FORM 85-02
June 1999
Revision 6
AMETEK
®
PK II Pneumatic
Deadweight Tester
Operating Instructions
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®
CALIBRATION INSTRUMENTS
T ABLE OF CONTENTS
Page
1.0 INTRODUCTION AND PRODUCT OVERVIEW ..................................................... 4
1.1 PRODUCT FEATURES ........................................................................................... 4
1.2 PK II PHYSICAL DIMENSIONS ............................................................................. 5
2.0 CORRECTION FACTORS....................................................................................... 6
2.1 Corrections for Gravity ........................................................................................... 6
2.2 Corrections for Temperature ................................................................................... 7
2.3 Corrections for Air Head ......................................................................................... 8
3.0 RECOMMENDED RECERTIFICATION PROCEDURE........................................... 8
3.1 Frequency of Certification ...................................................................................... 8
3.2 Materials Necessary for Recertification ................................................................. 8
4.0 SPECIFICATIONS ................................................................................................... 9
5.0 ASSEMBLY AND SETUP ......................................................................................... 13
5.1 Ball and Nozzle ........................................................................................................ 13
5.1.1Removing the Nozzle .............................................................................................. 13
5.1.2Removing the Ball ................................................................................................... 13
5.1.3Cleaning the Ball and Nozzle ................................................................................... 13
5.1.4Cleanliness Check .................................................................................................. 13
5.2 Leveling the Tester .................................................................................................. 13
5.2.1 Fast Leveling ........................................................................................................... 13
5.2.2Fine Leveling ........................................................................................................... 13
5.3 Connection .............................................................................................................. 14
6.0 OPERATING INSTRUCTIONS ................................................................................ 15
7.0 MAINTENANCE ....................................................................................................... 16
7.1 Output System ........................................................................................................ 16
7.2 Input System ........................................................................................................... 17
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T ABLE OF CONTENTS
Page
8.0 TROUBLESHOOTING ............................................................................................ 18
8.1 Correcting For Poor Weight Rotation ...................................................................... 18
8.2 Output and Internal Leakage ................................................................................... 18
8.2.1 Output Connection Leakage............................................................................. 18
8.2.2 Internal Leakage Within the Tester................................................................... 18
8.3 Replacing the Nozzle and O-Ring ............................................................................ 18
9.0 PARTS LIST ............................................................................................................. 19
TABLES
Page
2a Pressure in PSIG ..................................................................................................... 9
2b Pressure in Inches of Water @ 20°C ..................................................................... 10
2c Pressue in Grams per Square Centimeter .............................................................. 10
2d Pressure in Kilopascals ........................................................................................... 11
2e Pressure in Centimeters of Water @ 20°C ............................................................ 11
2f Pressure in Bar ........................................................................................................ 12
2g Pressure in Millimeters of Mercury ......................................................................... 12
PRODUCT WARRANTY
This instrument is warranted against defects in workmanship, material and design for one (1) year from
date of delivery to the extent that AMETEK will, at its sole option, repair or replace the instrument or any
part thereof which is defective, provided, however, that this warranty shall not apply to instruments
subjected to tampering or abuse, or exposed to highly corrosive conditions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES WHETHER EXPRESS OR IMPLIED AND
AMETEK HEREBY DISCLAIMS ALL OTHER WARRANTIES, INCLUDING, WITHOUT LIMIT ATION, ANY
WARRANTY OF FITNESS FOR A P ARTICULAR PURPOSE OR MERCHANTABILITY. AMETEK SHALL
NOT BE LIABLE FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES INCLUDING, BUT NOT
LIMITED TO, ANY ANTICIPATED OR LOST PROFITS.
This warranty is voidable if the purchaser fails to follow any and all instructions, warnings, and cautions
in the instrument’s Instruction Manual.
If a manufacturing defect is found, AMETEK will replace or repair the instrument or replace any defective
part thereof without charge; however, AMETEK’s obligation hereunder does not include the cost of
transportation which must be borne by the customer. AMETEK assumes no responsibility for damage in
transit, and any claims for such damage should be presented to the carrier by the purchaser.
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1.0 INTRODUCTION AND PRODUCT OVERVIEW
The AMETEK® PK II Pneumatic Deadweight Tester is a primary standard that produces a
pressure by applying force (weight set) over area (the ceramic ball and nozzle). The PK II
tester is NIST traceable and accurate to +0.015% of indicated reading using stainless steel
weights calibrated to international standard gravity at 980.665cm/sec2. The unit is intended
for low pressure applications up to 30 PSIG (2 bar). The PK II tester may also be calibrated
to the user’s local gravity or to inches or centimeters of H2O at 20°C per ISA recommended
practices, or to reference water columns at 60°F per AGA standard practices.
The PK II tester is self-regulating with accuracy independent of the operator. The tester
utilizes a frictionless ceramic ball which floats on a layer of air within a stainless steel
cylinder.
The PK II tester features a sturdy cast-metal base with integral quick-leveling system for
field or laboratory use. The case also contains a tripod fixture allowing the unit to be tripod
mounted in the field.
1.1 PRODUCT FEA TURES
The key features of the
PK II Pneumatic Deadweight Tester
are:
G Accuracy up to +0.015% of indicated reading
G Floating ball operation eliminates need to rotate weights during testing
G Self regulating input air flow maintains ball and weights in a float position and compen-
sates for variations in air supply pressure
G Rugged ceramic measuring ball withstands harsh environments and field use
G Monocontaminating fluid eliminates the need to clean instruments after calibration or
before use
G Close cover operation eliminates wind effects in field calibrations
G Multi-position ball valves for both the inlet and outlet connections ensures trouble-free
operation
G Certificate of Accuracy and Traceability available with area, mass and intrinsic correc-
tion factors
G Rugged aluminum housing offers long life. Top (Front) housing is reversible.
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1.2 PK II PHYSICAL DIMENSIONS
12.75 in
323.85 mm
8.875 in
225.4 mm
Figure 1.1
PK II Dimensions
(Models 104, 254, 304 and Medical)
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6.125 in
155.56 mm
3.0 in
76.2 mm
1.2 PK II PHYSICAL DIMENSIONS
12.75 in
323.85 mm
12.875 in
327.03 mm
Figure 1.2
PK II Dimensions
(Models 20SS, 30SS, 654, 854, 2000GM, 2010GM
200N, 201N, 500CM, 1000CM, 1500CM, 2000CM, 2B, 2B01)
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8.0 in
203.2 mm
2.0 CORRECTION F ACTORS
An error in pressure determinations may result from any uncertainty of the mass of the
loading weights and from the measurement of the effective area of the ball and nozzle.
Other sources of error, however, may not be easily recognized. Other sources of error
include the air buoyancy of the weights, gravity, thermal expansion and elastic deformation
of the ball and nozzle, and the air heads involved. All of these corrections, with the
exception of local gravity (except when specified), thermal expansion, and air heads have
been corrected for by AMETEK prior to the tester being shipped.
The following technique is suggested to compute the corrected tester output pressure
readings:
Gravity
Local gravity values differ depending upon geographic locations. Pressure is defined as
“force per unit area”, so that mass values must be converted to force values. To accomplish
this, the acceleration of gravity must be used. The acceleration of local gravity may be
determined by having a gravitational survey made of the local area with a gravimeter or by
contacting various governing bodies such as the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. Once the local value of gravity is known, the
pressure may be corrected using the following formula:
G
P
G
=
G
x P
W
N
Where:
P
G
G = local gravity
G
W
P
N
= tester output pressure corrected only for gravity
= gravity value for which the tester is calibrated
= pressure value of weights applied
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Temperature
If the coefficient of expansion of the ball and nozzle is positive, the effective area will
increase with increasing temperature resulting in a corresponding decrease in pressure.
Corrections can be made using the following formula:
P
P
=
T
Where:
P
G
P
T
T = ambient temperature (°C)
Air Head
When pressurized, a correction is required only when the gauge height or reference plane
of the unit being calibrated is either higher or lower than that of the pneumatic tester. The
reference plane of the tester is at the top of the nozzle. Heights above the reference plane
are negative, while heights below the reference plane are positive. Corrections can be
made using the following formula:
= tester output pressure corrected only for gravity
= tester output pressure corrected for gravity and temperature
1 + 1.67 x 10-5 (T - 23°C)
G
P
=
A
Where:
H = air head (Inches)
P
T
P
A
= tester output pressure corrected for gravity and temperature
= tester output pressure corrected for gravity, temperature and air head
PT (1 + H x 2.84 x 10-6)
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3.0 CALIBRA TION AND RECERTIFICA TION
The accuracy of measurements can only be ensured through calibration against reference
standards of a known and well characterized measurement uncertainty; reference standards that are ultimately traceable through a national standards laboratory to the International Bureau of Weights and Measures (BIPM), to a natural physical constant, or to consensus standards.
All AMETEK pressure calibrations are traceable in the United States of America to reference
masters calibrated by the National Institute of Standards and Technology (NIST).
Measurement performance is affected by the frequency and severity of use, the environment, test conditions, and by other factors. AMETEK recommends calibration on a prescribed interval/frequency in order to ensure optimal measurement performance and reliability.
Two types of calibration services are offered:
G Calibration with a Certificate of Conformance/Certificate of Compliance
A statement of conformity which documents that the listed device(s) conforms to published specifications, or the terms of the order/contract. It can provide, in addition, a
statement of traceability to NIST.
G Calibration with a Calibration Report/Certificate
A report that outlines detailed information about the calibration process. This includes
actual calibration data, traceability information, test conditions, and other factors as may
be applicable to the type of device being calibrated.
3.1 RECOMMENDED CALIBRA TION FREQUENCY
As a general rule, AMETEK
months.
Testers used on a more frequent basis should be tested more frequently.
pneumatic testers should be tested and recertified every 12
3.2 MA TERIALS NECESSAR Y FOR RECERTIFICA TION
Both the tester assembly and weight set should be returned to AMETEK in order to allow for
calibration of the tester as a “system”. Pressure is a derived parameter requiring determinations of both effective area and force (weight-mass). Instruments not sent to AMETEK as
a “system” can only be provided with certifications on the parameter calibrated, e.g. effective area or mass.
All materials should be securely packaged to prevent damage during transportation and
handling. Testers should be returned in their case. The ball/nozzle assembly should be
wrapped with adequate padding material and well secured to avoid shifting, movement and
to protect them from shock during transportation.
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