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New Calibration System Improves Gas Indicators For NSTAR.

NSTAR Gas came out of the dark ages with a new calibration system that utilizes state-of-the-art technology to further ensure accuracy and reliability in its combustionable gas indicators.

In the 1980s, NSTAR Gas (formerly Commonwealth Gas), used manual pump gas detectors calibrated by stand-alone gas containers. The company has six separate districts in Massachusetts. At that time, each district utilized gas detectors from different manufacturers, developed their own way of manually calibrating them, and kept their own schedules and records of the calibration data. CO detection was done using a manual pump device with disposable cartridges.

A decision was made in early, 1990 to purchase Gas Sentry detectors from Bascom-Turner Instruments and replace all detectors in the field. The Gas Sentry model is used for gas, air monitoring and CO leak detection and also for barhole gas measurements to locate underground leaks. The detectors were purchased to improve reliability, and safety for customers, the public and technicians. The detectors were well-received for two reasons. First; the ability to test for gas, air and CO leaks with one instrument was convenient and cost-effective. Second, the units have internal pumping mechanisms which eliminate the need for the constant manual pumping required by the old detectors.

At NSTAR Gas, performing and documenting the calibration and routine maintenance of over 160 gas detectors was time-consuming and nearly impossible to do properly. The standard procedure of sending all defective detectors back to Bascom-Turner for repair and calibration caused some concerns. Each detector sent to Bascom-Turner would be tied up for a minimum of one week and since the calibration records were kept at Bascom-Turner, it was difficult to keep track of each respective detector's maintenance and repair record.

In order to improve reliability and reduce the time required for these functions, NSTAR Gas bought a mobile calibration station built by Bascom-Turner that was specifically designed for use by our six divisions. This mobile docking station allowed documentation to be printed out at any time and was sent to each of our divisions on a rotating schedule to ensure that all detectors were calibrated on a regular basis.

This procedure caused problems including the system being held longer than planned in one area or another and also the actual shipping of the system between the six districts was complicated. We knew that we had developed a good system but we wanted to improve the reliability and create easy access for users, and improve scheduling for detector calibration and reporting.

In 2000, NSTAR Gas purchased the D-CAL Instrument Management System produced by Bascom-Turner Instruments. Five remote docking stations were installed in divisional offices along with one main local docking station in NSTAR's Dedham, MA office. Initial setup of the system required a one-time manual entry of data pertaining to NSTAR's detectors, docking stations, and offices. Initial set-up also required connecting all the docking stations to calibration gas, containing 2.5 percent methane and 100 ppm CO, and either pure methane or system gas and fresh air.

The 2.5 percent methane is delivered from gas dispensers and the system's gas is piped in from local area gas meters. This enabled the detectors to be calibrated on our system gas and reduced false readings from the field. Final connection of the docking stations to phone lines made the entire system operational. Bascom-Turner personnel assisted in the set-up, which required less than a full day.

The main local docking station automatically polls the remote docking stations nightly to update the master database with any new calibration data. This polling is performed after midnight over the regular phone lines. The local docking station then automatically faxes or e-mails office-specific calibration due and overdue reports to detector users and supervisors. If a detector fails to calibrate, a repair report is automatically faxed to the repair department indicating which component failed in the detector.

The D-CAL system eliminates the need for calibration technicians and system operators as it automates the entire sequence from calibration to sending reports to users, supervisors, and repair departments. Each docking station is capable of accepting any Gas-Sentry or Gas-Ranger detector and automatically calibrating it in 60 seconds. In order to perform the calibration, the detector is inserted in the clock and removed after the detector beeps and displays "CAL." Data such as before-and-after calibration readings, sensor sensitivities, and detector usage are automatically stored on the docking station's hard disk for either automatic or manual report generation.

The local docking station can be used in the manual mode to generate a variety of reports for viewing, printing, and faxing. It comes with a dedicated printer that provides a hard copy of these reports. The reports are grouped into three categories: unit, station and office data. All are selectable from the local docking station's D-CAL menus. The system provides NSTAR Gas with a series of useful reports ranging from detector specific information to calibration and repair reports. The specific detector reports allow the company to track detector locations, serial numbers, calibration and sensor sensitivity history.

General calibration reports consist of detectors overdue and last calibration date of the detectors by unit and area. Other areas of reports that the system generates are service history by unit, detectors requiring immediate service and detectors due for service. These reports can be viewed or printed in order by date. The mean time between failure (MTBF) at NSTAR Gas of each type of sensor and of individual detectors is generated from this service history data. The "Detectors Due for Service" report uses this MTBF data and applies it to all of NSTAR Gas' detectors. Entering service data and using these reports results in predictive maintenance, which decreases the likelihood of a detector failing in the field.

The D-CAL system also has backup and security features that allow for complete data backup to a floppy disk or zip drive, depending upon the size of the data files. System security is protected by the use of a specific password that must be entered to access all setups, editing and reporting features. The docking feature is kept active at all times to allow calibration of the detectors 24 hours per day. This level of security enables NSTAR to have a completely reliable data system and ensures that all equipment records are accurate and standardized.

The installation of Bascom-Turner's D-CAL system at NSTAR Gas has significantly improved our safety to customers, the public and our employees. The system has given us the ability to calibrate according to planned schedules and report on detectors that are scheduled for maintenance or in need of immediate repair. Our service technicians are often in hazardous situations that require the most accurate detectors available to determine gas, CO and oxygen levels. Our system provides technicians with added security performing their work, knowing the reliability of our program and the commitment that NSTAR Gas and Bascom-Turner Instruments provides to them.
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Title Annotation:From Bascom-Turner Instruments
Comment:New Calibration System Improves Gas Indicators For NSTAR.(From Bascom-Turner Instruments)
Author:Kelley, Kevin
Publication:Pipeline & Gas Journal
Geographic Code:1USA
Date:Sep 1, 2001
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