Where valves are used - Valve Magazine

MAGAZINEVALVE REPAIR EVENT COMING TO HOUSTON IN JUNE

SPRING 2016VOL. 28, NO. 2

ProcessingWhat WeConsume

THE BASICSOF STOPCHECKVALVES

THROTTLINGLIMITS FORGLOBE VALVES

VALVESELECTIONPRACTICES

EMISSIONSABATEMENTBY REPAIRSHOPS

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When wandering the grocery store aisles, it’seasy to forget that for every colorful package

that sits on the shelves, a myriad of processes go into preparingthe foods inside. Whether it’s cereal, breakfast pastries, cookies orcanned peaches, everything must be either steamed, dehydrated,pulverized, pasteurized or otherwise treated to fit into the cans,boxes and cellophane packages.

For every one of those processes, valves are employed in manyways, especially in the management of steam, the single mostcritical component of food processing. With the very safety of thefood supply at risk, regulation of the quality and quantity ofsteam is a challenging job for valves, actuators and control systems.

STANDARDSBecause safety is involved, many regulations and standards are inplace around the world. Yet there are few specific guidelines andnone that are accepted worldwide to manage the quality and purity of the steam that comes into direct contact with the foodor processing that food. In the U.S., there are basically three mentions in current regulations: Accepted Practices for a Methodof Producing Culinary Steam, the FDA Code of Federal Regulationsand a National Organic Standards Board review.

Food and BeverageProcessing

BY KATE KUNKEL

SUBJECT: Putting products on groceryshelves requires many complexprocesses and many of those processesare controlled with valves and relatedequipment.

KEY ISSUES:

! Types and levels of steam

! Valves for different steam grades

! Where clean is needed

TAKE-AWAY: Because safety isinvolved, the valves in this industrymust be top grade, especially whenthey control steam that may comeinto direct contract with the product.

Executive Summary

WHEREVALVES

ARE USED

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GRADES OF STEAMSeveral grades of steam are used infood processing and each has its ownlevel of contamination risk. Each alsopresents its own challenges for theequipment in process control.

Plant SteamIndustrial or plant steam is the lowestgrade of steam. It is the starting pointfor all steam used in food and beverageprocessing, but it’s the steam thatdoesn’t come into direct contract withthe food or drink product. In otherwords, it’s used in heat exchangers orused for hot water generation, in boil-ing pans and other areas. Softenedwater, reverse osmosis-treated or de-alkalized water is generally used forplant steam. This well-treated water iseasy on valve materials and causes fewcorrosion issues. The typical valvesused in these systems are standard-issue for the steam and power indus-try. They include gate, globe andcheck valves. Some applications mayalso allow the use of quarter-turnvalves as long as their design containsno pockets where fluid or debris couldcollect.

Even though plant steam does notcome into direct contact with the foodor beverages, it still needs to be at thecorrect pressures, and it must remainclean, dry and free from other gasesand air. This is achieved by the use ofplant steam control systems containingpressure control valves, filters andsteam traps.

While no hard and fast rules aboutplant steam materials exist, some foodand beverage manufacturers stipulateany steam products, including pressureregulation valves, that supply steameither directly or indirectly to a bever-age or food product must be construct-ed of a material sufficiently inert topreclude contamination of the food.For this reason, austenitic stainlesssteels such as 304ss, 316ss or 316Lssare often used.

Filtered or Culinary SteamThe next level of steam is filtered orculinary steam. Culinary steam is usedin applications used to sanitize theprocessing system. These are called“Clean in Place” (CIP) procedures, andthey are employed to ensure the proper

level of hygiene in pipes, valves, fit-tings and related components in thefood processing systems themselves.Air and steam filters are often integrat-ed into an overall system for the CIPprocess with appropriate valves, drains,pumps, pressure gauges, pressure reliefvalves and associated controls.

There also are portable productsdesigned specifically for CIP. Similar toa power washer for a car or sidewalk,these systems use super-heated steam

with power nozzles to sanitize andeliminate hazardous food-borne bacte-ria. Dry vapor-steam is the most effi-cient cleaning solution for food andbeverage facilities because mostpathogens can be eliminated at 160°F(71°C). Many of these systems produceconstant hot dry steam ranging from212-240°F (100-116°C).

Moisture reduction control systemsconsisting of steam traps and filters areemployed to keep the steam as pure as

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" Figure 1. An extract from the standard detailing the system components required for culinary steam

1. STEAM MAIN2. STOP VALVE3. STRAINER4. ENTRAINMENT SEPARATOR5. PRESSURE GAUGE6. STEAM THROTTLING VALVE (AUTOMATIC OR

MANUAL) OR ORIFICE7. DIFFERENTIAL PRESSURE MEASURING

DEVICE

8. STAINLESS STEEL FROM THIS POINT9. SAMPLING MEANS10. SANITARY PIPING TO PROCESSING EQUIP-

MENT11. SPRING LOADED SANITARY12. CONDENSATE TRAP13. FILTERING DEVICE14. STEAM PRESSURE REGULATING (REDUCING)

VALVE

PIPING ASSEMBLY FOR DIRECT STEAM INJECTION

© 3-A Accepted Practice for a Method of Producing Steam of Culinary Quality, Number 609-3

" Chocolate heater in a factory

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possible. When additional moisture isrequired in the fluid stream (for exam-ple, when chocolate or heavy greaseare involved), moisture control systemsand valves are used.

Clean SteamThe highest grade of steam is cleansteam, and it is typically raised frompurified water in a dedicated cleansteam generator. This is the area inwhich the foods or beverages are indirect contact with the steam. To cre-ate clean steam, a secondary generatorwith a controlled feed water system isused. Clean steam requires the use ofstainless-steel pipework and compo-nents that eliminate the potential forcorrosion of steam traps, valves andpipeline equipment.

As in other sanitary process pipingsystems, a paramount concern in foodand beverage processing is the needfor ease of cleaning. For this reason,the inside of all piping components,including valves, must be very smoothand free from crevices or pockets thatmight entrap fluid or debris or be diffi-cult to remove via standard cleaningprocesses. This limits the use of manyas-cast components because of their

inherent surface roughness. It alsorequires electro-polishing or otherprocesses to ensure that the bore ofthe fluid stream is free from potentialareas of fluid entrapment.

Standards and specifications for san-itary process lines are detailed in docu-ments created by the 3-A Standardsorganization (Figure 1). This is a stan-dards organization whose membershipis made up of industry professionals aswell as governmental agencies such as

the Food and Drug Administration. Most food-contacting valves are

made of 316 stainless steel for corro-sion resistance (or 316L if the valvehas welded end fittings), althoughother alloys are used for certain appli-cations. An important differencebetween general application valvesand those made for food service is thatthe food-related valves tend to beforged or machined out of bar stock,rather than cast. This is because cast

Steam Flow Valve # 29-15 psi

Steam

Cans of Product in Retort

Two Valves in Parallel

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Valve # 13-9 psi

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" Figure 2. Sterilization of cans

Used with permission from Richardson Industries

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valves are more likely to have pores,while forgings are more dense with nohidden cavities.

WHERE CLEAN IS VITALTypical segments of the food process-ing area where the steam might comeinto contact with the food are:

Retorts Retorts are vessels in which jars, bot-tles or cans are heated to cook andsterilize food products (Figure 2). Pre-cise temperature control is crucial hereso that the fragile containers in theretort do not rupture. Yet these con-tainers must be thoroughly heated toensure no bacteria survive.

Bubble-tight steam shutoff is essen-tial to prevent overheating and to keepsteam from entering the retort betweencycles. A globe-style control valve with3–15 psi signal controls the flow ofsteam sent to the equipment to sterilizecanned or bottled products.

There also are times when twovalves are used in this application. Inthis case, the valves operate at differ-ent pressures. An example is when thesystem requires fast start-up and thentight temperature control. The firstvalve would complete the entire spanwithin a 3–9 psi range. Once the retortis up to temperature, that valve beginsto throttle back and a 9–15 psi valvewill open and complete its span withinthat range. Once the retort is up totemperature, the 9–15 psi valve willthrottle back and perhaps shut entire-ly, leaving the 3–9 psi valve operatingto handle the flow.

Flash Steam PeelingAnother area where steam comes intodirect contact is in flash steam peelingsystems (Figure 3). In these systems,vegetables such as potatoes, carrotsand other root crops are fed into apeeler in batches. High-pressure steamis introduced, which causes rapidheating of the surface layer of thefood. When that pressure is theninstantly released, the resulting steamforms under the skin of the vegetable,causing it to flash off.

Valves required here would be thosefor maintaining the steam pressureand temperature from the boiler aswell as valves to open and close when

needed to dump waste or debris. Slid-ing gate or diaphragm control valvesare often used in this process.

BlanchingAnother process for removing skin isblanching. Blanching equipment is

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" Figure 3. Flash steam peelingUsed with permission from Spirax Sarco

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used to take the skin off vegetablessuch as carrots, green beans and peasby scalding. Blanchers also heat thevegetables to de-activate naturalenzymes that cause spoilage.

In steam blanching, the product istransported by a chain or conveyor beltthrough a chamber where steam isdirectly injected at about 212°F(100°C). Usually temperature in theheadspace (the unfilled space above thecontainer contents) is measured andthe flow rate of steam is controlled.

Forced convection blanchers aremade of nested chambers, which allowrecirculating steam with a fan thatinterconnects both chambers. The fanforces the flow of steam through apacked bed of product conveyed by amesh belt. Another technology is indi-vidual quick blanching (IQB), which wasdeveloped to minimize product treat-ment involving lack of uniformity. InIQB, a single layer of product is con-veyed through the steam chamber andeach ‘‘individual’’ piece of product imme-diately enters in contact with the steam.

Generally, in blanching processes, apressure relief valve with a pressureregulator is used to ensure a constant

low-pressure flow of steam, while acontrol valve throttles the flow basedon a temperature setpoint.

Chicken Processing When processing poultry, jacketedtanks are heated with steam to cooklarge quantities of chickens. Good con-trol and fast response are needed to

adjust to load changes. Ideally, valvesused here would be self-regulated. Onecommon option for this application isa temperature-regulated sliding gatecontrol valve.

Evaporation Evaporation is used to concentratefood products such as orange juice,

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INDUSTRY FORECAST TOGROW THROUGH 2022The U.S. food industry is forecast to grow ata steady rate of 2.9 percent compoundannual growth rate through the year 2022,according to a recent report from PMMI, theAssociation for Packaging and ProcessingTechnologies. The fastest growing two seg-ments are meat and snack foods.

The 2016 Food Packaging Trends andAdvances also reported that the U.S. trails the global market—global growth isforecast at almost twice the U.S. rate. The report says overall growth of the foodindustry, including food packaging, is driven by emerging markets such asArgentina, Brazil, China and India.

It also says that the most innovative food industry segments (snack food,meat, fruits and vegetables, and pet food) are using tools such as films that keepproducts fresher longer, recycled or biodegradable materials for packaging andsingle-service portioning.

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fruit roll-ups and similar products. The efficiency of the evaporation

process can be increased by usingthermo-compressors that recycle thevapor as a heating medium. For exam-ple, the process vapor can preheatincoming feed liquor. In these cases,each effect operates at a progressivelylower pressure.

Programmable logic controllers arenormally used to adjust pressures,temperatures and flowrates. Conden-sate contamination detection may berequired to ensure the condensate canbe returned to the boiler feed tank.

Typical final control elements usedfor this process often include globe-bodied control valves.

Direct Steam Injection Direct steam heating can be used forheating products if the steam is ofculinary quality and the product canbe diluted. This heating may be com-bined with other methods such asjacketed vessels, but steam injection isefficient, inexpensive and providesneeded agitation.

The steam may be injected usingsparge pipes for low-pressure steam or

injector nozzles for higher pressures.In-pipeline injection also is increasing-ly common.

Conveyor DryerSome methods of drying food requireproduction of hot air. Because manyfood plants already have steam onsite, steam is often used to heat theair using air heater batteries.

Conditioning of process hot air maybe required because the air used tosupply equipment such as fluidizedbed dryers or belt or tunnel dryersmay come into direct contact with thefood product. Valving in theseprocesses also must be clean and issubject to the 3-A specifications. Specially manufactured gate, globeand check valves with electro-polishedinterior surfaces are often used here.

CONCLUSIONWhile many of the valves used in foodand beverage processing are in steamlines, these certainly are not the onlyprocesses that use valves. For example,cryogenic (or flash freezing) can bedone dockside or on huge fish process-ing ships. Valves used in this process

must be especially robust to handlethe cryogenic temperatures. Butterflyvalves, often with stainless-steel bod-ies, are frequently used to control thisflow, and the valve seats are generallymetal because it is more durable inthese harsh conditions.

Homogenization of everything frommilk to peanut butter is also an area inwhich valves play an essential role. Inthis case, poppet valves are used formoderately abrasive products such asvegetable oils, and ball valves are usedwith abrasive products such as peanutbutter and pigments.

What all of this shows is that mod-ern food processing could not occurwithout a full range of valves, actuatorsand controls, and as processing meth-ods improve, so does the equipmentthat makes those methods possible.

It’s not something the average per-son thinks about when they sit downto a bowl of ice cream, but the foodand beverage industry, like many valveindustries, can only get bigger. VM

KATE KUNKEL is senior editor of VALVE Magazine.Reach her at [email protected]. Greg Johnson,president of United Valve (www.unitedvalve.com),also contributed to this article.

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