Wednesday, July 19, 2017

Condensate Return in a Steam System - Basic and Essential

food and dairy production plant
Efficient production of steam and return of condensate
are essential to the operation of this and many other
industrial operations.
Many industrial processes and plants, as well as commercial buildings, utilize steam in their operations. The generation and use of steam is one of the oldest industrial processes and is so well understood that it may be considered more of a utility than part an industrial process. Whatever the case, if your process or installation uses steam, then steam is a necessary input for successful operation. Keeping your steam system performing at capacity frees up time and resources for the more complex aspects of your work.

If steam is not consumed directly by the process as a component input, it is steam's heat of vaporization that is utilized by the operation. Efficient use of steam as a heating medium results in the conversion of vapor to liquid (water). Returning the liquid condensate back to the boiler for conversion to vapor again is a necessary step in the efficient operation of a closed loop system.

Condensate return systems are certainly not high technology, but keep in mind that a steam system may be the lifeblood of not just one, but many operations throughout a plant. Avoiding downtime in the steam system, of which the condensate return system is an integral part, ranks highly on the list of "Important Things for Plant Operations". Condensate return is critical.

Three general methods are employed to move the condensate from a collection vessel, a trap, to the feedwater side of the boiler. Gravity can be used when conditions permit. A pressure motive return arrangement uses steam pressure and a coordinated valve sequence to drive the condensate through the piping system and back to the boiler. Condensate pumps can also be employed as a positive means of moving condensate through the return piping system.

What are some strong attributes of a good and reliable condensate return pump?
  • Minimize or eliminate cavitation at high temperatures. Cavitation will impede pump performance and cause premature deterioration of pump and drive components.
  • Ability to handle a high load during cold starts through motor and pump design.
  • Design and configuration to handle high temperatures without deterioration of pump and motor.
  • Develop higher pressure at lower motor speeds for extended service life.
  • Avoidance of mechanical seals below water line.
  • Consider a single unit with dual pumps for handling high loads and extending service life.
Specifying and installing a solidly designed and built condensate return pump may require an investment of your time and consideration. The return on that investment will be reduced maintenance, repair, and downtime. hare your steam system challenges, from end to end, with knowledgeable application specialists. Combining your intimate operational knowledge and experience with their deep product knowledge and experience with many installations will yield a good solution.

Monday, July 17, 2017

Filled Impulse Lines With Pressure Sensors

industrial process measurement and control pressure transmitter
Pressure sensors or transmitters are installed directly to
process lines or vessels, or remotely using impulse lines.
Image courtesy Azbil NA, Inc.
Pressure sensors intended for use in industrial process measurement and control applications are designed to be robust, dependable, and precise. Sometimes, though, it is necessary or beneficial to incorporate accessories in an installation which augment the performance of pressure sensors in difficult or hazardous environments. There are some scenarios where the sensor must be isolated from the process fluid, such as when the substance is highly corrosive.

A way to aid pressure sensing instruments in situations where direct contact must be avoided is by using a filled impulse line. An impulse line extends from a process pipe of vessel to a pressure measurement instrument or sensor. The line can have a diaphragm barrier that isolates the process fluid from the line, or the line can be open to the process. There are best practices that should be followed in the design and installation of an impulse line to assure that the line provides a useful transmission of the process pressure to the sensor and whatever degree of isolation or protection is needed remains in effect.

The filled impulse line functions via the addition of a non-harmful, neutral fluid to the impulse line. The neutral fluid acts as a barrier and a bridge, allowing the pressure sensing instrument to measure the pressure of the potentially harmful process fluid without direct contact. An example of this technique being employed is adding glycerin as a neutral fluid to an impulse line below a water pipe.

Glycerin’s freeze point is lower than water’s, meaning glycerin can withstand lower temperatures before freezing. The impulse line connected to the water pipe may freeze in process environments where the weather is exceptionally cold, since the impulse line will not be flowing in the same way as the water pipe. Since glycerin has a greater density and a lower freezing point, the glycerin will remain static inside the impulse line and protect the line from hazardous conditions.

The use of an isolating diaphragm negates the need for certain considerations of fill fluid density, piping layout, and the need to create an arrangement that holds the fill fluid in place within the impulse line. System pressure will be transferred across the diaphragm from the process fluid to the fill fluid, then to the pressure sensor. It is important to utilize fluids and piping arrangements that do not affect the accurate transference of the process pressure. Any impact related to the impulse line assembly must be determined, and appropriate calibration offset applied to the pressure sensor reading.

An essential design element of a filled impulse line without an isolating diaphragm is that the fill fluid must be compatible with the process fluid, meaning there can be no chemical reactivity between the two. Additionally, the two fluids should be incapable of mixing no matter how much of each fluid is involved in the combination. Even with isolating diaphragms employed, fluid harmony should still be considered because a diaphragm could potentially loose its seal. If such a break were to occur, the fluids used in filled impulse lines may contact the process fluid, with an impact that should be clearly understood through a careful evaluation.

Share your pressure measurement requirements and challenges with experienced application specialists, combining your own process knowledge and experience with their technical expertise to develop an effective solution.

Friday, July 7, 2017

Industrial Uses of Steam - Part 2

industrial steam boiler gas fired
Steam is used throughout commercial, institutional, and industrial facilities in various ways. In addition to other direct pressure and propulsion/drive applications, steam can be utilized as ‘motive fluid’ to assist in the movement of liquid and gas streams in a piping system. Jet ejectors can pull vacuum in equipment like distillation towers, allowing for the separation and purification of vapor streams. Continuously removing air from surface condensers via steam results in the desired vacuum pressure on condensing turbines to stay uniform. The entrance and subsequent diffusion of the steam through an inlet nozzle results in a low pressure zone, where the air from the surface condenser gets transferred. Similarly, steam serves as the primary motive fluid for secondary drainers, which pump condensate out of vented receiver tanks, flash vessels, and other process control components susceptible to stall conditions.

Steam is applicable to a process called atomization, wherein steam mechanically separates a fluid. Burners use steam for atomization by having steam injected into the fuel, thus maximizing the efficiency of the unit’s combustion while concurrently minimizing soot production. These steam generators and boilers, powered by fuel oil, use steam atomization to partition viscous oil into smaller droplets. Flares, similarly, utilize steam atomization as an exhaust pollutant reducer. In said flares, typically, the waste gas mixes with the steam prior to combustion.

Along with motive fluid and atomization, steam is also a fantastic cleansing tool. The soot in soot blowers gets removed via a steam cleaning process. Oil or coal fuel sourced boilers need soot blowers to cyclically clean the furnace walls and eliminate combusted deposits. These regularly scheduled cleanings allow for the capacity, durability, and effectiveness of the boiler to remain consistent. The nozzle of the soot blower directs the steam, dislodging dry, sintered ash and slag. Hoppers then catch the dislodged substances and they are expelled with other combusted gases.

Steam can also add moisture to a process while simultaneously acting as a heat supply source. In paper production, paper moving over rollers at high speed is moisturized by the steam, ensuring that no miniscule breaks or tears are suffered during the production process. Pellet mills, which produce animal feed, directly inject steam to heat and, concurrently, add to the water content of the feed as the feed passes through the mill’s direct conditioner section. The water softens the feed and then partially gelatinizes the starch content, leading to firmer pellets overall.

Lastly, commercial and industrial facilities utilize low pressure steam as a primary source of seasonal heating and humidification. Finned or bare coils, coupled with steam humidifiers, condition the facility air, keeping the temperature regulated for both comfort and preservation of items like books and records. Steam coils heat the cool air, resulting in the relative humidity dropping. The controlled injection of dry, saturated steam allows for moisture addition to regulate the relative humidity in a smooth and precise manner via steam humidifiers installed in air ducts.

Share your steam generation and use challenges with steam system and combustion experts, combining your own knowledge and experience with their expertise to develop effective solutions.

Monday, June 26, 2017

Industrial Uses of Steam – Part 1

gas fired boiler in equipment room
Boilers are the most common production equipment
for industrial steam applications
Steam is used throughout industrial process control operations in various ways. The ability of steam to serve as a means to deliver heat and provide motive power to a facility or process keeps it in wide use throughout many industries.

Heating with steam can by of a direct or indirect nature. Direct heating uses steam distributed into or onto a substance to directly affect its temperature. In order to ensure success in direct heating, mixing needs to occur so that the temperature of the substance is uniformly impacted. Indirect heating uses one of the many available forms of heat exchangers to transfer heat from steam to process fluid across a physical barrier that isolates the process fluid from the steam.

Industries employ steam for many valuable uses. Food processing factories, refineries, and chemical plants utilize positive pressure steam. In most instances, steam is delivered to equipment, typically, at pressures above atmospheric and at a temperature exceeding 100°C. Process fluid heat exchangers, reboilers, air preheaters for combustion, and a range of other heat transfer equipment uses steam as the heat source. A shell and tube heat exchanger raises product temperature on its passage through the unit. Ideally, the heat exchanger expels condensate after removing the latent heat from the steam. Condensate can be collected and returned to the steam generation portion of the system, conserving much of the energy used to originally heat the water.

Hot water was the main agent traditionally used for heating at temperatures below 100°C. Using steam to heat at temperatures below the 100°C benchmark is an increasingly popular technique. Vacuum saturated steam can be applied in the same way as positive pressure saturated steam, but the steam temperature is adjustable by altering the pressure. The ability to change the pressure (and the temperature) allows for more precise temperature control when compared to using hot water. Another advantage of using steam over hot water is that the steam heating system is fast and precise. The desired temperature can be reached quickly and uniformly.

Another popular use for steam in industrial settings is as a propulsion or drive force. Steam turbines generate electricity in thermal power plants. A recent trend, developed to minimize wasted energy, is applying steam at increasingly higher temperatures and pressures. Superheated steam, used in steam turbines, acts as a counter to potential damage to the equipment resulting from condensate in the turbine section. Less chance of condensate in the turbine translates into a reduced risk of equipment damage or failure. Nuclear power plants, though, cannot utilize the advantages of superheated steam because of complications arising involving the steam and the turbine material. To combat this problem, high pressure saturated steam is utilized instead, with upstream separators installed to remove condensate from the steam flow. In addition to power generation, steam acts as the force behind turbine driven compressors and pumps, including gas compressors and cooling tower pumps.

Depending on the process being controlled and the specific industry’s demands, the simplicity and various applications of steam make this reliable medium a first choice for industrial operations. Share your steam system and use challenges with combustion and steam experts, combining your own knowledge and experience with their specialized expertise to develop effective solutions.

Tuesday, June 20, 2017

Wireless Transmitters In Process Measurement and Control

oil refinery
Industrial process instrumentation connectivity can present
substantial challenges.
In process control, various devices produce signals which represent flow, temperature, pressure, and other measurable elements of the process. In delivering the process value from the measurement point to the point of decision, also known as the controller, systems have traditionally relied on wires. More recently, industrial wireless networks have evolved, though point-to-point wireless systems are still available and in use. A common operating protocol today is known as WirelessHART™ , which features the same hallmarks of control and diagnostics featured in wired systems without any accompanying cables.

Wireless devices and wired devices can co-exist on the same network. The installation costs of wireless networks are decidedly lower than wired networks due to the reduction in labor and materials for the wireless arrangement. Wireless networks are also more efficient than their wired peers in regards to auxiliary measurements, involving measurement of substances at several points. Adding robustness to wireless, self-organizing networks is easy, because when new wireless components are introduced to a network, they can link to the existing network without needing to be reconfigured manually. Gateways can accommodate a large number of devices, allowing a very elastic range for expansion.

In a coal fired plant, plant operators walk a tightrope in monitoring multiple elements of the process. They calibrate limestone feed rates in conjunction with desulfurization systems, using target values determined experientially. A difficult process environment results from elevated slurry temperature, and the associated pH sensors can only last for a limited time under such conditions. Thanks to the expandability of wireless transmitters, the incremental cost is reduced thanks to the flexibility of installing new measurement loops. In regards to maintenance, the status of wireless devices is consistently transmitted alongside the process variable. Fewer manual checks are needed, and preventative measures may be reduced compared to wired networks.

Time Synchronized Mesh Protocol (TSMP) ensures correct timing for individual transmissions, which lets every transmitter’s radio and processor ‘rest’ between either sending or receiving a transmission. To compensate for the lack of a physical wire, in terms of security, wireless networks are equipped with a combination of authentication, encryption, verification, and key management. The amalgamation of these security practices delivers wireless network security equal to that of a wired system. The multilayered approach, anchored by gateway key-management, presents a defense sequence. Thanks to the advancements in modern field networking technology, interference due to noise from other networks has been minimized to the point of being a rare concern. Even with the rarity, fail-safes are included in WirelessHART™.

All security functions are handled by the network autonomously, meaning manual configuration is unnecessary. In addition to process control environments, power plants will typically use two simultaneous wireless networks. Transmitters allow both safety showers and eyewash stations to trigger an alarm at the point of control when activated. Thanks to reduced cost, and their ease of applicability in environments challenging to wired systems, along with their developed performance and security, wireless industrial connectivity will continue to expand.

Share your process measurement requirements and challenges with application specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.


Friday, June 16, 2017

Common Industrial and Commercial Process Heating Methods

Gas fired boilers in industrial facility
Gas fired boilers used the combustion of fuel to produce
steam which is utilized by other process equipment
Many industrial processes involve the use of heat as a means of increasing the energy content of a process or material. The means used for producing and delivering process heat can be grouped into four general categories.
  • Steam
  • Fuel
  • Electric
  • Hybrid
The technologies rely upon conduction, convection, or radiative heat transfer mechanisms, soley or in combination, to deliver heat to a substance. In practice, lower temperature processes tend to use conduction or convection. Operations employing very high temperature rely primarily on radiative heat transfer. Let's look at each of the four heating methods.

STEAM

Steam based heating systems introduce steam to the process either directly by injection, or indirectly through a heat transfer device. Large quantities of latent heat from steam can be transferred efficiently at a constant temperature, useful for many process heating applications. Steam based systems are predominantly for applications requiring a heat source at or below about 400°F and when low-cost fuel or byproducts for use in generating the steam are accessible. Cogeneration systems  (the generation of electric power and useful waste heat in a single process) often use steam as the means to produce electric power and provide heat for additional uses. While steam serves as the medium by which heat energy is moved and delivered to a process or other usage, the actual energy source for the boiler that produces the steam can be one of several fuels, or even electricity.

FUEL

Fuel based process heating systems, through combustion of solid, liquid, or gaseous fuels, produce heat that can be transferred directly or indirectly to a process. Hot combustion gases are either placed in direct contact with the material (direct heating via convection) or routed through tubes or panels that deliver radiant heat and keep combustion gases separate from the material (indirect heating). Examples of fuel-based process heating equipment include furnaces, ovens, red heaters, kilns, melters, and high-temperature generators. The boilers producing steam that was described in the previous section are also an example of a fuel based process heating application.

ELECTRICITY

Electric process heating systems also transform materials through direct and indirect means. Electric current can be applied directly to suitable materials, with the electrical resistance of the target material causing it to heat as current flows. Alternatively, high-frequency energy can be inductively coupled to some materials, resulting in indirect heating. Electric based process heating systems are used for heating, drying, curing, melting, and forming. Examples of electrically based process heating technologies include electric arc furnace technology, infrared radiation, induction heating, radio frequency drying, laser heating, and microwave processing.

HYBRID

Hybrid process heating systems utilize a combination of process heating technologies based on different energy sources or heating principles, with a design goal of optimizing energy performance and overall thermal efficiency. For example, a hybrid steam boiler may combine a fuel based boiler with an electric boiler to take advantage of access to low off-peak electricity cost. In an example of a hybrid drying system, electromagnetic energy (e.g., microwave or radio frequency) may be combined with convective hot air to accelerate drying processes; selectively targeting moisture with the penetrating electromagnetic energy can improve the speed, efficiency, and product quality as compared to a drying process based solely on convection, which can be rate limited by the thermal conductivity of the material. Optimizing the heat transfer mechanisms in hybrid systems offers a significant opportunity to reduce energy consumption, increase speed and throughput, and improve product quality.

Many heating applications, depending on scale, available energy source, and other factors may be served using one or more of the means described here. Determining the best heating method and implementation is a key element to a successful project. CTI Controltech specializes in combustion applications and the industrial production and use of steam. Share your process and project challenges with them and combine your facilities and process knowledge and experience with their engineering expertise to develop effective solutions.

Friday, June 9, 2017

Dual Input Industrial Temperature Transmitter - What You Can Do

dual input advanced industrial temperature transmitter
Dual input advanced industrial transmitter
has many built in functions
Courtesy Azbil
You will likely find temperature measurement to be a part of almost every industrial process. It is a mainstay of commercial and industrial processes and operations globally. Accurate measure of process, equipment, or product temperature provides operators with useful information that is utilized in countless ways. The range of available instruments and equipment for measuring temperature in industrial process settings is extensive, with devices or varied types, performance, and form factor to accommodate every application.

There are a variety of instruments and methodologies for measuring temperature, the most common of which is probably direct contact between the target substance and an appropriate temperature sensor. Industrial process applications are commonly served by thermocouples or resistance temperature detectors (RTD), chosen for their cost, accuracy, and flexibility of installation.

Every operating process is "critical" to some group of stakeholders. The process may be of great importance for a number of reasons:
  • The process output may serve as an input to another process with great value.
  • The process output may be of great direct value to the stakeholders.
  • The process may have significant levels of hazard associated with improper or out of control operation.
  • Out of control operation may result in substantial financial loss to the stakeholders.
When temperature is an important indicator of process function, whether for financial or safety reasons, the operator cannot tolerate a loss of the temperature signal. One manufacturer has an advanced solution in the form of a dual input temperature transmitter with built in functions that:
  • Switch to the backup sensor if the primary has a failure indication.
  • Alert the operator if the deviation between the two sensor readings indicates sensor drift. 
  • In wide range temperature applications, switch between sensors with differing measurement ranges for better accuracy.
Along with HART communications and other useful features, these advanced temperature transmitters can help reduce risk and increase performance and safety. Assess how these advanced devices can enhance your process performance. A product data sheet is included below. Product specialists can help with product configuration and selection, along with any application concerns you may have.