Category Archives: Pressure Transducers

relief valve

ASME Pressure Relief Valve Testing

Many processes involve the use of high pressure steam, water or air.  Piping systems carrying these fluids must be protected from over-pressures that could cause damage or injury.  A pressure relief valve is a device that opens to vent any pressure higher than the relief valve’s operating set point.  The water heater in your house, for example, has a pressure relief valve set to open at a pressure that is lower than the burst pressure of the heater tank.  That way if pressure inside the tank exceeds the relief valve’s set point pressure, the valve will open and vent the pressure before the tank is damaged – you get a wet floor but you don’t have to replace the heater tank.

Pressure relief valves come in all sizes and pressures and these are critical parts of a high pressure piping system carrying steam in an industrial plants, refineries, power plants, etc.  The ASME has established criteria for the size and set point pressures for relief valves operating in industrial systems.  Additionally, these valve are tested on a regular basis to insure that they open at the correct pressure and do not impede the flow of fluid as the pressure is vented.  The vales are tested at their operating pressures and temperatures, and the opening pressure and pressure drop through the valve as it vents must be measured.

There are testing laboratories that are used to test industrial pressure relief valves by simulating the operating conditions for water, air and steam.  One customer of Validyne has a test lab capable of generating up to 10,000 lbs. per hour of steam at 300 psig, air flows to 3500 SCFM at 500 psig and water flow rates of 500 gpm at 300 psig.  Pressure relief valves are tested depending on their operating conditions, and the valves are instrumented to verify correct operation at their set point pressure.

The Validyne product used to make relief valve measurements is the DP15 pressure transducers.  One transducer is used to measure the pressure upstream of the relief valve, a second DP15 measures the downstream pressure.  These transducers are 300 or 500 psi, depending on the test.    A third DP15 measures the pressure drop across the relief valve when it is flowing and this transducer is typically 100 In H2O full scale.  The DP15s are used because they can be mounted remotely from the control station.  A large steam relief valve, for example, is connected to piping with runs of 25 and 30 feet.  The DP15 can be mounted at the measurement point and the cable to the demodulator can be up to 50 feet with no compromise in calibration.

The pressure transducers are connected to Validyne CD23 demodulator with digital display.  The CD23 features large LED displays that are helpful for the operator to see while opening and closing large control valves during the test.  The display can be given directly in PSIG and the CD23 provides an analog output proportional to pressure that can be connected to a LabVIEW computer to record the pressures during the test. Alternatively the pressure sensors can also be connected to the USB2250 DAQ.

The Validyne CD23s and DP15s have given many years of service in this difficult environment and this reliability, plus the ability to interface to a data acquisition system make it a great solution for relief valve testing.

Pressure Sensors and External Carrier Demodulators

The most popular Validyne pressure transducers are the P55/P61/P365 series.  These all include a pressure sensor, carrier demodulator electronics package, a high level output signal, temperature and linearity correction as well as a compact form factor.  There are applications, however, where a better solution might be to separate the pressure sensor from the electronics, with the two connected by a cable.  This article describes when this approach makes the most sense.

Validyne offers the sensors and electronics package from the P55/P61 available as stand-alone components.  The DP15 series of pressure sensors is identical to that used in the P55 and P61, while the DP360 and DP363 are high pressure variants the same as used in the P365 and P368.  The CD16 standard analog output electronics or the CD17 USB-based electronics can be used with any of these sensors, and standard cables are available in a variety of different lengths to connect the two.

Pressure Sensors

When should a sensor be separated from the electronics?  The biggest reason to do this is to allow convenient re-ranging of the pressure sensor.  The full scale pressure range of Validyne sensors can be changed by replacing the sensing diaphragm.  There are 23 different full scale ranges available for the DP15, for example, and these run from a few inches of water to 3200 psi. Changing the diaphragm is straightforward; the connector and four body bolts must be removed to gain access to the sensing diaphragm, and the DP15 sensor makes this easy, requiring just a torque wrench and a vise.  With a little practice, the diaphragm in a DP15 can be replaced and re-calibrated with the CD16 or CD17 electronics in about 20 minutes.  The DP360 and DP363 high pressure sensors are similar in construction and also lend themselves to straightforward diaphragm replacement. Frequent re-ranging of the full scale of a Validyne transducer is common in laboratory situations where pressure measurements vary widely from day to day.  Test labs and university labs are typical places where a separate sensor and electronics package are used to best advantage.

Another reason for separating the pressure sensor from the electronics is to conserve space or limit the weight at the measurement point.  In tight locations, such as aircraft compartments or in submersible vehicles, the pressure connection may be in a relatively inaccessible space and the smaller footprint of the DP15 sensor, might fit better than the full P55.  If mass or weight is important, the sensor will be lighter than the full transducer and this will relieve any stress on the piping connections in areas where shock and vibration are a consideration.

It is important to realize that separating the sensor from the electronics will compromise the temperature correction as the temperature sensor is located on the electronics package and not at the pressure sensor.  A pressure sensor such as a DP15 used with a remote electronics such as the CD16 will be most effective in applications having a stable temperature environment.

 

Signs of a Faulty or Failing Differential Pressure Sensor

There are many different types of pressure sensors that are used to measure a number of applications and operations. From use in automobiles, measuring flow rates in pipelines, density measurements, and even for measuring the levels of fluids, a differential pressure sensor can be the best option.

The Basics of Operation

The differential pressure sensor is a method of measurement based on two different reference pressures. The sensor is designed to allow access to either side of a diaphragm by the liquids or gases. This creates a pressure against the central diaphragm on both sides.

A gauge is used to read or measure changes in the pressure on either side of the central diaphragm. This can include an increase in pressure on one side, or a drop in pressure on the other. The sensor measures the deformation of the diaphragm, and converts this change into an electric signal.. It can also transmit that information directly through USB, wireless, or other digital methods to computer systems that monitor, record, and control the flow or another variable.

Signs of Failure

The most common issue with a differential pressure sensor is damage to the diaphragm that causes it to be deformed, or to lose the ability to flex and respond to changes in pressure.

This is most often caused by extreme bursts of pressure that are atypical for the system. It can also be caused by installing the wrong size or type of sensor, given the operating conditions.

Another issue that can occur is damage to the port area of the sensor. This may occur if there is some type of debris or contamination within the system that lodges in the port or the tube, restricting the correct flow of the fluid into the sensor.

If your Validyne pressure sensor or pressure transducer is not performing as it should, contact sales@validyne.com so we can help you get it fixed!

Corrosion Resistance of Validyne Pressure Transducers

Pressure transducers are exposed to a wide variety of fluids and gases when used to measure pressure.  Corrosion of the pressure transducer sensor body will shorten service life and lead to costly downtime if material selection is not carefully considered.  This article will cover the basics of material selection for Validyne pressure transducers so that the best possible performance and adequate corrosion protection can be ensured prior to purchase.

Validyne offers three types of sensor body materials that will provide appropriate protection for most pressure measurement applications: 410 SS, 316 SS and Inconel.  316 SS and Inconel pressure transducers are supplied with a teflon-coated 410 SS sensing diaphragm needed for the Validyne inductive sensing technology to operate correctly.

410 SS

410 is the standard material for Validyne transducers and does best when used with air, inert gases, or hydrocarbon-based fluids.  Oxidizing environments – or fluids containing chlorides – will cause 410 SS to corrode and pit, sometimes rapidly.  Water-based fluids, fluids containing salts, or corrosive chemicals should not be used with 410 SS.

Validyne offers the P365 High Pressure Transducer and the P368 Digital High Pressure Transducer with the 410 SS option.

316 SS

316 SS is the standard steel for instrumentation and has a high degree of resistance to water-based fluids and mildly corrosive chemicals.  316 SS also does well in fluids with low concentrations of chlorides, but is attacked by nonoxidizing acids such as sulfuric and hydrochloric acid in most concentrations.  316 SS has good resistance to alkaline solutions, organic acids, and other organic compounds.

Validyne offers a wide range of pressure sensors and pressure transducers with 316 SS.  The DP15 Variable Reluctance Pressure Sensor Capable of Range Changes, P55 Pressure Transducer and P61 USB Pressure Transducer are some of the pressure transducers that can be ordered in 316 SS option.

Inconel

inconel pressure transducers

Inconel is a superior material, ideal for corrosive applications, and is best reserved for systems containing high concentrations of chlorides such as salt water or brine.

Validyne offers a full range of pressure sensors and transducers in inconel. From low-static pressure transducers to high-static pressure transducers, we offer the DP15 Variable Reluctance Pressure Sensor Capable of Range Changes, P55 Pressure TransducerP61 USB Pressure TransducerP365 High Pressure Transducer and the P368 Digital High Pressure Transducer.

Fluids to Avoid

Fluids containing hydrogen or hydrogen sulfide should not be allowed to come in contact with Validyne transducers. Almost all metals lose ductility when they absorb hydrogen, especially at temperatures below 100 °C. Hydrogen molecules can enter the sensor body metals at the grain edges and this will cause embrittlement of the metal that can lead to pressure boundary failure.  Additionally, hydrogen sulfide is poisonous and hydrogen gas is extremely explosive.

Corrosion of Validyne transducers is not covered by the warranty. The proper choice of sensor body material will enhance pressure transducer performance and increase the life of the pressure transducers.

Click here to contact us today to find out the different solutions we can provide for your pressure measurement application. 

Differential Pressure Transducer

What to Look for in Durable Differential Pressure Transducers?

At Validyne Engineering, we have almost half a century in the industry, providing a range of different low cost, highly accurate pressure sensors for many different industries and applications. Over time, we have provided these sensors to various industries and companies. We have also listened to the needs of our customers to develop the sensors, transducers and transducers to get the job done.

One of the most important aspects of our devices is quality. We produce a durable, rugged line of differential pressure transducers. We believe we have a top selection of these transducers for all industries and applications.

The Validyne Difference

All of our differential pressure transducers are designed to meet performance specifications in highly demanding environments. Most of the transducers we sell can be used for both liquids and gases. They have been extensively used in the field with test vehicles and aircraft as well as in all types of environmental conditions.

Our in-house team of designers and engineers, all with extensive experience in sensor component development and design, has the ability to incorporate the needs of our customers into specialized solutions for their applications. We are also able to take this knowledge and design transducers for general use that are superior to other designs on the market today.

Up to the Test

One of the biggest complaints we hear from people looking for transducers is their inability to survive difficult working conditions. Each of our components has been thoroughly tested to provide our end-users with the quality part to stand up to real-world use. We also provide support and assistance in helping you to choose the right component for any application.

Our transducers are able to handle changes in the environmental and ambient temperatures with minimal impact on the accuracy of the pressure readings. They are designed to provide precise readings with fast response, giving test engineers the data they require. Fully compatible with data management systems, they are easy to integrate into field or laboratory testing situations or where and as they are needed.

Easy to mount with pre-drilled holes, they have a small, compact size and low weight make these differential pressure transducers the right component for the job. They are able to stand up to spray and moisture and also capable of wet-wet operations. Our transducers are available in differential or absolute pressure, as well as the option for a CE approved model if so required.