Wednesday, October 11, 2017

Ball Sector Valves

industrial ball valves with actuators
Industrial ball sector valves with a variety of actuators
Image courtesy of Schubert & Salzer
The manufacturers of valves and other fluid control components for the processing industries have never been shy about tweaking designs to deliver better performance for a particular set of operating conditions. The available basic valve designs, along with their variants, create an immense catalog of potential candidates for each application.

One such design variant is the ball sector valve. It is a quarter turn valve, like its cousin the ball valve, but the trim is different. True to its name, the active closure structure is but a portion of what we know of as a common ball valve. Where a ball valve essentially has a sphere with a hole drilled through it, a ball sector valve more resembles a section of a hollowed out sphere with a shaped opening in the surface.

ball sector valve animation
Ball sector valve is a quarter
turn valve.
Image courtesy Schubert & Salzer
The closure in a ball valve can be floating or trunnion mounted. A ball sector valve will have a trunnion style mounted closure, with rigid support at the top and bottom. Ball valves, with their rotating fluid pathway resembling a short tube, are generally not the best option for flow control other than isolation. The ball sector valve functions similar to a sliding gate valve, providing an increasing or decreasing elliptical shaped opening as the shaft is turned.

Ball sector valves are well suited for applications involving isolation or control of viscous fluids, slurries, and other challenging fluids. Because of the construction and centric trunnion mounting, the seal area on the ball sector valve is kept free of the media, leading to reduced wear and superior longevity.

There are some good cutaway illustrations in the brochure included below that detail the valve construction. Share your fluid control challenges of all types with valve specialists, leveraging your own process knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, October 4, 2017

Refinery Explosion Analysis and Animated Video Reenactment

Industrial accidents range in severity and impact from minuscule to catastrophic. As operators, owners, or technicians involved with industrial operations, we all have a degree of moral, ethical, and legal responsibility to conduct our work in a manner that does not unduly endanger personnel, property, or the environment. Maintaining a diligent safety stance can be helped by reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from your own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. The video illustrates their animated reenactment and causal analysis of an explosion that occurred at a refinery in Louisiana in 2016. Check out the video and sharpen your senses to evaluate potential trouble spots in your own operation. Share any questions or concerns with process control specialists and reduce the level of risk at your facility.

Thursday, September 28, 2017

Breathing Air Purifiers

breathable air purifier system
A breathing air purifier unit processes
compressed air, making it suitable for respirators.
Image courtesy SPX Pneumatic Products
There are many instances throughout science and industry where tasks must be performed by human operators in environments without breathable air. In many of those cases, it is necessary to provide a positively pressurized enclosed space around the operator's face to isolate the breathing passages from potentially harmful vapors, dust, or pathogens in the work area.

Applications in the petrochemical industry, as well as asbestos abatement, paint and coatings, tank cleaning and more have specific jurisdictional requirements for the provision of breathing apparatus for worker protection. A compressed air source is processed as it passes through a purifier which imposes a six stage filtration process on the compressed air inlet prior to supplying the breathable air to safety hoods or masks.

  • Removal of solid and liquid particles or droplets greater than 1.0 micron.
  • Oil and liquid aerosol removal down to 0.1 micron.
  • Water vapor removal
  • Reduction of carbon monoxide level
  • Second particulate filtration stage to 1.0 micron
  • Activated carbon removes trace odors, oil vapor, and other components
Analyzing and monitoring the outlet air quality from the purifier unit is a good practice, to assure that target levels of oxygen, carbon monoxide, moisture, and carbon dioxide are maintained. OSHA and other jurisdictional bodies specify allowable levels for certain potentially harmful gases. The quality of the inlet air should be carefully assessed and protected during operation, since it is a primary determinant of the outlet air quality.

Share your process requirements with a pneumatic system specialist, combining your own knowledge and experience with their product application expertise to develop an effective solution.

Wednesday, September 20, 2017

Trunnion vs. Floating Ball Valves

trunnion mount ball valve for industrial pipeline use
Trunnion mount ball valves have upper and lower support
points for the ball.
Image courtesy International Standard Valve, Inc.
The design, construction, and function of a ball valve is generally well understood in the industrial fluid processing arena. Ball valves provide reliable quarter turn operation, compact form factor, and tight shutoff capability, making the ball valve a preferred choice for many applications. Some ball valves also provide shutoff of fluid flow in either direction. A primary valve trim design feature permits grouping of the many variants of industrial ball valves into two categories, distinguished solely by the way in which the ball is mounted in the body.

Floating ball valves use the seats and body to hold the ball in place within the fluid flow path, with the force of directional flow pushing the ball against the downstream seats to produce a tight shutoff seal. Many floating ball valves are capable of flow shutoff in either direction. The ball is rotated by a shaft connected at the top which extends through the pressure enclosure of the valve for connection to a handle or automated actuator. The floating nature of the ball limits the applicability of this design to smaller valve sizes and lower pressures. A some point, the fluid pressure exerted on the ball surface can exceed the ability of the seats to hold the ball effectively in place.

Trunnion mount ball valves employ the stem shaft and, you guessed it, a trunnion to rigidly position the ball within the body. The shaft and trunnion, connected to the top and bottom of the ball, establish a vertical axis of rotation for the ball and prevent it from shifting in response to flow pressure. The trunnion is a pin that protrudes from the bottom side of the ball. It sits within a bearing shape, generally cylindrical, in the base of the body.

Because of their structural design, trunnion mount ball valves are suitable for all pressure ranges and sizes.They are used by many manufacturers as a basis of design for their severe service ball valve offerings. A trunnion mount ball valve can also be advantageous for applications employing valve automation. Since the ball is not held in place by a tight fitting seal arrangement, operating torque tends to be lower for comparably sized trunnion mount valves, when compared to floating ball valves.

On page 3 of the brochure included below, the exploded view of a trunnion ball valve shows the location of the trunnion assembly.

Whatever your valve application challenge, share it with an industrial valve expert. Leverage your own process knowledge and experience with their product application expertise to develop an effective solution.

Thursday, September 14, 2017

Pressure Measurement Using Isolation Ring

The D81 Isolation Ring from Winters Instrument provides a solution for measuring system pressure in processes involving fluids with potential to clog or damage sensors and impulse lines. The isolation ring has a hollow elastomer that is located between two flanges. A fitting on the elastomer section allows for connection of a gauge or transmitter without disturbing the process fluid. Pressure in the piping system is mirrored by pressure within the hollow portion of the isolation ring, measured by the connected instrument. The instrument does not come in contact with the process fluid, nor are there any small diameter impulse lines to foul or clog. Applications in mining, water treatment, pulp and paper abound. Any challenging fluid is a good candidate for application consideration. Models are available up to 48" line size, with wafer, flanged, or threaded connections.

Share your fluid process measurement requirements with application specialists, combining your own knowledge and experience with their product application expertise to develop effective solutions.

Wednesday, August 23, 2017

Cooling Towers: Operating Principles and Systems

evaporative cooling tower made of HDPE plastic
Example of evaporative cooling tower, fabricated
from HDPE plastic to resist corrosion.
Image courtesy Delta Cooling Towers
The huge, perfectly shaped cylindrical towers stand tall amidst a landscape, with vapor billowing from their spherical, open tops into the blue sky. Such an image usually provokes a thought related to nuclear power or a mysterious energy inaccessible to the millions of people who drive by power plants every day. In reality, cooling towers – whether the hyperboloid structures most often associated with the aforementioned nuclear power plants or their less elegantly shaped cousins – are essential, process oriented tools that serve as the final step in removing heat from a process or facility. The cooling towers at power plants serve as both an adjuster of a control variable essential to the process and also as a fascinating component of the process behind power creation. The importance and applicability of cooling towers is extensive, making them fundamentally useful for industrial operations in power generation, oil refining, petrochemical plants, commercial/industrial HVAC, and process cooling.

In principle, an evaporative cooling tower involves the movement of a fluid, usually water with some added chemicals, through a series of parts or sections to eventually result in the reduction of its heat content and temperature. Liquid heated by the process operation is pumped through pipes to reach the tower, and then gets sprayed through nozzles or other distribution means onto the ‘fill’ of the tower, reducing the velocity of the liquid to increase the fluid dwell time in the fill area. The fill area is designed to maximize the liquid surface area, increasing contact between water and air. Electric motor driven fans force air into the tower and across the fill area. As air passes across the liquid surface, a portion of the water evaporates, transferring heat from the water to the air and reducing in the water temperature. The cooled water is then collected and pumped back to the process-related equipment allowing for the cycle to repeat. The process and associated dispersion of heat allows for the cooling tower to be classified as a heat rejection device, transferring waste heat from the process or operation to the atmosphere.

Evaporative cooling towers rely on outdoor air conditions being such that evaporation will occur at a rate sufficient to transfer the excess heat contained in the water solution. Analysis of the range of outdoor air conditions at the installation site is necessary to assure proper operation of the cooling tower throughout the year. Evaporative cooling towers are of an open loop design, with the fluid exposed to air.

A closed loop cooling tower, sometimes referred to as a fluid cooler, does not directly expose the heat transfer fluid to the air. The heat exchanger can take many forms, but a finned coil is common. A closed loop system will generally be less efficient that an open loop design because only sensible heat is recovered from the fluid in the closed loop system. A closed loop fluid cooler can be advantageous for smaller heat loads, or in facilities without sufficient technical staff to monitor or maintain operation of an evaporative cooling tower.

Thanks to their range of applications, cooling towers vary in size from the monolithic structures utilized by power plants to small rooftop units. Removing the heat from the water used in cooling systems allows for the recycling of the heat transfer fluid back to the process or equipment that is generating heat. This cycle of heat transfer enables heat generating processes to remain stable and secure. The cooling provided by an evaporative tower allows for the amount of supply water to be vastly lower than the amount which would be otherwise needed. No matter whether the cooling tower is small or large, the components of the tower must function as an integrated system to ensure both adequate performance and longevity. Understanding elements which drive performance - variable flow capability, potential HVAC ‘free cooling’, the splash type fill versus film type fill, drift eliminators, nozzles, fans, and driveshaft characteristics - is essential to the success of the cooling tower and its use in both industrial and commercial settings.

Design or selection of an evaporative cooling tower is an involved process, requiring examination and analysis of many facets. Share your heat transfer requirements and challenges with cooling tower specialists, combining your own facilities and process knowledge and experience with their application expertise to develop an effective solution.`

Friday, August 18, 2017

Thermodynamic Steam Traps

cutaway view thermodynamic steam trap
Cutaway view of disc type thermodynamic steam trap
Image courtesy of Spirax Sarco
Condensate return is an essential operation in any closed loop steam system. Steam that has lost its latent heat will collect in the piping system as hot liquid water (condensate). This liquid needs to be separated from the steam and returned to the boiler feedwater equipment without letting steam escape in the process.

Various items of steam utilization equipment and processes will result in condensate formation at different rates. The device that collects and discharges condensate to the return portion of the system is called a steam trap. There are numerous physical principals and technologies employed throughout the range of available steam trap types. Each has application limitations and strengths making them more or less suitable for a particular installation.

A thermodynamic steam trap relies on the energy provided by the condensate to move a disc which controls the flow of the condensate into the return system. The disc is the only moving part in the device. Condensate flows through a port to a chamber on the underside of the disc, lifting the disc and directing the flow to the return system or drain. Eventually, the fluid flowing into the chamber will reach a point where some of the condensate flashes to steam. A portion of this steam flows through a channel into the space above the disc, called the control chamber. The increase in pressure in the control chamber due to the steam influx pushes downward on the disc, seating it in a closed position. The trap, with the disc seated, remains in the closed position until the flash steam in the control chamber cools and condenses. Then the disc can be opened again by the inflow of condensate.

The thermodynamic disc trap is:

  • Easy to install
  • Compact
  • Resistant to damage from freezing
The single trap can cover a wide range of system pressure, and the simple construction translates into low initial cost. Properly matching any steam trap to its application is important. Share your condensate return and steam system challenges with specialists, combining your knowledge and experience with their product application expertise to develop effective solutions.