Batch plant maintenance

BATCH PLANTMAINTENANCEMaintenance PLAN of Concrete Batching Plant

November 14CCCC-LBG / DAD

REFERENCES

• ACI 117 SPECIFICATION FOR TOLERANCES FOR CONCRETE CONSTRUCTIONAND MATERIALS

• ACI 301 SPECIFICATIONS FOR STRUCTURAL CONCRETE

• ACI 304R GUIDE FOR MEASURING, MIXING, TRANSPORTING, AND PLACING CONCRETE

• ACI 311.1R ACI MANUAL OF CONCRETE INSPECTION

• ACI 311.5R PLANT INSPECTION OF READY-MIXED CONCRETE

• ASTM C 94 STANDARD SPECIFICATION FOR READY-MIXED CONCRETE

• EPA US ENVIRONMENTAL PROTECTION AGENCY

• NRMCA NATIONAL READY MIXED CONCRETE ASSOCIATION


ACI 117 SPECIFICATION FOR TOLERANCES FOR CONCRETE

CONSTRUCTION AND MATERIALS

2.4a CEMENTITIOUSMATERIALS

Concrete batching tolerances

Less than 30% of scale capacity

–0 to +4% of the required mass

30% of scale capacity or greater

±1% of required mass

2.4b WATER & ADMIXTURESConcrete batching tolerances

Total water content (measured by weight or volume)

±3% of the required amount

Added water or ice, and free water on aggregates

±1% of the total water content

Admixtures

±3% of the required amount

2.4c AGGREGATES

Concrete batching tolerancesIndividual material batching

±2% of the required mass





Supplementary Cementing MaterialsBy Rafat Siddique, Mohammad Iqbal Khan

ACI 301-SPECIFICATIONS FOR STRUCTURAL

CONCRETE

Art. 1.6.3.2.c

Obtain production samples ofmaterials at plants or stockpiles duringthe course of the Work and test forcompliance with ContractDocuments.

Art. 13.1.2.1.h Plant quality control—

Submit certification of precastconcrete plants in accordance withthe Precast/ Prestressed ConcreteInstitute (PCI) Plant Certificationprogram.

Alternatively, submit manufacturingprocedures and a quality control andtesting program to Architect/Engineerfor review and acceptance. Submitevidence of plant certification ordocumentation of manufacturingprocedures and quality controlprogram.

Art. 13.2.15.1

Specify if PCI plant certification andtesting and inspection program is notrequired. Documentation ofcertification of plant and personnel.


SUB 01 45 00-070 ITP CONCRETE PRODUCTION ITP-SUB-GEN-G-PAS-

05009_A-


ACI 304R - GUIDE FOR MEASURING, MIXING,

TRANSPORTING, AND PLACINGCONCRETE

• 3.5—Water and ice measurement

• 3.5.1 Batching equipment: Equipment and methods used should be capable of routine measurement within the 1% tolerance. All equipment for water measurement should be designed for easy calibration so that accuracy can be quickly verified.

• 3.5.2 Aggregate moisture determinationand compensation: Moisture metersshould be recalibrated monthly orwhenever the slump of the concreteproduced is inconsistent.

• 4.9—Maintenance

• Mixers should be properly maintainedto prevent mortar and dry materialleakage. Inner mixer surfaces should bekept clean and worn blades should bereplaced. Mixers not meeting theperformance tests referenced inSection 4.8 should be taken out ofservice until necessary maintenanceand repair corrects their deficientperformance.


ACI 311.1R ACI MANUAL OF CONCRETE

INSPECTION7. BATCHING AND MIXING


ACI 311.5R PLANT INSPECTION OF

READY-MIXED CONCRETE1.3—Inspector duties

1.3.1 To determine required inspections,the inspector should review and fullyunderstand the project specifications,plans, and other project documents.

The inspector should observe that thefacilities, scales, and truck mixers meetthe specified project requirements. Theprovisions of the following documentsshould normally be incorporated in theproject specification:

ACI 301; ASTM C 94/C 94M;

Plant qualification in accordance withthe (NRMCA) checklist for certification ofready-mixed concrete productionfacilities; and Local agencyspecifications.

1.3.2 Inspectors should conduct activities in accordance with all safety policies, health standards, and safe work practices in effect at the job site.

1.3.3 The inspector should verify properstorage of all materials on a daily basis.

All storage areas should be clean andfree of contamination.

Cementitious materials should be storedin weatherproof silos or similar structures.

Aggregate storage areas should providefor separation and free draining ofstockpiled materials.

Storage areas should be equipped withwater spray systems for maintainingaggregates in a saturated condition.Means for protecting and preventingfreezing of aggregates during winterproduction should also be provided.

Admixture storage areas should besuitably insulated.




1.3.4 All tests and inspections shouldbe conducted at the frequenciesrequired by the project specificationsin a manner that does not interfereunnecessarily with the manufactureand delivery of the concrete.

1.3.4 During the first batch beingshipped to the project under theinspector’s jurisdiction, the inspectorshould be present at the batchingconsole to verify that the specifiedtype and amount of materials,conforming to the approved designmixture proportions, are batched anddelivered to the mixer.

1.3.4 If the operation is automatedand recorded, the inspector shouldmake observations as often aspossible, preferably on a continuousbasis, but at least once per hour.

If the batching operation is manual,the inspector should be present atthe batching console during allbatching. The inspector should verifythat quantities of materials for eachbatch fall within the tolerances setforth by the project specifications.


SECTION 34 90 08:• 2.4.3.1 Materials shall be measured by weighing, except as otherwise specified in the

Contract documents or where other methods are specifically authorized. The apparatusprovided for weighing the aggregates and cement shall be suitably designed andconstructed for this purpose.• Each size of aggregate and the cement shall be weighed separately.• The accuracy of all weighing devices shall be such that successive quantities can be

measured to within one percent of the desired amount.• Cement in standard packages need not be weighed but bulk cement shall be weighed. The

mixing water shall be measured by volume or by weight (mass). The accuracy of measuringthe water shall be within a range of error of not over one percent.

• All measuring devices shall be subject to approval and shall be tested, at the Contractor'sexpense, when deemed necessary by the Contracting Officer.

• 2.4.3.2 When volumetric measurements are authorized for projects, the weight (mass)proportions shall be converted to equivalent volumetric proportions.• In such cases, suitable allowance shall be made for variations in the moisture condition of the

aggregates, including the bulking effect in the fine aggregate.• When sacked cement is used, the quantities of aggregates for each batch shall be exactly

sufficient for one or more full sacks of cement and no batch requiring fractional sacks ofcement will be permitted.

• 2.4.4.1 Batching: (c) Batching equipment and scales shall meet the requirements formeasurement and accuracy in ASTM C94



READY-MIXED CONCRETE

1.3.5 The inspector should verify thatcoarse- and fine aggregate gradationtests are being performed inaccordance with ASTM C 136 and thatthe results meet the projectrequirements. If deviation occurs, batchplant personnel and the client should benotified immediately, or previouslyauthorized action should be taken.

1.3.6 The inspector should verify thataggregate moisture contents areproperly determined in accordance withASTM C 566, and that the batchquantities of materials are adjusted tocompensate for free moisture in theaggregates.

If aggregate moisture contents arebeing measured by rapid methods, dailycorrelation tests following ASTM C 566should be conducted.

1.3.7 The inspector should determinethat the trucks are in good operatingcondition and not loaded beyondtheir rated capacities for mixing andagitation.

Trucks should also be inspected(safety regulations regardingconfined spaces should be followed,if applicable) for blade wear, build-up of concrete on the blades, and forproper mixing speed as described inthe NRMCA Quality Control Manual.Truck mixers should be equipped withcounters or similar means to enableverification of the number ofrevolutions applied to the drum.

1.3.8 The inspector should verify thatthe scales and other measurementsystems have been properlycalibrated within the time periodspecified by the project specificationsor referenced documents

1.3—Inspector duties




1.3.9 The capability of the productionfacility to produce concrete withinthe temperature limits of the projectspecification should also beevaluated and verified.

In hot weather, this generally requiresa system for spraying and coolingaggregates and a system forefficiently weighing and deliveringcrushed ice to the mixer in the rangeof 40 to 100 lb per yd3 (18 to 45 kgper m3).

1.3.10 For each batch of concretethe inspector should verify that theconcrete plant is furnishing to thepurchaser a delivery ticketconforming to ASTM C 94/C 94M. Aplace should be provided on theticket to reflect the followinginformation:

• Name of the concrete plant;

• Serial number of the ticket;

• Date;

• Truck number;

• Name of the purchaser;

• Project designation (name and location);

• Class or designation of concrete; Amountof concrete batched;

• Time batched;

• The amount of water withheld duringbatching, if any, and the admixtures thatmay be added at the jobsite; and

• Any additional information required bythe purchaser or the project specification.




1.4—Reports

1.4.1 The inspector should sign thedelivery ticket, issue an inspectionreport, or supply other evidence thatthe concrete batching has beeninspected.

1.4.2 The inspector should issue a dailyinspection report showing all testresults and documenting observationsmade during the day. Deficienciesand to whom they were reportedshould be clearly identified.

The ACI Manual of ConcreteInspection (SP-2) contains guidanceon reporting and samples of reports.


ASTM C 94-STANDARD SPECIFICATION FOR


Art. 6 & 9

6.6 A certified copy of all proportionsas established in Options A, B, or Cshall be on file at the batch plant.

9.3 Mixing water shall consist of wateradded to the batch. The addedwater shall be measured by weight orvolume to an accuracy of 1 % of therequired total mixing water.

9.4 Liquid chemical admixtures shallbe batched by mass or volume.Admixtures measured by either massor volume, shall be batched with anaccuracy of ±3 % of the total amountrequired.

Art. 1010.1 Means of control shall beprovided so that, as the quantitydesired in the weighing hopper isapproached, the material shall beshut off with precision. Weighinghoppers shall be constructed so as toeliminate accumulations of tarematerials and to discharge fully.

10.3 Scales shall be consideredaccurate when at least one staticload test within each quarter of thescale capacity can be shown to bewithin ±0.15 % of the total capacity ofthe scale or 0.4 % of the net appliedload, whichever is greater.

NOTE 11—The batching accuracylimit of 0.3 % of scale capacityestablishes a reasonable minimumweighing tolerance limit that isindependent of the quantity ofmaterial being weighed. It generallygoverns for smaller batch quantitiesweighed in weigh batchers (scales).

NOTE 13—The scale accuracy limitations of the National Ready Mixed Concrete Association Plant Certification meet the requirements of this specification.

ASTM International: C685/C685MStandard Specification for ConcreteMade by Volumetric Batching andContinuous Mixing


VARIATION IN CONCRETE PERFORMANCEDUE TO BATCHING

• The NRMCA Plant Certification requires producers to verify scaleaccuracy at least once every six months and arrange for promptrecalibration and correction if non-compliance is indicated or if theplant is moved or other maintenance impacts the weighing systems.

• NRMCA certification requires that volumetric measuring of volumetricmeasuring devices for water and chemical admixtures should bechecked for accuracy at least once every 6 months.

• The batching accuracy requirements in the NRMCA Plant Certificationprogram are as required in ASTM C94 and stated in Table 1.

• For weighed ingredients, accuracy of batching is determined bycomparison between the desired weight and the actual scalereading; for volumetric measurement of water and admixtures,accuracy is determined by checking the discharged quantity relativeto the target, either by weight on a scale or by volume in anaccurately calibrated container. Volumetric measurement iscommonly used for water and typically used for chemical admixtures.It is realized that on any single batch, at least one of the ingredientsmay be out of tolerance, as discussed later.

• For the NRMCA plant certification, inspectors are advised to reviewseveral batch records and to determine that the plant complies withthe batching accuracy by reviewing the average of at least 10batches of concrete.

• Improving batching accuracy can help attain more consistentperformance for fresh concrete properties that is important to thecontractor and to reduce variation of compressive strength ofconcrete


RECOMMENDED PRACTICES FOR BATCHING AND MIXING SCC:

• Always know and adjust for moisture in aggregates. Moisturemeters for sand are strongly recommended. When producingSCC, run a moisture test on all aggregates within 1.5 hours ofactual batching of SCC. If the plant does not have a moisturemeter, moisture should be tested throughout the day. At aminimum, determine aggregate moisture at the beginning of thework day, mid morning, and mid afternoon. Also check moistureany time new material is delivered to the plant.

• Once the admixture dosage is established, it should not varyunless water demand of the materials has changed. This could bedue to changes in any of the components – aggregates, cement,supplementary cementitious materials.

• Run gradations on aggregates a minimum of once per week orwhenever the SCC mix appears to have changed. If gradationshave changed, adjust mix proportions accordingly.

• Run a laboratory trial once per month, or whenever the mixappears to have changed, to expose possible water demandchanges.

• If a central mixer is used, monitor the mixer amp meter as ameasure of moisture level and water demand. Confirm that youramp meter can distinguish between an empty mixer and a highlyflowable SCC mix. If not, install a higher quality digital meter (0.1amp resolution). In the absence of HRWR, identify an amperagereading that corresponds to a slump which produces good SCCupon later addition of the SCC admixture. If the amp reading istoo high, adjust with water. The amp reading should be stablebefore adding the SCC admixture. Establish a second target forafter the addition of the SCC admixture. Adjust with admixture ifthe reading is too high. Changing amp readings are an importantindicator of changes in materials.

• If using a truck mixer, occasionally confirm moisture control andwater demand by measuring the slump before SCC admixtureaddition. Changes in “zero-admixture” slump are an indication ofchanges in sand moisture or water demand. The “zero-admixture”slump should be within ± 25 mm (1 in.) of the predefined target.

• Make sure the truck mixer is empty – as little as 5 L/m3 (1 gal/yd3)of water can make the difference between success and failure.Reverse ALL water and material out of drum before backing underthe batch plant. It is critical to make this point clear to truckdrivers.

• Mix SLOWLY. Poly-carboxylates that are designed to producehighly stable SCC develop workability more slowly than typicalhigh range water reducers. Fast mixing leads to poorreproducibility and can induce excess foaming, which is difficult toget rid of after the fact. The concrete should have a foldingmotion, not a slapping motion. For truck mixers, 1⁄2 speed (8-10rpm) is sufficient.

• Do not deliver the concrete until the contractor or finisher is ready.Standing trucks can cause an SCC pour to go very badly.

• As a general rule, addition of 5 L/m3 (1 gal/yd3) of water to SCCcan increase slump flow 50-75 mm (2-3 in.); while removing 5 L/m3(1 gal/yd3) reduces slump flow 50-75 mm (2-3 in.)

• Air content can have an impact on slump flow. The direction andmagnitude of this relationship depends on the materials, mixdesign, and the amount of air.


EPA –US ENVIRONMENTAL PROTECTION

AGENCYAir quality management The maximum level of concentration of solidparticles, at testing points determined inaccordance with this policy, is a total mass of 250mg/m3 of residual gases after completion of theprocess and before amalgamation with air, smoke orother gases.

In the case of concrete batching plants, cement,sand and aggregates can produce dust which mayenter neighboring premises and adversely affectamenity value.

The best way to avoid offsite problems is to preventthe release of the dust through good design andmanagement techniques. The provision of natural orartificial wind barriers such as trees, fences andlandforms may help control the emission of dust fromthe plant.

All concrete batching plant sites should demonstrategood maintenance practices, including regularsweeping to prevent dust build-up.

The prevailing wind direction should be consideredto ensure that bunkers and conveyors are sited in aleeward position to minimize the effects of the wind.Aggregate material should be delivered in a dampcondition, and water sprays or a dust suppressionagent should be correctly applied to reduce dustemissions and reduce water usage. Aggregatestored on site in stockpiles should be containedwithin three-sided storage bunkers with windshieldsthat project 0.5 meter above the bunker wall.

Conveyors must be designed and constructed toprevent fugitive dust emissions. This may includecovering the conveyor with a roof, installing sideprotection barriers and equipping the conveyor withspill trays, which direct material to a collection point.Belt cleaning devices at the conveyor head mayalso assist to reduce spillage. Mixer loading areasshould be roofed and enclosed on either two (drive-through) or three sides. Water sprays and/or dustcurtain of suitable design, or an effective airextraction and filtration system, should be installed tosuppress dust generated during mixer truck loading.

Weigh bins and hoppers should be enclosed onthree sides and roofed where a front-end loader isused. The roof should extend 2 meters in front of thebin. Any raw material spills should be removedpromptly by dry sweeping. Water should not be usedin the process of cleaning up spills except where thearea drains to a wastewater collection point wherewashing down would be preferable to generatingdust by sweeping.

An approved fabric filter incorporating a fabric-cleaning device should be installed on each cementstorage silo.

Adequate access to the filters should be provided toallow for regular inspection and maintenance. Apollution control equipment register (PCER) shouldbe used to record, on a weekly basis, the following:pressure drop visual conditions of exhaust materialincidents of filter media failure/replacement.

Water managementPotential pollutants in batching plant waste waterand storm water include cement, sand, aggregates,chemical admixtures, fuels and lubricants. The siteshould be designed and constructed such thatclean storm water, including roof run off, is divertedaway from contaminated areas and directed to thestorm water discharge system. Underground storagetanks should be tested annually for integrity.

Contaminated storm water and process wastewatershould be captured and recycled. Concreteagitator bowls and chutes must never be washedout to the storm water system or roadways.

Process wastewater and contaminated storm watercollected from the entire site should be diverted to asettling pond, or series of ponds.

In general a high standard of yard and equipmentmaintenance will considerably reduce the potentialfor discharge of sediment to the wastewatercollection and recycling system.

Regular inspection and maintenance of the system isnecessary to avoid discharges of contaminatedwater from the site. These inspections andmaintenance should be recorded. Areas where spillsof oils and chemicals may occur should beequipped with easily accessible spill control kits toassist in prompt and effective spill control, accordingto the EPA Guidelines, Bonding and spillmanagement. Staff should be familiar with spillresponse and notification procedures


NATIONAL READY MIXED CONCRETE ASSOCIATION


NRMCA CERTIFICATION• NRMCA Personnel Certifications:

• Certified Concrete Sales Professional (CCSP)• Certified Sustainability Professional• Concrete Delivery Professional Certification• Concrete Field Testing Technician Grade II• Concrete Green Building Certification• Concrete Sustainability Professional

Certification• Concrete Technologist Level 2 "Technical

Short Course"• Concrete Technologist Level 3• Concrete Technologist Level 4 "Durability

Course"• Effective RMC Supervisor Certification• Environmental Professional Certification for

the Ready Mixed Concrete Industry• Fleet Manager Certification

• NRMCA Plant Certifications:• Quality: Plant and Truck Certification• Quality Certification Program• Environmental Stewardship: Green-Star

Certification Program• Sustainability: Sustainable Concrete Plant

Certification• Plant Manager Certification

• NRMCA Safety Certification (Online)• OSHA 10-Hour Safety Certification for

General Industry• Pervious Contractor Certification• Plant Manager Certification• Sales Manager Ceritification

• NRMCA Product Certifications:• NRMCA Certified Environmental Product

Declaration


CHECK LIST FOR READYMIX CONCRETE PRODUCTION FACILITIES

• Cementitious Materials

• .1 Bins or silos are tight and with freemovement to discharge opening [ ]

• .2 Separate storage is provided fordifferent types of cementingmaterials to prevent contamination– common bag houses shouldshake down into the least affectedcementing material [ ]

• .3 Intra-plant handling preventscontamination [ ]

• .4 All cementitious feed pipes aremarked and designated (e.g. GU,HS, Fly Ash, etc)[ ]

RAW MATERIALS



• Aggregates

• .1 Aggregates stockpiles arearranged to assure that eachaggregate as removed is clean,distinct and not intermingled withothers

• .2 Procedures for unloading andstoring aggregates prevents harmfulsegregation [ ]

• .3 Intra-plant handling andtransportation prevents harmfulsegregation [ ]

• .4 Separate storage bins orcompartments for each size andtype of aggregate are properlyconstructed and charged toprevent mixing of different sizes andtypes [ ]

RAW MATERIALS



• Water

• .1 Adequate supply with pressuressufficiently constant or regulated toprevent interference with accuracy ofmeasurement where flow meters areused to measure mixing water – the flowmeter shall be calibrated anddocumented at intervals of no morethan six months [ ]

• .2 The concrete producer must providecertification that the water used meetsthe requirements of CSA A23.1 at alltimes. Water for concrete productionmay be from one of the followingsources:

• Potable source (water is supplied by agovernment/commercial agency) [ ]

• Non-potable source (satisfactoryhistory of strength and durabilitymade with the water has beendemonstrated) [ ]

• Water from concrete productionoperations [ ]

RAW MATERIALS



Admixtures

.1 Storage of liquid admixtures isprovided to prevent damage byfreezing or contamination

2 Agitation is provided for liquidadmixtures that are not stablesolutions [ ]

.3 Each admixture shall be measuredand discharged separately [ ]

RAW MATERIALS


CHAPTER 4: Production Facilities

4.1 Compliance with Standards:

Production facilities and deliveryvehicles conform to the requirementsof ASTM C94.

• For delivery vehicles providestatement on procedures andfrequency to evaluate bladewear and buildup in truck mixers.

• Review statement by company on frequency of verification of accuracy of scales and volumetric measuring devices.

• Review records of one scale verification record– load test data sheet required.

4.2 Monitoring Batching Accuracy:

Provide description of:

• Procedures used to identify and address out of-tolerance batches. Indicate the specific individual with responsibility for monitoring batching accuracy.

• Describe corrective actions used for consistent out of tolerance situations.

• Provide two batch records from each plant within the last 3 months. Records should indicate target and actual quantities batched for cementitious materials, aggregates, batch water and admixtures. Tolerance information should be included in batch records.

QUALITY CERTIFICATIONPROGRAM

Procedures stated to monitor and to address out of tolerance batches

• Review procedures used to identify out-of-tolerance batches and decision process and responsibility for addressing these situations.

• Review corrective action.

• Review 2 batch records from each plant in submission within the last 3 months.


CHAPTER 4: Production Facilities

4.3 Control of Mixing Water.

Procedures stated to control mixingwater to within the ASTM C94tolerance of ±3%

Review procedures used for control ofmixing water to include, but notlimited to:

• Frequency of verifying accuracyof plant water measuring devices,procedure used and accuracyrequirements.

• Verifying accuracy of measuringdevices (volumetric to 1.5%, scalesas per scale check) andfrequency

• Addressing mixer wash-water priorto batching.

• Control of mixing water additionat the slump rack.

QUALITY CERTIFICATIONPROGRAM

• Verifying accuracy of watermeasuring devices on truck watertanks – procedure and frequency(water meters accurate to ±2%,sight gages accurate to ±1gallon).

• Process for trim water holdbackand communicating limits ofwater addition to the purchaserand procedures required bydrivers at the jobsite

Review sample of 1 delivery ticketsfrom each plant in the submission ofdelivered loads documenting therecording of jobsite water additionand signature of purchaser.


PLANT CERTIFICATIONGUIDANCE TO CONCRETE PRODUCERS SEEKING

AND MAINTAINING PLANT CERTIFICATION

SCALE ACCURACY VERIFICATIONScale accuracy should be verified anytime the plant ismoved, maintenance activities on the plant impact theweighing systems, or when there is a concern on scaleaccuracy determined from the batchman operatingthe batching process or the quality of concrete.

There are some differences in what the scalecompanies are accustomed to doing and what isrequired by the NRMCA plant certification and ASTMC94. The following should be communicated with thescale company before they do scale checks:

• Minimum quantity of test weights should be at 10% ofscale capacity. Aggregate scale capacities willgenerally govern the minimum amount of testweights required – about 4000 lbs is typically needed.(There may be situations where the plantconfiguration does not permit the minimum testweights to be used and that has to be verified by theplant inspector).

• Test weights should be certified to be accurate to0.01% of their indicated load within the last twoyears. This is typically not a problem with commercialscale companies.

• Scale checks should be done through range of useof the scales. Scale companies may only verify itthrough 50% of the scale capacity.

• Up through 50% of the scale capacity, scale checksshould be done using a build-up test load using acombination of product and test weights in aprocess called a substitute test. Scale incrementsshould not be skipped. In substitute testing, productin the scale should only be to the load previouslyverified – as close as possible.

• Over 50% of the scale capacity, strain test loading ispermitted. An unknown quantity of product ischarged and the incremental weight indication withthe test weights is verified. At least two points shouldbe tested in this portion of the scale – through typicalrange of use.

• Scale accuracy requirements (ASTM C94) is thegreater of• ±0.15% of scale capacity (governs at the lower

end)• ±0.4% of applied test load• If it's not accurate the scale has to be adjusted.

• A copy of the scale verification data sheets shouldbe obtained to indicate details of the test loadsused, test load increments, load indications and loaderror. A certificate just indicating a scale is OK is notacceptable.


• Additional Information

• a. Each scale is comprised of a suitablesystem of lever and/or load cells, whichwill weigh consistently within thetolerance specified by the MRMCA, withloads indicated either by a beam with abalance indicator or a full reading dial ordigital readout display verifyingaccuracy.

• b. Each scale must be calibrated at aminimum of 2 points and at 20% and 80%of the scales normal operating capacity.

• c. The Scale Manufacturer or ScaleCompany must supply the necessarydocumentation that governmentapproved test weights are used, whichare certified and traceable.

• d. The Scale Manufacturer or ScaleCompany must provide a procedure orcheck list which is used for the inspectionand to document all mechanical checks,calibration test results and anydeficiencies in the scale or weighingsystem.

• e. The Scale Manufacturer or ScaleCompany’s qualified technician must signthe MRMCA Scale Check Data Formcertifying that all requirements have beenmet.

• f. All scale check and calibrationreports/records must be kept on site andmust be available for inspection at alltimes.



SCALE ACCURACY VERIFICATION




WATER METER ACCURACY VERIFICATION

Accuracy of water meters should beverified at least once every six months.Maintain documentation of theseverifications for review by the inspector.Accuracy of water meters is the same asthat required for batching accuracy±1.5%. Measure accuracy using a largeenough volume of water – at least 50gallons. Methods include:

• Discharge water into a 55-gallon drumand weigh the quantity – can besuspended from the cement scale.

• Perform this at least 3 times to obtain anaverage.

• Some discharge 200+ gallons into atruck mixer if truck scales are available.After weighing the truck, water isdischarged and the truck is weighedempty to determine water in the drum.

• Discharge water into a calibratedcontainer of at least 50 galloncapacity. Calibrations on the containershould be accurate enough tomeasure to within the requiredaccuracy tolerance.

When water is measured by weight,accuracy requirements for scales apply.

November 14CCCC-LBG / DADCOE CRD-C 143-62 Handbook for Concrete and Cement Specifications For Meters For Automatic Indication Of Moisture ln Fine Aggregate



ADMIXTURE DISPENSER ACCURACY VERIFICATION

The batching accuracy of dispensers of liquid admixturesshall be checked at least every 6 months. This dispenseraccuracy check is usually performed by collecting thechemical admixture into a calibrated container. It isacceptable to use a dispenser measuring unit as thecalibrated container.

The process for checking accuracy using a calibrateddispenser measuring unit is as follows:

• A dosage quantity check should be performed for eachdispenser.

• Determine the target quantity based on a typicaldosage rate within the recommended dosage range.

• Dose target quantity of admixture into the dispensermeasuring unit and hold for visual measurement.

• Calculate and confirm accuracy.

When the admixture is measured by a meter and batchedthrough a direct feed admixture system (with no dispensermeasuring unit), the accuracy check is conducted using acalibrated flask/container. The process for checkingaccuracy using graduated flask or container:

• A dosage quantity check should be performed for eachdispenser.

• Determine the target quantity based on a typicaldosage rate within the recommended dosage range,but usually limited to under 5 gallons.

• Dose target quantity of admixture into calibratedflask/container for measurement.

• Calculate and confirm accuracy.

The company can perform their own dispenser accuracychecks instead of calling the dispenser representatives. Ifthe meter is not accurate, the admixture dispenserrepresentatives should be called in to calibrate thedispensing system. Documentation of admixture dispenseraccuracy verification should be retained for review by theinspector.

Some producers collect admixture at the point ofdischarge into the mixer to verify the accuracy of thedispensing system. This process checks the integrity of thelines through which the admixture flows in addition to thedispenser accuracy.




MOISTURE PROBE ACCURACY VERIFICATION

Follow manufacturer’s directions forverifying accuracy.

• The accuracy of moisture probesshould be relative to an aggregatemoisture measurement by dryingout an aggregate sample on a hotplate or microwave oven (ASTMC566). The aggregate sampletested should be obtained from asclose to the location of the moistureprobe measuring the aggregatemoisture.

• There is no stated accuracy(tolerance) for moisture probes inthe NRMCA Check List. Using therequired accuracy (±1.5%) for watermeters can be considered as abasis for requiring corrections to thedevice (calibration).

• Maintain documentation of thesechecks and provide for review tothe inspector.


SUMMARY

ITEM Frequency Other

Monitoring Batching Accuracy Review 2 batch records from each plant in submission within the last 3months.

Review procedures used to identify out-of-tolerancebatches and decision process and responsibility foraddressing these situations.Review corrective action.

Control of Mixing Water Review sample of 1 delivery tickets from each plant in the submission ofdelivered loads

Scale accuracy verification Anytime the plant is moved, maintenance activities onthe plant impact the weighing systems, or when there is aconcern on scale accuracy determined from thebatchman operating the batching process or the qualityof concrete

Water meter accuracy verification & Water Flow Meter

At least once every six months. When water is measured by weight, accuracyrequirements for scales apply.

Admixture dispenser accuracy verification

Checked at least every 6 months

Moisture Probe accuracy verification ACI 304.R/3.5.2 Aggregate moisture determination and compensationMoisture meters should be recalibrated monthly or whenever the slump of theconcrete produced is inconsistent.

Follow manufacturer’s directions for verifying accuracy

All measuring devices shall be subject to approval and shall be tested, at theContractor's expense, when deemed necessary by the Contracting Officer.

Section 34 90 08Art. 2.4.3

consistency-recording meters, such as those operating from the amperage

Some draw on the electric motor drives for revolving-drum mixers, have alsoproven to be useful. The most positive control method for maintaining batch-to-batch uniformity, however, is a regularly scheduled program of tests of thefresh concrete, including unit weight, air content, slump, and temperature.


PLANT MAINTENANCE PLAN



DAILY

1. Inspect oil and filter on aircompressor and drain tank,manifolds, and all water traps.

2. Inspect and fill all oilers on plant.

3. Inspect all air cylinders.

4. Inspect tension on all V-drive belts.

5. Inspect conveyor belts foralignment and excessive wear.

6. Perform housekeeping items, suchas cleaning up dust and debris.

First, the mechanism of lubricating oilshould be change often.

Before work, the machine shouldhave an empty running.

Second, check whether there iswater in the bucket of ingredients; ifyou find some, clean it up.



DIARIO

1. Inspeccione el aceite y el filtro de airedel compresor y el tanque de drenaje,colectores, y todas las trampas deagua.

2. Inspeccione y rellene todos losengrasadores en planta.

3. Inspeccione todas las botellas de aire.

4. Inspeccione la tensión de todas lascorreas V-drive.

5. Inspeccione las correastransportadoras para la alineación y eldesgaste excesivo.

6. Lleve a cabo los elementos delimpieza, tales como la limpieza depolvo y escombros.

En primer lugar, el mecanismo deaceite lubricante se debe cambiarcon frecuencia.

Antes del trabajo, la máquina debetener un funcionamiento vacía.

En segundo lugar, comprobar si hayagua en el cubo de ingredientes; siencuentra alguna, limpiarlo.



Weekly

1. Lubricate all bearings (ONE PUMP ONLY).Included are head and tail pulleys on allconveyors, snubber roller on loadingconveyor, head and tail bearings oncement feeder screws, wheel bearingsupports on turn head, etc.

2. Lubricate all aggregate gate pivotpoints.

3. Replace or blow clean all air filters on aircompressor and aeration blowers.

4. Inspect and tighten all bolts andbearing set screws.

5. Inspect and/or adjust all beltwipers.

6. Lubricate packing at the bottomand top ends of the cement feederscrews with oil.

7. Inspect all bags in cement bagfilters.

Be very careful with the batching'scontrol instrument, because this is anelectronic instrument, once exposedto the sun or rain or lightning, it will bedamaged and seriously affect theaccuracy of the ingredients, whichaffect the progress. The batching'scontrol instruments should be placed,by erection, in a facility that will besun proof, rainproof, dustproof andlightning protected.



Semanal

1. Lubrique todos los cojinetes (UNABOMBA SOLAMENTE). Se incluyen en lacabeza y la cola poleas en todos lostransportadores de rodillos, cojinetes decarga amortiguador en transportadoras,cabeza y cola de tornillos alimentadoresde cemento, cojinete de la rueda apoyaen la cabeza a su vez, etc.

2. Lubrique todos los puntos de pivotepuerta agregados.

3. Vuelva a colocar o golpe limpio todoslos filtros de aire en el compresor de aire ysopladores de aireación.

4. Inspeccione y apriete todos lospernos y tornillos de fijación delrodamiento.

5. Inspeccione y / o ajustar todos loslimpiadores de correa.

6. Lubricar embalaje en la parteinferior y los extremos superiores delos tornillos de alimentación decemento con aceite.

7. Inspeccione todas las bolsas en losfiltros de bolsa de cemento.

Tenga mucho cuidado con elinstrumento de control de ladosificación, ya que este es uninstrumento electrónico, una vez quese expone al sol o la lluvia o losrayos, se dañará y afecta seriamentela exactitud de los ingredientes, queafectan a los progresos. Instrumentosde control de la dosificación debenser colocados, por la erección, enuna instalación que va a ser aprueba de sol, impermeable, aprueba de polvo y relámpagosprotegidos.



Monthly

1. Inspect oil level in all gear reducers.

2. Adjust skirt boards as needed.

3. Adjust and tighten conveyor beltsas needed.

4. Change oil in air compressor.



Mensualmente

1. Revise el nivel de aceite en todoslos engranajes reductores.

2. Ajuste faldones, según seanecesario.

3. Ajuste y apriete las cintastransportadoras, según seanecesario.

4. Cambie el aceite del compresorde aire.



Semiannually1. Change oil in all conveyor gearreducers.

2. Remove bags in cement bag filtersand blow clean.

3. Tighten or replace all V-belts asneeded.

4. Inspect scale and water meteraccuracy.

5. Inspect hanger bearings in feederscrews and replace as needed.

6. Inspect and acidize boiler.

7. Inspect and/or replace binaeration pads



Semi-anualmente1. Cambie el aceite en todos losreductores transportadora.

2. Retire las bolsas de filtros de bolsa decemento y golpe limpio.

3. Apriete o reemplace todas las correasen V, según sea necesario.

4. Inspeccione la precisión de escala yagua metros.

5. Inspeccione los cojinetes de lasuspensión en los tornillos dealimentación y reemplace según seanecesario.

6. Inspeccione y acidificar la caldera.

7. Inspeccionar y / o reemplazar lasalmohadillas del bin aireación


Batch plant maintenance

Engineering

Transcript of Batch plant maintenance