Drying Out

The process of curing of castable does not end with wet curing. After wet curing for 24 hours, the castable should be air dried for a minimum of 24hours. Subsequently it has to be dried out gradually by using Flue Gas to remove the water content inside the castable as detailed in Ciria Doc. No. 205- 1522. Drying out has to be done meticulously and carefully.

6.0 QUALITY ASSURANCE PLAN - SITE INSTALLATION

ACTIVITY:

A successful refractory lining owes equally to good application practices as to the quality of material. As refractory linings are applied manually, it is essential that the applicator should be aware of the various quality control requirements and its impact on the life of installed linings. Thus it is advisable that the applicators are tested to check their awareness of the various requirements and given proper instruction on good working practices.

Equipment's used for the various lining activities should be thoroughly checked to ensure that they are in proper working condition before they are brought to site.

Proper quality control of installation can be segregated as

• Installation Pre Cautions

• Inspection and Test Plan

Installation Pre Cautions:

Only sufficient quantity of the correct type of material should be brought near the equipment to be lined, prior to lining activity.

Storage requirements and precaution against inclement weather should be met at the installation site for the material stocked.

Care should be taken while shifting the material to avoid damages.

Different type of blankets and boards should be stored separately to enable identification at work site also.

Installers should be properly instructed by qualified persons prior to all types of installation activity on good working practices and the requirements of the job.

While mixing mortar for brickwork only sufficient quantity should be mixed. In case of any excess the same should be covered with a thin layer of water on top to prevent contact with air. The same may be drained off prior to use of the mortar.

All equipment's and hand tools should be properly cleaned at the end of working shift.

Batch No. of castable used should be noted down along with the location of installation of castable.

Inspection and Test Plan for Site Installation Activity Anchor Welding

Anchor welded to the casing must be securely attached without any weld undercut. Any anchor properly welded shall be capable of withstanding being bent upto 15 degrees from its initially welded plane to the direction o greatest resistance and back without evidence of any weld failure. The anchor weld should be inspected by hammer test wherein striking of the anchor would give a good ringing sound when hit with a hammer. The inspection of anchors can be random. Visual inspection of welding is also done.

Castable Lining:

The main objective of physical testing of samples made at site is to assess and judge the quality of installed lining to

some extent without disturbing the lining. Thus the essence of sampling is to ensure that the sample represent the installed lining in all aspects, including the material batch, method of installation etc and is marked properly to correlate the sample to the installed portion of the unit.

Sampling for application by casting:

One sample per section of the lining for each quality and batch of castable being installed is made during the actual installation.

Each sample consists of 3 nos. 50mm ± 4mm cubes, which are cast in metal moulds. The metal moulds are cleaned, slightly oiled and kept ready for sampling. When the installation work / castable lining is ongoing the cubes are cast with the same material. The cubes are then cured, carefully coded and marked. The codes are then mentioned on the lining drawing to indicate the location where the parent material, from which sample was cast, is lined. The batch number of the castable is also noted while sampling to enable correlation of the sample with the batch of the material.

The cubes per batch of Castable are then kept together and randomly 3 cubes are selected for testing. 3 cubes per lot (supplied batches of each type of Castable material) of Castable material are then sent for testing (Bulk Density and Cold Crushing Strength). The cubes after wet curing of 24 hours are allowed to air dry for 24 hours before being sent to testing to an approved laboratory or the laboratory specified by the customer/client. The cubes are tested for bulk density and cold compressive strength after oven drying at 105°C, B.D. as per ASTM C 134 & CCS as per ASTM C 133 standards. The results are then compared with the acceptance criteria with an additional tolerance of 10% of the material. Ie for Cold Compressive strength, the permissible value shall be the minimum value as per acceptance criteria less 10% and no limit for the maximum value. Similarly for Bulk Density, the permissible value shall be the maximum value as per acceptance criteria + 10% and no limit for the minimum value. Thus permissible values are

Bulk Density : Max of (Acceptance Criteria Value + 10%)

Cold Crushing Strength : Minimum (Acceptance Criteria Value – 10%)

In case of any significant variation in test results, another set of 3 bars from the same lot is sent for testing. All other sample shall be preserved with their tag nos. for future use if any. An inspection checklist as detailed below shall be used at site to ascertain the quality maintained during installation of materials.

Cracking