Tuesday, October 31, 2017

Super-fast Changeout of Sanitary Temperature Sensor

ReoClick Sanitary Temperature Sensor
Diagram 1
Many BioTech & Pharmaceutical companies test their temperature sensors with in-house calibration baths in order to ensure sensor accuracy. Accurate temperatures are so critical to ensuring a consistent product, that calibration checks are required before each batch is started.

Most existing temperature sensors have a threaded connection which would twist and tangle the extension wires when unthreaded for calibration. The only alternative to unthreading the connection is to disconnect the wires from the terminal. This wastes time and complicates the calibration process.

Manufacturer REOTEMP engineered a great solution. A product named "ReoClick" makes disconnecting and re-connecting the sensor from the process easy. With the click of a button, the temperature sensor is released from the the process, leaving the female adapter in place (see diagram 1). The sensor is then placed into a temperature bath for a quick calibration check and snapped back into service in a matter of seconds.

To make the design even better, REOTEMP incorporated a replaceable temperature element. The element can be easily removed when sensor replacement is eventually needed. This allows the customer to reuse their existing leadwire assembly, male insert, and female adapter (see diagram 2).

ReoClick Sanitary Temperature Sensor
Diagram 2

Along with those cost savings, the customer has avoided the usual headache associated with replacing a competitor’s elements: disconnecting wires, terminal blocks, reconnecting components, etc..

For more information about the ReoClick sanitary sensor, contact Power Specialties by visiting http://www.powerspecialties.com/article_54_REOTEMP.cfm or calling (816) 353-6550.

Tuesday, October 24, 2017

The Pro's and Con's of Industrial Thermocouples and RTD's

Thermocouples and RTDs are the two most common type of industrial temperature sensors. A thermocouple is a temperature sensor that produces a micro-voltage relative to a temperature change which can be measured, conditioned, and amplified into a standard process signal. RTD’s are temperature sensors that measure a change in electrical resistance relative to the temperature surrounding the RTD element. Each have their advantages and disadvantages, and should be applied understanding their respective strengths and weaknesses.

RTD’s are commonly used in applications where repeatability and accuracy are important considerations. Properly constructed Platinum RTD’s have very repeatable resistance vs. temperature characteristics over time. If a process will be run at a specific temperature, the specific resistance of the RTD at that temperature can be determined in the laboratory and it will not vary significantly over time. RTD’s also allow for easier interchangeability since their original variation is much lower than that of thermocouples. For example, a Type K thermocouple used at 400°F has a standard limit of error of – 4°F. A 100 Ohm DIN, Grade B platinum RTD has an interchageability of – 2.2°F at this same temperature. RTD’s also can be used with standard instrumentation cable for connection to display or control equipment where thermocouples must have matching thermocouple wire to obtain an accurate measurement.

In the same configuration, you can expect to pay from 4 to 10 times more for an RTD than for a base metal thermocouple. RTD’s are more expensive than thermocouples because there is more construction required to make the RTD including manufacture of the sensing element, the hooking up of extension wires and assembly of the sensor. RTD’s do not do as well as thermocouples in high vibration and mechanical shock environments due to the construction of the sensing element. RTD’s are also limited in temperature to approximately 1200°F where thermocouples can be used as high as 3100°F

Thermocouples can be used to temperatures as high as 3100°F, generally cost less than RTD’s and they can be made smaller in size (down to approximately .020” dia) to allow for faster response to temperature. Thermocouples are also more durable than RTD’s and can therefore be used in high vibration and shock applications.

Thermocouples are less stable than RTD’s when exposed to moderate or high temperature conditions. In critical applications, thermocouples should be removed and tested under controlled conditions in order to verify performance. Thermocouple extension wire must be used in hooking up thermocouple sensors to thermocouple instrument or control equipment. Use of instrumentation wire (plated copper) will result in errors when ambient temperatures change.

Both thermocouples and RTD’s are useful instruments for determining process temperature. RTD’s provide higher accuracy than thermocouples in their temperature range because platinum is a more stable material than are most thermocouple materials. RTD’s also use standard instrumentation wire to connect to the measurement or control equipment.

Thermocouples are generally less expensive than RTD’s, they are more durable in high vibration or mechanical shock applications and are usable to higher temperatures. Thermocouples can be made smaller in size than most RTD’s so they can be formed to fit a particular application.

Contact Power Specialties by visiting http://www.powerspecialties.com or calling (816) 353-6550 for more information on temperature sensors.

Abstracted from Pyromation's White Paper "How to Select and Use the Right Temperature Sensor".

Monday, October 23, 2017

Understanding Overpressure and Overpressure Protection for Yokogawa DPharp EJX/EJA-E Series Transmitters

The video below demonstrates what overpressure is, how it effects pressure transmitters, and the mechanism Yokogawa deploys for overpressure protection for on their DPharp EJX/EJA-E series.

For more information on Yokogawa in Iowa, Kansas, Nebraska, or Missouri, contact Power Specialties by visiting http://www.powerspecialties.com or calling (816) 353-6550.

Tuesday, October 17, 2017

Type K Drives on Fly Ash Hopper Rotary Gates Save Vast Sums of Money and Time

Type K Series AH damper drives
Type K drive on rotary gate.
A power generating facility in the mid-West just took for granted that purchasing and replacing 40-50 pneumatic cylinders PER YEAR to operate fly ash hopper rotary gates (valves) was normal. The maintenance department just chalked up the expenditure to “normal maintenance” due to this very tough application.

The application requires the pneumatic conveyors, operating under the precipitators, collect the flyash and push into collection bins using compressed air. In this application, pneumatic cylinders stroke full open, and closed, every 90-120 seconds, 24 hours a day, 7 days a week. That works out to around a grueling 720 cycles per day in a dirty, hot, and abrasive environment.

Fly ash is a term used for by-products of combustion and flue gases. Nearly half of this fly ash is reused for purposes such as dry wall production and cement mixes. Because of it's abrasive qualities and high temperatures, fly ash is a difficult material to handle reliably. It's handling takes a particularly tough toll on the valves and drives that control it's movement.

A decision was made to replace the air cylinders with Rotork Type K Series AH damper drives after a visit from a local sales engineer. Along with the new drives, high-cycle “no-play” linkage kits (that eliminate hysteresis) were retro-fitted to the existing ash hopper equipment.

After five years in service, there have been no failures.  Not a single work order has been issued, no spare parts have been required, no seal kits installed and no units have been removed for servicing for any reason. Eliminating the cost of 50 air cylinders a year was quite significant, but even greater was the savings from the time and labor eliminated from their annual replacement.

For more information on this application, or on any damper drive application, visit Power Specialties at http://www.powerspecialties.com or call (816) 353-6550.