Tuesday, December 6, 2016

Pressure Regulating Valves

industrial pressure regulator valve for steam brass
PIlot operated pressure regulator
intended for use in a steam system
Courtesy Pentair - Cash Valve
Many processes and equipment employ pressure regulating valves, the function of which is to maintain a desired outlet fluid pressure under varying conditions of supply pressure or outlet flow.

There are many pressure regulating valve variants, specifically designed to address a range of process conditions or offset a performance characteristic deemed undesirable in another design. Each variant has a suitable place in the range of possible applications, with cost, size, and complexity primary differences among the different offerings.

In its simplest form, a pressure regulating valve (PRV) consists of a flow restricting element, a measuring element, and a setpoint element. Outlet pressure applies force to the measuring element, often a diaphragm. As the outlet pressure increases, the diaphragm will move the flow restricting element toward the closed position, reducing the flow from the inlet. The restricting element is commonly a plug, disk, or some other recognizable valve trim arrangement. The setpoint element, likely a spring, provides a counterbalancing force on the diaphragm. When the force applied to the diaphragm by the outlet pressure reaches equilibrium with the counterbalancing force applied by the spring, movement of the restricting element stops. In this way, outlet pressure is controlled without the need for electric power, sensors, transmitters, or even a process controller. The entire assembly is self-contained and requires little attention.

Selecting a PRV for an application requires coordinated consideration of process performance range, desired conditions, and valve attributes to produce a selection that will provide the desired service. A valve improperly selected for an application may perform poorly. Some of the items to be considered include:
  • PRV Type
  • Body size
  • Construction
  • Pressure Ratings
  • Maximum Flow Rate
  • Outlet Pressure Range
  • Accuracy
  • Inlet Pressure
  • Orifice Diameter
  • Response Speed
  • Turn-Down Ratio
A PRV is not a safety device, so independent means must be provided to protect the system from excessive pressure. Product specialists are a good source of help in selecting a properly sized and configured valve for an application. Share your fluid process control challenges with a product application specialist, combining your process knowledge with their product application expertise to develop effective solutions.


Friday, December 2, 2016

Diaphragm Valves For Heavy Duty Industrial Applications

industrial diaphragm valve with handle metal body and metal diaphragm
Series 611 Industrial Diaphragm Valve
Courtesy Gemü
Diaphragm valves are suitably used for applications requiring hermetic isolation of the valve bonnet and stem from the flowing media. They also are capable of throttling flow and are generally tolerant of particulate matter entrained in the media. Selecting body and diaphragm materials that are compatible with the media are primary elements of achieving a successful application.

Gemü, a globally recognized manufacturer of diaphragm valves and other control components, offers a line of industrial metal diaphragm valves available in a range of materials and sizes to accommodate heavy duty applications.
  • Suitable for inert and corrosive liquid and gaseous media
  • Chemical resistant bonnet
  • Insensitive to particulate media
  • Valve body and diaphragm available in various materials and designs
  • Compact design
Share your fluid process control challenges with application specialists, combining your process knowledge with their product expertise to develop effective solutions.

Thursday, November 17, 2016

Shell and Tube Heat Exchanger Refurbishment

shell and tube heat exchangers tube bundle removed for refurbish
Two shell and tube heat exchangers getting refurbished
at industrial site. Tube bundles have been removed.
Shell and tube heat exchangers are regularly employed throughout industrial and commercial sites as a means of producing heated or cooled fluids. They consist of a pressure vessel and an internal tube bundle. The flow paths of the pressure vessel and the tube bundle are isolated from one another, giving a shell and tube heat exchanger four nominal connections.

  • Vessel inlet
  • Vessel outlet
  • Tube bundle inlet
  • Tube bundle outlet
Most often, the subject process fluid to be heated or cooled will flow through the pressure vessel, contacting the surface of the tube bundle contained within. If the heat transfer fluid flowing through the tubes is warmer than the process fluid in the vessel, heat will conduct through the tube wall into the process fluid, increasing its temperature. If the fluid in the tube bundle is cooler than the process fluid in the vessel, the process operates in the reverse fashion. Construction details of shell and tube heat exchangers can vary, but the basic operating scheme remains constant.

The lack of moving parts and ruggedly constructed nature of shell and tube heat exchangers tends to grant them a good measure of longevity for most applications. Regardless of any exceptions to that statement, there will eventually come a time when refurbishment or replacement is needed. If the pressure vessel is serviceable, or can be made so with a reasonable amount of cost, replacing the tube bundle may be the main element of an operation aimed at returning the heat exchanger to like new service.

Tube bundles are just that, bundles of tubes. With the right set of dimensional information and specifications, an identical fabrication can be purchased and put in place. It is not always necessary to revisit the original manufacturer. If drawings are still on file for the unit, sufficient information can be gleaned from them to produce a replacement tube bundle that will provide rated performance.

Ordering up a replacement tube bundle is not complicated, but the operation can be smoothed out through contact with involvement of an experienced engineer that can make sure all the necessary information is on hand and step you through the process. 

Tuesday, November 8, 2016

Spiral-Trol Valve Disassembly Video

globe valves control valves pneumatic actuator
Globe control valves with pneumatic actuators
Spirax-Sarco
Spirax-Sarco is a globally recognized manufacturer of valves, traps, and a host of other steam system specialties. Their Spira-Trol line of globe valves can be employed throughout a steam of other process fluid system to provide accurate flow regulation. The valves are available with several options of electric or pneumatic actuators, as well as positioning controllers.

The video included below provides a demonstration of the simplicity involved in disassembling the valve in-line for regular maintenance or inspection. The video is short, as is the length of time needed to access the valve internals. These valves are designed for easy maintenance.

Share your fluid process and steam control challenges with application experts. The combination of your process knowledge and their product application expertise will deliver effective solutions.

Tuesday, November 1, 2016

New High Pressure Float Type Steam Trap

steam trap high pressure float type
Model FTC62 High Pressure Steam Trap
Courtesy Spriax Sarco
Steam is utilized by industrial operations as a source of heat and power. Commercial and institutional facilities widely employ steam as a heating source. The overall cost of operating a steam system is generally significant, regardless of the size of the organization. Designing a system to deliver efficient performance and maintaining that performance throughout many years of expected operation requires continuous monitoring and attention.

One facet of efficient operation is to remove condensate from the steam system and return it to the boiler. This operation is the primary function of a steam trap. Additionally, a steam trap will also remove non-condensible vapor from the system. Liquid water and non-condensible vapor both will undermine efficiency in a common steam system.

There are many versions of steam traps available, and it is important to match the capacity and performance range of the trap to the steam system. Spirax-Sarco, globally recognized steam system specialties manufacturer, has added  a new steam trap model series to their already extensive offering.

The FT62 Series, which is available with a carbon steel (FTC62) or stainless steel (FTS62) body, has stainless steel internal components. It is intended for application on light and heavy condensate loads on steam systems with differential pressure up to 900 psig (62 bar).  The unit includes an integral air vent and an easily maintainable in-line strainer.

More information is provided below, with good illustration of the exterior and interior setup of the steam trap. Share your steam system requirements and challenges with experienced application specialists, combining your facility and process knowledge with their product application expertise to develop effective solutions.


Wednesday, October 26, 2016

Continuous Liquid Level Measurement Using Bubbler Method

bubbler or downpipe liquid level measurement schematic
Bubbler or Downpipe Liquid Level Measurement Schematic
Courtesy King-Gage
Measuring liquid level in a tank or vessel can be accomplished in a number of ways, all of which require some arrangement of instrumentation to either infer the liquid level through measurement of a related physical property, or directly deliver the liquid level visually using a scaled gauge arrangement. One indirect method of level measurement, referred to as the bubbler or downpipe method, is so named because it employs a purging gas that continually vents from the bottom of a dip tube extending into a tank of liquid. Through a simple apparatus, the level of a liquid can be inferred by the amount a back pressure exerted upon the gas flowing through the tube.

Probably the greatest advantage of this method of liquid level measurement is that the subject liquid does not contact the sensing instrumentation. The only portion of the apparatus in contact with the liquid is a tube immersed into the tank. Selecting the proper material for the immersed tube is left to the user. An additional feature of this method is the entry of the sensing tube from the top of the tank, eliminating the need for a fitting below the liquid level surface.

Basically, a purge gas flows through the immersion tube and may bubble out the immersed end of the tube, which is open to allow the contained liquid to exert a hydrostatic pressure on the purge gas. The back pressure on the gas that is exerted by the liquid contained within the tank will vary directly with the depth of the liquid. The back pressure can be correlated to a liquid level. Further calculations, which would include the tank shape, dimensions, and the liquid density can provide an indication of the volume and mass of the liquid.

It is possible for a user to assemble the components necessary to put a bubbler level indicator into operation, but King-Gage produces a device which consolidates purge control, pressure measurement, level signal transmitter, and necessary connections into a single compact device. There are versions of this level transmitter for electric and pneumatic output signals. They also include an additional level of protection in the form of an internal diaphragm that further isolates the device from the measured medium.

More details, along with some good illustrations, are provided in the document below. Share your process measurement challenges with application specialists, combining your process expertise with their product application knowledge to develop effective solutions.


Tuesday, October 18, 2016

Knowledge Base for Steam System Components

steam system schematic showing area of steam utilization
Steam utilization schematic showing array of products (blue)
Spirax Sarco
Steam, ubiquitous source of industrial power and commercial heat, ranks as a substantial continuing expense item for any organization where it is utilized or produced. Designing, installing, and managing steam system operation effectively can generate immense cost savings over less rigorous approaches.

An effective method of good decision making involves tapping into the experience and expertise of those that have gone before, accomplished what you plan to attempt. For steam systems, Spirax Sarco is a premiere source of information, knowledge, and expertise. The company has been deeply involved in the production and utilization of steam for many years, designing and manufacturing components utilized throughout the entire process.
steam system schematic showing components utilized in production of steam
Steam production schematic showing array of products (blue)
Spirax Sarco
In the steam generation section of an operation, the company provides a extensive array of interrelated products.
  • Blowdown Heat Recovery Systems
  • Blowdown Vessel
  • Boiler Feedtank Systems
  • Boiler Level Controls and Alarms
  • Bottom Blowdown Valves and Systems
  • Condensate Contamination Detection
  • Electrically Actuated Two Port Control Valves
  • Pipeline Strainers
  • Sample Coolers
  • Safety Valves
  • Spirax Range of Flowmeters
  • Steam Trap Performance Monitoring
  • Tank Level Controls
  • TDS Control
  • Vacuum Breakers
Throughout the balance of the steam system, the list of components available from the company expands even more, illustrating Spirax Sarco's depth of knowledge about steam system components and how they function together to deliver efficient and safe steam system operation.

Reach out to experts with your steam system challenges, combining your facility and process knowledge with their product application expertise to develop effective solutions.