Tuesday, December 30, 2014

Heat Exchangers for Liquid-Gas Vaporization

Tube bundle for heating
Tube bundle for heat transfer.
Hydrocarbon and non-hydrocarbon based gases can be more efficiently stored and transported in a liquified state, providing higher media density and corresponding product weight per container. Upon reaching their final destination, the liquid can be reheated, returning to a gaseous state for distribution and use. Typical liquified gases include natural gas, oxygen, butane, propane, and nitrogen.

There are several ways to affect the physical change from liquid to gas, and picking the best option is dependent on criteria such as; 1) available energy sources; 2) plant location; 3) climate conditions; and 4) plant infrastructure.

The change from liquid to gas phase usually requires one or more vessels properly sized and designed to accommodate the vastly increased volume of the evaported liquid, handle the storage or distribution pressure of the gas, and be compatible with the process media. In most plants today, the gradual process of warming the liquified gases is done with steam-heated or oil-heated "heat exchangers" or "tube bundles".

Some heat exchanger systems may, instead of steam, use steam-heated intermediary fluids such as oil, water, or glycol-water solution to provide a smoother rate of heat transfer to the evaporating liquid. This method can employ two heat exchangers, one transferring heat from steam to the intermediary fluid, then another to transfer heat from the intermediary fluid to the liquified gaseous product to evaporate it.

Steam heated, closed-loop circulation systems play an important role in providing an efficient, low-cost and compact method to accommodate liquid vaporization. Steam is available in many industrial plants, providing a comparatively inexpensive and readily available source of heat energy. Heat exchangers are available in a range of pre-engineered capacities and forms, but it is quite common for these components to be custom fabricated to meet very specific requirements. Engineers can design their own systems from the component level, or provide performance requirements to the manufacturer and have a skid mounted unit produced, ready for connection to electric power (for control systems), energy source (steam, oil or water) and process inlet and outlet lines.

These systems can be quite technical, with numerous design considerations. The path to maximized safety and efficiency includes consultation with a heat exchanger expert as part of specification and design process. A combination of your high level process knowledge and their product and application expertise will yield the best outcome.

Wednesday, December 24, 2014

Happy Holidays and Happy New Year from Mountain States Engineering and Controls

Happy Holidays from MSEC
We at Mountain States Engineering and Controls believe the magic of the holidays never really ends, and the most important gifts we share are family and friends. Thank you for a wonderful 2014 and we wish you peace, love, and prosperity in the upcoming year.

Tuesday, December 23, 2014

High Performance Butterfly Valve Exploded View

Here is a short video that quickly displays the components of a high performance butterfly valve. High performance butterfly valves are used in the oil and gas, commercial HVAC, chemical processing, mining, pharmaceutical, water & wastewater industries. High performance butterfly valves come in wafer and lug bodies, have bodies made of carbon steel, stainless steel, or other alloys, and work under higher pressures and temperatures than "rubber lined" butterfly valves.

Wednesday, December 10, 2014

Improving Maintenance and Reliability of Bubbler Systems


According to Wikipedia "an air bubbler system uses a tube with an opening below the surface of the liquid level. A fixed flow of air is passed through the tube. Pressure in the tube is proportional to the depth (and density) of the liquid over the outlet of the tube."

A common problem with many bubbler systems used in water and wastewater systems is long term accuracy and reliability issues. The need for scheduled maintenance is required because of the possibility of  tampering, failed solenoids, changing air flow rates, or clogged downpipes due to crystal formation - particularly in wastewater applications with high entrapped solids.

A better approach is to use a level transmitter for purge control. This solution offers a highly engineered single component that is easily retrofitted to bubbler installations. These purge transmitters automatically maintain an extremely low flow continuous purge (less than 0.02 scfm) regardless of liquid depth, and minimizing formations of crystals in the downpipe. The lag time during dynamic level changes is also eliminated. Furthermore, bubbler operation is tamperproof because there is no external regulator or needle valve (or rotameter) – internally a fixed differential is maintained over a precision flow orifice.

Transmitter purge (or bubbler) technology works reliably in the presence of vapors, and, unlike ultrasonics, can be used in media temperatures of more than 350°F. Bubblers are normally used in applications where foam, solid debris, sewage sludge, or turbulence make ultrasonic, radar, or float switch devices ineffective. The purge transmitter is relative compact in size and allows for installations in tanks where other systems won’t fit.

The purge control transmitters require a compressed air supply (35-150 psig/2.4-10.3 bar) and provide a two-wire 4-20mA output that can be transmitted over substantial distances. The transmitter can be mounted directly outdoors or within small enclosed spaces at the measuring point or up to a hundred feet away.

More information on the purge transmitter may be download here.

Sunday, November 30, 2014

Operation of the Spirax-Sarco 25P Pressure Reducing Valve

Spirax Sarco 25P
Spirax Sarco 25P Series
The Spirax-Sarco 25P series pilot-operated reducing valve is widely used in steam systems. Accurate and stable pressure control can be realized irrespective of a change in upstream steam pressure or fluctuation of downstream load.

The Spirax-Sarco 25P series pilot-operated reducing valve is unique in that one, or several, pilot valves can be installed or exchanged on the same valve. Besides being stable and reducing pressure, it can also control the temperature, the upstream pressure or the remote switch. 

Operation

Normal positions before start-up are with the main valve closed and the pilot valve held open by spring force or air pressure.

Entering steam passes through the pilot valve into the main diaphragm chamber and also out through the control orifice. As flow through the pilot valve exceeds flow through the orifice, control pressure increases in the diaphragm chamber and opens the main valve. As steam flows through the main valve, the increase in downstream pressure feeds back through the pressure sensing line to the underside of the pressure diaphragm. 

When the force below that diaphragm balances the compression force of the spring above it, the pilot valve throttles. The control pressure maintained in the main diaphragm chamber positions the main valve to deliver just enough steam for the desired delivery pressure. Adjustment of the spring or air pressure above the pressure diaphragm changes the downstream pressure set point. 

When steam is no longer required, the sensing line pressure increases closing the pressure pilot and the control pressure bleeds back through the control orifice. This allows the main valve to hold the desired reduced pressure, and it may close tight for a dead-end shutoff.

Typical Installation Layout

Spirax Sarco 25P Operation

Mountain States Engineering & Controls carries a large stock of Spirax-Sarco steam specialties. For more information, or for help with your pressure reducing valve, contact:

Mountain States Engineering & Controls
1520 Iris Street
Lakewood, CO 80215
www.mnteng.com
303.232.4100 Phone
303.232.4900 Fax
Email: info@mnteng.com

Friday, November 21, 2014

Pressure and Temperature Switches Glossary - Important Terms to Know Part 2

CCS Dualsnap pressure switch
CCS Dualsnap
pressure switch
Pressure and temperature switch terms part two, courtesy of CCS Dualsnap (Custom Control Sensors).

NACE (National Association of Corrosion Engineers) — Nonprofit technical association that develops and maintains standards that deal exclusively with protection and performance of materials in corrosive environments. The membership represents a cross–section of industry concerned with corrosion prevention and control.

NEC (National Electrical Code) — The American national standard that contains provisions considered necessary for safeguarding persons and property from hazards arising from the use of electricity. Generally, the code covers electric conductors and equipment installed within or on public and private buildings or other structures.

NEMA (National Electrical Manufacturers Association) — A voluntary organization that adopts standards for electrical equipment. NEMA standards are designed to eliminate misunderstandings between the manufacturer and the purchaser and to assist the purchaser in selecting and obtaining the proper product for a particular need.

Monday, November 17, 2014

Pressure and Temperature Switches Glossary - Important Terms to Know Part 1

Dualsnap (CCS) Pressure Switch
Dualsnap (CCS)
Pressure Switch
The following two part series, courtesy of CCS Dualsnap (Custom Control Sensors) provides some very important terms to know when applying or purchasing industrial pressure switches and temperature switches.

ACCURACY (REPEATABILITY) — Accuracy is the maximum operational set point deviation of a single sensor (a pressure, temperature, or flow switch) under one given set of environmental and operational conditions. CCS Repeatability is within +/- 1% of set point.

ACTUATION AND DEACTUATION POINT — The actuation point (sometimes called the set point) is the exact point at which the electrical circuit controlled by
the switching element is opened (or closed) on increasing pressure or temperature. The deactuation point is the opposite, or the point at which the electrical circuit is closed (or opened) on decreasing pressure or temperature.