Pneumatic Valve Actuator Assembly Designed to Prevent Water Hammer

Kinetrol vane actuator and
dashpot assembly

Water hammer occurs when the flow of fluid in a pipe rapidly changes. The result can be very high pipe pressures, mechanical stress on pipe supports, and possible reversal of flow. If not controlled it can cause pipe bursting, broken pipe supports and joint leakage.

The "hammering" is due to a pressure wave created by the instantaneous change in fluid velocity when a valve is suddenly closed or opened. Controlling valve closure time is one of the most economical ways to minimize water hammer. To do this efficiently, while still meeting the process requirements, the use of a variable speed mechanism to control valve stroke is used. One unique, economical and space savings approach is to use a pneumatic vane actuator coupled with a rotary damper (or dashpot).

Rotary dashpots are precision fluid damping devices which give a smooth resistance to shaft rotation which increases with angular velocity.

In this case, a pump station in the USA was having repeated problems with a large, open reservoir hydraulic actuator used to dampen valve opening and closing.  It was overly cumbersome and costly to maintain.

In its place, the pumping station installed Kinetrol Size 14 double acting actuators with digital speed controllers and Kinetrol LJ rotary dampers (with through-shafts to facilitate position feedback) installed on 12” Pratt butterfly valves.

The addition of the bi-directional, sealed dashpots smooth the normal travel, damp any valve flow induced disc oscillations, and provide at least 40 seconds travel time on air and/or electrical power failure.

Using pulsed outputs with programmable delay between steps, the actuators provide a 10 minute opening & closing time for the full 90 degree travel. The system is adjustable between 3-15 minutes with less than one degree increments., and other opening and closing ranges are available.  The actuators use fail-free logic, but fail-hold & fail-safe are available.

These assemblies were commissioned in early Fall of 2017 and are working very well. Their use will be replicated at other pump stations operated by the same customer.

This open reservoir hydraulic actuator was huge and a maintenance headache. 

Corrosive Flow Control Requirement? Use Thermoplastic Valves and Corrosion Resistant Rotary Actuators

Thermoplastic valves with corrosion
resistant actuators, springs and positioners.
(Kinetrol)

Thermoplastic valves made of materials such as Polyvinyl chloride (PVC), Acrylonitrile-Butadiene-Styrene (ABS), Glass Fibre Polypropylene (GRPP), Anti-Static Polypropylene (ASPP), and Polyvinylidene fluoride (PVDF) are becoming the material of choice for more and more chemical process applications. Increasingly, you see these valves in industrial and commercial applications in pharmaceutical production, power generation, chemical processing, and water treatment. There reasons are obvious: chemical resistance; high purity standards; abrasion resistance; lighter weight; lower cost; and ease of installation.

Thoughtful actuator selection is required when plastic valves are specified. While the mechanics in applying pneumatic actuators to plastic quarter-turn valves is no different than metallic valves, the characteristics of the process and application can have significant impact on the performance the automated valve.

The assumption is that, if a thermoplastic valve is required, there is an higher probability the of exposure to corrosive media, or the automated valve assembly is located in a corrosive atmosphere, and therefore a corrosion resistant pneumatic actuator is preferred. Considering this, an actuator with internal and external parts protected by epoxy resins or special paints should be applied. Additionally, actuator spring systems should be designed in way to prevent exposure to corrosive media.

Corrosion resistant
rotary vane actuator
with special external
coating. (Kinetrol Blueline).

The rotary vane actuators manufactured by Kinetrol standardly meet theses requirements. Engineered specifically for high-cycle, dirty, and corrosive applications, these very hardy, compact actuators come standardly with an epoxy stove enamel finish, stainless steel internal and external hardware, with spring units that are totally sealed from the atmospheric contaminants. For applications requiring greater corrosion resistance, such as caustic wash-down or salt-laden environments, an optional "Blueline" coating can be applied,

Happy New Year from Kinetrol USA!

All of us at Kinetrol USA wish our customers, distributors, colleagues and friends a very happy and prosperous 2018!

Kinetrol Blueline Pneumatic Actuator - Features

Features of the Kinetrol Blueline pneumatic actuator:

• Durable Blueline coating meets FDA and BfR L1 specifications. 
• Corrosion resistant zinc (non-incendive) or aluminum alloy case. 
• Easy stop adjustment at each end of stroke for accurate seating. 
• Long life epoxy or PTFE internal finish. 
• Integral vane/shaft casting - only one moving part.
• Manual override square and position indicator. 
• Space filling/energy absorbent sideplates (polymer or metal). 
• Double opposed, Polyurethane, lip seals for effective sealing and long maintenance free life.
• Stainless steel expanders ensure long term lipseal / case contact

For more information, visit https://www.kinetrolusa.com/blueline

Kinetrol Actuator Feature Video

Here's a new Kinetrol vane actuator feature video. Please take a minute to watch. Hope you enjoy.

Pneumatic Actuators Well-suited for Offshore Valve and Damper Applications

Offshore Platform

Offshore oil rigs present special challenges for valve and damper actuators, namely high vibration, limited space, and salt-laden atmospheres.

Corrosion

Corrosion resistant housing
and sealed spring.

Corrosive marine environments takes a harsh toll on the internal parts of actuators. Continuous exposure to salt quickly corrodes the external housing and inevitably enters the actuator and corrodes the internal springs and gears.

Vibration
Constant structural vibration, caused by the dynamic forces generated by compressors, pumps, and engines, leads to poor equipment reliability and eventual failure. Pulsating and shaking forces expedite wear on mechanical connections such as gears and yoke mechanisms, with many gear failures due to resonant vibration.

Space
Oil platform actuators, control valves, safety valves, and piping systems are configured very similarly to their terra firma cousins, with the major difference between land and platform equipment being reduced weight and size. Space is at a premium and it is critical to keep equipment as compact as possible.

Single moving part.
No gears or yokes.

A Better Alternative for Marine and Offshore
Kinetrol rotary vane actuators provide an excellent solution, well-suited for off-shore and marine applications. A durable epoxy stove enamel finish and corrosion resistant zinc (non-incendive) or aluminum alloy case protect the actuator from the harsh environment.

Size comparison for similar output.

The integral vane/shaft casting (a single moving part) and space filling/energy absorbent sideplates (polymer or metal) protect the actuators from the vibration, shaking, and shock.

Finally, Kinetrol vance actuators only require 1/3 to 1/2 the required installation space of similarly equipped rack and pion actuators.

For more information, contact Kinetrol USA by visiting https://www.kinetrolusa.com or calling 972-447-9443.

Vane, Shaft and Seal Design: The Critical Difference in Pneumatic Rotary Valve Actuators

Click images for larger view.

The vane actuator produces rotary motion through the application of air pressure to a "vane' attached directly to an output shaft.

There are several manufacturers of pneumatic, rotary vane valve actuators on the market. Outwardly they appear similar. Internally, there's a world of difference in their design and their performance.

In higher quality vane actuators, the vane and shaft are machined from a single piece of steel. Casting and machining adds cost, but also adds performance. Lower quality actuators save cost by using a 2-piece vane/shaft combination. These are more likely to be affected by backlash or lost motion.  In other words, a one-piece shaft and vane assembly transfers 100 percent of the vane movement directly to the shaft. Two-piece designs may lose movement over time, reducing control and accuracy.

Higher quality pneumatic vane actuators incorporate a pair of “lip seals” around the vane. The durable and resilient polyurethane seals provide two key benefits; eliminating the need for o-rings; and eliminating shaft seals. Dual, opposing lip seals are located each side of the vane. They isolate the vane and shaft from the air supply and create an area from the shaft through the center of the vane that remains unpressurized, eliminating the need for pressure seals around the top and bottom of the shaft.

Some lower quality vane actuator designs use an o-ring around the entire vane, exposing the o-rings to mechanical stress and rolling. Higher quality actuators back their polyurethane lip seals with stainless steel expanders that maintain the integrity of the seal to the actuator housing.

The heart of the pneumatic vane actuator is simple design. Manufacturers often promote the concept of "a single moving part", referring to the vane/shaft/seal assembly. But despite this claim, all pneumatic vane actuators are not the same. You owe it to yourself and your organization to "look under the hood".  See what level of engineering and quality you're really getting.