Q. How will installation of a Magnehelic® gage 150' away from the pressure source affect accuracy?
A. Accuracy will not be affected, but response
time will be increased in
proportion to the length of the tubing.
Q. Which Capsuhelic® gage ports could be connected to the pressure source in liquid service?
A. The bottom ports. This allows bleeding of entrapped air from the top ports to
eliminate reading error due to compression of entrapped air in the gage. Bleed fittings should be installed in the top ports.
Q. Can the standard Magnehelic® or Capsuhelic® gage be installed outdoors?
A. Yes. Front covers are sealed with "O" rings. Capsuhelic® vent holes are
plugged with foam, and the new high impact acrylic lens material is very resistant to ultra-violet fogging.
Additional care is recommended to lead pressure connections downward from the gage and provide as much protection
from the elements as possible.
Q. Can a standard Magnehelic® gage be used for natural gas or propane service?
A. No. As the silicone diaphragm will be attacked by these gases. A Buna-N
diaphragm should be specified.
Q. What happens when a Magnehelic® gage equipped with the low temperature option is operated below -20
degrees Fahrenheit (-29 degrees Celsius)?
A. Below that temperature the accuracy of the gage deteriorates beyond our
published specification due to stiffening of the diaphragm.
Q. What restrictions, if any, are imposed for the Magnehelic® and Photohelic® gages in
vacuum service?
A. In applications involving higher vacuums than 20" Hg, leakage due to gage
housing porosity becomes the limiting factor.
Q. May a standard gage be reconfigured in the field from automatic to manual reset?
A. Yes. By simply making a wiring change on the relay terminal board per the
information in the instruction bulletin.
Q. How much may the published pressure and temperature specifications for Dwyer gages and controls be
safely exceeded?
A. Published specifications may not be exceeded! To do so will void the
warranty as well as expose the customer, the stocking representative, and Dwyer Instruments to product liability action.
Q. Is National Institute of Standards and Technology traceability available for the Magnehelic® Gage?
A. No. But Magnehelic® gages can be given a special 6 point calibration check
with an NIST traceable master gage and a certificate can be supplied.
Q. How do I hook up my Magnehelic® Gage?
A. In Bulletin A-27 under operation, it explains how to connect the
Magnehelic® to the following applications: positive pressure, negative pressure, and differential pressure.
Q. What is an RMR Photohelic®?
A. The RMR operates just the same as a standard Photohelic,
however, the RMR unit has a cable (available in various lengths) between the gage head and the power pack so that
the power pack can be mounted remotely. Typically this is done where the space is limited in a control panel.
Q. What is the NEMA rating of a Photohelic®?
A. Our standard is considered to be NEMA 1 rated for general
purpose. We do have weatherproof (Nema 4X) and explosion-proof (Nema 7 & 9) enclosures available.
Q. Can the Spirahelic® gage be mounted in the horizontal position?
A. Yes, all that is required is calibration in the horizontal position during
assembly. Lead-time would be 2 weeks.
Q. Are air velocity scales available?
A. Yes, the information we require to supply the proper range is the velocity
(fpm or m/s) or velocity pressure (inches of water or kpa) and density of air (lb/ft3 or g/cm3).
Q. How do I hook up my Magnehelic® gage for an air velocity application with a pitot tube?
A. In our online primer
on flow products work, we explain very well how to take air velocity readings. The total pressure connection on the pitot tube
is connected to one of the high pressure ports on the gage. The other high pressure port is plugged. The static pressure
connection on the pitot tube is connected to one of the low pressure ports on the gage. The other low pressure port is plugged.
Q. Why must Dwyer pressure switches be mounted with the diaphragm in the vertical plane?
A. In other than a vertical plane, the diaphragm can sag and cause a shift in
set-point or a change in the adjustable set-point range. The switch may even fail to reset at the minimum
set-points. This is the same phenomena that causes inaccuracy in Magnehelic® and Capsuhelic®
gages when mounted in other than a vertical position.
Q. How can a standard 1910 pressure switch be used to sense pressure in an oven operating at
200 degrees Celsius?
A. Use metal tubing for sensing lines long enough to safely dissipate the heat.
Q. For which pressure switch applications are gold contacts recommended?
A. For "dry circuit" applications where little or no current is flowing in the
circuit to help burn off contact dirt and oxidation. Switches used with solid state circuits often fall in this category.
Q. Will a Dwyer pressure switch be damaged if the pressure exceeding the maximum set-point is applied to the
switch?
A. No. Not unless the total rated operating pressure is exceeded.
Q. Does Dwyer offer a fully UL/FM/CSA approved explosion proof pressure switch?
A. Yes. The 1950 Series.
Q. Regarding pressure switches, what is the difference between rated pressure and maximum surge
pressure?
A. Rated pressure is the maximum continuous or cyclic operating pressure;
maximum surge pressure is safe for the switch housing but may damage the internal components.
Q. Can the standard H2 pressure switch be used with water?
A. No. The brass or SS housing must be specified for compatibility
reasons. The aluminum housing can leak into the switch.
A. The flow rate is read at the maximum width portion of the float regardless
of shape.
Q. What factor is used to correct for different flowmeter inlet pressure?
A. None, if the flowmeter is exhausting to the atmosphere. If back-pressure
is present due to downstream plumbing or restrictions, use the
conversion curves and formulas for gases.
Q. Why are top mounted valves recommended for flowmeters used for vacuum service?
A. To maintain atmospheric pressure in the indicating bore and therefore
preserve accuracy; an inlet restriction would reduce pressure in the bore. This is essentially the opposite
situation to outlet back-pressure in a pressure system which increases pressure in the bore and also affects
accuracy. Remember that all standard Dwyer flowmeters are calibrated for standard atmospheric pressure and
temperature in the bore.
Q. Is the Rate-Master® or Visi-Float® Flowmeter compatible with any media?
A. The Rate-Master® Flowmeter is manufactured from a polycarbonate
plastic and the Visi-Float® Flowmeter is manufactured from acrylic. Compatibility charts need to be reviewed
to determine if these materials of construction are compatible with your media.
Q. Are special ranges available for the Rate-Master® and/or Visi-Float® Flowmeter?
A. Yes, other ranges are available which are not specified in our catalog.
Please feel free to contact Dwyer with questions on these ranges.
Q. How do I make the conversion for a specific gravity different than air or water?
A. In our online primer
for using flow products, there is a formula to make this conversion.
Q. Which flowmeters are available with NIST traceability?
A. All Dwyer Mini-Master®, Rate-Master®, and
Visi-Float® flowmeters are available with NIST traceability on all air ranges except for RMA-1, RMA-11,
RMA-150, and RMA-151 models.
Q. Is a Dwyer Certificate of Conformance offered with any of the flowmeter models?
A. A standard Dwyer Certificate of Conformance can be offered with all Dwyer
Mini-Master®, Rate-Master®, and Visi-Float® flowmeters on all water ranges
(or other compatible liquids).
Q. How will the calibration of a standard Dwyer flowmeter be affected when used to measure the flow
of hydrogen?
A. The readings will be low due to the lower specific gravity of hydrogen
compared to air. This error can be corrected utilizing the conversion curves in Bulletin F-41 or in OEM quantities
special calibrations can be provided.
Q. Can the UF10 be used to measure flows of liquids with entrained air bubbles or particles?
A.No, the UF Series should be used with clear
or cloudy liquids that are free from all particulates or air which could effect
the reading.
Q. Can the Model TM2 Flow Totalizer be used to totalize the amount of air flowing through my TF2110
flow sensor?
A.No, the TM2 Flow Totalizer has a pulse input
while the TF2110 flow sensor has a voltage output. The TM2 can only be used with
the Series TF Turbine Flow Sensors that are rated for liquid
service not gases.
Q. What is the advantage of using a manometer rather than a Magnehelic® gage?
A.Dwyer Instruments manufactures many different types and styles,
of manometers with various accuracies and prices for different applications as well as the Magnehelic® gage.
For example, some of the many manometers we manufacture are Hook Gage Manometers with ±0.001
inches water column accuracy; Microtector® Portable Electronic Point Gage to ±0.00025 inches water
column accuracy; Handheld Digital Manometers with ±0.5 inches water column accuracy; very inexpensive
Mark II Molded Plastic Air Filter Gages at ±3% inches water column accuracy. The key point is that we offer
many manometers and the selection depends on your specification, application, convenience needs and pocketbook.
Some of the key factors to consider that affect manometer performance and usage are:
Characteristics of Indicating Fluid
Readability
Leveling
You should read "Measurement of Pressure with the Manometer" in our catalog to fully understand the importance of
these factors and their affect on your reading with the manometer instrument
For many applications people prefer to use our Magnehelic® (dial style) gage with ±2% inches of water
column accuracy because of convenience, accuracy, etc., plus when compared to manometer it eliminates indicating fluid,
need for leveling, and some prefer the readability.
If you consider manometers and Magnehelic® gages to measure low air or gas pressures positive, negative,
or differential, you have a wide selection to choose from and your application needs can be met with our very broad
product line at a great value
Q. Are Dwyer manometers considered traceable to the National Institute of Standards and Technology?
A. While the manometer itself is not traceable, the master gage used to
check the calibration is traceable and we can so certify.
Q. Why doesn't 1 inch on the scale of a 1223-12-D manometer equal 1 inch on a ruler?
A. The calibration scale on the manometer has been compensated for the
specific gravity of red gage oil which is less than water.
Q. Since water will not mix with oil, why can't a D-style manometer be used to measure water pressures?
A. The weight of the water itself is also being measured which results in
erroneous readings.
Q. What are the principle advantages of red gage oil over water for use in manometers?
A. Red gage oil is slow to evaporate, won't freeze, is more readable and
produces slightly expanded scales for better reading resolution.
Q. Will the water manometers freeze?
A. Yes, if the temperature drops below 32 degrees Fahrenheit, the fluid in the
manometer will freeze. The fluid used in "W/M" style manometers is water-based with a small amount of fluorescent
green oil to enhance the meniscus. The other gage oils have a lower freezing point, however, it is recommended that
the manometers be stored above 32 degrees Fahrenheit.
Q. How does a manometer measure gage and differential pressure?
A.Manometers simply measure the pressure by indicating the amount of
displacement a liquid of known weight undergoes when a force is applied. This concept is best explained through
illustrations in our Bulletin D-21 or in our online primer
on how to use pressure products.
Q. Is routine maintenance required for a Dwyer red gage oil type manometer?
A. Yes. The zero point should be checked periodically as well as the oil level.
After a year of service, particularly with dirty air, the oil should be replaced to assure that specific gravity
changes are not affecting the accuracy of the reading.
Q. Can a Model 603A-4 transmitter supplied with a 5" w.c. span be readjusted in the field to have a full
span of 25" w.c.?
A. Yes. The 603A series for the most part is a field-spannable transmitter.
Since 0-25" is the maximum range of a Model 603A-4 as shown on the catalog page this can be done.
Q. What are the advantages of using a transmitter in a two-wire configuration as compared to a three or four-wire
configuration?
A. A two-wire configuration is the most popular wiring hook-up used today for
transmitters. It simplifies initial hook-up and troubleshooting, saving the customer time and money.
Q. Which Dwyer transmitters are UL and/or CSA approved? FM approved?
A. UL approved transmitters: 639 series. CSA approved transmitters: none.
FM approved transmitters: 636, 637, 638 and 639 series.
Q. How can the 4-20mA output signal of our transmitters be converted to a 1-5VDC or 2-10 VDC output signal
in the field? Do any of our transmitters come standard with a voltage output already in place?
A. The 4-20mA output signal from our transmitters can be converted to a 1-5VDC
or 2-10 VDC signal by inserting a 250 ohm or 500 ohm resistor respectively into the output loop.
A. Warm-up Time can be defined as the amount of time it takes the transmitter
to "settle down" after initially being powered up to be able to provide its most accurate readings. Response Time
is the amount of time required for the output to change after the input has changed. Loop Resistance is the maximum
amount of resistance that can be in the current loop without dampening the transmitters output. Loop Resistance is
a direct relation of input voltage.
Q. A customer would like to get switching capability, local pressure indication, and a 4-20mA output signal
all in one device. Do we have a product to offer them?
A. Yes. The 3000SGT is a combination switch with high and low
setpoints, a gage, and transmitter with 4-20mA output signal.
Q. What is specified by the temperature coefficient and how is it important to my readings?
A. As the ambient temperature changes, the output current will drift slightly.
The temperature coefficient specifies the amount of drift per °F/°C. Since the temperature affects the
transmitter output, the temperature coefficient is important to accuracy of your reading.
Q. In some case, a turndown ratio is listed under the transmitter specification - what does this mean?
A. The turndown ratio specifies the adjustable range of the transmitter.
For example, if the turndown ratio is specified as 5:1 and the minimum range is 0-10 psi, you will be able to
determine that the maximum range is 0-50psi.
Q. I have broken the vane on my Model VT140, is a replacement vane available that I can attach in the field?
A. No, the VT140 would need to be returned to Dwyer in order to attach a new
vane since the unit would need to be recalibrated with the new vane in place.
Q. What precautions should be taken when making an outdoor installation?
A. Keep the junction box above the nearest low point in the conduit run and make
sure the conduit connection is sealed to prevent condensation from running into the switch.
Q. Is the V4 body machined from solid bar stock or a casting and what is the significance to the customer?
A. The V4 body is machined from solid bar stock which makes it much stronger
than a casting and totally leak proof; castings frequently leak because of their porosity.
Q. Why is the method of mounting a V4 of concern?
A. The vane and magnet keeper assembly near
the hinge pin are very close to the mounting threads. Combined with the fact
that pipe fittings are available in many variations, this produces
a possibility that the customer will mount the switch in a fitting that prevents
the vane from swinging. To make things worse, there is usually no way the customer
can tell that this has happened. Mounting in a threaded branch connection
avoids this clearance problem.
Q. How is "deadband" defined as related to the V4 switch?
A. Deadband is the difference between the switch actuation flow and switch
deactuation flow; in general, V4 flow switches have a 45% deadband meaning deactuation occurs at approximately
55% of actuation flow.
Q. Can a V4 switch be installed in a vertical run of pipe?
A. Yes, but not the standard model. Vertical pipe installations must be
specified on the order and require a special spring loaded cane. Only for use in vertical up-flow applications.
Q. What precautions should be taken when installing a V4 switch in an extremely high flow application?
A. Installation with a 2 1/2" threaded branch connection is
recommended to allow the vane to swing out almost parallel to the flow to reduce
stress on the vane and pressure drop in the system.
Q. What is specified by the temperature coefficient and how is it important to my readings?
A. As the ambient temperature changes, the output current will drift slightly.
The temperature coefficient specifies them amount of drift per °F/°C. Since the temperature affects the
transmitter output, the temperature coefficient is important to accuracy of your reading.
Q. In some case, a turndown ratio is listed under the transmitter specification - what does this mean?
A. The turndown ratio specifies the adjustable range of the transmitter. For
example, if the turndown ratio is specified as 5:1 and the minimum range is 0-10 PSI, you will be able to determine
that the maximum range is 0-50 PSI.
A. Stainless steel vane, ceramic magnet, brass or stainless steel body.
Q. What material is used as a seal between the process fluid and the electrical portion of the switch?
A. The body material; as with the V4, there is no separate "seal" since the body
is machined from solid stock
Q. What is the pressure drop across a V6 Flow switch?
A. All pressure drop information is supplied in Bulletin E-22 which is supplied
with each unit.
Q. Are custom vanes for the V6 available?
A. Yes, we can supply customer vanes for the V6. The information we would
require is as follows: pipe size, flow direction (horizontal, up, down), mounting, pressure, temperature, specific
gravity, flow rates (maximum normal, actuation/de-actuation).
Q. Why should a customer be discouraged from buying a V6 without a tee and installing it in his own tees?
A. Two reasons: One, the customer will frequently tighten the body in the tee
one turn too many, resulting in the vane hitting the tee. This bends the vane and it can jam up even after the
switch is backed out one turn to its proper position. Two, there is also a wide variation in tee dimensions
between manufacturers which aggravates the problem.
Q. What type of pressure drop is expected in the V6-LF?
A. 5-10 PSI, however, it will vary in proportion to the flow rate.
Q. If a customer complains the impeller in his sight flow indicator is not turning, what is most likely the
problem?
A. Usually the impeller is fouled or the indicator is doing its job and actually
indicating no flow.
Q. If a customer claims the plastic impeller dissolved in plain water, what probably happened?
A. The customer exposed the sight flow indicator to fluid temperatures of
400-500 degrees Fahrenheit, considerably in excess of the published temperature specification.
Q. What sight flow indicator options are recommended for applications at the high end of the specified
temperature range?
A. The bronze impeller and tempered glass options should be specified.
A. Actuation means that the flow rate has reached a point where the microswitch
trips or the contacts of the microswitch change state. De-actuation means that the flow rate has decreased to a
point where the microswitch returns to its normal state.
Q. Why is the minimum specific gravity important on the L4 and L6?
A. If a medium has a lower s.g. than the rated minimum for a float, the float
will sink through the media and the switch will not operate.
Q. What else needs to be specified when ordering an L4-TOP?
A. The vertical and horizontal lengths of the float arm.
Q. Can the V8 float switch be used with acids due to its material of construction?
A. No. The V8 contains a 316SS pin and spring as well as a ceramic 8 magnet
that are not compatible.
Q. Can the V10 flow switch be mounted for use in a vertical up-flow application?
A. Yes. The standard V10 has a spring return on the vane which allows for
mounting in any position.
Q. How is the F7 level switch converted from N.O. to N.C. or vice versa?
A. The float is removed and replaced upside down.
Q. How does the F7-MHS Level Switch attach to my tank?
A. Drill a 1/2" hole in the side of your tank. With the F7-MHS body inside the
tank, insert the screw and exposed wires through this hole and secure the unit in place with the corresponding nut.
A. The ratio of energy emitted by an object to the energy emitted by a blackbody
at the same temperature. The emissivity of an object depends upon its material and surface texture:a polished metal
surface can have an emissivity around 0.2 and a piece of wood can have an emissivity around 0.95.
Q. I am purchasing the 667-0D Programmable DIN Rail Transmitter - do I need to purchase the software as
well?
A. Yes, you will need the PCS1 Windows Software and adapter in order to
program your transmitter to the correct range.
Q. I did not receive feet with my CR10 Circular Chart Recorder - should I return this unit?
A.No, the feet are no longer supplied with the CR Circular Chart Recorders.
Q. Do I need to supply my own thermocouple for the MR10 Temperature Recorder?
A. No, a 5 ft beaded thermocouple is supplied with the unit.
Q. What is the key feature of both Proximity position indicators and level switches that sets these products
apart from all competitors?
A. Magnetic coupling.
Q. Hi-FlowTM control valves call out ANSI B16.104 Class IV flow leakage.
What does this mean?
A. ANSI B16.104 is a testing specification for control valves. This
specification has actually superseded by ANSI/FCI 70-2 Class IV. The class IV designation defines the allowable
amount of leakage through the valve seat in the closed position. Class IV allows for .01 percent of the rated flow
(Cv), to pass through the seat. Class IV is common for metal to metal seated valves.
Q. What if I need parts for my Hi-FlowTM control valve?
A. Many Hi-FlowTM valves have been in service for
15+ years with all original parts. However, since Hi-Flow TM valves are commonly used in
steam service, a severe application, some parts may wear over time. Unlike other control valves, Hi-FlowTM
valves are designed with removable seat rings making repair or replacement of components an option. Although all parts are
available, you will probably never need more than a seat ring, plug assembly, and stem packing to have a valve that is like new.
Q. What are Plast-a-Vane® butterfly valves?
A. Plast-a-Vane is a trade name for the W.E. Anderson line of butterfly
valves. Plast-a-Vane® is derived from the unique thermoplastic disc used in our valve design. The disc is made
from Noryl® GFN-3, a General Electric thermoplastic resin. This resin has excellent chemical compatibility
and can be used in media ranging from glycol to most concentrations of sulfuric acid. The smooth molded surface resists
abrasion and provides low operating torques. In addition to Noryl®, disc materials include Aluminum-Bronze
alloy, 316 Stainless Steel, and epoxy coated ductile iron.
Q. What two basic types of position indication are provided with the Proximity position indicator?
A. Visual (mechanical) and electrical.
Q. How many different size housings does Proximity provide for position indication? How many switches in a
single housing?
A. Two sizes: 2-switch and 4-switch housings.
Q. What is IP68?
A. I.P. = Ingress Protection; submersible certification - all tests - solids
(0-6) and liquids (0-8).
Q. What two types of continuous signal feed back can Proximity provide with the position indicator?
A. Resistive (potentiometer) and current (transmitter).
Q. What are the two dry product level switch model types? What ranges do they cover? How are they adjusted?
How many set-points do they have?
A. GSD3DA - gravity (elastomer) suspension, aluminum housing, polyurethane
diaphragm, standard 15 amp switch. PSD16A - pneumatic (fabric), suspension, aluminum housing, filter fabric
diaphragm, polyester 150 micron permeability, standard 15 amp switch. They can be adjusted to any level. They are
adjusted by a screw adjustment. One setpoint available.
A. We now offer many of the most common metric scales on almost every
cataloged product at no cost. A index of these metric models is located in the reference section of our printed catalogs.
Other scales can be done as a special order for a reasonable setup charge. The conversions from English to Metric
can be found on the back inside cover of our catalog. The most common metric pressure units are kpa, pa, bar, mbar
and mm of W.C.
Q. How often do our pressure gages need to be recalibrated?
A. There is no set life span for any of our products, as it varies based on
usage. For critical applications, the unit should be tested 2-3 times a year. Under normal circumstances, the units
should be tested annually.
Q. Does Dwyer offer any certification on their products?
A. Yes, at an additional cost, contact our
service group for pricing; we are able to provide NIST certification on our pressure
gages up to 40" w.c. and our flowmeters. We can also issue a certificate of
conformance at no charge for all of our products stating that they meet our published specifications.
