How to Improve Formingand Save EnergyArticle published in GLASS WORLDWIDE, 2011

Mauro Ferrero

How to Improve Formingand Save Energy

« epending on local conditions, almost 50% of the glass cost is energy».

This basic principle is the key to understanding why it is so important to reduce the use of energy

during glass container production. Reducing energy costs allows us to work on the largest

component of finished product cost. Energy is an essential component in glass manufacturing

and it comes in many forms. In this article, we examine the electrical power, used to generate

the huge flow of compressed air necessary to operate the IS machines of every manufacturer.

D

The generation of compressed air, inboth high and low pressure lines, is achievedusing air compressors and it is common tofind utility rooms with 600-800 kW ofinstalled power in glass factories. The totalcompressed air consumption depends onthe specific settings of the IS lines thusmaking every single glass factory a uniquecase.However one element is common to all glassworks: the generation of compressed airtakes a big bite out of the power bill of thefactory.Let's make a simple calculation:Cost of power: approx 0,12 Euro/kWh (inItaly).Assuming 8.700 working hours in one year,hence every single kW costs 1.050Euro/year.If we go back to the total consumption of theair compressors and we assume that we havean installed power of 800 kW with a realpower consumption of approx 700 kW(depending on the loading/unloading cyclesand assuming approx 90% on loadingcondition), than the pure cost of the energyused by air compressors is 730.000Euro/year.Of course, energy cost varies significantlyfrom one country to another and it can bevery different. Unfortunately, energy in Italyis one of the most expensive in Europe andthere are no signs of improvement on thisissue. However, even adapting the energycost to what is typical in France, one of thebest cases in Europe, and considering avalue of 0,07 Euro/kWh, the samecalculation would produce a total cost ofapproximately 426.000 Euro/year. Still aserious amount of money.Thus the question: is it possible to use less air

and to shut down part of the aircompressors?The answer is yes and the purpose of thispaper is to analyze the use of vacuum not as areplacement of compressed air but as acombined force able to reduce theconsumption of air and, at the same time, tohelp the forming process of the containers.

What do these bottles

have in common?

Chinese restaurants all over Europe andother countries. Tsingtao is the fifth largestbrewery in the world with a total volume of50 Million hectoliters in 2009.The bottle on the right is the proprietarybottle of “Birra Peroni”, a common Italianbeer, found in every super market.

The weight difference is astonishing(-45.7% of glass) and there is a lot of“technology” and development to go fromthe green bottle weighing 522 grams for 66cl. to the amber bottle that uses only 283grams of glass for the very same capacity.This “technology” covers every single aspectof container making and starts from the rightmix all the way to the lehr. However in the ISlines one essential player in light weightcontainers manufacturing is the use ofvacuum assisted forming.

The use of vacuum on the blow side isone of the most common applications. It hasbeen in use for years, it requires moulds with

Vacuum on the blow

side

Picture 1 - 66cl capacity beer bottles, Chinese andItalian production

Picture 2 - 522 grams vs 283 grams

Very little if we exclude that they are bothmade of glass and they have the samecapacity of 66 cl.The bottle on the left is made for Tsingtao,probably the most popular Chinese beer,available almost everywhere including

vacuum vents and channels and the ISmachine must be arranged for the use of it.Today, all IS manufacturers propose vacuumon the blow side as a standard feature.Vacuum is achieved through a series of tinyventing holes connected to channels in thesides of the mould and are evenly distributedon the upper part of the container beginningat the height of the shoulder of the bottle andgoing up towards the neck. They are oftenhidden in the engraving, when this is present,and in this case vacuum also helps themovement of the glass inside the small grovesthat will give the bottle its proprietary look.The diameter of the vacuum venting holesvaries from a minimum of 0,4 mm to amaximum of 0,7 mm. The diameter is anoption of the mould maker and it depends onthe container shape and use.Vacuum works as an additional force,together with the blow of compressed air andthe combination of push & pull of the twoactions helps the forming process byincreasing its speed, contributes to an evendistribution of the glass on the side of thecontainer and allows to reduce the gobweight.Removing the air that remains entrappedbetween the side of the container and the sideof the mould also helps to remove the heatfrom the mould keeping its temperatureunder control.An additional benefit of the useof vacuum is that it allows to slightly reducethe use of compressed air that is, at leastpartially, replaced by vacuum. Reducing theblow of air reduces the use of compressed airthus saving energy.One of the systems used to show the “vacuumat work” in glass forming is to stop the action

of the blow head of the IS machine. In thiscase only vacuum is used to form thecontainer. The effect of a good vacuum onthe blow side is so strong that it is possible tocomplete the forming of the container usingonly vacuum. Unfortunately it is not possibleto use only vacuum in the standardproduction because the containers would bestill too hot at the end of the forming.Nevertheless it clearly shows how and towhat extent vacuum can influence theforming process.

Vacuum on the blank

sideVacuum can be used on the

blank side with very interestingadvantages in compressed airsavings as well as in the quality ofthe container and in theproduction speed.The idea is to “pull down” thegob with vacuum instead of“pushing down” the gob with thesettle blow. In this case vacuumcan almost replace the use of thesettle blow and experiencesg a t h e r e d w i t h Q u a n t u mEngineered Products havedemonstrated that the use ofvacuum on the blank side maydramatically reduce the settleblow angles from usual 35/40°,down to 4 to 5°. That is aboutsaving 85 - 90% of compressedair and time dedicated to thisoperation.

Picture 3 - IS machine in operation producing different containers (courtesy of Bottero S.p.A.)

Cost of vacuum and cost

of air

Producing vacuum

efficiently

It is extremely difficult to evaluate thecost differences comparing flows. Howeverit is possible to compare the cost of a specificoperation when it is made with vacuum orwhen it is made with air. In short and withoutentering in too many details, we can statethat, if and when a specific operation can bedone using vacuum instead of air, than thecost to produce that energy is about onefourth of the cost to produce compressed air.

Contrary to compressed air, vacuum isdifficult “to be seen”, often misunderstoodand even more often regarded as a“secondary utility”. Furthermore, whilecompressed air is always produced bycentralized systems, vacuum is oftenproduced “on board” with small pumps thusnot taking advantage of the possible savingsof a centralized system.Vacuum can be produced in several waysand our experience has shown that veryoften it is produced with poorly engineeredequipment or with obsolete technologiesloosing, in this way, the advantage of analternative and cheaper force to compressedair. A vacuum pump is a piece of technologyand it deserves the engineering and know-how of a high technology equipment. First of

Picture 4 - Glass mould with vacuum venting holes in the upperpart (courtesy of Busellato Glass Moulds Srl)

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all, a vacuum pump must be a vacuum pumpfrom the very beginning of the project. Theuse of reversed compressors or “any” pumpcan bring unpleasant surprises in terms ofefficiency or Life Cycle Cost of the equipment.The rotary vane technology used inPneumofore pumps is, by far, the mostefficient way to produce vacuum in industrialapplications. A rotary vane pump is designedto be a vacuum pump, while rotary screwpumps are general ly compressors“transformed” into pumps. The efficiencyand the consistency of performance of arotary vane pump is just an impossible targeteven for the best liquid ring pumps, eitherwith water or oil sealing liquid.The rotary vane technology is based on thesliding movement of vanes inside the slots ofthe rotor. The total contact surface betweenthe edge of the vanes and cylinder is muchsmaller than the total contact surfacebetween the two screws between them andthe inner surface of the cylinder. When therotary screws come to the end of their life theymust be replaced bringing a significant repaircost. A rotary vane pump can bedisassembled and, after re-polishing thecylinder, will deliver again the originalperformance.Pneumofore offers a wide range of rotary

vane pumps, result of 85 years ofexperience in vacuum and hundreds ofinstallations with thousands of pumps inoperation all over the world. From polarclimates to tropical locations air cooledrotary vane vacuum pumps keep deliveringthe same solid performance year after yearof operation offering the lowest Life CycleCost available in this market.

Picture 5 - Mould with stipped finishing and vacuum venting on allthe surface (courtesy of Strada Srl)

As the glass fills the finish, the vacuumalso helps to cool and set the finish.With this process, the finish can be madeand set with reduced settleblow.By using the vacuum to help load deeperand set the finish, the gob will flow betterand easier into the finish.

Picture on the left:

Picture on the right:

Blank mould with vacuum loading(courtesy of Quantum Engineered Prod.)

Loading gobs entering the blank moulds(courtesy of Emhart)

Mauro Ferrero is Director ofSales at Pneumofore since2 0 0 7 . H i s t e c h n i c a leducation and intensecommercial experiencemake him a successfulmanager and member of thePneumofore Council. Thehollow glass industry is one ofhis strong application fields,also due to his continuousp r e s e n c e a t r e l a t e dworldwide conferences andf a i r s . D i r e c t c o n t a c tferrero@pneumofore.com

Via N. Bruno, 34 - 10098 Rivoli (TO) - ItalyTel. +39.011.950.40.30 - Fax +39.011.950.40.40info@pneumofore.com - www.pneumofore.com

7/20en sep11