MSC Performs Large-Scale Field Calibration During Lab Start-Up Phase

During the startup phase of a major laboratory project, several significant challenges emerged. One critical issue involved the building's HVAC instrumentation, which had been specified for factory calibration. However, sufficient time had elapsed that the instruments' factory calibrations would expire during the commissioning phase. The project's commissioning process needed to proceed on schedule with fully calibrated instruments throughout the entire phase, requiring immediate field calibration of all critical and semi-critical instruments. Mechanical Service Corporation (MSC) was brought in to provide this essential support.

Instrumentation Scope and Calibration Challenges

All laboratories utilized Vaisala combination temperature and humidity sensors for monitoring local environmental conditions. Pressurization instruments for labs, airlocks, and corridors consisted of Setra pressure transmitters, while HEPA filter differential pressure transmitters (DPTs) used Photohelic gauges. Additionally, the HVAC air handling units (AHUs) required calibration of their temperature, humidity, and pressure sensors.

With substantial calibration work required in a compressed timeframe to support successful commissioning, the team strategically decided to perform instrument calibration systematically by system and area. This approach enabled commissioning to begin on specific AHUs and their served laboratories almost immediately.

Resolving the Static Pressure Reference Point Issue

An important discovery emerged during building startup and balancing: the static neutral reference point located in the penthouse mechanical area was not functioning as a true zero reference for the building's DPTs and exhibited verified fluctuations. Through systematic testing during startup, the team determined that elevators running to the penthouse were pushing shaft air into the penthouse area, causing the neutral static reference point to fluctuate.

The solution involved relocating the zero reference point to a carefully selected outside location using a high-quality ambient static pressure sensor, effectively resolving the reference point issue.

Field Calibration Execution and System Improvements

Factory calibration wasn't a viable option given the timeline constraints. MSC deployed additional calibration equipment, enabling senior technicians to perform simultaneous calibrations across multiple areas. Following a detailed plan and schedule, teams worked ten-hour days alongside the test and balance contractor and commissioning agent to expedite progress. Of the hundreds of instruments calibrated, approximately a dozen required replacement.