Friday, January 19, 2018

Flowmeter Basic Considerations

Multivariable flowmeter transmitter mass flowmeter flow temperature pressure
This multivariable vortex flowmeter provides output
of temperature, pressure and flow.
Image courtesy Azbil N.A.
Flow measurement, the quantifying of a point passage rate for gasses and liquids, is used throughout process applications in power generation, chemical manufacturing, petrochemicals, pulp and paper, water and wastewater, bio-science, semiconductor and many other manufacturing processes. There are two measurements of fluid flow in use: volumetric and weight or mass.

Flowmeters are used to measure the rate or quantity of fluid flow in an open or closed system. They are frequently found installed on piping systems, though there are also instruments capable of measuring liquid flow in open channels. The various measurement technologies have differing installation criteria, with some requiring placement of a sensing element in the flow path, others merely in contact with the flow medium, and still others with no media contact needed at all.

Flow measuring devices can be categorized in a few ways:
  • Inferential Types: Such as variable area flowmeters (rotameters), target flow meters and turbine flow meters.
  • Electrical Flow Meters: Such as electromagnetic flow meters, ultrasonic flowmeters and laser doppler anemometers.
  • Mechanical Type: Such as orifice plates, venturi tubes, flow nozzles, pitot tubes, positive displacement meters and mass flow meters.
  • Other: Such as vortex shedding flow meters, Coriolis, cross-correlation flowmeters, purge flow regulators, flow meters for solids flow measurement and flow switches.
Flow measurement instruments can be integrated into existing fluid transfer systems or installed on new lines, either inline or via insertion. Inline flowmeters mount in the piping system using downstream and upstream connections. Immersion flowmeters use a probe or sensor penetrating the piping, positioning the sensor in the flow stream.

For best results, it is important to heed manufacturer recommendations for installation. There are various flow characteristics that may have an adverse impact on measurement accuracy. Providing flow conditioning structures or maintaining minimum required straight runs on the upstream and downstream piping may be a requirement for some instruments. Each measurement technology will have installation recommendations and limitations.

For proper selection criteria, you should always know the physical state of the process media (solid, liquid, gas, steam), the condition of the media (clean, dirty, viscous, corrosive, flammable), piping size and range of flow rate. The process pressure and temperature can have an impact, as well.

Share your flow measurement challenges with a process measurement specialist and leverage your own knowledge and experience with their product application expertise to develop an effective solution.

Thursday, January 11, 2018

Sanitary Tank Bottom Valve

two-way sanitary tank drain valve cutaway view
Cutaway view of specialty ball valve configured as a
tank bottom valve.
Image courtesy PBM Valve Solutions
PBM Valve Solutions manufactures a special ball valve adaptation that functions as a drain valve, or bottom valve, on sanitary process tanks. This is just one of many specialties from the company that provide the perfect solution for targeted application challenges in fluid processing.

The IGENIX® two-way valve has a formed inlet pad that facilitiates drainage and minimizes the pocket area above the ball. The full size port and several other features accommodate the needs of sanitary process operations.

More information is provided in the cutsheet included below. Share your fluid process challenges with the specialists at CTi Controltech, leveraging your own knowledge and experience with their product application expertise to develop an effective solution.

Friday, January 5, 2018

Vortex Flowmeters

multivariable vortex flowmeter with temperature and pressure compensation
This vortex flowmeter combines, volumetric flow,
temperature and pressure measurement into a single instrument.
Image courtesy Azbil, N.A.
Vortex shedding flowmeters provide consistent process fluid flow rate measurements across a wide range of applications. These flowmeters measure the volumetric flow rate of steam, gas, and low viscosity liquids, boasting both versatility and dependability when used in conjunction with process control systems.

Vortex shedding refers to the phenomenon wherein flowing gas or liquid forms vortices around a solid obstruction placed in the flow path. The measurement technology returns an indication of the process fluid velocity, which can then be used with other data to calculate volumetric or mass flow. Vortex technology is well suited for many applications involving cryogenic liquids, hydrocarbons, air, and industrial gases. Vortex flow measurement does require contact between portions of the measurement instrument and the process media, so these flowmeters are commonly fashioned from a range of corrosion resistant materials. Compatability between the instrument construction materials and process media must be considered for every application.

The process of measuring the flow involves both the flowmeter and the ability for other instrumentation to measure the vortices themselves in order to calculate velocity. Ultrasonic sensors have become popular tools for measuring vortices. Applications involving flow measurement of high viscosity fluids are not well suited for vortex technology because extremely viscous fluids do not behave in the same manner as lower viscosity fluids when their flow path is obstructed. Splitting higher viscosity fluids into concordant vertices is extremely difficult due to the internal friction present in highly viscous liquids.

Additionally, in order to split these process liquids, the piping through which the process material flows must be straight, and disturbance or vibration in the pipe may impact the measurement. A vortex flowmeter will be in a fixed installation. This stationary element, operating without electrodes, can be advantageous for flow measurement in chemical applications utilizing low viscosity fluids.

The vortex shedding flowmeter is widely used for the measurement of steam flow. The high pressure and elevated temperature of steam, along with the variation that exists in most steam systems, have little negative impact on the operation of a vortex flowmeter. Vortex shedding flowmeters are volumetrically based in terms of measurement, but their output can be combined with other fluid measurements and data to calculate mass flow. A product variant commonly available will combine the vortex flow measurement with temperature and pressure compensation, delivering three process measurements from a single installed device.

Whatever your flow measurement challenge, share it with process measurement specialists and leverage your own knowledge and experience with their product application expertise.

Friday, December 22, 2017

Combining Rupture Discs With Pressure Relief Valves

rupture disc
Applying a rupture disc in concert with a safety relief
valve can deliver real benefits.
Image courtesy Continental Disc Corporation
Common elements of any pressurized system include safety and pressure relief valves. Their general purpose is to stop system pressure from exceeding a preset value, preventing uncontrolled events that could result in damage to personnel, environment, or assets. Their operating principle and construction are comparatively simple and well understood.

Long term exposure of a relief valve to process media can result in corrosion, material buildup, or other conditions which may shorten the useful life of the valve, or worse, impair its proper operation. This excessive wear will increase the ongoing cost of maintaining or replacing a prematurely worn valve. One other aspect of relief valves can be the reduction in their seal integrity or force as the system pressure approaches the setpoint. This could possibly lead to fugitive emissions, an undesirable condition.

An effective approach to mitigating some of the effects of exposure to the process media is to install a rupture disc upstream of the safety valve inlet. Isolating a relief or safety valve from the process media through the installation of a rupture disc upstream of the valve inlet will eliminate exposure of the costly valve to effects of the media. It is necessary to establish proper rating and selection for the rupture disc to avoid any impairment of the overall operation of the relief valve, but the selection criteria are not complex. A number of benefits can accrue with this concept.
  • Rupture disc isolates the valve from the media, allowing application of less costly valves fabricated of non-exotic materials.
  • Rupture discs are leak free and bubble tight, eliminating possibility of fugitive emissions from the safety relief valve, especially when system pressure may approach valve setpoint.
  • Relief valve inventory can be evaluated for reduction.
  • Longer valve life.
  • Less downtime.
The additional cost for the rupture disc enhancement can have a reasonable payback period, with all factors considered. In any case, the rupture disc protection makes for a cleaner relief valve installation. The document provided below provides some additional application recommendations and details.

Rupture discs and holders are available in sizes and materials for most applications. Share your ideas with a product specialist, combining your process knowledge with their product application expertise to develop an effective solution.

Thursday, December 7, 2017

Quarter Turn vs Linear Valves

fully lined ball valve
This lined ball valve is an example of a
quarter turn valve.
Image courtesy Flowserve - Atomac
Different types of valves are designed and applied for different roles in the process control. Linear valves and quarter-turn valves are two different types of valves utilized throughout industry to regulate and control fluid flow. Their design and construction reflect the intent of the valves’ application, with each being suited for a different class of use.

All valves operate by providing control of the position of an internal structure that impedes fluid passage to some degree. Generally, fluid flow at the valve can be characterized as one of three conditions, unrestricted (valve fully open), stopped (valve fully closed), and throttled (valve partially open). Process operational requirements will dictate whether just two (fully open and fully closed) or all three of those conditions will be needed. Many aspects of the fluid, the process, and the surrounding environment come into play when making an appropriate valve selection. Not always an easy task.

Linear valves are generally characterized by their straight line motion that is used to position the valve plug, disc, diaphragm or other flow controlling element. The shape, size, and arrangement of the linear valve trim is generally intended to empower the operator with a range of flow through the valve. Through its positioning, the linear valve is able to regulate fluid flow at a slower, but more accurate rate. The valves can move a disk or a plug into an orifice, or push a flexible material, such as a diaphragm, into the flow passage. Gate valves and fixed cone valves are common examples of linear motion valves. Linear valves are best applied as flow controllers, and are often suited for frequent operation and repositioning.

Quarter turn valves traverse from fully open to fully closed by a 90 degree rotation of a shaft connected to the controlling element. Their comparatively simple operation allows for a design that is rugged and compact. One distinction of the quarter turn valves is their ability to quickly reposition from open to closed positions. Torque requirements to operate the valves are generally low to moderate. Ball and butterfly valves are examples of quarter turn valves.

Depending on the specific scenario, linear valves and quarter-turn valves are optimal choices for particular process environments. The accuracy of the linear valve and its ability to move in a linear fashion as opposed to a quarter-turn comes coupled with easy maintenance and decreased likelihood of cavitation. Both valve types enjoy widespread use and should generally not be viewed as competing designs for the same application. Each has a range of applications where it excels.

Share your fluid flow control challenges of all types with valve specialists, leveraging your own knowledge and experience with their product application expertise to develop effective solutions.

Tuesday, November 28, 2017

Application Survey for Industrial Flame Arrester

detonation flame arrester
Detonation flame arrester is one of several configurations
applicable to various installations.
Image courtesy Groth Corporation
A flame arrester operates by removing heat from the flame as it attempts to travel through narrow passages with heat-conductive walls. The arrester will stop a high velocity flame by absorbing heat away from the flame head, which lowers the burning gas/air mixture below its auto-ignition temperature, and creating an atmosphere where the flame cannot be sustained. The channels or passages in the flame arrester are designed to very efficiently conduct heat outward, but still allow the gasses to flow.

Many in-line flame arrester applications are used in systems that collect gases emitted by liquids and solids called vapor control systems. The gases are typically flammable. If an ignition occurs, a flame inside or outside of the system could occur with potentially catastrophic outcomes.

A vapor destruction system is a type of vapor control system that includes enclosed flare systems, elevated flare systems, burner and catalytic incineration systems, and waste gas boilers.

Vapor recovery systems are another type of vapor control system that uses in-line flame arresters. These systems include compression systems, vapor balancing, refrigeration, adsorption, and absorption.

Flame arresters are used in many industries including chemical, refining, petrochemical, pulp and paper, oil exploration and production, pharmaceutical, sewage treatment, landfills, power generation, and bulk liquids transportation.

The document below is a handy flame arrester application questionnaire. Please always consult with a properly qualified applications specialist prior to specifying, purchasing, or applying flame arresting devices.

Friday, November 17, 2017

Scotch Marine Boilers

cutaway view of two pass scotch marine boiler dryback configuration
Cutaway view of two-pass Scotch Marine Boiler
Image courtesy Williams & Davis Boilers
Boilers have a long history in the industrialization of the world. They were a primary source of motive power for many decades in the industrial revolution. Boilers continue to be an important source of both heat and motive power.

There is no shortage of lexicon in the boiler industry, with many legacy names for particular boiler designs. A Scotch Marine Boiler is a firetube boiler that was historically employed on ships. Firetube boilers channel the furnace combustion and resulting flue gases through an enclosure (for the furnace) and smaller diameter tubes. The shell of the boiler contains the water and steam, with the furnace and firetubes immersed within. Heat is transferred from the furnace and tubes into the water, producing hot water or pressurized steam as the unit design intends. Most of the heat from fuel combustion is passed to the water from the furnace chamber, with much of the remaining heat from the flue gases transferring from the firetubes. Once leaving the firetubes, the gases pass out of the boiler to a flue or chimney.

A dry-back boiler uses an enclosed chamber at the rear of the boiler to distribute the gases exiting the furnace section into the many firetubes. It is essentially just a box with the open entries to the firetubes and the open exit from the furnace penetrating its walls. The dry-back design facilitates access to the tubes for inspection and service.

There are other boiler configurations that serve to maximize various aspects of cost, service, and performance. Share your steam and hot water requirements with boiler and combustion specialists, leveraging your own knowledge and experience with their expertise to develop an effective solution.