Wednesday, October 31, 2018

Saturated Steam Table

A saturated steam table shows temperatures and pressures for water at the liquid/vapor transition (i.e. points lying along the liquid/vapor interface shown in a phase change diagram), as well as enthalpy values for the water and steam under those conditions. The sensible heat of water is the amount of thermal energy per pound necessary to raise water’s temperature from the freezing point to the boiling point. The latent heat of vapor is the amount of energy per pound necessary to convert water (liquid) into steam (vapor). The total heat is the enthalpy of steam (thermal energy per pound) between the listed condition in the table and the freezing temperature of water.

By definition a saturated steam table does not describe steam at temperatures greater than the boiling point. For such purposes, a superheated steam table is necessary.

Mead O'Brien
https://meadobrien.com
(800) 892-2769

Saturated Steam Table



Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

Data for this saturated steam table was taken from Thermal Properties of Saturated and Superheated Steam by Lionel Marks and Harvey Davis, published in 1920 by Longmans, Green, and Company.

Monday, October 29, 2018

Triple Offset Butterfly Valve Operation and Features

Triple offset butterfly valves provide superior performance, increased durability, reliability and lower ownership cost than traditional valves.

Triple offset butterfly valves are recognized for excellent flow control characteristics, zero leakage, and reliability. They are designed for superior performance in high pressure and extreme temperature applications. Their design includes metal seats which are inherently fire safe. They maintain their zero leakage seal even in extreme operating conditions. Finally, triple offset butterfly valves typically weigh less than similar sized valves, allowing for easier installation and maintenance.

TRICENTRIC®, the leading manufacturer of triple offset valves, engineer their products to meet stringent industry requirements and offer cost savings to the end user through improved life cycle costs, reducing emissions, reducing downtime and requiring lower maintenance costs.

Triple offset butterfly valves have a huge installed base and a commonly used in a range of industries including:
  • Aerospace
  • Conventional power 
  • Nuclear power
  • Oil & gas / refining
  • Desalination
  • Chemical processing 
  • Pulp & paper mills
  • Military
https://meadobrien.com
(800) 892-2769


Monday, October 22, 2018

Hot Water for Industry from Mead O'Brien

Mead O'Brien, in partnership with Armstrong International, delivers accuracy, simplicity and unparalleled performance in instantaneous hot water generation, distribution and precision temperature control.

From a single product, to a complete fully integrated system, Mead O'Brien can provide a hot water solution to meet your most demanding needs.

Products include standard and application-customized steam/water instantaneous water heaters for any process application requiring very specific temperatures, from chilled water to temperatures as high as 212°F (100°C), as well as Mixing Centers, VFD Pump Assemblies, Hot & Cold Water Hose Stations, Gas-Fired Water Heaters, and Digital Control Valves.

https://meadobrien.com
(800) 892-2769




Sunday, September 30, 2018

Industrial Thermowells: Sometimes Taken for Granted, but Critically Important

Ashcroft Thermowells
Thermowells come in a wide variety
of shapes, materials, and sizes.
(Courtesy of Ashcroft)
One of the most important accessories for any temperature-sensing element is a pressure-tight sheath known as a thermowell. This may be thought of as a thermally conductive protrusion into a process vessel or pipe allowing a temperature-sensitive instrument to detect process temperature without opening a hole in the vessel or pipe.

Thermowells are critically important for installations where the temperature element (RTD, thermocouple, etc.) must be replaceable without de-pressurizing the process.

Thermowells may be made out of any material that is thermally conductive, pressure-tight, and not chemically reactive with the process. Most thermowells are formed out of either metal (stainless steel or other alloy) or ceramic materials.


A simple diagram showing a thermowell in use with a temperature sensor (RTD) is shown here:
thermowell installation
Typical RTD thermowell installation.
As useful as thermowells are, they are not without their caveats. All thermowells, no matter how well they may be installed, increase the first-order time lag of the temperature sensor by virtue of their mass and specific heat value. It should be intuitively obvious that a few pounds of metal will not heat up and cool down as fast as a few ounces’ worth of RTD or thermocouple, and therefore the addition of a thermowell to the sensing element will decrease the responsiveness of any temperature- sensing element. What is not so obvious is that such time lags, if severe enough, may compromise the stability of feedback control. A control system receiving a “delayed” temperature measurement will not see the live temperature of the process in real time due to this lag.

For more information on thermowells, contact Mead O'Brien by visiting https://meadobrien.com or by calling (800) 892-2769.

Thursday, September 27, 2018

Five Important Criteria in Applying Pressure Gauges

Ashcroft pressure gauge
Process pressure gauge.
(Ashcroft)
Pressure gauges are installed in countless industrial and commercial applications around the world. From hygienic pharmaceutical process lines, to the most unpleasant and hostile areas in chemical, power, and food processing plants.

While there are millions of possible combinations of shapes, sizes, options and materials, pressure gauges all share the five  following application criteria, required for safe use and long product life.
Ashcroft diaphragm seal
Diaphragm seal.
(Ashcroft)


1 - Process Media Properties: Media that is corrosive, sludgy, or that can solidify is a potential problem for pressure gauges. In non-corrosive, non-clogging media applications, a direct connection without intermediate protection can be applied. For process media that could potentially clog or chemically affect the gauge's wetted parts, a diaphragm seal should be used.

2 - Process Media Temperature: Very hot media, such as steam or hot water, can elevate the gauge's internal temperature leading to failure or an unsafe condition. For high temperature applications, the use of a "pigtail siphon" or diaphragm seal is recommended. Siphons act as a heat sink and lower the exposure temperature. Diaphragm seals isolate the gauge from the higher temperatures.

Siphon
Pigtail siphon.
3 - Ambient Operating Temperature and Environment: It is important to know the ambient environmental rating for any process instrument. Elevated ambient temperatures, moisture, vibration, and corrosive atmospheres can all affect accuracy, calibration, and safety. Choose the proper housing and mechanism materials if oxidizing or reducing atmospheres exist, and consider the addition of ancillary devices, such as remote diaphragm seals to physically relocate the gauge away from the hostile area.

Snubber
Snubber
4 - Severe Pressure Fluctuations: In applications where dramatic line pulsations or strong over-pressure conditions are a possibility, the use of pressure restrictors, snubbers, or liquid-filled gauges will extend the service life of the pressure gauge.

5 - Mounting: Pressure gauges are standardly available with bottom (radial) and back connections. NPT (National Pipe Thread Taper) threaded connections are generally the standard. Many other process connections are available though, such as straight threads, metric threads, and specialized fittings. Make sure you know how the gauge is being connected. When mounting, pressure gauges should be almost always be mounted upright.

For more information about pressure gauges, contact Mead O'Brien by visiting https://meadobrien.com or by calling (800) 892-2769.

Tuesday, September 18, 2018

Limitorque Fluid Power Systems (LFPS)

Limitorque Fluid Power Systems is a group of modular scotch yoke fluid power actuators designed to deliver maximum torque with the lowest possible displacement and overall size. These heavy-duty, fluid-powered valve actuators and control systems are design primarily for the oil and gas industry. The group is categorized into three major sub-groups:
  • Gas Powered Actuators - The Limitorque LDG direct gas actuator is designed to operate on high pressure pneumatic supply, including pipeline gases, nitrogen and any other equivalent high pressure source.
  • Hydraulic Actuators - LHS and LHH are Limitorque’s range of hydraulic, quarter-turn, scotch yoke actuators. Designed to meet or exceed the most current and stringent safety and reliability standards for application in the oil and gas industry LHS and LHH are suitable for on/off and modulating control of all quarter-turn valves. 
  • Pneumatic Actuators - Limitorque’s LPS and LPC are pneumatic quarter turn scotch yoke actuators, featuring a robust design suitable for heavy duty services, and among the longest design lifespans and maintenance intervals in the industry.
Download the Limitorque Fluid Power Systems PDF here.

Mead O'Brien
www.meadobrien.com
(800) 892-2769