Monday, June 29, 2015

Gate Valve: A Good Choice for Your Application?

Automatically operated gate valve
Gate Valve With Actuator
Courtesy Orbinox
Fluid flow control is an essential component of many industrial applications. Because of its prevalence, and the variety of applications, there are many types, sizes, and arrangements of flow control valves available to meet practically any need. The challenge for the specifying engineer is to select the valve type and arrangement that will provide the needed performance, while also fulfilling the need for safe performance and a desire for low maintenance burden. Sorting through the wide array of valves and targeting the correct valve technology or type can quickly narrow your focus to a much smaller circle of products to research and consider.

Industrial gate valves, like all other valves, regulate fluid flow by reducing or expanding the area through which the process fluid must pass in a closed system. It is the manner in which that restricting area is changed that serves the major discriminating factor among the different valve types. In the case of a gate valve, a sliding round or rectangular piece, known as the gate or disc, is moved by a mechanism and transects the fluid flow path. Closing the gate, completely transecting the flow path, will restrict the flow to its fullest. As the gate is retracted and the opening size increases, flow is increasingly enabled. The movement of the gate, along with valve body and mechanism construction, give this valve type an array of positive and negative attributes.

High Marks for Gate Valves:

  • Low resistance to fluid flow when the valve is completely open. Generally, the cross sectional characteristics of a gate valve will mimic those of the connected piping system. Additionally, gate valves do not impose any change in the flow direction of the fluid as it passes through the valve body.
  • Low force and energy requirements are needed to change the valve opening position (the position of the gate). Since gate movement is perpendicular to the direction of flow, it is not necessary for the mechanism to counteract the full pressure drop of the fluid in the system.
  • Gate valves can be bi-directional, controlling flow in systems that may incorporate a reversal of the flow direction.
  • The installed gate valve is shorter in length than most other designs.
  • Gate valves employ a slow closure rate. The accompanying slow reduction in fluid shutoff can inhibit physical shock (hammering) in the connected piping system.

manually operated gate valve
Manually Operated Gate Valve
Courtesy Orbinox
Things that appear as positives in favor of gate valve selection on one application may not be as desirable on another.

Gate Valve Potential Negatives:

  • Valve seals are exposed to the fluid flow when the valve is open. This might make the seals vulnerable to the wearing effects of entrained foreign matter or other components of the process fluid. The end result could potentially be prematurely worn sealing surfaces and a failure of the valve to seal properly.
  • Gate valves are generally slow to open and close. This attribute might make them a poor selection for an application requiring rapid or immediate action.
  • The gate valve will require an extended overhead service area, compared to other valve types. This may have an undesirable impact on locating the valve where desired.
  • Fluid flow control applications that require throttling of the flow are generally not good candidates for a gate valve. Fluid flow through a partially open gate valve may cause the closure mechanism to vibrate. Additionally, there are concerns associated with potential erosion of the gate and seals due to increasing fluid velocities when the valve is partially open

These, and other, very basic considerations may help point your product search in the right direction. One additional recommendation is that you contact an experienced valve specialist and take advantage of their knowledge and experience fulfilling other applications similar to yours.

Wednesday, June 10, 2015

Process Measurement and Control Essentials – Industrial Pressure Transmitters

Industrial Liquid Level
Transmitter

Courtesy Yokogawa Corp.
The measurement and control of fluid pressure is ubiquitous throughout many industrial processes. Measurements of pressure, directly and indirectly, provide real time information about what is happening in places that cannot be seen, such as inside a pipe, tank, or machine. The very nature of “process” suggests movement and change, the control of which is necessary to produce a consistent desirable outcome. Industrial pressure transmitters employ specific technologies and physical principals to derive a measurement of process pressure, then deliver or transmit, the measured value to a controller or recording device.

Fluid pressure tells a process operator much about what is currently happening. The pressure variable can be used to determine, among many industrial process elements:

  • Degree to which the process is conforming to a recipe or specification
  • Whether machinery is performing within its specified operation range
  • If conditions of the process remain within the bounds established for safety
  • A quantity measurement of flow, mass, or volume

Industrial Differential Pressure Transmitter
Differential Pressure
Transmitter

Courtesy Yokogawa Corp.
Global industrial processes have widely varying physical arrangements, operating environments, and measurement requirements. Manufacturers of industrial pressure transmitters have responded with an immense array of transmitter technologies, arrangements, and configurations. When selecting the best suited pressure transmitter for your application, consult a sales engineer and consider some of the following:

  • Signal requirements – Type, distance, possible sources of interference
  • Device environment – Hazards, extreme conditions of temperature or corrosion
  • Accuracy and stability of measurement
  • Response time to changes in the process condition
  • Ratings and certifications required for the device
  • Configuration, arrangement, and mounting aspects of the transmitter device

Explore the differing technologies and how they can be best applied to implement or improve your process. Experienced sales engineers can be a useful sounding board for discussing your needs. Take advantage of their extensive experience with a wide array of process applications.

Process Measurement and Control - Selecting the Right Flow Meter Technology



Vortex Flow Meter - Yokogawa Corporation
Vortex Flow Meter
Courtesy Yokogawa Corp.
Magnetic Flow Meter - Yokogawa Corporation
Magnetic Flow Meter
Courtesy Yokogawa Corp.
Many industrial process control operations require fluid flow measurement as an essential element in the process design. Accurate flow measurement can be obtained with the proper application and installation of a flow meter as part of the fluid transfer system.
Industrial flow meters employ differing technologies to directly or indirectly measure fluid flow rates. Among the many available technologies for fluid flow measurement, vortex flow meters, magnetic flow meters, Coriolis flow meters, and rotameter flow meters are among some of the most common found in industry.
Coriolis Flow Meter - Yokogawa Corp.
Coriolis Flow Meter
Courtesy Yokogawa Corp.
Rotameter Flow Meters - Yokogawa Corporation
Rotameter Flow Meters
Courtesy Yokogawa Corp.
Each of the separate technologies have attributes which can make them more suitable to certain applications. Selecting the most appropriate flow measurement technology for an application is one of the initial and crucial steps to designing a well functioning fluid measurement system.
Selection criteria, such as fluid temperature, pressure, and velocity will be part of the selection process. Additional considerations include whether the fluid may be abrasive, corrosive, clean or dirty. The state of the fluid, liquid or gas, must also be considered.
The table below provides quick general guidance on which technologies to consider, based upon the factors outlined above. This will help you better focus further product selection research efforts.
Industrial Flow Meter Selection Table - Yokogawa Corporation
Flow Meter Technology Selection Table
Courtesy Yokogawa Corporation of America
Selecting the right valve is not always an easy task, especially since it may be something that you do infrequently. Manufacturers often have knowledgeable local representatives that are experienced in this field and more than willing to contribute their expertise to your selection process.