Several Common Batching Equipments

This article is about several batching equipments often used in industrial weigh Batching. All materials shall be mechanically batched by mass except the water and admixture which may be batched by volume.

1 Batching Scales

The batching equipment used for determining mass shall conform to the applicable requirements of NIST HB 44, except that the accuracy shall be plus or minus 0.2 percent of scale capacity. The Contractor shall provide standard test reference masses and any other auxiliary equipment required for checking the operating performance of each scale or other measuring devices. The tests shall be made at the frequency required in paragraph TESTING AND QUALITY VERIFICATION FOR CONTRACTOR QUALITY CONTROL in the presence of a Government representative.

2 Batching Tolerances

a. Tolerances on Mass MATERIAL PERCENT OF REQUIRED MASS
Cementitious materials
0 to plus 2
Aggregate
plus or minus 2
Water
plus or minus 1
Chemical admixture
0 to plus 6

b. Volumetric Tolerances

For volumetric batching equipment, the following tolerances shall apply
to the required volume of material being batched:
Water: plus or minus 1 percent.
Chemical admixtures: Zero to plus 6 percent.

3 Grout Mixer

The batching equipment grout mixer shall be a machine especially designed for the mixing of grout and shall be capable of mixing grout mechanically to a uniform consistency. The mixer shall be maintained in satisfactory operating condition and kept free of hardened grout. Should any grout mixer at any time produce unsatisfactory results, its use shall be promptly discontinued until the condition is corrected. The grout mixer shall be provided with an acceptable device to lock the discharge mechanism until the required mixing time has elapsed. Use of revolving-drum concrete mixers will not be permitted.

4 Agitator Tank

The batching equipment agitator tank with batching controllers shall have at least the same capacity as the mixer and shall be equipped to agitate the grout effectively and continuously. All grout entering the tank shall be passed through a wire sieve. The sieve size shall not be less than 4.75 mm (No. 4) and not greater than 9.5 mm (3/8 inch).