Emerson Exchange 365

For a while car designers experimented with digital speedometers but got rid of them in favor of the old-fashioned needle and scale. We may like digital things, but our brains are still analog. That’s probably why traditional pressure gauges have never gone away.

Emerson’s Wally Baker reexamines this discussion in a recent article in Flow Control magazine titled Selecting Pressure Gauges: New Advances on an Old Technology. Wally reminds us that users like pressure gauges for their simplicity and analog display, but they don’t like the mechanical headaches:

Traditional gauges have some serious drawbacks to consider in the selection process. Gauges operate using delicate mechanisms with springs and gears, making them vulnerable to shock and damage. Most operators have seen typical failures with broken glass, bent indicator needles or needles pointing straight down from broken gearing.

So is the day of the pressure gauge over? Not by a long shot, but figuring out the best choice can be a challenge. The article offers advice on four key points:

1. Ruggedness – Some models are designed for environments in which pipes vibrate or moving equipment may cause impacts.
2. Material of construction – While the cheapest devices are mostly brass, industrial-grade gauges are usually made of stainless steel or other durable materials.
3. Inlet configurations – Most larger gauges have a male-threaded inlet, usually ½-inch national pipe thread (NPT) or M20. Some offer more specialized options for more complex mounting situations, such as adding a siphon.
4. Overpressure and burst pressure limits – An overpressure limit says how much a unit can withstand without damage. Burst pressure is where some component fails, usually the Bourdon tube, blowing the case open and releasing process fluid to the atmosphere.

Wally goes into more depth, but for users who work with pressure transmitters, like our 3051, these represent new and often different considerations. Terms like snubber, isolator and siphon become part of the mechanical gauge world—and making the wrong selection of gauge or accessories can make for a frustratingly short lifespan. The alternative, as the article points out, is to retain the convenience and functionality of a mechanical gauge while getting rid of all the mechanics, by using an electronic gauge, like the Rosemount Wireless Pressure Gauge:

Some of the newest designs combine the benefits of an electronic transmitter with the usefulness of a traditional mechanical design. They use a strain-relief sensor rather than a Bourdon tube, processing the signal electronically rather than mechanically. The needle is driven by a tiny motor, so only one moving part is present, making the mechanism far more resistant to shocks and other extreme operating conditions.

So we retain or regain the ability to think analog when we can look at the face of the dial and see the needle and scale. In an instant we know where we are in the overall range, and get a sense of whether we’re high, low or just about right. That’s the beauty of an analog device. But at the same time, we gain digital advantages:

Using sophisticated electronics, these new gauges are also able to monitor their own statuses. No way exists to verify a mechanical gauge is working properly short of removal from the process and testing, but a glance at an electronic gauge can show its operational status by a blinking LED. Even the battery life has been extended thanks to low-power electronics and highly efficient designs.

Electronic gauges also solve the old problem, what good is a gauge if nobody is there to read it? Using WirelessHART, the Wireless Pressure Gauge can send its reading and diagnostic information to a DCS or other plant automation system:

[The Rosemount] wireless pressure gauge contains all the features of an electronic gauge while adding the capability to transmit its pressure reading via a WirelessHART mesh network. This additional communication capability adds “future-proofing” so it can be used in a sophisticated networking environment as the Industrial Internet of Things moves into more manufacturing applications. The wireless capability might not be needed today, but it may be soon.

The Wireless Pressure Gauge fills an important gap in the range of pressure measuring devices. On the one end, there’s the 3051 pressure transmitter with a high degree of sophistication and designed to work in a fully automated environment. On the other hand, there are inexpensive but failure-prone mechanical gauges. The Wireless Pressure Gauge fits nicely between the two.

Find out how people like you are using the Wireless Pressure Gauge. Join our Emerson Exchange365 community, and look for the Pressure Group to interact with your peers and our experts.