Monitoring pressure relief valves helps producers and manufacturers maintain safe and sustainable operations. In this 12-minute YouTube video, Elevating Safety & Efficiency: Emerson’s Revolutionary Approach to Pressure Relief Valve Monitoring, Emerson’s Ricardo Garcia demonstrates how this monitoring works and introduces the innovative bellows leak detection solution.
Transcript
Hi, I’m Ricardo Garcia, product manager for digital transformation PRV [pressure relief valve] monitoring. Today I’m here in Stafford, Texas to talk more about our Monitoring Solutions.
Why do we do monitoring? Undetected pressure relief events can lead to serious consequences in plants. We’ve categorized these consequences into four main buckets as we see as the reasons why the market is starting to adopt PRV monitoring.
The first one and probably the most important one is emissions. When these valves go off we’re putting emissions out into the atmosphere. Number two is productivity. Product losses and energy and process optimization is something we can achieve through PRV monitoring.
Number three is reliability and this pertains to how available our process is and how we optimize our asset utilization. And then, number four is safety. PRVs are a compromise between safety and emissions, so we protect personnel by knowing when these PRVs are going off.
Next we’ll talk more about the each individual solutions more in depth. This transmitter is capable of detecting pressure relief events when a valve goes off. The Rosemount 708 acoustic transmitter is a wireless only, non-intrusive device that’s also valve agnostic. And what we mean by those two things, non-intrusive means that it can just go strapped on the outlet of any PRV and that it takes us to the other portion—the agnostic type. So it goes on the outlet of a direct spring valve as well as a outlet on a pilot-operated valve. It can go on the outlet of an Emerson valve or a competitor’s valve.
And it works the following way. It uses two variables. The first one is it measures the acoustic turbulence at the outlet of the PRV when the valve opens. And then, the second one to validate what’s a positive, a true pressure relief event versus a false positive, it uses temperature validation by measuring the skin pipe temperature at the outlet.
Next we’re going to open up the isolation valve underneath this valve to create a pressure relief event and the 708 is going to catch that. In this graph, we’re graphing the system pressure with a different pressure transmitter that’s not part of our solution. We’re also graphing the pressure at the inlet of the Omni PRV.
But more importantly we’re graphing the two variables from the 708 mounted at the outlet piping of the Omni. The first one in blue we’re graphing the acoustic counts that go from 0 to 150. This will indicate when there’s acoustic turbulence at the outlet of the pipe. In green, we’re graphing the skin pipe temperature also at the outlet piping of the PRV. For our demonstration, since we’re using compressed air and at ambient temperatures, there will not be a change in skin pipe temperature. But in the real world scenario when we have temperature or product that is hot or cold, we will see a rate of change accompanying the acoustic count change.
So as we can see here, the graph shows us when the valve opened and when the valve closed. There is no way to correlate the acoustic counts to how much the valve was opening. So basically, the information that we get from the 708 is discrete. Valve is closed all the way up to here and then it opens and it recloses at this point giving us a time stamp of when the pressure relief event happened, as well as the duration of the pressure relief event.
This is our differential pressure transmitter, which we use for our high-pressure and low-pressure Emerson pilot-operated relief valve monitoring. The way that this works is the main valve has a pressure pickup port. We take the high side of the differential pressure transmitter into the pressure pickup port at the inlet of the main valve, and we take the low-side of a differential pressure transmitter into the dome at on top of the main valve.
There is a direct correlation between the differential pressure between these two points and the valve lift percent. There’s also a direct correlation between valve lift percent and flow. We’re going to operate this modulating-style pilot valve by opening gradually the regulator upstream of the PRV.
First, I’m going to throttle this valve on or about 30% open, and then we’re going to simulate another over-pressure event happening, and the valve will go into further lift, and then we’ll close the valve back down.
In this graph, we’re graphing a system pressure with a different pressure transmitter that is not part of our solution, as well as the inlet pressure. But more importantly we’re graphing the lift percent from the Rosemount 3051 that’s attached to our 400 series pilot. In this graphing software we’ve added the mathematical formula to convert differential pressure to lift percent.
As you can see from the graph, we just saw the differential pressure gets correlated to that valve percent lift as we track the lift over time. Having this information can help you quantify what was really happening at the outlet of a PRV when your PRV was open so you can quantify the flow through that valve.
We use bellows out in the field when there’s cases where variable back pressure is present. But metal formed bellows can fatigue over time because they’re always under constant pressure and exposed to corrosive media and high temperatures. What happens is over time that bellow can break. This is an example of a real-life bellow that broke in the field. Because of preventative maintenance cycles, these bellow ruptures can go undetected for long periods of time.
So Emerson has developed a new solution to detect when a bellow leaks in the field. Our solution entails two components. The first one is the backup piston. The backup piston ensures that even in the case of a bellow’s failure, the valve remains balanced against back pressure. It also reduces the fugitive emissions through the bonnet vent by up to 90%. The other component of our solution is a pressure transmitter that’s tubed into the adapter. This pressure transmitter notifies the personnel immediately of a pressure relief event and also gives you the amount of information needed to calculate how much the leak is flowing.
For this demonstration, we’re simulating the effects of back pressure with this adapter on the outlet flange. We’re going to open up this line and expose the valve to back pressure. There is a bellows inside this valve that has a pinhole leak. When we open up the back pressure, we’re going to see flow through the bonnet vent and the transmitter and the graph is going to catch that immediately.
In this graph, the only thing we’re graphing is the pressure at that secondary chamber that gets created between the bellows and the backup piston. With a undamaged bellows, you should never see any increase in pressure in that secondary chamber. Any increase in pressure that you see in that secondary chamber means that the bellows has been compromised.
A customer can interpret this logic and provide instant notification of a bellows failure to their operators. Also they can use the information from this graph as well as the clearances from the piston that we provide to convert this pressure into a flow.
We use a Rosemount 3051 or a Rosemount 2051 for our differential pressure transmitter and bellows detection solution. There are some benefits when we use the Rosemount 3051. The first one is accuracy. The accuracy on a Rosemount 2051 is 05% of the span calibration, and the accuracy on the 3051 is slightly better with 04. There’s also the added benefit of advanced diagnostics, which are mostly available on a 3051, which can tell you more information about the health of your transmitter.
Finally, there’s the added benefit of Bluetooth connectivity using the 3051, which can help you set up from the comfort of an office if you’re close enough to the transmitter. Or, not having to climb all the way up to where these valves are located. We have the capability of selecting either wired or wireless with all our solutions except for the 708. The 708 is wireless only for all of our other solutions. It’s customer preference and whether they have an already an existing wireless infrastructure.
We have different options on how to interpret the data that we get from these devices in the field. For the Rosemount 708, we could either bring in that raw data and interpret it in our control system using logic. Or, you could use a prepackaged software called Plantweb Insight that does the analytics already for you. It filters out what’s a false positive from a true pressure relief event.
On all of our other solutions that data has to be brought in and interpreted at the local control system. We are working on getting these other solutions up to Plantweb Insight to have a turnkey solution if that’s what the customer desires. But currently, you’d have to convert the differential pressure signal into a lift percent with equations that we as Emerson provide.
And it’s the same for the bellows lift detection. If you wanted to calculate flow, we’ll give you the formulas that you need to calculate flow.
After demonstrating these technologies today, I hope it is clear that Emerson has different solutions for pressure relief events or monitoring valve health, like we do with the bellows leak detection. For more information, please visit the PRV Monitoring website or contact me directly.
Thanks for watching.
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