Pressure gauges are perhaps one of the most important instruments in a plant’s tool belt. They are critical for both safety and process reliability. However, their importance seems to be underestimated, or even ignored.
A major analog pressure gauge manufacturer has found that in any given plant, *25% of gauges are broken and another 40% need immediate corrective action.
This alarming statistic is reflective of two problems. First, we don’t take pressure gauges as seriously as we should. Second, analog pressure gauges break too easily.
So with that in mind, we wanted to discuss which of those broken analog pressure gauges should be replaced with a more accurate, more durable digital pressure gauge.
We came up with 3 basic categories where a digital pressure gauge should be required:
Accuracy is never more important than during calibration and testing. While a typical analog gauge might offer moderate accuracy – with an error band of only 1% - digital pressure gauges step it up in a big way. It’s easy to find a digital gauge with an error band of only 0.1%. That’s 10x better!
Here are a few examples from our customers:
Infusion Pump Alarm Calibration
An infusion pump puts liquid into your circulatory system, typically through an IV. You might also think of it as an IV pump. Their reliable operation is absolutely critical for the safety of the patient and the liability of the healthcare institution.
The pump has a critical alarm called the “Downstream Occlusion Alarm.” This alarm tells the doctors and nurses when the IV tube has become obstructed. The alarm is pressure based. When pressure builds up on the discharge side of the pump, the alarm sounds.
To keep the alarm in spec, a pressure gauge is used to set the alarm. However, the accuracy must be 0.1% in order to ensure proper performance. Therefore, a digital pressure gauge is a must.
In fact, many infusion pumps are calibrated using our PG5 with a range of 30.0 psig and an error band of only ±0.03 psig, or 0.1% of full scale.
Brake Leak Detection
To accurately detect a leak in a brake system, a sensor must be able to detect minute changes in pressure on a relatively large full scale. This is only possible with digital pressure gauges, and requires a very high resolution – resolutions of 0.01 and 0.001 are quite common.
A prominent locomotive manufacturer uses our digital pressure gauges to monitor their brake lines. They’re looking for pressure changes as low as 0.023 psi on a 20.00 psi gauge.
No Interpretation Needed
No matter the application, really, any reference gauge – what you call a gauge that’s used to test, calibrate, or monitor other vital equipment – should be a digital pressure gauge.
When accuracy is on the line, it’s difficult to trust anything else. A digital pressure gauge tells you exactly what the pressure is at any given point in time, no guessing at numbers or needle position. No interpretation required.
Visibility on an analog gauge is at a bare minimum. Checking pressure requires constant rounds with a clipboard, walking, climbing, or ducking to get to wherever the gauge may be. And control is essentially non-existent. Analog gauges are strictly for monitoring.
Digital gauges, on the other hand, help you improve both visibility and control. They’re much easier to read, eliminate guessing at the exact needle position, can be read at a distance, and can come with outputs for integration with your SCADA system. Some even have trip points for basic stand-alone control of valves, pumps, or alarms.
Sending a signal to your SCADA lets you modernize your measurement at critical locations while maintaining a local display for operators on the floor. You don’t have to choose between a pressure gauge and a transmitter anymore.
Here are a few examples of our customers improving visibility and control:
Vehicle and Equipment Lifts
We have a few OEM customers using our digital gauges as displays for their lifting equipment. This task was once done with an analog gauges, but is much better served with digitals.
The primary reason is better visibility. Not only is digital display easier to read, but our gauges also do the conversion from psi to just about anything else – like weight.
One example comes from Tinker Air Force Base, where they operate B-52 bombers. When the aging B-52 is down for maintenance, the crew uses up to 38 jacks to lift the aircraft off the floor. They use our 4.5-inch diameter PG10 high visibility digital pressure gauge on each jack to ensure an even distribution of weight.
Keeping the weight evenly spread out is critical to protect the older airframes from structural damage. The B-52 has been out of production since 1962, but through upgrades and careful maintenance, the existing fleet is estimated to remain in service until 2045.
Using a very accurate and very visible digital pressure gauge allows the maintenance crew to carefully lift the aircraft for service without shortening its expected lifespan.
Pump Control
Seasoned pump consultants like the world-renowned Larry Bachus would tell you that proper pump control requires pressure gauges. While accuracy is less important for pump control, visibility and control are vital.
Digital pressure gauges are advantageous because they offer outputs and trip points that can be used to signal the SCADA system and light up alarms or shut down pumps. They also convert psi to head to help the operator compare the measurement to the pump curve.
Most recently, a sugar mill in Central America invested in some PG7s for pump monitoring and control with great success. The digital format makes reading the gauges much easier when vibration picks up – a common occurrence in any processing plant.
We even offer a pressure gauge with a cable between the sensor and the display, so you can remove the electronics from the vibration, heat, or mess of the connection point to the process.
Digital pressure gauges offer a lot of advantages to pump control, especially in hard to reach places, dirty environments, or high vibration.
Considering A Transmitter
A good rule of thumb is to use a digital gauge whenever you’re considering replacing your old analog gauge with a transmitter. A digital pressure gauge with an output will give the same benefit of a transmitter, plus the local display of a gauge, for about the same cost.
You can tackle visibility and control with one device, whether it’s in the control room or on the plant floor.
Our analog gauge counterparts have found that many gauges are in various states of disrepair. The problem may be a lack of understanding of how to properly use gauges; it may be a reduction of the workforce; or it might just be a problem of instrument durability.
Of course, it’s likely a mixed bag at every plant. Digital pressure gauges, however, can help with at least two of those potential causes.
Replacing analog gauges in harsh environments with digital gauges makes a lot of sense. Without moving parts, and with better resistance to overpressure, digitals are intrinsically more durable. Which means a leaner workforce can keep them in service much easier.
Perhaps even more important, a digital gauge doesn’t have a long bourdon tube that can foul up.
Filter Monitoring
A great example from one of our customers is filter monitoring. Pressure gauges are often used to monitor filters, whether to pull a differential measurement, or to monitor the upstream, or suction, pressure for an increase.
One customer monitors the upstream pressure in a paper towel manufacturing plant. These filters remove paper pulp from waste ink used in the printing process. The filters can clog rapidly, potentially damaging downstream equipment if not changed quickly.
A bourdon tube would easily foul with so much paper pulp in the ink, where the digital gauge is unaffected – no diaphragm seal required. Additionally, the gauge sends a signal to the HMI control system to notify personnel when the filter needs changing.
The bottom line: use digital pressure gauges whenever you need accuracy, better visibility, control, or durability out of your pressure gauge. Doing so will reduce the number of gauges you have in disrepair and will improve the overall safety and reliability of your plant.
There are several options that will specialize your digital gauge for your specific application. Contact us to learn more about how digital pressure gauges will provide you with better measurement.
*http://www.designnews.com/author.asp?section_id=1386&doc_id=268779
