Wednesday, August 31, 2016

Rupture Disc Sizing Technical Bulletin

rupture disc
Rupture disc (Fike)
The objective of this bulletin is to provide detailed guidance for sizing rupture discs using standard methodologies found in ASME Section VIII Div. 1, API RP520, and Crane TP-410. To assist in the sizing process, contact Flow-Tech at 410-666-3200 for help.

Overpressure Allowance

When sizing pressure relief devices, the Code defines the maximum pressure that may build up in the pressure vessel while the device is relieving. This pressure varies depending on the application of the device. The following table defines the various overpressure allowances.

Rupture Disc Sizing Methodologies

There are 3 basic methodologies for sizing rupture disc devices:
  • Coefficient of Discharge Method (KD) — The KD is the coefficient of discharge that is applied to the theoretical flow rate to arrive at a rated flow rate for simple systems.
  • Resistance to Flow Method (KR) — The KR represents the velocity head loss due to the rupture disc device. This head loss is included in the overall system loss calculations to determine the size of the relief system.
  • Combination Capacity Method — When a rupture disc device is installed in combination with a pressure relief valve, the valve capacity is derated by a default value of 0.9 or a tested value for the disc/valve combination. See technical bulletin TB8101 for specific application requirements when using rupture disc devices in combination with PRVs.

Monday, August 29, 2016

Flow Measurement of Activated Sludge

Flexim flowmeter
Better, non-invasive,
alternative for
activated sludge.
Reprinted with permission from Flexim

A wastewater treatment plant that serves 1,800 households includes several mechanical and biological wastewater treatment facilities.

The mechanical treatment consists of a screening system and an aerated circular grit trap. The biological treatment is carried out in a combi-tank (biological treatment stage outside, secondary clarifier-settler basin inside).

The plant also includes facilities for the removal of nitrogen which is carried out by intermittent nitrification/denitrification. In addition, the plant also has a static sludge thickener. The activated sludge, which has been formed in the biological treatment stage through the growth of microorganisms, slowly separates via gravity in the secondary clarifier basin.

A portion of the activated sludge is fed back into the biological treatment stage as return sludge and mixed with the newly added nutrient-rich wastewater. The amount of return sludge should always be in a defined ratio to the current feed quantity. For this reason, the flow rate of the recirculation pipeline has to be measured.

The installation of a wetted magnetic-inductive flowmeter, which is very common in the water and wastewater industry, would have required modifications to the piping and subsequent expensive civil engineering work. The only available manhole location on the buried recirculation pipeline has not been suitable for retrofitting a magnetic-inductive flowmeter. Moreover, the pipeline in the manhole is always submerged in water.

Retrofitting the measurement point with a FLEXIM non-invasive ultrasonic flow meter, including IP68 fully submersible transducers, proved to be a convincingly simple, accurate, reliable and cost effective solution.

There is no need to open the pipeline when mounting the transducers onto the outside of the pipe and therefore no interruption to operation. The cramped installation point in the flooded shaft does not pose a particular challenge to FLEXIM’s measuring system: the IP68 transducers can be operated while permanently submerged and, since they were installed, they have been providing highly reliable measurements for automatic control of the pumps that convey the return flow quantity of the activated sludge.

Advantages
  • Reliable and accurate flow measurement of activated sludge for automatic pump control
  • Secure automatic control of the recirculation proportional to the demand
  • Easy to retrofit measuring point during ongoing operation, without any pipe work and without the need to modify the existing pipeline system
  • No expense for civil engineering and excavation work
  • Submersible IP68 transducers guarantee long-term stable measurements

Monday, August 22, 2016

Measuring pH and ORP eBook

Get your copy of this 72 page
eBook (courtesy of Yokogawa)

Measuring pH/ORP is very common, but taking true measurements and correct interpretation of the results is not self-evident. Certain effects can potentially cause problems if not taken into consideration.

The purpose of this book is to provide a comprehensive understanding of pH/ORP measurement and how to achieve reliable results. Basic information on the principles of measuring pH/ORP, the construction of the sensing elements and their basic use in process applications are provided.

A part of achieving accurate and reliable pH/ORP measurements requires sufficient and correct maintenance and storage conditions. Prevention of common errors during maintenance and storage, as well as consistent detection of loop failures is important. This book describes how these can be avoided and how failures can be detected.

This book is accompanied with a frequently asked question and answer section as well as an appendix that includes helpful information like a Chemical Compatibility Table and a Liquid-Application-Data-Sheet, which can be used to describe the user’s application.

Tuesday, August 9, 2016

Non-contact, Radiometric Level Detection for Liquids or Solids

Radiometric level detection
Radiometric level detection
(courtesy of RONAN)
Radiometric level detection, using a very low gamma level source, is designed to deliver outstanding performance in a wide range of difficult applications and process conditions for both liquids and bulk solids which include the most dangerous materials such as caustic, toxic, corrosive, explosive, and carcinogenic irrespective of their viscosity and temperature.

These level gauges meet “As-Low-As-Reasonably-Achievable” (ALARA) guidelines. Source activity is customized depending on vessel and process parameters such as diameter, wall thickness, material, and measurement span to ensure optimum sensitivity, economy and safety while keeping the source activity to a minimum.

An exclusive “Radiation Low Level” (RLL) source holder uses up to 100 times less gamma energy than comparable gauges, and is the only source holder recognized by the NRC to be so safe that it does not require the stringent documentation, training or handling procedures of other systems.

How it Works

Radiometric level detection
Sources and Detector Mounted
External to Vessel 
Radiometric level measurement provides a safe and efficient, non-contact method to measure liquids or solids in harsh process environments. Each system consists of a gamma source, detector and microprocessor.
  • The gamma source, typically mounted external to the vessel emits energy through the vessel walls collimated in a direction towards the detector mounted on the opposite side of the vessel. The gamma energy reaches the detector when the vessel is empty. As the process level rises in the vessel, the gamma energy reaching the detector will decrease in an inversely proportional relationship to the level. 
  • The detector measures the level of energy and sends a proportional signal to the microprocessor. 
  • The microprocessor linearizes, filters, and correlates this signal to a level measurement. 
The entire system is mounted external to the vessel and can be easily installed and maintained while the process is running ... without expensive down time, vessel modifications or chance of accidental release.

Applications
Radiometric level detection
Low Level Source and Detector
Mounted External to Vessel

  • Solids or Liquid Measurement 
  • Measurement Not Affected by: 
  • Internal Obstructions. i.e. Agitators Extreme Process Temperatures 
  • Caustic Processes 
  • Violent Product Flow 
  • Sterile Process 
  • Changing Process 
  • Variable Product Flow 
  • Automatic Compensation for Vapor Density Changes 
  • Automatic Compensation for Foam or Gasses 
  • Automatic Compensation for Process Build-Up 
  • Detectors Contoured to the Shape of Vessels 
  • Upgrade Utilizing Existing Sources 
Features and Benefits
  • Accurately Measures the Most Complex Processes 
  • Solid Crystal or Flexible Scintillating Fill- Fluid 
  • Excellent Measurement Reliability due to Proprietary Filtering Technology 
  • Level Detection of Multiple Interfaces 
  • Low Maintenance / No Component Wear 
  • Auto-Calibration
For more information in Maryland or Virginia, contact:
Flow-Tech
410-666-3200 MD
804-752-3450 VA