Modifying A Hand Operated Globe Valve To Be Remotely Controlled

If it has a motor in it, then intrinsic safety cannot be applied as a protection concept.

Good grief, though! What hard work! Why not just buy one? And if the right type of actuator cannot be found, why not use an intelligent I/P converter in the safe area and drive the valve with wind?

Unfortunately, I can't afford one. I'm doing research for a company but have very little knowledge about valves even though I've spent a considerable amount of time learning about their basic structure and operation. However, the many options of control and networking such as fieldbuses and control software overwhelm me. I don't know what an intelligent I/P converter is but I will research it. I also don't know how I would drive the valve by air but most importantly I don't know what methods I could use to connect the valves to a safe area. The actuator has to be powered by something and mostly likely with wireless control electricity will have to be used somewhere. So yes, it is difficult problem.

Then mug-up on the principles of electrical safety in potentially explosive atmospheres. BS5345 and its eurochildren will give advice on what can be done and what can't. Also, check out the websites of a few local valve distributors and see what can be learned.

The reason that air is used for valve actuation is that it is non-incendive and non-sparking, and ideal, therefore, for use where other methods of signal ttransmission and power actuation are constrained by the application within an potentially explosive atmosphere.

If the actuator must be electric <sigh> then EEx d will be about the only protection technique applicable for Zone 2 and Zone 1 use.

There isn't an electric valve actuator built that is suitable for Zone 0.

You want to automate a flow stream on a Profibus control system and you can't afford to replace a manual metering valve with an automated valve? Your budget needs a reality check.

I think I may of confused you. I'm just doing research for a company, which I am doing quite well on, but coming up with a way to wirelessly automate valves that meter 100% oxygen is the part that I'm having difficulty with. I'm not buying anything. I just need suggestions on a safe way to operate the valves wirelessly. I will take PWSlack's advice and try to figure out a solution with air/pneumatics, which I considered before but I didn't know about current to pressure converters so it seemed impossible until now.

Sorry for the confusion.

Please go to. http://www2.emersonprocess.com/en-US/brands/tescom/Pages/Tescom.aspx

When you say you can't afford to buy a motor valve - have you considered the cost(labor) you are going to expend, not to mention the trial & error??? Save yourself weeks of aggravation!

If your end goal is wireless comm, you need to consider what communications hardware link and protocol will be used to as a control signal by a positioner to drive an actuator, which drives the valve to its position to regulate the flow.

THE conventional control signal in the industrial world is analog 4-20mA. You mentioned an alternative, Profibus. But there are two Profibuses, DP and PA. To my knowledge, Profibus DP has commercially available wireless solutions (Elpro, Phoenix Contact, others) because it runs on an RS-485 hardware link, but I haven't seen Profibus PA wireless components.

A huge number of valve positioners, nowadays a 'smart' device that receives the control signal and regulates the air pressure to the valve acuator, use HART, a digital protocol that rides on top of the conventional 4-20mA control signal. A number of HART wireless devices are coming to market, since the publication of a wireless HART standard about a year. I know Siemens' PS2 positioner has a Profibus PA option, which, as I read its spec sheet, is rated EEx ia, intrinsically safe.

So, today you've got commercial wireless for
- Profibus PA
- 4-20ma
- HART

The degree to which any of the above are intrinsically safe is model specific. I'm inclined to think HART can be I/S given its deployment. I do know that the Banner Engineering DX99 radio is intrinsically safe 4-20mA wireless for Class 1, Div 1 (it doesn't do HART).

All this assumes that you locate a vendor for a modulating control valve with an actuator and positioner suitable for oxygen service, which has a control input for one of the above control signals.

While it is common for valve positioners to have a fieldbus (Profibus, HART, Foundation Fieldbus) control signal option, I'm not sure whether there's any fieldbus I/P. The inherent concept of 'I/P', 'current-to-pneumatic', does not necessarily exclude HART (which runs on a 4-20mA current loop), but I'm not sure there's a commercial market for such. Maybe Google could help on that.

FYI, a topic like this would garner more specific attention in the instrumentation forum.

Once again Carl E your advice is golden. I have stated that I'm not familiar with valves in my two posts that I've posted here on CR4 just so I don't miss out on anything new about what I think I know already but in actuality I realized that even before my first post I knew about 90% of what everyone has told me so far. However, your info in this post has added to that knowledge in the succinct manner in which I was looking for. In addition to PWSlack's info about I/P converters, you have helped me narrow my scope on what I should research to solve the final piece of my puzzle. Also I never know which forum category to posts these things in so much thanks for that.

Profibus also has a newer technology I wanted to give a try. It is mostly Ethernet based. It is called PROFInet IRT and it boasts a speed of 1Gb/s. I mainly just want to use a TCP/IP protocol for communication.

There is one question I have about valve positioners and valve actuators that I couldn't find a clear answer to on the web or books I have access to: How does the actuator and positioner actually fit on the valve itself? More specifically these hand operated valves the company wants to use are small if you look at the data sheet I provided in the first post, but how do you actually get the positioners and actuators on them? It seems like a silly question but I need a picture or just a clear description to understand.

Once again, much thanks to you.

Tescom (Emerson) makes actuators for their valves. STOP re-inventing the wheel!!!!! You're going to spend so much time on what's already been done! I have thousands of valves in my facility. A few hundred are Tescom.

Believe me I would if I could but I'm supposed to modify whatever valves they pick. However, since they are asking for a reccommendation then I guess that's what I'll do. I don't know how well it will go over with them but you guys know a lot more about valves than I do and if the concensus is to get the valve-actuator-positioner combo then that is what I shall try to push.

It isn't clear to me what kind of flow rate you're talking about, but given that the valve had a knob and not a handwheel, I'll assume it's fairly low flow.

The low flows that I've used in the past are Research Control valves:
http://www.badgermeter.com/Industrial/Valve-Products/Research-Control-Valve.aspx

The valve connects to a bonnet or a bracket that holds the actuator. The bottom one is another brand ball valve.

The reason for everyone is telling you to get a new valve/actuator/positioner is exactly the issue you bring up: putting it all together.

Unless you wanna be a '60's hotrodder and measure and cut and weld to make all the pieces fit together and line up and work properly, one buys an entire assembly from a single vendor who makes sure all the pieces fit together and line up. It is NOT a trivial task. Assembling the pieces isn't, but making them in the first place is.

A note on Profinet. As I recall from a Profinet seminar a couple years ago, Profinet is designed for motion control, it even got its own IP (?) port assignment, hence the high speed throughput. I suspect that you'll might find very, very limited implementation of Profinet in the process world, which is where a typical panel mounted, low flow modulating valve lives.

Sounds you be off a valve package with controller.

Having had to retrofit actuators in the past it is usually simpler, cheaper and saves many headaches to get the package unless it is a very large valve or cannot be removed.