Podcast: 3 Types of Control Valve Trim. Episode #2

In this episode of Stuff You Should Know about Oil and Gas, Kyle Andrews, Product Applications Trainer at Kimray, explains the three primary types of control valve trim: Snap Trim, Nominal Trim, and Equal Percentage Trim.

Topics in 3 Types of Control Valve Trim

Which trim is best for liquid dump valves, gas back pressure valves, pressure relief valves and more.

Resources mentioned in this episode:


Curtis: Hello and welcome to the stuff you should know about oil and gas podcast. My name is Curtis Winkle and I’m here with Kyle Andrews. Kyle is an account manager at our Oklahoma City store. And he does a lot of good for a lot of customers, provides great customer training, those kind of things.

All right, the subject we want to talk about today is types of control valve trim.

So, there are three types that we offer in our High Pressure Control Valves, right? So, what is valve trim? Why is it important? Tell us a little bit about it.

Kyle: All right the three different types of valve trim are equal percentage, nominal, and snap. Those are the three trim types that we offer.

Curtis: And they have alternate names, right?

Kyle: Yes, especially snap trim. So, snap trim could be also a quick-opening or carbide trim or CB. And Linear could be nominal as well.

Curtis: Alright, so we’ve got snap, AKA quick-opening carbide. Then we got nominal, AKA linear and then we’ve got equal percentage.

Kyle: Equal since there’s really no other EP for sure.

Curtis: So, there are three primary types that we offer. Can you break it down for us when we talk about trim, are there a few components we’re talking about?

Kyle: So, there’s going to be a valve seat. And then there’s going to be a ball and a stem. So, there’s two components there.

The ball and the stem are one piece soldered together. And then the valve seat. And the ball seats inside that seat, cutting off the flow.

Curtis: That’s the main path where flow is going is between that ball and seat.

Kyle: Yeah and the differences between these different trim types is the curvature of that seat. That’s what changes between these trim types.

Curtis: Okay. So, the ball is not necessarily going to change. The material might change, but it’s not correct? So, the main thing we’re talking about is the change of the seat and the trim. So, what is snap trim?

Kyle: The goal of snap trim is to get the valve to open up as quickly as you can. So, once the valve, there’s a carbide insert in that seat. And where the ball rests on it and seats off. So, it’s a very small contact area. So, once that ball moves off seat, the valve opened up very quickly. If you’re looking at the flow curve of the snap trim, I think it’s at about 50% of stem travel.

So, when you’re 50% open, you’re at a hundred percent flow. So, it opens up very quickly. A reason for that is when you’re using that in an erosive surface, so you have sand or other solids in your liquid or you want that valve to open up very quickly. You don’t want it to just barely open because it cuts out the trim.

Curtis: The sand is going to eat away.

Kyle: Exactly. So, to save the trim and make it last longer, you want to use snap trim in those types of applications. So liquid dump valve or erosive liquid.

Curtis: People are dealing with erosion a lot now. Is that right? Primarily, you recommend that during flowback or for the life of the well?

Kyle: As long as they’re solids present. So, yes definitely during flowback, but certain producers have seen sand still coming back 9- 12 months after flowback. It can last quite a bit of time.

Curtis: Is it formation sand or proppant?

Kyle: It’s proppant and everything that they fracked the well with still coming back.

It can last quite a while and you just want to keep that carbide trim in there as long as possible, until that sand goes away.

Curtis: So, if they’re getting carbide trim and they’re going to snap. Do we recommend carbide with the ball as well?

Kyle: No, the carbide that we’re talking about is the insert that’s in the seat.

Curtis: Okay. So, that’s the main area that’s vulnerable. That’s why it’s made with carbide.

Kyle: Also, when you’re using carbide trim, if you’re retrofitting a valve and if you’re using a through body valve with carbide trim, the carbide trim will probably outlast the valve body. So, if you have highly an erosive application, you want to make sure you’re using an angle body valve.

Curtis: Yeah, go into that a little bit. So why angle body? What is going on in the through body?

Kyle: The flow path over the trim is that you’re coming from up over the ball and up over the seat. So, when the ball opens up off the seat, you’re going up over and through. And with the through body valve, the flow has to change directions several times.

Curtis: This is what they call like the S curve, right?

Kyle: Right, in a globe valve. So, what ends up happening when you have a lot of sand, is when you’re changing directions ends up hitting the bottom of the valve and wearing that out cause it has to change direction that once it comes up over the seat, it hits that valve body and has to change direction and to get out of the valve.

Curtis: So, is that through the seat or just around the seat?

Kyle: It wears a pinhole directly underneath the seat in the body to mitigate that you need to use an ankle body valve. So that way, as soon as it comes up over the seat, where’s that pin hole out in the through body? That’s the exit. It just going straight out of the valve and it’s in the pipe at that point. So, using it in highly erosive applications, using carbide trim and an angle body valve, that’s the best thing you can do.

Curtis: Okay, so how about these other ones? So that the nominal trim, where is that? The best application for nominal.

Kyle: So nominal trim or linear or can be used in a bunch of different applications. But mainly it’s just used for liquid dump valves. It’s not erosive. Oil dump valves, water dump valves if there’s no sand or erosive material. Some people use it for gas regulation, as long as it’s sized correctly, it can be used for gas regulation.

We don’t recommend it necessarily. So, equal percentage, let me back up. Nominal can be used for liquid dump applications. Some people use it for gas regulation. We don’t necessarily recommend that.

Curtis: What do we recommend for gas regulation?

Kyle: Equal percentage trim. And with nominal trim, it’s also called linear.

So 50% open should be about 50% of flow. 10% open should be about 10% flow. Every trim size is a little bit different and we have flow curves for each trim size on our website that you can look at, but linear trim, mostly used for liquid dump applications and some gas regulation.

The advantage of using equal percentage trim and gas regulation is it opens up very slowly.

Curtis: Okay, so we’re moving to the third one, that’s equal percentage. The best application for that is gas regulation?

Kyle: Gas regulation and the reason being, if snap trim opens up extremely quickly, equal percentage trims kind of on the other end, it opens up slowly. A 10% movement in valve opening isn’t going to equal a 10% increase in flow. It’ll be less than that. When you’re sizing for gas regulation and you’re using equal percentage trim, I like to size from anywhere in the 15% to 50% open range after 50% equal percentage trim opens up more quickly.

So, when you’re sizing you want to stay within that first 50% of stem travel for equal percentage. If you’re wanting to use equal percentage trim and applications, like gas control. So, pressure control or applications where you’re wanting to throttle. EP trim can be used in a liquid dump application if it’s sized correctly. EP doesn’t mean you can only use it in gas applications. You can use it in liquid applications as long as it’s sized correctly.

Curtis: So, when you say throttling, it’s going to be not quite closed, not quite open for a lot of its life or ….?

Kyle: Correct. So, it’s not going to be open and shut.

It’s going to be partially open, controlling flow or pressure just because of the small change in flow when it opens and closes. It’s consistently and constantly hunting to keep that set point.

Curtis: So, what’s an example of an application that you want equal percentage trim?

Kyle: Pressure regulation.

Curtis: Okay. So back pressure or ….?

Kyle: Yes, back pressure, pressure reducing and anytime you’re wanting to control a pressure set point or even if you’re wanting to control flow of something, EP is the best way to go.

Curtis: Alright Kyle, so we talked about the three main types of trim. They’re snap, nominal and equal percentage. Let’s talk about the materials that these things are made with. What are the common applications where we’re looking at different materials?

Kyle: Yeah, so there’s three different ones. There’s going to be standard applications. There’s going to be a corrosive applications and erosive applications.

Curtis: Alright, so elaborate.

Kyle: Standard is a D2 tool steel as the material. Erosive applications are going to be carbide material.

Curtis: We’re dealing with sand solids in our flow?

Kyle: Yes, and earlier I mentioned carbide, or snap trim.

So, carbide is a material, but we also refer to that as our snap trim as carbide trim. So, it’s what we call our snap trim, but it’s also a material. Now in applications where carbide trim is failing or it’s not lasting as long as you want to zirconia trim can be used. It’s another step up from carbide trim and erosive service. It lasts much longer. It’s also much more expensive, but you get what you pay for and so it’s going to last quite a while.

Curtis: So, if I want to go absolute top shelf, I got sand like crazy. I want to go angle body, zirconia, and snap trim?

Kyle: Yeah, that’s going to be the best bet for erosion.

Curtis: Ok, so that last condition is corrosion?

Kyle: Yep. So corrosive applications so things like we have sour gas, CO2 we’ll need when working with salt water or anything that corrodes away that material, you’ll want to use 3/16 stainless steel.

Curtis: Okay. So, it’s better than the carbide or the D2 at withstanding any kind of corrosive elements in your flow.

Kyle: Yeah.

Curtis: Methanol gases or..?

Kyle: Yeah.

Curtis: Alright Kyle, I appreciate your time. Thanks for joining us on the Kimray podcast. We’ll have links to the material that we mentioned, and there’s a great chart on the three types of control valve trim and a video we’ve made, and any other of the products that we talked about in the show notes. We’ll catch you next time on the Kimray podcast.

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