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Last updateWed, 23 Aug 2017 6pm

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Valuable Insight from Valve Actuator Users

Valuable Insight from Valve Actuator UsersA technician downloads data from an actuator at a wastewater treatment plantOnce valves and actuators are installed and commissioned on site, the manufacturer’s involvement often lapses to an occasional service call. However, because they’re unaware of the subsequent life of the automated valve, they miss valuable feedback that an end user could give on how that equipment performs.

What users can provide

The perceptions users have of how actuators perform as well as the likes and dislikes those users have of a product are not always evident to the manufacturer. Too often manufacturers make design decisions based on assumptions, thereby missing the real requirements of the user. For example, because of the growing use of smart actuators in many industries, many designers assume users need or want certain features that “smart” can offer. But how many of the features are essential and which are redundant?

To gain insight, CPLloyd Consulting Inc. went straight to end users for feedback on actuator experiences. The results show issues that are common across the industries canvassed.

Overall, valve actuators are given high marks for reliability and performance, but problems with actuator sizing and stem lubrication are often mentioned.

These extracts of certain questions from the survey give a sampling of what can be learned.

WHAT THEY SAID

Electrical foreman, potable water treatment plant, Pennsylvania

What actuators do you use, and why?
We use electric actuators only; it’s always been that way. Although we did have a pneumatic unit on a plant bypass valve, we replaced it with an electric DC unit run on standby batteries.

Electric actuators you can pretty much leave alone; they require little maintenance. We have high humidity, and there is some chlorine in the plant. Occasionally, there may be a corrosion problem, but it’s usually minor.

Failures are infrequent and if a valve fails to operate we get an alarm from the actuator.

What would you like valve actuators to do that they don’t do now?
In terms of technology, we don’t need any more than is available. In fact, we don’t use many of the diagnostic features. We have our own maintenance programs and additional information from the actuator would just confuse the issue. For example, a “change oil” alarm, such as you have on automobiles, would be redundant.

Valuable Insight from Valve Actuator Users 2Potable water treatment plant

How do you train your people on valve actuators?
We get most of our new product training from the actuator manufacturer, either by literature or support from the local rep. We do our own operator training in house.

What is important to you when you think of valve automation?
There are no improvements needed on the hardware. However, we do need good local support. The ability to pick up the phone and have technical help is important. This is mostly local, but if factory expertise is needed, we need it promptly as well.

Equipment is specified and procured by others in our organization, but we have not had problems with actuator support from the manufacturer’s local representatives.

Pipeline expert, Canada

What actuators do you use?
We use electric and electro-hydraulic actuators on our pipeline systems and have an installed base of about 15,000 actuators. Not many are pneumatic.

What would you like to have known earlier in your career that you now understand about valve actuators?
I would like to have learned more on the torque management aspects of automated valves when I first became involved with actuators. Torque levels are important, for example, on triple offset butterfly valves where the sealing is a direct function of applied torque. In general, torque management is poorly understood by users. The forces needed to close a valve and then reopen it, either electrically or manually, are not easily understood for the various valve applications. Also, the torque demand during travel is often unknown.

The drive train in valve actuators has remained fundamentally the same for some time—electric motors driving a mechanical gearbox. But consulting engineers still are unable to pick up on poorly sized actuators. Problems occur occasionally with undersized actuators that have to be replaced. Oversized actuators are rarer, but can damage valves if high torques are applied. Our local representatives are quick to resolve these issues when they occur, so the impact is reduced.

What challenges do you face with actuators?
The challenges with automated valves are in educating operators and introducing new technology. My company has good data collection capabilities, but a poor understanding of practical torque demand data. We could improve our operations with predictive maintenance and save costs using smart actuators. Operations insist on older technology actuators that are simpler and easier to understand, but miss out on newer developments that could help overall operations.

Do electric actuators need much in the way of maintenance?
In general, our actuators are problem free; this is typical for electric valve actuators. The main requirement for routine maintenance is on the stem nuts. These need regular inspection and lubrication to prevent premature wear and failure.

What else would you like your valve actuators to do for you?
On some of our valves, modulating capability is important, such as the control butterfly valves regulating the flow into multiple meter runs. Electro-hydraulic modulating actuators have this capacity, but are expensive.

Some valves close too quickly and can cause hydrodynamic shock in our pipelines. We need an easy way to slow down the valve closing speed as it approaches shut off.

The National Energy Board is mandating emergency shut down (ESD) valves on more installations. Some engineers are designing plants with diesel generators to power small numbers of electric actuators for ESD. There needs to be a more cost-effective solution.

Are there any features on your actuators that you like or dislike?
It is very hard to determine if some valves have seated correctly. Our practice is to set the position switches to trip just above the seating position and allow the actuator momentum to overrun this position and seat the valve. However, in icy conditions, this may give a false indication of valve seating.

Do you need much support from the manufacturer or the local representatives of that manufacturer?
We rely a lot on the local actuator representation for technical support and automation expertise. Fortunately, we are lucky to have a responsive local representative.

How do you train your technicians on valve actuators?
Knowledge on valve actuators is passed from senior to junior technicians in our organization—the tribal knowledge system of training. This makes local support from manufacturers and representatives imperative.

Senior Electrical Engineer, Shell Refinery, U.S.

What actuator types do you have at your facility?
We have about 500 motor-operated valves (MOVs) and some pneumatic actuators, mostly on control valves.

What would you like to have known earlier in your career that you now understand about valve actuators?
I wish I had understood that the control and feedback aspects need not be achieved only with the conventional hard-wired connections. Digital communications are a much better method.

The sizing of actuators for valves is so important. Often, engineering contractors and suppliers will size actuators for the theoretical process conditions. However, this does not take into account the process changes and aging effects on the valve. Over time, torque demand increases. I would prefer actuators to be sized to the maximum capacity of the valve.

What challenges do you face with actuators?
Getting the actuator limit switches set correctly is a big challenge. For gate valves that stop on torque, the close position limit switches may not always activate. This is often because of process material build up in the valve, which prevents full travel.

Do your actuators need much care and attention; what failures to you typically see?
We have seen spurious operations of MOVs. We have had some printer circuit board failures due to high vibration on the plant; some mechanical gearbox failures, but not many, if any, motor burn outs.

The main requirement for maintenance is on the valve stems, which need regular greasing. We do our major maintenance during turnarounds. We also download data from the actuators for trending.

Do your actuators do everything you need? What else would you like?
Most MOVs are located in classified areas. The data extraction tools for smart actuators need to be certified for use in a “Class 1 div 2 group C & D” environment. Permitting, for the use of non-certified devices, takes additional time versus a certified device.

Are there any features that you particularly like or dislike? What is the most important attribute that you need in a valve actuator?
The maintenance and operations interface needs to be more intuitive on smart actuators. We don’t want to have to use a manual to understand alarms and status symbols.

The local manual operator control interface—those manual switches for opening and closing the MOV—need to be very robust. Operators do not treat these devices gently.

The indication screens on smart actuators need to be easy to read, clear and visible.

Is factory support important?
Absolutely. It’s important for the manufacturer to have both service and spare part support. We like manufacturers to carry a supply of spares locally. Independent manufacturers’ representatives can do this, but we expect a good level of technical expertise.

Do you train your personnel on maintenance?
We train our technicians on troubleshooting, but it would be easier with an intuitive actuator interface.

Conclusion

It is surprising that some basic functions of electric actuators are still not performing to users’ requirements. Also, changes in valve conditions often effect performance of the automated valve after a period of time.

Although it is not always easy to get direct end-user feedback, the effort can be rewarding. For actuator manufacturers, designers and distributors, talking to end users can provide valuable insight into the effectiveness of smart actuator features as well as inspire new solutions to user problems.

Chris Warnett is the principal of CPLloyd Consulting Inc., which provides marketing and applications expertise for the valve automation industry and its customers. He has over 37 years of engineering, sales and marketing experience in valve automation. Warnett is also the author of the Amazon.com best-selling book Valve Actuators (2015).  

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