Quick Answer
Prism Calibration Centre (NABL CC-2480) provides calibration for Gujarat's cement plants: kiln thermocouple calibration (Type S/B, 1200–1500°C), weigh feeder and belt scale calibration, clinker temperature pyrometers, and QC lab instruments (Blaine fineness, particle size, compressive strength testing machines).
Key Takeaways
- Kiln thermocouple calibration covers 1200°C to 1500°C (Type R, S, B thermocouples).
- Weigh feeder and belt scale calibration per OIML and BIS standards.
- Particle size analyser calibration for cement fineness (Blaine method).
- Compressive strength testing machine calibration per IS 516 and EN 196-1.
- BIS product certification (IS 269, IS 455, IS 1489) requires NABL-calibrated test equipment.
Cement Plant Instruments Calibrated
- Kiln inlet/outlet thermocouples (Type R/S/B, 900–1500°C)
- Preheater and cooler temperature instruments (Type K, 400–1000°C)
- Clinker pyrometers (infrared, 800–1600°C)
- Weigh feeders and belt conveyors (mass flow weighing)
- Cement storage silo level instruments
- Compressive strength testing machine (IS 516 calibration)
- Vicat apparatus and Le Chatelier flask (setting time)
- Particle size analyser (laser diffraction, Blaine fineness)
BIS Cement Testing — Calibration Requirements
IS 269 (OPC), IS 455 (SRC), IS 1489 (PPC) — all BIS cement specifications require quality testing in an accredited laboratory with calibrated test equipment. Compressive strength cubes must be tested in a calibrated cube crushing machine. Fineness (Blaine) must be measured with calibrated apparatus. NABL calibration by Prism satisfies these BIS testing requirements.
What NABL accreditation adds here
BIS certification requires that your test equipment be calibrated, and that the calibration be traceable. A NABL-accredited certificate carries that traceability on its face — the reference standard, its own certificate number, and the measurement uncertainty. An unaccredited calibration report does not, which is why BIS auditors reject it.
Recommended Intervals by Instrument
A cement plant is a hard environment for instrumentation: high temperature, continuous dust loading and constant vibration. Intervals that would be comfortable in a laboratory are too long on a kiln line.
| Instrument | Interval | Why this interval |
|---|---|---|
| Kiln thermocouples (Type R/S/B) | 6 months | Noble-metal thermocouples drift measurably above 1200°C; contamination accelerates it |
| Preheater and cooler sensors (Type K) | 12 months | Lower operating temperature, slower drift |
| Clinker and shell pyrometers | 12 months | Optics foul with dust, shifting emissivity response |
| Weigh feeders and belt scales | 6 months | Material build-up and belt tension change the calibration |
| Cube compression testing machine | 12 months | Required under IS 516 for valid strength results |
| Blaine apparatus and particle size analyser | 12 months | Directly determines reported fineness |
| Silo level instruments | 12 months | Dust coating affects radar and capacitance sensors |
Where an instrument sits on a BIS-reported parameter — strength, fineness, setting time — treat the interval as a commitment, not a guideline. Those are the records a certification audit samples first.
The Kiln Thermocouple Problem
Kiln temperature is the measurement most likely to be wrong and least likely to be questioned. A Type S thermocouple sitting at 1450°C is operating near the top of its useful range, where two separate mechanisms degrade it.
Contamination of the noble metal
Silica and alkali vapour from the raw meal migrate into the platinum-rhodium wire over time, changing its thermoelectric output. The sensor continues to read, but reads low.
Grain growth and mechanical fatigue
Prolonged high-temperature exposure coarsens the wire grain structure, making the thermocouple brittle and shifting its characteristic further.
Cold junction and extension lead error
Compensating cable degrades in hot cable trays and at terminal boxes, adding error that has nothing to do with the sensor itself.
Calibration against a traceable reference
The sensor is compared against a NABL-traceable reference at points spanning its working range, so the deviation at operating temperature is known rather than assumed.
A kiln running 20°C hotter than indicated burns more fuel than it needs and shortens refractory life; one running 20°C cooler produces under-burnt clinker and free lime that shows up in strength results weeks later. Either way the cost dwarfs the calibration.
Calibration for Gujarat Cement Plants
Gujarat's cement capacity is concentrated around Kutch, Junagadh, Amreli and Porbandar, with grinding units closer to the industrial belt. Most of this work is done onsite, because kiln instrumentation cannot be removed and sent away.
- Onsite thermocouple and pyrometer calibration during planned kiln shutdowns
- Weigh feeder and belt scale calibration with certified test weights at the plant
- QC laboratory instrument calibration — compression machine, Blaine apparatus, Vicat, balances
- Certificates issued under NABL CC-2480, accepted in BIS and ISO 9001 audits
Shutdown windows are short and fixed, so scheduling matters more than anything else on these jobs. Send us your instrument list and shutdown dates and we will build the visit around them rather than the other way round.
Frequently Asked Questions
Can Prism calibrate kiln shell pyrometers (scanning type)?
Yes. Prism calibrates infrared scanning pyrometers used for kiln shell temperature monitoring using a NABL-calibrated blackbody source at relevant temperatures.
Does Prism calibrate cube crushing machines for cement testing?
Yes. Prism calibrates cube compression testing machines per IS 516 and EN 196-1 for compressive strength testing of cement mortar cubes (50 mm × 50 mm).
How often should cement plant instruments be calibrated?
Annual calibration for most instruments. Kiln thermocouples (subject to high-temperature drift) should be calibrated every 6 months. Weigh feeders should be calibrated every 6 months in continuous operation.
Can Prism calibrate belt weighers / conveyor belt scales?
Yes. Prism calibrates belt conveyor scales (weigh feeders, integrating belt weighers) using calibrated test chains or material test run method per OIML R 50 and IS 6117.
Does Prism provide on-site calibration for cement plants?
Yes. Prism has experience with on-site calibration at cement plants, including kiln instrument calibration during planned shutdowns and weigh system calibration at quarry crushing stations.
Written by
Er. Parthiv Kinariwala
Managing Director · Prism Calibration Centre · NABL CC-2480 · Ahmedabad
Er. Parthiv Kinariwala founded Prism Calibration Centre in 2004 and has over 20 years of hands-on experience in calibration engineering, NABL accreditation, and industrial compliance. His team performs 10,000+ calibrations annually from the Vatva GIDC laboratory, serving 5000+ industries across Gujarat.
Prism Calibration Centre — Vatva GIDC, Ahmedabad
Prism Calibration Centre
F-101, Rudraksh Complex 2, Phase 3, GIDC Vatva, Near Jasoda Nagar Cross Road, Ahmedabad — 382445, Gujarat, India
Phone: +91 98245 26444
Email: info@prismcalibration.com
NABL: CC-2480 · ISO/IEC 17025:2017
Hours: Mon–Sat, 9:00 AM – 7:00 PM