SITE INFORMATION AND CORRESPONDENCE

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P\ J In addition to the 1ANSI B40.1-1985 standard,the following additional instructions and warnings should be read and understood before using this product. A very important aspect of selecting and installing pressure gauges is S. Fatigue the consideration of the hazards that will result in the event the gauge As with any spring.the bourdon will fail after extended use and re- fails. i lease the pressurized medium.The larger the number of applied pres- fhe primary causes of failure are misapplication and/or abuse of the sure cycles and the greater the extent of the pressure cycle,the earlier gauge.Those people who are responsible for the selection and installa- failure will occur.The fatigue failure may be explosive.Since such a tion of pressure gauges must recognize conditions which will ad- failure will be hazardous to personnel or property,precautions must versely affect the ability of the gauge to perform its function or which be taken to contain or direct the release of the pressurized medium in a will lead to early failure.These conditions may then be discussed with safe manner- the manufacturer to'obtain his recommendations. 6- Frequency d Accuracy Evaluation Failure may constitute: Where the pressure measurement is critical and gauge failure or gross I. Loss of accuracy. inaccuracy will result in hazard to personnel or property, the gauge 2. Clogging of the pressure port,or damage to the internal mecha- should be checked for accuracy and proper operation on a periodic nism so that there is either: basis. a. no indication when pressure is applied or7, Use with Oxygen . . . i b. there is an indication of pressure even though none is applied- Gauges used for measurement of oxygen pressure must be free of e pressure 3. A leak in the pressure containing parts or joints, contamination within thcontaining E 4. A crack or fatigue failure of the bourdon- P ng portion.Various levels 5. Bursting of the bourdon due to severe overpressure, of cleanliness are specified in ANSI B40-1-The gauge itself and the equipment to which the gauge is attached(pressure regulators.cylin- ! ` 6. An explosion within the system due to a chemical,reaction of the dens, etc.) must be kept clean so as not to contaminate the gauge. f pressure medium with contaminants causing the bourdon to Filters on the equipment must be examined periodically and cleaned explode, or replaced-The sudden in-rush of a high pressureas will momentar- When specifying, using or installing a pressure gauge, the following g factors must be given attention: ily create a very high temperature which in the presence of oxygen may ignite the contaminant causing a violent explosion. Therefore, 1. Operating Pressure when the valve on the oxygen supply tank is opened,to admit oxygen to Do not continuously operate the gauge at more than 7572 of the span. the regulator,the valve should be opened very slowly so as to allow the 1 Bourdon tubes are necessarily highly stressed, especially in ranges pressure to build up slowly. In order to accurnplish this it is recum- over 1000 psi and cohtinuous operation at full scale will result in early mended that the tank valve be opened momentarily and then closed fatigue failure and subsequent rupture. snugly but not excessively before attaching the regulator.This will not 2. Materials only blow out accumulated dirt in the valve.but will also place the Be certain the materials of the pressure containing portions of the valve in a condition that will permit it to be opened slowly rather than gauge are compatible with the pressurized medium.Gauges are com- suddenly breaking loose as a result of being closed too tightly. When monly made of copper alloys(brass,bronze.etc.)and may be subject bleeding the oxygen tank prior to attaching the regulator.be certain to stress corrosion or chemical attack- Bourdons have relatively thin the valve opening is directed away from any open flame and the walls, and the accuracy of the indication is directly affected by any operator. When opening the oxygen tank valve,the operator must not reduction in the wall thickness.Use of the same material for the bour- stand in front of or behind the gauge and must wear eye and face don as used for the tank or associated piping is not necessarily good protection.In this position if there is an explosion due to contaminated practice.A material having a corrosion rate of.001%year may be suit- equipment any particles projected from the gauge will not be propelled able for the piping,but will be entirely unsuitable for a bourdor having directly at the operator. a wall thickness of,for example..046 inches-It is imperative perativc that the S. Use with Hydrogen proper bourdon material be selected for the service on which the Steel bourdons including 400 series stainless steel are subject to hy- gauge is used.Gauges specially constructed for corrosion service are drogen embrittlement when stressed. Measurement of gas or liquids available- containing hydrogen(such as natural gas,sour oil)require the use of 3. Cyclic Pressure&rid Vibration special materials for the bourdon. Continuous.rapid pointer motion will result in excessive wear of the 9. Venting of Case internal mechanism and cause gross errors in the pressure indicated Vents provided in the pressure gauge case(clearance around pressure and possibly early fatigue failure of the Bourdon.If the pointer motion connection.rubber grommets,pressure relief back.etc.)must not be is due to-mechanical vibration.the gauge must be remotely mounted closed or restricted from operating,There is always the possibility that on a non-vibrating surface and connected to the apparatus by flexible the pressure medium will be admitted to the case interior as a result of tubing. If the pointer motion is due to pressure pulsations-a suitable a leaking joint or bourdon tube failure. If this occurs. the pressure } damper must be used between the pressure source and the gauge. medium must be vented from the case so as not to build up sufficient 4. Accuracy at Low Pressure End of Span pressure to rupture the case or window. However, venting will not Pressure gauges should not be used to measure pressures less than prevent rase rupture in the event of a violent explosion. 10%r of the span.The accuracy of a pressure gauge is normally stated 10. Ligttid Filled Gauges as,"percent of span'- The accuracy of commercial Grade B gauges Performance of pressure gauges used in severe vibration or pulsating (see ANSI B40.1 for'various grades of accuracy)is±3%of span over pressure service, can be improved by filling the gauge case with a the first quarter of the scale.If,for example,a 4100 psi Grade B gauge viscous fluid- Gauges constructed in this manner necessarily require is used to measure 6 psi•the accuracy of measurement will be :3 psi sealed cases to prevent the escape of the liquid. However, some or =3017r of the applied pressure. In addition, the scale of pressure means of venting the case must be provided. In some instances. this gauges is often laid out with a "start"(take-up) which can result in vent is sealed to prevent loss of fluid during shipment, and must be further inaccuracies when measuring pressures which are a small per- released after the gauge is installed. Be certain to follow the installa- centage of the gauge span.For the same reasons,gauges should not be tion instructions for properly venting the gauge after installation,The used for the purpose of indicating that the pressure in a lank,auto- liquid filling most commonly used is a mixture of glycerin and water. clave, etc- has been!completely exhausted to atmospheric pressure. Depending on the accuracy and the span of the gauge and the possibil- Glycerin can combine with strong oxidizing agents including(but not ity that a "start" (take-up) is incorporated at the beginning of the limited to)chlorine,nitric acid and hydrogen peroxide,and result in an scale. hazardous pressure may remain in the tank even though the explosion which can cause property damage and personal injury. If gauge is indicating zero pressure. A vent valve must be used to com- gauges are to be used In such service,do not use glycerin filled gauges; pietely reduce the pressure before unlocking covers,removing fittings, consult the factory for proper filling medium. etc. Wmml --Mtisuse of this product may cause explosion and personal injury.Do not use without first reading and understanding these instructions and the apparatus installation and opertaling instructions. Important—Read other side for additional instructions and warnings. Farm f 1421 k }