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About:
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Pressure Transmitter
</p>
<p>
<a href="http://www.onlysft.com/pressure-transmitter/" target="_self">Pressure
transmitter</a>s are a common and well understood technology especially within the
petroleum, petrochemical, refrigeration and fuel gas markets and they are extremely
economical compared to other technologies.
</p>
<p id="B9781782421696500061-p0150">
Pressure transmitters are a common and well understood technology especially
within the petroleum, petrochemical, refrigeration and fuel gas markets and they are
extremely economical compared to other technologies. If a level is to be made in an open
vessel a pressure transmitter (PT) is placed at the bottom and the head pressure caused by
the weight of the liquid can be used to calculate the height of the liquid. Differential
pressure transmitters can be used on pressurised vessels using the same principles (9).
</p>
<p id="B9781782421696500061-p0155">
Level measurement using pressure transmitters cannot be deployed in primary separators
as the change in temperature will impact the measurement, the change in density of the oil
during operation will impact the measurement and any fluctuation of the
oil/gas differential pressure control valve or pressure disturbances would also
impact on the reading.
</p>
<p id="B9781933762005500268-para108">
Portable dP gauges are used to monitor the dP across strainers, online densitometers,
DB&B valves, prover interchange valves, and other devices. All pressure gauges shall be
equipped with calibration stickers indicating the last test or calibration date and who
performed the calibration. The calibration sticker should be clearly visible and
constructed of a rugged material. All recordings on the sticker should be made with
indelible ink. The dial gauge cover should be clear and abrasive resistant. The
pressure gauge should be readable with permanent figures and markings and equipped with a
blowout disc for safety. The scale shall be in graduations of no greater than 2 psig with
longer graduations at each 5 psig and numbered at not greater than 10 psig intervals. The
error at any point on the scale should not exceed ±2 psig. The maximum
allowable working pressure (MAWP) of the dP gauge should be at least equal to the MAWP
for the measurement facility.
</p>
<p id="B9780128239162000060-p0270">
A <a href="http://www.onlysft.com/pressure-transmitter/differential-pressure-
transmitter/" target="_self">differential pressure transmitter</a> is a device that
translates physical force to an electrical signal. The most common type of force transducer
uses a diaphragm, piston, bourdon tube, or bellows to sense the physical force and various
strain/force-sensing devices to convert the deflection of the physical element to an
electrical signal. Traditional strain-sensing devices include the following: capacitive
cells, piezoresistive strain gauges, piezoelectric quartz material, and electromagnetic
devices.
</p>
<p id="B9780128239162000060-p0275">
In the United States, companies such as Rosemount, Cameron/Barton, Foxboro, and
Ultrasystems have provided transmitters that specialize in safety system pressure
measurements. These transmitters may still function successfully on some iPWR designs, but
many will have to be reengineered for different mounting configurations, size constraints,
and environments. Many iPWR designers, when faced with a modification program, may choose
to go with new technologies rather than modifying the old ones. The new technologies may
offer advantages in size, redundancy, accuracy, and environmental resilience. Some of these
new technologies include microelectromechanical system (MEMS) sensors, fiber optic sensors,
and ultrasonic sensors.
</p>
<div>
<p id="B9780128239162000060-p0280">
In the optical fiber category, a company called Luna Innovations has developed and
successfully tested fiber optic pressure sensors, like the one shown in Fig. 6.1, in a
research reactor environment. These fiber optic pressure sensors have been shown to operate
in radiation environments with flux levels much higher than those compatible with most
electronic pressure sensors. With traditional technology, it is necessary to protect
traditional electronic <a href="http://www.onlysft.com/pressure-transmitter/gauge-
pressure-transmitter/" target="_self">gauge pressure transmitter</a> from harsh radiation
conditions near the core; this requires the use of long pressure sensing lines, which limit
the response time to pressure transients and increase the number of wall penetrations. Luna
’s fiber optic pressure sensors are designed to operate in harsh environments. When these
pressure sensors were combined with Etalon-based fiber optic temperature sensors providing
temperature compensation, drift effects were minimized. The attractiveness of this
technology for iPWRs is obvious, with the elimination of sensing lines, the minimization of
penetrations, the small size of the sensor, the rapid response to pressure fluctuations,
and the operability in high radiation fields. With these attributes, this technology bears
merit for primary and secondary side pressure measurement (Dickerson et al., 2009).
</p>
</div>
<p id="B9780128195048000044-p1665">
Pressure or DPT transmitters have been used to measure liquid levels of open
or pressurized tanks, respectively, with proper calibration taking care of the density
value of the subject liquid. These types are used for level measurements of boiler drums,
all heaters, deaerators, condenser hotwells, condenser surge tanks, and all
dosing tanks.
</p>
<p id="B9780128195048000044-p1670">
For open tanks, a pressure tapping at a suitable location is connected through the
impulse line, to the high-pressure port of the DPT with the low-pressure port open to
atmosphere. The pressure (or DP) sensed by the DPT is proportional to the level with a
known liquid density (ρ) and force due to (earth’s) gravity (g). With proper calibration,
the potential transform can now be used as a level transmitter.
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