Quality Control in Tunnel Kiln Construction
Many tunnel kilns suffer various quality defects starting from raw material procurement, mostly hidden structural performance flaws. Since tunnel kilns operate continuously under high-temperature thermal conditions, it is essential to first verify whether all purchased building and refractory materials fully meet design performance standards. All adopted materials shall reach or exceed specified design requirements, and unqualified materials below standard specifications are strictly prohibited.
1. Kiln Foundation Construction Quality Control
Uneven settlement and structural cracks frequently occur on many kiln foundations. The core reason is that designers fail to fully understand the actual operating state of tunnel kilns and design kiln foundations following ordinary civil building standards. As special high-temperature thermal operation equipment, tunnel kilns require independent design standards for settlement joints and expansion joints, which must not be unified with common building structures.
Strict material selection rules apply to foundation concrete: limestone gravel is forbidden for thermal deformation risks; flexible ductile steel bars are preferred; medium-grade cement is the optimal choice, avoiding both high-grade and low-grade cement.
2. Internal Kiln Track System Quality Control
Common track faults include thermal elongation, kiln car derailment, track beam fracture and track surface protrusion. Main causes are poor kiln car sealing leading to excessive track surface temperature, improper track material selection (using inferior railway rails instead of standard steel rails), non-standard reserved expansion joints and missing fixed baffle installation. Insufficient expansion joint reservation and poor concrete quality are the two main triggers for track beam cracking and subsequent track deformation.
3. Sand Sealing Structure Quality Control
Loose sand sealing plates cause sand leakage onto running tracks, blocking normal traveling of kiln cars. Sand sealing troughs must adopt high-temperature resistant materials matching actual working temperature, and low-temperature resistant inferior materials are totally unfit for this component.
4. Kiln Wall & Kiln Roof Construction Quality Control
Kiln inner walls and vault roofs are direct flame contact areas with the highest damage risk. All refractory materials used here must pass professional quality inspection and laboratory testing before construction, and random use of untested refractory products is forbidden.
Classified refractory materials shall be allocated reasonably according to functional zones: separate materials for high-temperature zones, low-temperature zones, thermal insulation zones and heat insulation zones respectively.
Main causes of kiln wall cracks: substandard masonry construction, excessive preheating temperature leading to unreasonable internal moisture discharge, impractical kiln drying plans, insufficient kiln drying experience and inadequate overall kiln body protection measures.
Kiln roof slab falling and brick shedding result from unqualified roof refractory raw materials, irregular masonry techniques, insufficient construction inspection, loose suspension fasteners, oversize brick gaps causing flame leakage and overheating damage, as well as inferior thermal insulation materials leading to structural collapse.
5. Kiln Body Fastener System Quality Control
Vertical columns, suspension beams, tension rods and other metal fasteners are core load-bearing structural components of the whole tunnel kiln. Strict material selection and standardized construction are required with no cutting corners allowed. Only positive tolerance structural steel is applicable for thermal stress resistance in high-temperature working environments. Loose fasteners easily cause kiln roof sagging, kiln wall deformation, cracks and roof slab dropping, hence the vital importance of qualified high-strength kiln fasteners cannot be ignored in daily operation.
6. Pipeline & Fan Matching System Quality Control
Pipelines and supporting fans undertake core functions including heat balance adjustment, waste gas exhaust, cold & hot air circulation and moisture removal. Different functional pipelines need targeted customized materials, especially for tunnel kilns dedicated to coal gangue and fly ash fired bricks.
For raw materials with high sulfur content, internal anti-corrosion treatment for all pipelines and anti-corrosion type fans are mandatory. Excessive sulfur content will cause severe corrosion to ventilation equipment and pipelines, drastically shortening service life (some damaged within 3-5 months only). Enterprises must conduct sulfur content detection on raw materials in advance to effectively extend the overall service life of the entire tunnel kiln production line.