Showing posts with label pressure. Show all posts
Showing posts with label pressure. Show all posts

Thursday, August 3, 2017

Pressure Sensor Accessories - Filled Impulse Line

welded isolating diaphragm for pressure sensing line
An isolating diaphragm, such as this variety
pictured, can be used as a barrier between
process fluid and sensing line fill.
Image courtesy REO Temp 
Pressure sensors intended for use in industrial process measurement and control applications are designed to be robust, dependable, and precise. Sometimes, though, it is necessary or beneficial to incorporate accessories in an installation which augment the performance of pressure sensors in difficult or hazardous environments. There are some scenarios where the sensor must be isolated from the process fluid, such as when the substance is highly corrosive or otherwise damaging to the pressure sensor.

A way to aid pressure sensing instruments in situations where direct contact must be avoided is by using a filled impulse line. An impulse line extends from a process pipe of vessel to a pressure measurement instrument or sensor. The line can have a diaphragm barrier that isolates the process fluid from the line, or the line can be open to the process. There are best practices that should be followed in the design and installation of an impulse line to assure that the line provides a useful transmission of the process pressure to the sensor and whatever degree of isolation or protection is needed remains in effect.

The filled impulse line functions via the addition of a non-harmful, neutral fluid to the impulse line. The neutral fluid acts as a barrier and a bridge, allowing the pressure sensing instrument to measure the pressure of the potentially harmful process fluid without direct contact. An example of this technique being employed is adding glycerin as a neutral fluid to an impulse line below a water pipe.

Glycerin's freeze point is lower than waters, meaning glycerin can withstand lower temperatures before freezing. The impulse line connected to the water pipe may freeze in process environments where the weather is exceptionally cold, since the impulse line will not be flowing in the same way as the water pipe. Since glycerin has a greater density and a lower freezing point, the glycerin will remain static inside the impulse line and protect the line from hazardous conditions.
pressure transmitter
Filled impulse lines protect pressure
transmitters from the adverse impact
of aggressive process fluids.

The use of an isolating diaphragm negates the need for certain considerations of fill fluid density, piping layout, and the need to create an arrangement that holds the fill fluid in place within the impulse line. System pressure will be transferred across the diaphragm from the process fluid to the fill fluid, then to the pressure sensor. It is important to utilize fluids and piping arrangements that do not affect the accurate transference of the process pressure. Any impact related to the impulse line assembly must be determined, and appropriate calibration offset applied to the pressure sensor reading.

An essential design element of a filled impulse line without an isolating diaphragm is that the fill fluid must be compatible with the process fluid, meaning there can be no chemical reactivity between the two. Additionally, the two fluids should be incapable of mixing no matter how much of each fluid is involved in the combination. Even with isolating diaphragms employed, fluid harmony should still be considered because a diaphragm could potentially loose its seal. If such a break were to occur, the fluids used in filled impulse lines may contact the process fluid, with an impact that should be clearly understood through a careful evaluation.

Thursday, December 22, 2016

Multifunction Calibrator Keeps Process Instruments "In Tune"

Genii 620 multifunction calibrator shown on pressure station
GE Multifunction Calibrator
Shown with pressure calibrator accessory
Courtesy GE Measurement & Control
Industrial process operations are populated with sensors, transmitters, and other measuring instruments of many varieties. This instrumentation is not installed without good reason, with each data point providing valuable and necessary information with regard to process status and safety. Regular maintenance and calibration of measurement instrumentation is a necessary part of maintaining quality, efficiency, and safety.

With so many different types and manufacturers of instruments, purchasing and maintaining calibration equipment can become and unwieldy process in itself. GE Measurement & Control meets the challenge by incorporating numerous calibration capabilities into a single high accuracy unit with flexibility and ease of use. The unit can simultaneously source and measure an extensive array of signals, providing capability to use a single calibrator for a long, maybe even complete, list of instruments installed at your site. Utilization of the multifunction calibrator can potentially reduce the total number of instruments in your calibration shop, with a commensurate reduction in cost, documentation, and time commitment to keep your calibration instrument arsenal ready for use.

A datasheet with all the details is included below. Browse the data sheet and reach out to a specialist with your calibration requirements and challenges. Work together to develop an effective solution for your operation.

Monday, January 11, 2016

Process Control - Five Categories of Instrument Protection

Industrial process temperature and pressure gauges
Instrument protection is a key element of process design
and equipment layout
The performance of every process is critical to something or someone. Keeping a process operating within specification requires measurement, and it requires some element of control. The devices we use to measure process variables, while necessary and critical in their own right, are also a possible source of failure for the process itself. Lose the output of your process instrumentation and you can incur substantial consequences ranging from minor to near catastrophic.

Just as your PLC or other master control system emulates decision patterns regarding the process, the measurement instrumentation functions as the sensory input array to that decision making device. Careful consideration when designing the instrumentation layout, as well as reviewing these five common sense recommendations will help you avoid instrument and process downtime.

Process generated extremes can make your device fail.

Search and plan for potential vibration, shock, temperature, pressure, or other excursions from the normal operating range that might result from normal or unexpected operation of the process equipment. Develop knowledge about what the possible process conditions might be, given the capabilities of the installed process machinery. Consult with instrument vendors about protective devices that can be installed to provide additional layers of protection for valuable instruments. Often, the protective devices are simple and relatively inexpensive.

Don't forget about the weather.

Certainly, if you have any part of the process installed outdoors, you need to be familiar with the range of possible weather conditions. Weather data is available for almost anywhere in the world, certainly in the developed world. Find out what the most extreme conditions have been at the installation site....ever. Planning and designing for improbable conditions, even adding headroom, can keep your process up when the unexpected occurs
Keep in mind, also, that outdoor conditions can impact indoor conditions in buildings without climate control systems that maintain a steady state. This can be especially important when considering moisture content of the indoor air and potential for condensate to accumulate on instrument housings and electrical components. Extreme conditions of condensing atmospheric moisture can produce dripping water.

Know the security exposure of your devices.

With the prevalence of networked devices, consideration of who might commit acts of malice against the process or its stakeholders, and how they might go about it, should be an element of all project designs. A real or virtual intruder's ability to impact process operation through its measuring devices should be well understood. With that understanding, barriers can be put in place to detect or prevent any occurrences.

Physical contact hazards

Strike a balance between convenience and safety for measurement instrumentation. Access for calibration, maintenance, or observation are needed, but avoiding placement of devices in areas of human traffic can deliver good returns by reducing the probability of damage to the instruments. Everybody is trained, everybody is careful, but uncontrolled carts, dropped tools and boxes, and a host of other unexpected mishaps do happen from time to time, with the power to inject disorder into your world. Consider guards and physical barriers as additional layers of insurance.

Know moisture.

Electronics must be protected from harmful effects of moisture. Where there is air, there is usually moisture. Certain conditions related to weather or process operation may result in moisture laden air that can enter device enclosures. Guarding against the formation of condensate on electronics, and providing for the automatic discharge of any accumulated liquid is essential to avoiding failure. Many instrument enclosures are provided with a means to discharge moisture. Make sure installation instructions are followed and alterations are not made that inadvertently disable these functions. Moisture also is a factor in corrosion of metal parts. Be mindful of the extra degree of protection provided by special coatings or materials that may be options for your instruments.

Developing a thoughtful installation plan, along with reasonable maintenance, will result in an industrial process that is hardened against a long list of potential malfunctions. Discuss your application concerns with a knowledgeable instrument sales engineer. Their exposure to many different installations and applications, combined with your knowledge of the process and local conditions, will produce a positive outcome.

Monday, October 19, 2015

Welcome to Flow-Tech's Maryland & Virginia's Process Control Blog

Virginia and Maryland Process Control
Serving Maryland and Virginia
Flow-Tech, Inc. has been specifying and applying process instrumentation and control valves in the Maryland and Virginia markets for over 40 years. Flow-Tech's outstanding growth in sales and reputation is directly a result of our consultative sales approach, delivered by our team of knowledgeable and experienced Sales Engineers.

We see this blog as an extension of that process where today's customer can learn and discover at their own time and place, narrow the selection of products and vendors, and then  arrange for me focussed presentation with a salesperson.

This blog will be populated with post we think you will find interesting and education in the area of process instrumentation and control. It will be updated frequently, so please check back often.