Last updateThu, 20 Oct 2016 8pm


Warriors, Welding and Wooing the Workforce

Warriors, Welding and Wooing the Workforce

For the last several years, one of the b...

New Test Standards for Low-E Compliance

New Test Standards for Low-E Compliance

Creating practical, unified standards fo...

Avoid Water Hammer Problems in High-Pressure Hydraulic Systems

Avoid Water Hammer Problems in High-Pressure Hydraulic Systems

Water hammer, high-velocity fluid flow a...

The Weekly Report

New Products

  • ja-news-2
  • ja-news-3

Industry Headlines


Industry Headlines

Automation Technology Launches New Maintenance Service


Automation Technology, LLC (ATI) announces the formation of ATI Frontline Services, a specialized maintenance service dedicated to providing oil and natural gas pipeline customers and other end users with expert field and shop valve actuator and accessory installation, testing, repair, replacement and...


GE Oil & Gas and SKF Sign Collaboration Agreement


SKF and GE Oil & Gas have signed a non-exclusive, license-based collaboration agreement, aimed at further developing the use of active magnetic bearing technologies within the oil and gas sector. The partnership also provides the basis for future collaboration, to widen the scope of applications o...


First New U.S. Nuclear Reactor in 20 Years Starts Operation


The nation’s first new nuclear generation in 20 years has officially entered commercial operation after the Tennessee Valley Authority’s (TVA)  Watts Bar Unit 2 successfully completed an extensive series of power ascension tests and reliably operated at full power for more than three ...


Task Force Issues Recommendations to Curtail Natural Gas Blowouts


The Interagency Task Force on Natural Gas Storage Safety, established in the wake of last year's massive natural gas leak at California's Aliso Canyon site, just issued a new report intended to help reduce the risk of future such incidents. The report chronicles lessons learned from the Aliso Canyon l...


Fed’s Beige Book Points to Modest Economic Growth


Reports from the twelve Federal Reserve Districts suggest national economic activity continued to expand during the reporting period from late August to early October. Most Districts indicated a modest or moderate pace of expansion ; however, the New York District reported no change in overall activit...


U.S. Factory Production Rose 0.2% In September


Industrial production edged up 0.1% in September after falling 0.5% in August. For the third quarter as a whole, industrial production rose at an annual rate of 1.8% for its first quarterly increase since the third quarter of 2015. Manufacturing output increased 0.2% in September and moved up at an an...


A Primer On Worm Gear Operators

vmsum12_worm_gears_1A remote gas pipeline installation in Pinedale, WyomingManual gear operators continue to provide a viable, age-old solution with a few 21st century twists. Understanding how these products work, as well as the tradeoffs and costs associated with manual operators, can help end users select the right technology for the application.

Over the past 30 years, valve automation has dominated the flow control industry. But even though power actuation captivates the attention, imagination and the lion’s share of growth in the market, manual valve actuation also continues to expand, receiving its own innovations. In this article, we provide an introduction to the basic principles behind these workhorse operators and discuss current trends in the market. We also consider the benefits and associated costs that come with manual worm gear designs. Please note that for ease of reference, a glossary of terms has been added; the definitions provided are industry specific and only intended to cover the depth and scope of this article (click here).


Manual worm gear operators can be found in nearly every valve application throughout the world. Manual operators have no power requirements, no hydraulic or pneumatic pressure unit to maintain and can be used in the most remote locations. From submarine duty to mining, water works to oil and gas pipelines, if torque is required, manual worm gear operators are there.

To begin, it may help to view the world through the eyes of the application engineer. We push up our stylish horn rim glasses, open our 20-tab spreadsheet product selector and ask: “Torque or thrust?” The first consideration in selecting an actuator is the type of force required. Torque, that rotational or twisting force necessary to position ball valves, plug valves, butterfly valves, etc., will be the focus of this article.

Let’s look at the fundamental challenge our application engineer faces, which is: “How do we provide a means to safely and effectively position the valve?”

vmsum12_worm_gears_2Figure 1. A simple lever can work when just a small amount of torque is needed.If the valve torque is small enough, a wrench or lever of adequate length or a handwheel of the appropriate diameter provide simple solutions to our dilemma (Figure 1). Both the handwheel and the lever increase mechanical advantage by applying principles explained by Archimedes more than 2,000 years ago. Levers, while efficient and cost-effective, remain impractical or undesirable for many applications, however. At some point, the force required to position the valve exceeds the feasibility of a simple lever; this is where worm gear operators enter the picture.

We have used gears for thousands of years to harness energy from wind, water and beasts. Think of gear mechanisms as a series of interacting levers and screws. In our application, gears are used to amplify torque. In short, we use gears to convert force to work.


vmsum12_worm_gears_3Figure 2. A simple cylindrical single-start worm and worm gear set.Worm gear operators are used for actuation because they offer high torque multiplication and load-carrying capability in a small, low-cost package. Figure 2 presents an example of a typical worm gear set found in a manual worm gear operator.

Following conventional American Gear Manufacturers Association (AGMA) (www.agma.org) gear design standards, if a single-start worm is the drive and an 80-tooth worm gear is the driven, the ratio would be expressed as 1:80 (the formula is available in the glossary). That’s a lot of ratio in a small package. But these numbers only tell us that it takes 80 worm revolutions (drive) to complete one revolution of the worm gear (driven). The ratio tells us about the mechanism’s effect on speed but little about torque. To understand the effect on torque, we need to know the mechanical advantage (MA). In a perfect machine, a 1:80 ratio would net an MA of 1:80 (expressed as 80), meaning that for 1 unit of force applied, 80 units of force are generated.

Does this mean free torque? Unfortunately, no. The energy of the universe is constant and as with everything, there is an associated cost.


What are the costs associated with amplifying force through our manual actuator? The first cost is hard cash—the worm gear actuator will cost more than a lever or handwheel.

Second, machines are not perfect, which is demonstrated in efficiency losses through heat and wear. As it turns out, standard single-start metal worm gear sets are less than 35% efficient by design. Also, worm gear sets with a worm thread angle and design, which net an efficiency of approximately 35% and greater, are not typically self-locking, and without self-locking characteristics are not suitable for a number of applications. Based on a website sample of the top manufacturers, 32% is the approximate average efficiency for manual worm gear operators. This simple formula explains what happens to mechanical advantage in a 32% efficient gear train:

80 x .32 = 25.6 MA

The MA would be approximately 25, not 80. That is nearly 55 points of mechanical advantage lost to ­inefficiency.

Third, and not captured in manufacturer’s data sheets, is the cost in the exchange of force for distance. We increase force by simply making more trips, or more specifically, more turns on the handwheel to cycle the valve.

  • Latest Post

  • Popular

  • Links

  • Events


Looking for a career in the Valve Industry?

ValveCareers Horiz

To learn more, watch the videos below or visit ValveCareers.com a special initiative of the Valve Manufacturers Association