CalMaster™ Calibrated Leak
Standards
Instruction and
Maintenance Manual
2.1 Makeup of a Leak Standard 1
3.1 Using Information on Label 3
3.3 Use in Vacuum and Sniffing Applications 9
3.4 Dual Reservoir Leak Standards 10
4.0 Calibration of Leak Standards 11
8.1 Calculate Absolute Pressure from Calibration Certificate 15
8.2 Calculate the Gauge Pressure for Local Atmospheric (Barometric) Pressure 15
9.1 Convert Pressure to Absolute Pressure 16
LACO Technologies, Inc. is committed to full customer support of every aspect of its CalMaster™ Leak Standards. Technical help and sales information is available during regular business hours (US Mountain Time) at 1-800-465-1004 or 801-486-1004. Questions can also be e-mailed to info@lacotech.com.
A leak standard is a device that, under prescribed conditions, emits a controlled flow of a specified gas. This device consists of a leak element (either a physical orifice or a gas-permeable membrane) that allows gas to pass through to the outlet of the device at a controlled rate. That rate, called the leak rate can be accurately quantified by means of calibration.
For available CalMaster™ leak standard configurations, See Appendix A: Specifications and Part Number Matrix .
The presence and types of inlet ports or fill valves depends upon the requirements and style of the leak standard. Leaks standards that require periodic re-pressurizing are typically supplied with a pressure gauge as part of the leak standard, while leak standards that have an external gas pressure source will not (with some exceptions) have a pressure gauge supplied. Still, other leak standards have factory-sealed fill valves and are designed to be re-pressurized only by the factory.
A pressure gauge may be supplied with the leak standard and is typically supplied with leak standards designed to be re-filled by the customer. For refill instructions, See Refilling.
An isolation valve at the outlet port may be supplied for convenience in operating the leak standard. For use instructions, See Safety.
Leak standards are available in many types and configurations. Proper use and care of a leak standard is dependent upon its type and style. For more information, See Safety .
The following safety precautions should always be followed. LACO Technologies, Inc., is not responsible for damage to persons or equipment that results from improper or inappropriate use of a leak standard.
When venting a refillable reservoir, point valve away from face, body, and other people. For refill instructions, See Refilling .
Special precaution should be taken regarding certain LACO Technologies custom fill valves having metal/solder tamper-resistant seals (see picture). Under no circumstances should this seal be broken, loosened, melted, or removed. Doing so may result in serious injury to persons or damage to property. Should this seal be compromised by accidental or other means, contact LACO Technologies immediately for further safety precautions.
All leak standards include a calibration label bearing important calibration information; where size permits, important physical data regarding the leak standard is also included. In all cases, such information is also found on the calibration certificate.
A number that denotes the specifications of the leak standard, including (but not limited to) leak element type, calibration gas, nominal leak rate, number of calibration points, isolation valve type, reservoir type, and connection type. See Appendix A: Specifications and Part Number Matrix for details on components of a model number.
A constant that allows for a leak rate correction when the leak standard is used at a temperature other than the calibration temperature. The correction is made using the following equation.
Gas pressure needed to achieve the leak rate on the label. For open-style or refillable leak standards, this pressure must be supplied during use. Do not exceed this pressure, as doing so may damage the leak standard and/or cause personal injury. Pressure in leak standards supplied with a pressure gauge should be monitored and refilled using the supplied gauge as the pressure reference (not a different gauge), as calibration of the leak standard was performed using the supplied gauge. Open-style leak standards not supplied with a pressure gauge should be pressurized using a reference pressure gauge that has been calibrated traceable to national and international standards (e.g. NIST). In many cases, the calibration pressure is denoted in relative terms (e.g. PSIG), meaning atmospheric pressure variations (due to elevation) affect this value. A correction factor to the pressure may need to be applied in these cases. The calibration certificate will note when a correction factor may be needed, and document LF-110, "Addendum to Calibration Certificate--Leaks with Pressure Gauges" is included with the certificate as a reference for making this correction. See Appendix F: Accreditation Certificate for details.
This applies to leak standards with reservoirs. Such leak standards have an included gas supply that depletes over time. The leak rate of all leak standards is dependent largely upon the pressure of the gas supply; as that supply diminishes, so does the leak rate. The depletion rate on the label, expressed in terms of percent of leak rate per unit time, allows the user to account for this depletion and estimate a corrected value (as well as determine an adequate recalibration interval; see below). The correction is performed using the following equation.
Depletion rate is an important factor in determining recalibration intervals for leak standards. In general, the higher the depletion rate, the lower the recalibration interval should be.
Many leak standards are equipped with an isolation valve; while storing such a leak standard with the isolation valve closed may reduce the depletion rate in some cases, this technique should not be considered an alternative to recalibration, or justification to disregard depletion rate. Where depletion rate is a significant issue, a special valve, called a "zero-volume" valve, can be supplied with new leak standards. When kept closed during non-use, a zero-volume valve effectively reduces the depletion rate to zero.
The measured value of the leak rate of the leak standard, as determined by calibration. Leak rate values are also expressed in terms of the outlet pressure conditions, which are typically vacuum or atmosphere.
Appendix B describes corrections that may be required for leaks flowing to atmospheric pressure. The table below includes conversions between different leak rate units.
To convert from volumetric flow units to mass flow units use the following equation.
Expressed as a percent of the leak rate. All measurements, including leak rate measurements, have a degree of uncertainty associated with them. This number defines the window, centered at the calibrated leak rate value, in which the true leak rate likely falls. For example, if a leak standard has a calibrated leak rate of 2.00 x 10-7 cc/sec and its uncertainty is ±10%, the true leak rate is likely between 1.80 x 10-7 and 2.20 x 10-7 cc/sec.
Calibrations performed at LACO with associated uncertainty calculations are in compliance with ANSI/NCSL Z540-1-1994, Mil-Std 45662A, and ANSI/ISO/IEC 17025 (1999). For more information, see section See Calibration of Leak Standards.
Leak standards with a built-in pressure gauge may require being re-pressurized periodically (due to gas depletion; see above). Re-pressurization is recommended when the gas pressure shown on the gauge is more than 2% change from the calibration pressure (as indicated on the calibration label and certificate). Leak standards that do not have a pressure gauge should not be refilled; rather, it should be returned to the factory for recalibration.
If re-pressurization is necessary, the following steps should be carefully followed to avoid damaging the leak standard, altering the calibration, or causing personal injury. Only clean, dry gas of 99.99% purity or better should be used. Ensure that all valves, hoses, and piping are clean and particle free before using them to refill leak standards.
Leak standards that leak into vacuum should be connected to the vacuum system with an appropriate connection. For example, flange connections should use a clean, properly sized and centered o-ring, with a proper clamp, and tapered thread connections should be sealed with Teflon tape or other thread-sealing substance.
Avoid connecting leak standards to vacuum systems where an oil-sealed rotary vane pump will be continually pumping on, or exposed to, the leak standard. Over time oil may backstream from the pump to the leak standard and contaminate it with oil. A leak standard that has oil at its outlet port is likely contaminated and should be returned to the factory for recalibration and/or repair.
Leak standards that leak into air (atmosphere) can be subject to many errors when used to calibrate a sniffer leak detector. An appropriate sized probe should be used to minimize errors. Readings can be affected depending on sniffer probe location, or if a sniffer probe is used with a leak standard with vacuum connections.
Some halogen leak standards use a dual-reservoir to contain refrigerant in both gas and liquid form. These leak standards require special instructions and care.
Pressure may be adjusted to obtain any leak rate that is within the range specified on the calibration curve supplied with the calibration certificate (and/or attached to the leak standard). Pressure, as indicated on the gauge, must match the pressure value corresponding to the desired leak rate from the calibration curve.
To increase pressure: insure that the leak standard is upright and sitting flat; slowly open the "Increase" valve while monitoring the pressure gauge; when the desired pressure is reached, close the valve. Do not exceed the maximum pressure of the gauge, as this may damage the gauge.
To decrease pressure: slowly open the "decrease" valve; when the desired pressure is reached, close the valve.
Store leak standards at moderate temperatures; do not expose leak standards to temperatures less than -20°C or greater than 150°C, or store them for long periods of time at extreme temperatures.
Store leak standards in a clean, dry area; protect from dust, moisture, oil, and other potential contaminants. Place cap or other clean covering over leak port during storage. Protective carrying/storage cases are available from factory.
Leak standards with a permeation leak element should be stored with the isolation valve (if equipped with one) open.
Do not attempt to clean a potentially contaminated leak element; if operability is in question, return the item to vendor for repair evaluation.
Ensure that flanges, threads, and other connecting surfaces are protected from scratches, dings, etc.
LACO's calibration laboratory is operated in compliance to the most recent ISO standards for calibration laboratories. We are independently accredited by A2LA to ISO17025 and ANSI/NCSL Z540-1994. Refer to See Appendix F: Accreditation Certificate and See Appendix G: Scope of Accreditation.
LACO uses several methods to measure and calibrate the leak standard. The calibration method selected for any given leak depends on the calibration gas, range of the leak standard, the outlet conditions of the leak standard (vacuum or atmospheric pressure), and the desired uncertainty.
LACO uses two types of calibration methods: primary, and secondary or transfer standard methods. The primary calibration methods incorporate measurements of basic physical properties such as time, volume, and pressure. These methods measure the leak rate of the leak standard under test by measuring the pressure or volume change induced by gas flowing into a known system. The secondary calibration methods use a calibration transfer standard that has been calibrated on a primary system or at a primary standards laboratory. The leak rate of the leak standard under test is measured and compared to that of the known reference standard. The actual calibration method used on a particular leak standard is referenced by calling out the calibration procedure on the certificate of calibration.
Leak standards equipped with a pressurized gas reservoir may be subject to special shipping requirements. Consult local and federal requirements to insure that you are in compliance when shipping and transporting leak standards.
When returning a leak standard to LACO for repair or calibration contact our sales department at 1-800-465-1004 or 801-486-1004 or info@lacotech.com to obtain shipping information and a Return Materials Authorization (RMA) number. Always package the leak standard in a sealed package to protect it from dust and moisture.
CalMaster™ calibrated leak standards are warranted to be free from defects over the lifetime of the standard. Pressure gauges are warranted for one year. The warranty does not cover damage to leak standards due to mishandling or improper use. The warranty is only valid while the leak standard is calibrated at LACO Technologies, Inc. on the recommended calibration interval, typically yearly. If a warranty request is made, LACO Technologies, at its own discretion, will repair or replace the leak standard, including labor and materials. Leaks that are found to be nonfunctional at time of calibration shall be repaired free of charge. The customer, however, is responsible for the calibration cost. The customer is responsible for any and all shipping charges.
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Target value: <3%/year; actual depletion rate is dependant on pressure, reservoir size and leak rate. |
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Refer to section See Uncertainty |
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*Non-hazardous, non-radioactive
This appendix applies to calibrated leaks supplied with reservoir pressure gauges and for calibrated leaks without reservoirs where the customer supplies a pressure gauge.
The leak rate of gas leak standards is related to the absolute gas pressure applied to the leak element. A typical bourdon tube pressure gauge supplied on calibrated leaks measures gauge or relative pressure, which changes with elevation. Use the following formulas to convert the pressure reported on the calibration certificate to the correct pressure at your elevation (barometric pressure).
P(atmospheric) = local atmospheric pressure measured from a barometer or Table See Elevation vs. Atmospheric Pressure below, in atmospheres.
This appendix applies to calibrated leaks that flow to atmospheric pressure where the atmospheric pressure during the calibration of the leak may be different compared to the atmospheric pressure during the use of the leak.
The leak rate of gas leak standards is related to the absolute gas pressure applied to the leak element and the atmospheric pressure at the leak outlet. A correction must be made to leaks used at a different atmospheric pressure from the calibration atmospheric pressure. The atmospheric pressure can generally be estimated by knowing the elevation. Use the following formulas to correct the leak rate for your atmospheric conditions.
Using Equations See P1= P(atmospheric) + P(leak)/14.7 and See Q = K ( P12 - P22 ) for viscous flow leaks, or K = Q / ( P12 - P22 ) above, the leak constant K, and Table See Leak Rate Calculation below, calculate the corrected leak rate. Calculate P1 from equation 1 above using atmospheric pressure from Table See Leak Rate Calculation below. Use atmospheric pressure from Table See Elevation vs. Atmospheric Pressure for P2.
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P1 = (1.0) + 20/14.7 = 2.36 atm
Q (corrected) = 1.20 x 10-3 (2.362 - 1.02) |
From progressive designs to virtually unbreakable construction, the quality of CalMaster™ gas leak standards stands above the competition. LACO manufactures a wide variety of leak standard designs utilizing most gases. Whether you require a standard model or one that is customized to your particular application, we will provide you with the highest quality service and support. Your confidence in our leak standards is backed by our NIST traceable, accredited (A2LA / ISO 17025) calibrations and our lifetime product warranty.
From the Highest Vacuum to the Lowest FlowOur calibration laboratory operates in compliance to the most recent ISO standards for calibration laboratories. We are independently accredited by A2LA to ISO17025-1999 and ANSI/NCSL Z540-1994. Our lab follows American Vacuum Society recommended practices and all calibrations are NIST-traceable.
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Vacuum Gauges |
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Ionization--Cold Cathode--Quartz/Piezo Pirani Thermocouple-- |
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