulator as a dump valve.

For machines consider an in-linedevice to build-up one complete integralmodular preparation assembly for ease ofpiping, location and servicing.

(ii) Decide upon which parts of thesystem can suffer from problems on initial startup, or resetting where excessive initial speedscan lead to wear problems or entrapment, orwhere an emergency stop/dump function isrequired.

Employ one soft start/dump valve foreach section of the system operated in this way.The larger the system the longer the dump oremergency stop function will take to fully emptythe system.

Locate soft start/dump valves in theFRL assembly at the downstream end to preventhigh back flows through the lubricator.

(iii) Where large volumes of air are tobe exhausted consider fitting a silencer if the aircannot be piped away to a convenient position.

Where rapid cycling of exhaust ispresent fit a heavy duty silencer.

Where the exhaust air can be heavilyladen with lubricant, usually from equipmentrequiring high levels of lubrication fit acoalescing exhaust silencer.

OTHER PRODUCTS FOR SAFESYSTEMS

Other air line products that can help create safepneumatic systems -

Preset pressure regulators - whereunauthorized adjustment of the set pressure canbe injurious to personnel.

Guidance Document: HS (G) 39Lockable shut-off valves - ensure that a

‘safe to work’ procedure can be adopted withoutjeopardy from the unauthorized re-application ofpressure.

Legislation: BS EN 983 5.1.6Guidance Document HS (G) 39Tamper resistant kits - can be fitted to

pressure regulators, filter/regulators, reliefvalves and lubricators to ensure that flow,pressure and other settings are secured againstunauthorized adjustment.

Legislation Reference: BS EN 983 5.1.9

18

NORGREN AIR PREPARATION PRODUCT OVERVIEW

UNRIVALLED PRODUCTRANGE

Norgren, the world leader in air

preparation offers an unrivalled

range of products to enable you to

produce clean compressed air and

use it economically and safely.

Whatever your need from the

simplest factory installation to a

complex medical application,

Norgren has the right air prepara-

tion equipment for you.

19

Figure 35.EXCELON SYSTEM

Figure 36.OLYMPIAN PLUS SYSTEM

NORGREN AIR PREPARATION PRODUCT OVERVIEWThese pages show the main product families,together with just a few of the morespecialized standard products. In addition weproduce hundreds of products to customersspecifications, utilising the vast experienceNorgren has accumulated over the past 70years.

All the main ranges include :-General Purpose FiltersHigh Efficiency FiltersVapor Removal FiltersGeneral Purpose RegulatorsFilter/RegulatorsOil-Fog and Micro-Fog LubricatorsSoft Start/Dump ValvesShut-Off ValvesRelief valvesThese are supported by a wide choice

of mounting methods and accessoriesPorting BlocksPressure SwitchesLevel ControlsService IndicatorsManifold Blocks

OLYMPIAN PLUS

Olympian Plus is the new generationFRL system, which sets new standards for easeof use and flexibility. The unique plug in featureallows quick installation or removal of units witha simple quarter turn of the clamp ring. Theeasily connected yoke systems allows speedyassembly of combination units.

Packed with features to make fieldmaintenance easy and convenient OlympianPlus is ideal for industrial installations. Equallythe wide range of system accessories mean itoffers the OEM user a highly flexible solution.

Olympian Plus is available in basic 1/2inch , with optional 1/4, 3/8 and 3/4 porting.

OLYMPIAN 15 SERIES

The 15 Series is the basic 1" version ofthe Olympian system. Available in 3/4 through 11/2 inch ports it offers a flexible solution forlarger machines and high volume industrial use.

EXCELON

Excelon is a completely new airpreparation system from Norgren. Althoughdirect ported, thanks to a patented Quikclampconnection system, Excelon can be used whereboth stand alone units or modular assembliesare required.

It offers exceptional performance in acompact well styled unit. It is ideal for OEM’soffering a flexible modular system with usefulaccessories such as pressure switches andmanifold blocks. The quick release bayonetbowl, high visibility liquid level indicator andeasy to operate patented Quikdrain are just a fewof the features designed with ease of mainte-nance in mind.

There are two sizes in the Excelonrange.

EXCELON 72 is basic 1/4 (withoptional overporting to 3/8). However there isnothing basic about its performance, which isactually better than many competitors 3/8products.

EXCELON 74 is a 1/2 inch range(optional 3/8 and 3/4).

20

PORTED UNITS

The ported products have no modular connec-tion system, and are generally used as standalone units. They cover a wide range of basicport sizes from 1/8" (07 Series) through 2" (18Series).

07 SERIES

The miniature range offers goodperformance units for smaller flow requirements.Here regulators are the most common productand in addition to the catalogued units Norgrenoffers a vast array of options. Units are availablein a range of body materials, with internalcomponents chosen to deliver the specificperformance characteristics requested by thecustomer.

11 SERIES

A basic 3/8" size the 11 Series is alsooffered with 1/4" and in some cases 1/2" ports.These are well proven reliable units often usedas an alternative to a true 1/2" product, wherethe flow requirements are not high.

18 SERIES

The 18 Series is a basic 2 inch rangedesigned for factory air mains or high flow OEMapplications such as shot blasting or textilemachines.

PRECISION REGULATORS

Norgren has several different precision regula-tors, each offering the designer a particularcombination of performance characteristics fromwhich to select the best unit for the application.Many specials are produced in addition to thecatalogued options.

11-818

Compact, high precision regulators forair gauging, laboratory use and precise pilotcontrol.

11 400

For high accuracy pilot control of largeregulators and relief valves.

R24 MICRO TROL

Exceptionally high flow with excellentrelief performance.

R38

Instrument regulator produced inaluminum or stainless steel.

R27

High precision regulators featuring awide choice of operators.

SPECIALIZED PRODUCTS

STAINLESS STEEL

Norgren produces units which meet NACErequirements for use offshore and in harshprocess environments. The 38 Series regulatorand filter regulator are 1/4 NPT units offeringhigh flow with good precision. The 22 Seriesfilter, regulator and lubricator are basic 1/2" andfor lower flow applications there is the 1/4" 05Series.

WATER REGULATORS

Regulators with plastic or brass bodiessuitable for general or potable water duty.

RELIEF VALVES

In addition to the relief valves whichare part of the main FRL families Norgren hasseveral specialized units including Pop Typeand the air piloted 40AC.

ELECTRONIC REGULATORS

Norgren can offer fully programmableelectronic regulators for use with any standardindustrial PLC. The R26 Pneu-Stat electronicregulator gives stable output over long periodsand is ideal for closed loop pressure control inapplications such as welding machines whichrequire many different pressure settings.

21

GLOSSARY

After Cooler:A heat exchanger mounted on acompressor outlet to extract the heat ofcompression.

Ambient:The conditions, usually temperature, inthe vacinity of the equipment undernormal working conditions.

Back Pressure Regulator:A device connected to a system in sucha way that the system pressure is heldeffectively constant by control of theoutlet flow to atmosphere.

Check Valve:A device which allows flow in onedirection only.

Coalescing:The action causing small particles tounite to form larger particles.

Deliquescent Dryer:A dryer using material which absorbswater vapor to such an extent that thematerial ultimately dissolves into thewater it absorbs.

Desiccant:An adsorbing material used in somedryers. Many such dryers are regenera-tive in that they use some of theirenergy to dry the material making itsuitable for reuse.

Drip Leg Drain:A device at the bottom of a down legfrom a distribution main or a systemlow spot to remove condensed waterfrom the system. Such devices arenormally fitted with automatic drainvalves.

Dump Valve:A valve which is connected to atmos-phere in such a way as to rapidlyexhaust the system pressure.

Emulsion:A mixture of oil and water.

Failure Flow:The maximum flow through a device ata given pressure with the valve open tomaximum extent.

Flow Characteristics:A characteristic of a pressure regulator

which shows the variation of outletpressure with varying outlet flow ratesat a constant supply pressure.

Free Air:Air flow measure in dm3/s at STP(1 013mbar and 21°C) (ISO R554). Allair flows are converted to this to makesystem sizing easier.

Initial Droop:The amount of pressure drop incurredby a pressure regulator in going from aflow (static) condition to a small flow(dynamic) condition.

Micro-Fog:A suspension of light oil fractions inair, typically less than 2µm in sizewhich can travel long distances,through complex passageways.

Micron (micrometer):A measurement of size on millionth ofa meter (symbol µm).

Oil-Fog:A suspension of oil fractions in air,heavier and larger than Micro-Fog,suitable for heavy duty lubrication.

Pilot Operated Regulator:A regulator which has its outletpressure controlled by the outletpressure of another (piloting) pressureregulator, and not by an integraladjustable spring load as with standardpressure regulators.

Porting Block:A modular device for allowing severalair take-off from a main air flow controlset.

Pressure Drop (Droop):The amount of pressure loss incurredby the flow of air through a device.

Pressure Reducing Valve/PressureRegulator:A device which is used to lower airpressure in a pneumatic system to adesired working level.

Regulation Characteristic:A characteristic of a pressure regulatorwhich shows the variation of outletpressure with varying inlet pressure ata constant flow rate.

Relative Humidity:The ratio of the actual amount of watervapor present in a given volume of air,

to the amount of water vapor necessaryto saturate the same volume of air atthe same temperature.

Soft Start Valve:A device which on initial pressurizationof a system allows the pressure tobuild up slowly to a pre-determinedintermediate level before allowing astep-up to full line pressure to beachieved.

22

REFERENCE TABLES

23

Figure 37.

FRICTION LOSS IN PIPE FITTINGS IN TERMS OF EQUIVALENTINCHES OF STRAIGHT PIPE.

0.31" .039" 0.59" 0.79" 0.98" 1.26" 1.57" 2"Tee (straight through) 0.15 0.15 0.21 0.34 0.46 0.55 0.67 0.92Tee (side outlet) 0.76 0.76 1.01 1.28 1.62 2.14 2.47 3.1890° elbow 0.43 0.43 0.52 0.64 0.79 1.07 1.25 1.5945° Elbow 0.15 0.15 0.24 0.30 0.38 0.49 0.58 0.73Ball valve* 0.01 0.03 0.09 0.12 0.15 0.22 — —

* Self exhausting – full open

Figure 38.

MAXIMUM RECOMMENDED FLOW * THROUGH ISO 65 MEDIUMSERIES STEEL PIPE.

Applied Nominal Standard Pipe Size (Nominal Bore) – inchGauge 0.24 0.31 0.4 0.6 0.8 1.0 1.3 1.6 2.0 2.6 3.1Pressure Approximate Pipe Connection – inchpsi 1/8 1/4 3/8 1/2 3/4 1 1-1/4 1-1/2 2 2-1/2 35.8 0.6 1.3 2.9 5.5 8 15 32 53 95 145 25314.5 1.1 2.5 5.9 10 15 29 59 95 168 274 48423 1.7 3.6 8 15 23 42 84 126 253 389 69536 2.3 5.3 12 21 32 59 120 179 358 558 98958 3.6 7.8 17 32 48 93 187 284 547 863 152691 5.3 12 27 49 74 137 280 421 821 1305 29,653116 6.5 15 33 62 93 175 354 537 1032 1642 30,263

145 8.2 19 41 76 114 215 438 663 1274 2031 30,937

*Air flow rates in scfm free air at standard atmospheric pressure of 15 psi.

General notesThe flow values are based on a pressure drop (∆P) as follows:10% of applied pressure per 100’ of pipe .02" – .05" nominal bore inclusive5% of applied pressure per 100’ of pipe .07" – .03 mm nominal bore inclusive

Figure 39.

DRYER COMPARISONDryer Type Pressure Atmospheric Drying Media Power Initial Cost Pre Filters After Filters Maintenance

Dew Point Dew Point Replacement Consumption Cost

Refrigerated 36°F 73°F Nil For Medium General purpose None Regular maintenancerefrigeration motor and coalescing of refrigeration motor

Regenerative -40°F -135°F Infrequent For drying desicant High General purpose Coalescing SmallDesiccant and coalescing

Deliquescent 50°F -59°F Regularly, Nil Low General purpose Coalescing Rechargingminimum and container6 monthly coalescing

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