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Portable Instrument Calibration

1. refers to an instrument s measuring accuracy relative to a known concentration of gas Gas detectors perform relative measurements rather than independently assessing the quantity of gas present they measure the concentration of the air sample and then compare it to the known concentration of the gas the instrument is configured to sample This known concentration serves as its measurement scale or reference point If the instrument s reference point has moved then its reading will also move This is called calibration drift and happens to most instruments over time When an instrument experiences calibration drift it can still measure the quantity of gas present but it cannot convert it into an accurate numerical reading Regular calibration with a certified standard gas concentration updates the instrument s reference point re enabling it to produce accurate readings What Causes Calibration Drift Over time gas detection instrument readings can fall out of their calibration specifications in several ways Normal degradation of electrochemical sensors used for toxic gas and oxygen detection This is the major cause of calibration drift Low humidity and high temperatures can cause more rapid electrolyte consumption _ Exposure to sensor poisons materials that are harmful to the sensor Harsh storage and operating conditions e g instrument is dropped submerged in liquid If a sensor has been severely damage
2. job dass The resulting number is the subtotal for that employment dass This subtotal is then multiplied by the company s Experience Modification Factor e mod The e mod is company specfic and reflects an individual employer s loss experience relative to that of other employers in a similar dass of business An e mod of 10 means that an employer s loss record is about An e mod of less than 10 means that their loss record is better than average and one greater than 10 means that their loss record is worse than average Since a company s base premiums are multiplied by its e mod not only does a higher factor increase rates a lower factor decreases them The difference between premium costs for a company with a good safety record and one with a poor safety record can therefore be quite significant For example Employer X has an e mod of 0 4 and Employer Y has an e mod of re If their l pakaa iLe FAE A their premiums are X 75x 175x 1000 1 750 over a DO difference And of course regularly practidng proper safety measures induding instrument calibration certainly benefits a company s Safety record If that isn t incentive enough it s also important to understand that since e mods are on 3 year periods a poor modification factor can have a dramatic effect on not just one year but three years of a company s premiums For instance a company s 2001e mod is When Should You Bump Test When Should
3. untrained or unqualified individuals Phone 412 967 3000 and not until the product instructions induding any wamings www MSAnet com or cautions provided have been thoroughly read and under x stood Only they contain the complete and detailed information U S Customer Rebbe Center Phone 14800 MSA 2222 conceming proper use and care of these products Fax 1800 967 0398 ID PRO8 0034 May 2001 E MSA 2001 Printed in USA Phone 800 267 0672 FAX 436 663 5908 MSA Mexico Phone 01800 71754 I1L Selecting an Instrument Calibration Safety Issues In the past few years much work has gone into simplifying the instrument calibration procedure From a safety standpoint there is still no substitute for having a ae trained technician adjust the reading of an instrument to a known concentration of gas With today s microprocessors however the alternatives can be equally effective given appropriate training Some questions to ask before buying your next gas detector 1 Doesthe detector have appropriate levels of tamper resistance to prevent users from inadvertently entering calibration mode An instrument s degree of tamper resistance should be dosely matched to the experience and training of the end users Prevention of inadvertent adjustments by untrained users may be of utmost importance to many companies so be sure to carefully consider a detector s lockout capabilities Does the autocalibration on your monitor have adequate safet
4. You Calibrate In the past there has often been confusion regarding proper calibration procedures and frequency To darify this issue the International Safety Equipment Association ISEA has issued a position statement on instrument calibration for use in confined spaces According to this document A bump test or full calibration of direct reading portable gas monitors should be made before each day s use in accordance with manufacturer s instructions using an appropriate test gas If the instrument fails the bump test it must be adjusted through a full calibration before it is used ISEA recommends more frequent testing if sensor contaminants may be present In their calibration statement the ISEA allows for less frequent calibration verification under certain conditions see below However the time interval between checks should never exceed 30 days If conditions do not permit daily testing to verify calibration less frequent verification may be appropriate if the following criteria are met 1 During a period of initial use of at least 10 days in the intended atmosphere calibration is verified daily to be sure there is nothing in the atmosphere that is poisoning the sensor s The period of initial use must be of suffident duration to ensure that the sensors are exposed to all conditions that might have an adverse effect on the sensors If the tests demonstrate that it is not necessary to make adjustments then the time i
5. ams by providing in some cases automatic storage of calibration records MSA Intemational Phone 491 967 334 Fax 401 967 3451 Offices and representatives worldwide For further information Portable Instrument Calibration Saving lives and more Rick Hartman Product Line Manager William Berner Risk Manager The Benefits of Regular Portable Instrument Calibration I Worker Safety Il Financial Incentives A Reduced Worker Compensation Premiums B Reduction of Lost Employee Time and Lost Job Bids Calibration The Key to Accurate Readings Gas detection instruments are used to detect low levels of toxic and combustible gases and oxygen deficiency or enrichment an explosion hazard Since users cannot rely on their sense of smell to alert them to odorless hazards gas detectors are necessary whenever a worker enters an area with the potential for atmospheric hazards Most instruments are equipped with both a waming and an alarm condition The warming condition alerts the user that the environment has a low concentration of gas and is therefore potentially hazardous the alarm condition indicates that the gas concentration exceeds the programmed hazard threshold and the area is approaching a hazardous level Whether an instrument wams and or alarms at the proper time depends not only on its detection abilities but also on its ability to translate its findings into an accurate reading Calibration
6. ar instrument calibration is to prevent inaccurate gas concentration readings that could lead to the injury or even death of workers and other personnel Correct calibration of an instrument helps ensure that the instrument will accurately respond to the gases that it is designed to detect waming users of hazardous conditions before they reach dangerous levels In addition to detecting and correcting for calibration drift regular calibration assures the user that the instrument is functional Gas detection instruments are often subjected to harsh operating and storage conditions where they can be damaged Through visual inspection a unit may appear to be fine but could actually be damaged intemally Any of these factors could affect instrument performance leading to inaccurate readings or even instrument failure Regular calibration is the only way to be certain that a detector is fully functional Regular calibration procedures and enforcement also set the tone for a safety consdous work environment Workers are reminded daily that their company makes safety a priority making workers more likely to keep safety prindples in mind throughout the workday The Financial Incentive for Calibration In addition to injuring people workplace accidents can damage equipment machinery building structures and other company assets Effective safety procedures induding regular instrument calibration can help reduce the number and severity of such
7. calculated based on their loss record for 1998 999 and 2000 Experience Modification Factors can increase or reduce premiums by an average of 1D to 25 percent making them worthy of a company s attention Indirect Cost Savings Lost Employee Time and Lost Job Bids In addition to saving on premiums a company can also cut costs by reducing the lost work time of its employees Taking active measures to minimize workplace accidents and injuries is one of the most effective ways to achieve this If an experienced employee cannot work because of an acddent or inddent the company suffers from a loss of efficiency becoming less productive When the position is essential to the company s operations and cannot remain open until the employee retums to work then the employer must pay to replace that employee and or train another employee to fill in Since replacement and training costs can be very high this is another area in which a company can save money by reducing its number of acddents and injuries through proper regular instrument calibration In addition to lost employee time indirect effects of workplace accidents and injuries can potentially extend to indude a loss of the company s market share and sar customer confidence due to reduced reduced quality and increased costs which can lead to smaller profit margins or increased product pricing In addition to a possible three year negative effect on the bottom line a poor e mo
8. d can also haunt manufacturers and service providers in situations where there is dose competition for business In these cases a review of the bidder s qualifications may be requested which often indudes their safety history The OSHA Process Safety standard is one of the forces behind such reviews It requires chemical and emical manufacturers to be responsible not only for their own safety record but also for the safety records of the various contractors and suppliers employed to work on their premises A contractor s or supplier s e mod is therefore routinely asked for by many employers who are subject to this standard In competitive situations where bids are relatively equal but Contractor A has a favorable e mod of 0 8 while Contractor B has a negative e mod of 18 the better e mod may well be the deciding element Regular Instrument Calibration A Procedure You Can Live With As you Can see there are many reasons for a company to implement and enforce regular proper instrument calibration procedures By doing so they help guard the Safety of their workers and property while also achieving significant finandal savings All of this from an act that can take just minutes a day Note This Bulletin contains only a general description of the corporate Headquarters Box 426 lucts shown While uses and performance capabilities are PO described under no circumstances shall the products be used Pittsburgh PA 15230 USA by
9. d it may need to be replaced In this case when calibration is attempted the instrument will either display a failure or it will not allow the user to fully adjust the display reading Bump Tests vs Full Calibration There are two methods of verifying instrument calibration a functional or bump test and a full calibration Each is appropriate under certain conditions A bump test is a means of verifying calibration by exposing the instrument to a known concentration of test gas The instrument reading is then compared to the actual quantity of gas present as indicated on the cylinder If the instrument s response is within an acceptable range of the actual concentration then its calibration is verified When performing a bump test the test gas concentration should be high enough to trigger the instrument alarm If the bump test results are not within the acceptable range then a full calibration must be performed A full calibration is the adjustment of the instrument s reading to coindde with a known concentration generally a certified standard of test gas In most cases a full calibration is only necessary when an instrument does not pass the bump test or after it has been serviced For recommended calibration frequency and procedures see box When Should You Bump Test When Should You Calibrate The Importance of Proper Regular Calibration The Number One Reason Worker Safety The primary reason for proper regul
10. events But in addition to pening worker and plant safety companies can also it by recognizing several strong finandal incentives for performing regular calibration These incentives can be divided into two categories Direct cost savings and Indirect cost savings Direct Cost Savings Reduced Worker Compensation Premiums Instrument inaccuracy due to improper calibration or a lack of regular calibration can lead to serious accidents Exposure to excessive levels of toxic gas can cause workers serious illness and even death Combustible gas explosions are often catastrophic injuring or killing personnel and destroying property In the United States an employer s worker compensation costs are generally loss experience rated so the higher the number and greater the severity of accidents the higher a company s worker compensation premiums will be The worker compensation premium calculation is fairly straightforward There are designated classes of employment i e manufacturing driver derical sales and each is assigned a specific base rate These rates vary for the different job dasses according to the calculated risk level for each job dasses in which workers are more likely to be involved in acddents are higher risks and therefore have higher rates and vice versa This set rate for each dass of employment combined with a few other items is then multiplied by each 100 of payroll for all of the company s employees in that
11. nterval between checks may be lengthened but should not exceed 30 days When calibrating an instrument always consult the instrument user s manual for the manufacturer s recommended calibration procedure For verification of accuracy Calibration gas should always be certified and traceable to the National Institute for Standards and Traceability NIST
12. y limits The greatest change in calibration in the last 5 years has been the advent of autocalibration which typically allows the user to press a sequence of buttons to enter calibration The instrument software then automatically adjusts the span readings to preset concentrations When performing an autocalibration the instrument range below the factory setting These limits are known as the autocalibration safety limits The autocalibration Safety limits are designed to allow calibration of the instrument when an expected amount of sensor drift has occurred and to prevent calibration should a calibration error or other problem requiring additional instrument servicing exist Therefore it is important to ask the manufacturer what limits they have on the autocalibration adjustments 3 Can autocalibration be disabled For some users the ability to prevent unauthorized adjustments to the meter s calibration may be very important Be sure to verify this capability if such protection is part of your safety program 4 Does it have an automated calibration system available Automated computer based calibration systems are becoming more common From a safety standpoint the main advantage of these systems is their repeatability They can be less prone to individual user error and can help assure proper calibration of medium to large fleets of instruments These systems can also be of great assistance in formal confined space progr

Portable Instrument Calibration

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