PRESSURE GAUGE INSTALLATION, OPERATION AND MAINTENANCE I&M008-10098-5/02 (250-1353H) 1M AMR 5P1/08
CONTENTS 1.0 2.0 Page Selection and Application 1.1 Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.2 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 1.3 Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 1.4 Oxidizing media . . . . . . . . . . . . . . . . . . . . .
CONTENTS Page 7.0 Diaphragm Seals 7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.4 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
contain heavy particulates (slurries) or (c) are very viscous including those that harden at room temperature. 1.0 SELECTION & APPLICATION Users should become familiar with ASME B40.1 (Gauges – Pressure Indicating Dial Type – Elastic Element) before specifying pressure measuring instruments. That document – containing valuable information regarding gauge construction, accuracy, safety, selection and testing – may be ordered from: 1.
2.3 Steam service – In order to prevent live steam from entering the Bourdon tube, a siphon filled with water should be installed between the gauge and the process line. Siphons can be supplied with ratings up to 4,000 psi. If freezing of the condensate in the loop of the siphon is a possibility, a diaphragm seal should be used to isolate the gauge from the process steam. Siphons should also be used whenever condensing, hot vapors (not just steam) are present.
mounting. Gauges should be kept free of piping strains. The gauge case mounting feet, if applicable, will ensure clearance between the pressure relieving back and the mounting surface. also be drained from the case and the front ring loosened before autoclaving. 3.0 INSTALLATION 3.6 Flush mounting – Also known as panel mounting. The applicable panel mounting cutout dimensions can be found at www.ashcroft.com 3.
4.5 Other considerations – These include (a) bent or unattached pointers due to extreme pressure pulsation; (b) broken windows which should be replaced to keep dirt out of the internals; (c) leakage of gauge fill; (d) case damage – dents and/or cracks; (e) any signs of service media leakage through the gauge including its connection; (f) discoloration of gauge fill that impedes readability. f. Gauges showing significant friction error and/or wear of the movement and linkage. g.
Calibration chart – After recording all of the readings it is necessary to calculate the errors associated with each test point using the following formula: ERROR in percent = 100 times (TRUE VALUE minus READING) ÷ RANGE. Plotting the individual errors (Figure 1 on page 10) makes it possible to visualize the total gauge characteristic. The plot should contain all four curves: upscale – before rap; upscale – after rap; downscale – before rap; downscale – after rap.
TYPICAL CALIBRATION CHART INDICATED VALUE (PSI) True Value – PSI Increasing – Without RAP Increasing – With RAP Decreasing – Without RAP Decreasing – With RAP 0 40 80 120 160 200 –.4 +.8 +.4 –.4 –.8 +.4 0 +1.0 +.5 –1.0 –.5 +.8 –.4 +1.4 +1.2 +.8 +.6 +.4 0 +1.1 +1.0 +.6 +.4 +.4 ERROR (% OF FULL SCALE) True Value – % of Range Increasing – Without RAP Increasing – With RAP Decreasing – Without RAP Decreasing – With RAP 0 20 40 60 80 100 –.20 +.40 +.20 –.20 –.40 +.20 0 +.50 +.25 –.05 –.25 +.
6.1 Calibration – Rotary Movement Gauges – Inspect gauge for accuracy. Many times gauges are simply “off zero” and a simple pointer adjustment using the micrometer pointer is adequate. If inspection shows the gauge warrants recalibration to correct span and/or linearity errors, proceed as follows: movement should be rotated counter clockwise. Rotating the movement one degree will change this error by approximately 0.25%.
ASHCROFT SYSTEM ASSEMBLY Fig. 2 BOURDON TUBE SEGMENT TIP HAIRSPRING PINION LINK ROTARY MOVEMENT BACKPLATE SOCKET TYPE 1082 EXTERNAL ZERO ADJUST FEATURE* Fig. 3 B A INSTRUCTIONS FOR USE: LOOSEN RING LOCKING SCREW “A’’ OBTAIN REQUIRED ADJUSTMENT BY ROTATING KNOB “B’’ CLOCKWISE OR COUNTER-CLOCKWISE. TIGHTEN SCREW “A’’ DOWN ON KNOB “B.’’ *Applicable only for test gauge with hinged ring design.
Fig.
d. Remove pointer and reassemble dial and dial screws (finger tight). h. Repeat steps 4 through 8 until span is correct. e. Lightly press pointer onto pinion. i. Remove the pointer. f. Check accuracy at full scale. If error exceeds 1% return to step 1, otherwise proceed. j. With 25 inches of Hg vacuum applied, reassemble dial, dial screws (finger tight) and pointer. g. Check accuracy at midscale. If error exceeds 1% slide dial left or right to compensate. k.
1009 DURALIFE® PRESSURE GAUGE CALIBRATION V 25 s 15
filled prior to being placed in service. Ashcroft diaphragm seal assemblies should only be filled by a seal assembler certified by Ashcroft Inc. Refer to section 3.3 for a cautionary note about not applying torque on either the instrument or seal relative to the other. 7.0 DIAPHRAGM SEALS 7.1 General – A diaphragm seal (isolator) is a device which is attached to the inlet connection of a pressure instrument to isolate its measuring element from the process media.
8.4 Ashcroft Pulsation Dampener – Type 1106 Ashcroft pulsation dampener is a moving pin type in which the restricted orifice is the clearance between the pin and any one of five preselected hole diameters. Unlike a simple throttle screw/plug, this device has a selfcleaning action in that the pin moves up and down under the influence of pressure fluctuations. tions must pass before they reach the bourdon tube.
9.0 RESOURCES 9.1 Training Videos 9.1.1 Test gauge calibration 9.1.2 1009 Duralife® gauge calibration 9.1.3 Duragauge® gauge calibration 9.1.4 Diaphragm seal filling 9.2 Pressure Instrument Testing Equipment 9.2.1 Type 1305D Deadweight Tester 9.2.2 Type 1327D Pressure Gauge Comparator 9.2.3 Type 1327CM “Precision” Gauge Comparator 9.3 Tools & Tool Kits 9.3.1 Type 2505 universal carrying case for 1082 test gauge 9.3.2 Type 266A132-01 span wrench for 1082 test gauge 9.3.
Ashcroft Inc., 250 East Main Street Stratford, CT 06614-5145 U.S.A. Tel: 203-378-8281 Fax: 203-385-0408 (Domestic) Fax: 203-385-0357 (International) email: info@ashcroft.com www.ashcroft.com Visit our web site www.ashcroft.com All sales subject to standard terms and conditions of sale.
