Tuesday, December 19, 2017

Blowdown Tanks in Steam Systems

schematic of boiler blowdown tank with thermostatic cooling valve
Schematic for applying blowdown tank in steam system.
Image courtesy Colton Industries
Blowdown, in a steam system, serves as a means to remove condensate or reduce the accumulation of minerals and contaminants in a boiler. The temperature and pressure of the effluent precludes its discharge into most municipal sewers, requiring a means to collect the discharge and reduce its temperature prior to final disposal.

A blowdown tank is designed as a receiver which vents flash steam to atmosphere and provides for cooling of the condensate prior to final discharge. A vent connection at the top of the tank is normally routed to a safe discharge location outdoors. In some cases, a condenser may be applied to the vented steam. The condensate collects in the tank and cools as heat is radiated from the tank walls, generally steel or stainless steel. Faster cooling can be accomplished with the incorporation of a thermostatic cooling valve that mixes cold water with the condensate.

The blowdown tanks have no moving parts and few requirements for maintenance. Good practice calls for periodic inspection for wall erosion and corrosion. An inspection hatch provides access to the tank interior.

Share your steam system requirements and challenges with specialists, leveraging your own knowledge and experience with their product application expertise to develop effective solutions.



Wednesday, December 13, 2017

Storage and Process Tanks

industrial sanitary stainless steel process tanks
Industrial process tanks use measurement instruments
to reveal the nature of their contents.
Storage and process tanks are employed throughout a broad range of industrial, research, and commercial applications. The design and construction of the vessels varies widely, but there are a few measurement and control functions common to almost all applications. Whether general purpose or very specialized, a process or facility operator with a tank will need to know…
  • Nature of the contents. What is in the tank.
  • Quantity of material in the tank. This can be expressed as weight, mass, level or volume.
  • Condition of the material in the tank. This can include temperature, pressure, or a range of other specific attributes which may have a bearing on the process or operation for which the material is to be used or applied.
Instrumentation and fixtures of varying styles and types are used to provide information relating to the three areas noted above. A broad range of tank level measurement techniques and instruments are employed to quantify tank contents. Specialized sensors can be used to measure conductivity, pH, and a host of other material aspects.

Industrial storage tanks are used as containers for everything from water to fuels to chemicals. Contents may be pressurized or blanketed with ignition suppressing gases, such as nitrogen. The construction of a process tank must meet requirements for safety and functionality related to its specific use. Well known commercial applications include those in food, beverage, and dairy sectors. Every industrial or commercial use will have standards for physical safety, product safety and quality, as well as requirements for effective integration into whatever system the application presents.

Mixing tanks perform a different function in the control process as opposed to storage tanks. Mix tanks are involved in batching and blending processes. Made of glass, plastic, sturdy rubber, or stainless steel, mixing tanks blend different substances together to create materials for production. The refined mixing process occurs as certain amounts of liquids are funneled into the tank from lines leading to the tank. The tanks may be provided with specialized fixtures or apparatus to facilitate the combining of constituent substances. Depending upon the application, the components may not all be liquid.

The term “tanks”, per se, encompasses practically an entire industry in itself. The variety of sizes, forms, materials, and accessory features is enormous. Share your tank instrumentation and measurement challenges with process measurement specialists, leveraging your own knowledge and experience with their product application expertise to develop an effective solution.

Friday, December 8, 2017

Comprehensive Planning for Heat Trace and Surface Heating Challenges

refinery with workers
Applications for process heating are numerous and varied,
found throughout industrial and commercial settings. 
Keeping process or inventory liquids from freezing, or becoming extremely viscous, can be an important part of a commercial or industrial operation. Freeze damage to equipment, piping, containers or their contents can result in a wide array of consequences, all of them likely to be negative.

Developing an overall plan for freeze protection can be advantageous to attacking each application on an independent basis.
  • Having a common vendor for all freeze protection equipment and supplies can help designers develop a knowledge base about how to meet application challenges with specific products, speeding implementation time. Service techs become familiar with applied products and methods, building their skills and efficiency at installing and maintaining applications throughout the facility.
  • Identify all locations where freeze protection is needed. Develop a baseline of the methods employed and equipment installed to meet the needs of each location. Good records form the basis for good maintenance and the ability to make decisions regarding the operation and performance of each system.
  • When selecting the products or methods to employ for freeze protection, consider the environment in which the hardware will be installed. Will it require protection from physical damage, chemical attack, or extreme weather. Is the installation space considered a hazardous zone, requiring special certifications for the heating equipment?
  • The availability and control of applied heat can also be important. Is there a need for the heating system to deliver highly variable amounts of heat across the range of possible operating scenarios, in order to avoid overheating the process or stored materials? How quickly will the system need to ramp up to the desired operating temperature or respond to changes in an operating process?
These questions, and probably others specifically related to your application, should be part of the consideration for freeze protection applications. Enlisting the cooperation of a process heat specialist can apply leverage to your own process knowledge and experience to develop an effective solution to each challenge.

Check this link and request a copy of the Freeze Protection Planning Guide.

Friday, December 1, 2017

The Possible vs. The Probable

Overhead view of the Arkema plant in Corsby, Texas.
Image from United States Chemcial Safety Board 
Process stakeholders have concerns and responsibilities regarding operational safety, environmental impact, profitability, and more. At almost every level, the risk of loss, damage, or disaster is scrutinized and evaluated. Steps may be taken to prevent or reduce the impact of some negative event. Other risk reduction methods might be put into play to provide relief from losses suffered. Whatever the case, it is safe to say that much industrial effort is invested in predicting a broad range of "what if" scenarios.

The recent events at the Arkema chemical plant in Crosby, Texas bring to light the limitations we, as process operators of any type, may put on our own thinking and actions. Though investment was made, and was ongoing, to improve aspects of the plant, the operation was still brought to a standstill and a fire ensued that brought the involvement of the US Chemical Safety Board. This resulted because natural events that were likely deemed impossible became reality, with insufficient contingency operations in place to handle the situation.

What is important about the event is what we can all learn from it, what we can use to modify and improve our own methods of evaluating risk and implementing protections to prevent loss and damage. Essentially, the plant was overwhelmed by storm induced flooding that was unprecedented. Grid and backup power sources were rendered inoperable and material that required refrigeration to maintain a safe condition no longer was provided with the needed cold storage environment.

arkema chemical plant timeline hurricane harvey US chemical safety board
Timeline of events related to a fire at the Arkema chemical plant in Crosby, TX
Image is from US Chemical Safety Board 
The relationships between an operation and its surrounding environment are not static. The probability of any event occurring is never zero. When probabilities are perceived as being very small, they might be ignored, but low probability events can and do eventually become part of the plant environment. Developing strong contingency plans and incorporating design elements into an operation that account for events that seem impossible, but are actually of very low probability, is a good industrial practice that hardens the process or facility against disaster.

Share and discuss your concerns and plans with process instrumentation and control specialists, leveraging your own knowledge and experience with their resources to develop a better solution.