The calculation formula is as follows:
Where:
D - pipeline diameter, mm
Q - flow rate, m3/h
v - permissible flow speed in m/s
The specific volume of saturated steam at a pressure of 10 bar is 0.194 m3/kg, which means that the volumetric flow rate of 1000 kg/h of saturated steam at 10 bar will be 1000x0.194=194 m3/h. The specific volume of superheated steam at 10 bar and a temperature of 300°C is equal to 0.2579 m3/kg, and the volumetric flow rate with the same amount of steam will already be 258 m3/h. Thus, it can be argued that the same pipeline is not suitable for transporting both saturated and superheated steam.
Here are some examples of pipeline calculations for different environments:
1. Medium - water. Let's make a calculation at a volumetric flow rate of 120 m3/h and flow velocity v=2 m/s.
D= =146 mm.
That is, a pipeline with a nominal diameter of DN 150 is required.
2. Medium - saturated steam. Let's make a calculation for the following parameters: volume flow - 2000 kg/h, pressure - 10 bar at a flow speed - 15 m/s. In accordance with the specific volume of saturated steam at a pressure of 10 bar is 0.194 m3/h.
D= 
= 96 mm.
That is, a pipeline with a nominal diameter of DN 100 is required.
3. Medium - superheated steam. Let's make a calculation for the following parameters: volume flow - 2000 kg/h, pressure - 10 bar at a flow speed of 15 m/s. The specific volume of superheated steam at a given pressure and temperature, for example, 250°C, is 0.2326 m3/h.
D= 
=105 mm.
That is, a pipeline with a nominal diameter of DN 125 is required.
4. Medium - condensate. In this case, the calculation of the diameter of the pipeline (condensate pipeline) has a feature that must be taken into account when making calculations, namely: it is necessary to take into account the share of steam from unloading. The condensate, passing through the condensate trap and entering the condensate pipeline, is unloaded (that is, condensed) in it.
The share of steam from unloading is determined by the following formula:
Share of steam from unloading = 
, Where
h1 is the enthalpy of condensate in front of the steam trap;
h2 is the enthalpy of condensate in the condensate network at the corresponding pressure;
r is the heat of vaporization at the corresponding pressure in the condensate network.
Using a simplified formula, the share of steam from unloading is determined as the temperature difference before and after the condensate trap x 0.2.
The formula for calculating the diameter of the condensate pipeline will look like this:
D= 
, Where
DR - share of condensate discharge
Q - amount of condensate, kg/h
v” - specific volume, m3/kg
Let us calculate the condensate pipeline for the following initial values: steam flow - 2000 kg/h with pressure - 12 bar (enthalpy h'=798 kJ/kg), unloaded to a pressure of 6 bar (enthalpy h'=670 kJ/kg, specific volume v" =0.316 m3/kg and heat of condensation r=2085 kJ/kg), flow speed 10 m/s.
Share of steam from unloading = 
= 6,14 %
The amount of unloaded steam will be equal to: 2000 x 0.0614 = 123 kg/h or
123x0.316= 39 m3/h
D= 
= 37 mm.
That is, a pipeline with a nominal diameter of DN 40 is required.
ALLOWABLE FLOW RATE
The flow velocity indicator is an equally important indicator when calculating pipelines. When determining flow rate, the following factors must be considered:
Pressure loss. At high flow rates, smaller pipe diameters can be selected, but this will result in significant pressure loss.
Pipeline costs. Low flow rates will result in larger piping diameters being selected.
Noise. High flow speed is accompanied by increased noise effect.
Wear. High flow rates (especially in the case of condensate) lead to erosion of pipelines.
As a rule, the main cause of problems with condensate drainage is precisely the undersized diameter of the pipelines and the incorrect selection of condensate drains.
After the condensate drain, condensate particles, moving through the pipeline at the speed of steam from unloading, reach the bend, hit the wall of the rotary outlet, and accumulate at the bend. After this, they are pushed along the pipelines at high speed, leading to their erosion. Experience shows that 75% of leaks in condensate lines occur in pipe bends.
To reduce the likely occurrence of erosion and its negative impact, it is necessary for systems with float steam traps to take a flow velocity of about 10 m/s for calculation, and for systems with other types of steam traps - 6 -8 m/s. When calculating condensate pipelines in which there is no steam from unloading, it is very important to make calculations as for water pipelines with a flow rate of 1.5 - 2 m/s, and in the rest take into account the share of steam from unloading.
The table below shows flow rates for some media:
Wednesday | Options | Flow velocity m/s |
Steam | up to 3 bar | 10-15 |
3 -10 bar | 15-20 |
|
10 - 40 bar | 20-40 |
|
Condensate | Pipeline filled with condensate | |
Condensato-steam mixture | 6-10 |
|
Feed water | Suction line | 0,5-1 |
Supply pipe |
Choosing a Better Steam Trap/ Armstrong International, Inc. //
Trap Magazin, 1993. – Vol. 61, No. 1.- P. 14-16.
The article “Selecting the Most Suitable Steam Trap” was published in the corporate magazine “ICI Engineer”, owned by one of the world’s largest chemical group companies, ICI PLC London, England. The group has a turnover of $22.5 billion annually and employs more than 128,000 people, of whom about 25% work in American plants, with the remaining operations in 35 countries and more than 600 cities.
The article was reprinted by Armstrong Intl with permission from the editors of the magazine.
The culmination of seven years of monitoring and testing the steam traps of two steam trap manufacturers at their Huddersfield and Grangemouth plants, combined with performance and flow-through steam loss tests in the laboratories, has resulted in the revised ICI Design Guide “Selection of Steam Traps“ (EDG PIP. 30.01A).
Trap Magazine Editor's Note
Engineers at two ICI fine chemicals plants in the United Kingdom conducted seven years of observations of the performance of various types of steam traps, the results of which are described in this article. Because Armstrong recommends that steam trap selection be based on practical experience - Armstrong's own, that of Armstrong's representatives, and others who have accumulated it while providing drainage for similar equipment - this article is being republished so that all interested parties can benefit from ICI's experience. .
The old standards for the selection of steam traps had many shortcomings, the most significant being that they did not take into account either the type of equipment being drained or the method of drainage. Steam traps selected in this way were often used in conditions for which they were not designed. This applies in particular to thermodynamic steam traps, on which most standards were mainly based and which were considered at factory level to be “a steam trap for all occasions”.
Steam trap performance monitoring began at the Grangemouths plant in 1980 and two years later at the Huddersfield plant following complaints from maintenance workers about the short life of steam distribution drains.
To establish the types of steam traps in service and to verify how they were selected for specific conditions, surveys including test programs were carried out. Already the first results made a depressing impression.
A survey of 415 steam traps at one plant found that 19% were faulty and 63% were found to be unsuitable for specific conditions.
In a survey of 132 steam traps on steam distribution lines, 42% were faulty.
Monitoring the service life of steam traps also began in 1980 and continues today.
The actual average service life of different types of steam traps is given in Table 1.
Table 1. Average service life of different types of steam traps
Type of steam traps Service life in systems with different steam pressures
High 45 kg/cm2 Medium 14 kg/cm2 Low 2.1 kg/cm2
1. Thermodynamic 10-12 m-tsev 12 m-tsev 5-7 years
2. Float valves with thermostat *) not applicable. 1-6 students 9 students - 4 years
3. With an overturned glass 18 m-tsev 5 - 7 years old 12 - 15 years old
4. Thermostatic unloaded not applicable. 6 m - 5 - 7 years old
5. Thermostatic bimetallic *) 3 - 12 months 2 - 3 years 7 - 10 years
*) - depending on the model and manufacturer.
To determine the energy-saving properties of various types of steam traps, steam leakage tests were carried out on test benches in the laboratories of two manufacturers. The tests were carried out in laboratory conditions: in a room with an air temperature of 20 °C. The heat loss of the steam trap body was not measured. The test condensate load was 10 - 20 kg/hour, which is close to the characteristic loads of steam pipeline drains.
The most interesting result was that thermodynamic steam traps (the most widely used general-purpose steam traps) are the worst in terms of energy efficiency and, compared to inverted-cup steam traps, have a much shorter service life.
These tests also found that mechanical types of steam traps (i.e., inverted bowl and float) provide complete removal of condensate from steam cavities at both low and high condensate flow rates, while thermostatic type steam traps tend to accumulate condensate in these cavities with increasing load. In addition, thermobimetallic steam traps tend to operate erratically. Therefore, the revised Steam Trap Selection Guide contains an updated table for steam trap selection.
Steam traps with inverted glassUse as the main type for drainage of any process equipment and steam pipelines, i.e. in all cases where there should be no condensate in the steam cavity.
Float steam traps with air release thermostat
Use for process equipment, especially temperature control, in systems with steam pressures below 3.5 kg/cm2, or when the use of inverted float traps does not allow the release of significant volumes of air.
Thermostatic unloaded steam traps
Use on non-critical steam satellites and heating systems.
Thermostatic bimetallic steam traps
Use for low temperatures or for defrost protection on steam satellites or heating systems. Recommended models must be adjusted to maximize the use of condensate heat or to prevent overheating of the heated product. Body parts must be made entirely of stainless steel.
Thermodynamic steam traps
Limited use is allowed for drainage of main steam lines and steam satellites at steam pressures up to 17 kg/cm2 as a forced alternative to steam traps with an inverted float, as well as for prompt replacement during repairs at higher pressures, if previous experience of their use in these conditions has shown that they can work satisfactorily. Due to their poor energy-saving properties and relatively short service life, their use is not recommended. (Not allowed at Huddersfield and Grangemouth plants.)
Steam Trap Tournament at Shell Plant - Canada
It could be called a big international elimination race, or the Steam Trap Olympics, or an energy conservation tournament. The competition covered almost the whole world and lasted 10 years. The winner was the Shell plant in Canada in the Montreal area. The prize is $1 million in steam energy savings per year.
The competition began in the mid-70s, shortly after the announcement of the oil embargo. The cost of steam production at the Shell plant at the beginning of that decade fluctuated between 40 and 50 cents per 1,000 pounds of steam ($0.9 to $1.1 per ton). After the cost of steam doubled within a year, it became obvious that something had to be done.
The Shell refinery in the Montreal area is the largest of Shell's five refineries in Canada. The plant operated more than a dozen steam boilers with capacities ranging from 60 to 190 thousand pounds of steam per hour (27 to 86 tons/hour). More than 4,000 steam traps were installed in steam and condensate systems. This background is important because in 1975, plant management decided to look at energy consumption from a cost-cutting perspective. As part of a comprehensive program, reducing steam consumption was also part of the means to achieve the goal of reducing the plant's energy consumption by 30% by the end of 1985.
In July 1975, a survey was conducted of all steam traps installed at this refinery. It was determined that the majority were bimetallic steam traps, and accounting data showed that an average of 1,500 new steam traps were purchased per year between 1973 and 1975.
First stage of the elimination race
It was decided to carry out extensive testing of different types of steam traps under similar conditions. At the time of the survey, the number of Armstrong steam traps in the plant was less than 2%, and there were about a dozen types and models in service.
The Shell plant tested about 900 steam traps, 100 of each of 9 models manufactured by 6 different companies. Types tested included inverted float, thermodynamic, bimetallic and other thermostatic traps made in the USA, Canada and across the pond.
These steam traps have been installed in various 14 and 7 kg/cm2 steam pressure and low pressure steam systems and have been closely monitored. The criteria for evaluating steam traps were transient steam loss and failure rate.
Some steam traps failed after just a few months, others lasted longer.
Steam traps removed due to failure were grouped and retested to obtain a time to failure value for each model.
Based on the results of these 2-year tests, it was determined that one of the thermodynamic steam traps and the Armstrong Model 1811 stainless steel inverted bowl traps showed the greatest potential.
Shell solution - go with the winner
In the 60s, thermobimetallic steam traps were adopted as standard for the Shell plant, but it turned out that their failure rate was 20 ... 27% per year. After the first stage of testing, Shell changed its standard in favor of those two types of steam traps that became the winners of the first stage of the “knockout race”.
In 1977, the Shell plant administration, together with the energy working group, decided to improve the technical level of the entire steam-condensate system and replace 4,200 steam traps. Half of the newly installed steam traps were Model 1811 steam traps from Armstrong, and the other half were thermodynamic steam traps from another company. Shell retained only these two types as standard and removed all other steam traps from custom specifications and inventory. Maintenance personnel could only replace faulty steam traps with one of these two types, which were available in reserve.
Comprehensive monitoring of the functioning of each model was again organized.
The number of refusals dropped to 3...5%. The failure rate of 2,100 steam traps with an overturned glass from Armstrong over the past 6 years was about 1.8%. This means that the failure rate of the competing model - thermodynamic steam traps - was significantly higher than the average value of 3 - 5% (approx. 6.2%).
The next decision made by the administration in 1984 was the decision to use only inverted cup steam traps as standard.
The driving force behind the decision was the long service life of this type of steam trap, as well as a new feature in the form of a universal connecting adapter on the 2011 model, which allows the steam trap to be installed at any angle relative to the axis of the pipeline. As the remaining thermodynamic steam traps fail, Shell will replace them with inverted-cup steam traps. These models are equipped with almost all steam satellites, as well as other equipment of steam systems operating on both low pressure steam and 14 kg/cm2 steam.
The effort pays off
Roy Gunnes, head of the energy team at Shell's Montreal refinery, reports that the results have more than justified the effort. He said, “Over the last 7 years, steam consumption has decreased from 24 million pounds per day to 15 million pounds” (from 15,900 t/d to 6,800 t/d).
The goal set by Shell for a 10-year period (1975 - 1985) was to reduce energy consumption to 30%. The actual reduction in steam consumption for 1984 exceeded the set goal and amounted to 35.2% compared to the base year 1972.
Through measures to reduce steam consumption, the refinery saved more than $20 million from 1978 to 1984. Savings were achieved both through modernization and automation of technology, and through the adopted program for steam traps. Since the start of work on steam traps, the cost of steam has increased 13 times. During the same time, production volume at the plant also increased.
Roy Gunnes reports that these measures made it possible to decommission 8 small steam boilers with a capacity of 60,000 pounds of steam per hour each (approx. 27 t/h). He also stated that some equipment's rotary drives had been replaced by electric drives as a result of the rising cost of steam. “As for steam traps, most of the savings were achieved through constant monitoring,” said R. Gannes.
This refinery uses a marginal fuel cost formula that can bring all types of energy to a standard form.
This is known as the Liquid Fuel Equivalent Barrel Formula.
The energy saved as a result of the steam trap program is equivalent to approximately $1 million per year.
After finally taking into account the cost of new steam traps and the costs of installing them as part of the entire program, it turned out that the payback period for the money spent was almost 6 months. In other words, the program of work to replace and standardize steam traps ensured a return on the funds spent on it in less than six months.
Effective activities of the energy saving group
Responsibility for checking all steam traps at least twice a year is assigned to two senior technical specialists of the energy conservation group.
A tag is placed on faulty condensate traps and a report about them is sent to the dispatch service. Repairers receive from her the specific location of these steam traps along with a work order.
Each steam trap dismantled is recorded with the reason.
If a steam trap fails within the 3 year warranty period, it will be returned to the manufacturer for investigation and reimbursement if necessary.
TO steam traps are gaining ground in inventories
Shell is able to empirically determine the average number of failures and maintain the stock of steam traps at the required level. In the past, Shell purchased steam traps on a monthly basis. Now Shell, knowing from experience the number of failures, predicts the annual need in advance and makes purchases once a year. Shell also ensures that the required stock is maintained. Since the refinery is always working on new projects, if steam traps are required, they are taken directly from the warehouse for those projects. R. Gannes reports that since the plant purchases a significant number of steam traps at once and regulates its own inventories, it can enjoy more favorable discounts.
He subsequently estimated that the cost of steam traps was comparable to the labor cost of installing and maintaining them in the system. Paying labor is expensive. It is possible that this is why the plant chose the 2011 model from Armstrong, says R. Gannes. Their long lifespan means they don't need to be replaced as often as before.
Train to win
Experience and training are vital for members of the Energy Conservation Working Group. Senior technicians such as Alain Laplante and Yvon Cyr have been working at the Shell plant for many years. It has become clear that people are key to ensuring an effective energy conservation program. These senior technicians know the plant and everyone who works there.
Both are essential to the success of the program. All team members have attended Armstrong's energy conservation seminars and take advantage of any additional opportunity to increase their knowledge of steam and steam traps.
The Shell plant has a rotation program so that members of the energy conservation team remain on the team long enough to gain influence, but not so long that complacency develops. This rotation facilitates the penetration of fresh ideas into the energy conservation program. During the time that has passed since this article was written, J. Beauchamp was appointed head of the working group on energy saving, replacing R. Gannes.
Reputation is gained by success
The Gunnes report states that the energy conservation program is highly visible and the reputation of team members at all levels of the organization is high. Twice a year, the group prepares and submits to the administration a report on the results of the program and proposals for new projects.
Advice from professionals
When asked what advice can be given to other companies thinking about implementing an energy saving program, R. Gannes answers:
“Get support from management. Without this, all planned measures lose their mandatory nature. Management expects results, and if investments in steam conservation work result in significant savings, then many people become your supporters.
It is very important that suitable individuals are selected to organize the work of the program. These people should be respected not only by management, but also by operators, foremen and repairmen.”
Gunnes concludes that without the commitment of Shell plant management and the support of its employees, it would not have been possible to conduct all of the tests mentioned, replace more than 4,000 steam traps, and save more than $1 million a year in steam production funds.
REFERENCE
(about the Shell oil refinery - Montreal East).
Located in the Montreal area, the Shell refinery was founded in 1932 and was brought into production in 1933 with a capacity of approximately 5,000 barrels of crude oil per day (about 800 m3/day).
The number of employees at that time was 75 people. In 1985, the plant employed approximately 700 people, and production capacity had increased to 120,000 barrels per day (19,080 m3/d).
Over the past decades, the plant has continuously expanded. The products of this modern facility include gasoline, lubricating oils and a wide range of other refined petroleum products. This plant is the largest of Shell's 5 oil refineries in Canada, and one of the largest oil refineries in Eastern Canada.
Water for steam production is taken from the St. Lawrence River. Steam production accounts for 30 to 35% of total energy costs. During the winter months, steam consumption is 740,000 lb/hr (335.7 t/hr), falling to 560,000 lb/hr (253.7 t/hr) during the summer months. The main amount of steam is produced by four high-pressure boilers (600 psi = 42 kg/cm2) and one waste heat boiler (200 psi = 14 kg/cm2). There are also several small waste heat boilers. An average of 15.2 million pounds of steam (about 6,900 tons/day) is produced daily, which is significantly less than the 24 million pounds (about 10,890 tons/day) produced in 1977.
The Weyerheuser pulp and paper mill recovers nearly $1 million annually through its steam energy management program. Global competition requires careful planning and management of production, but don't convince the employees of the Weyerheuser pulp and paper mill in Plymouth, North Carolina. By examining every aspect of their plant's operations, they were able to reduce costs by nearly $1 million per year by implementing an extensive steam energy management program.
The giant plant, operating since the early 1930s, was purchased by the Weyerheuser company in 1960. Although the final product - paper - has not undergone fundamental changes over the years, its production technology has been significantly updated.
The Plymouth mill produces fine paper, as well as medium-weight paper, fluff paper and linerboard. Currently, 5 paper-making machines and 5 wood pulp production shops provide an average output of 2,300 tons of products every working day.
On average, the plant produces 1.95 million pounds of steam per hour (884.5 tph), 90% of which is used in the technology. Because steam production is so large, even relatively small faults such as a steam trap installed on a high-pressure steam line can quickly increase losses.
Self-sufficient energy supply system
The plant produces steam and electricity necessary for technology and heating independently. Unused energy from the plant is supplied to the local power company.
The plant operates 4 steam boilers. Steam is generated by two wood waste boilers (pressure 1,275 psi = 90 kg/cm2); one mixed fuel boiler (pressure 650 psi = 45 kg/cm2) and one waste heat boiler (pressure 875 psi = 62 kg/cm2). These boilers burn coal, wood waste and black liquor, a by-product of wood pulp production. Maximum steam consumption occurs in winter, when 2.3 million pounds of steam per hour (1,043 tph) are produced.
The Plymouth plant operates approximately 1,250 steam traps. Armstrong model 411G steam traps are used to drain the main steam lines (pressure 650 psi = 45 kg/cm2), and for drainage of lower pressure steam lines (150 psi = 10.5 kg/cm2) supplying steam to paper dryers and other process equipment. equipment - different models of condensate traps “Armstrong” 800 series.
For a number of years, the enterprise's steam-condensate system was not a priority for maintenance personnel. Lack of awareness of the savings potential of a properly managed system, coupled with a strong national economy, diverted attention to other needs.
“However,” explains Billy Kasper, Weyerheuser Equipment Operations Supervisor, “all this changed in the early 1980s when our company began, with the help of Armstrong, to look for ways to improve the management efficiency of the steam-condensate system.
By identifying sources of loss, new opportunities can be found
“Although energy management should be an important part of the operation, the idea to switch to energy conservation, which arose as a result of the steam trap maintenance program, came to light about six years ago,” says B. Kasper.
At the same time, an internal energy audit was carried out. “When this report was presented to our operations manager, he determined that our energy costs per tonne could be significantly improved,” continues Kasper.
One of the cost-cutting opportunities identified by the report was related to the loss of flying steam. An energy audit showed that about 60% of the 1,000 thermodynamic condensate traps installed at the plant were leaking or allowed free flow of steam. Since a large number of steam trap failures were observed on high-pressure steam lines, the energy losses were quite noticeable.
To eliminate the problems caused by leaks and steam leaks, Weyerheuser chose to replace the failure-prone thermodynamic steam traps with Armstrong inverted float steam traps. These Armstrong steam traps were ideal for the harsh operating conditions encountered at the plant, where impurities and other contaminants quickly accumulated in steam lines. “We have verified that the design of Armstrong inverted float steam traps provides good maintainability and is highly reliable,” notes B. Kasper.
Knowledge is key
It was identified early on that personnel responsible for equipment maintenance required training. In addition, B. Kasper considered it logical to appoint one person responsible for implementing the steam trap maintenance and repair program. He explained that the choice was not difficult to make.
“Randy Hardison, a specialist with 23 years of experience at Weyerheuser, had the energy and enthusiasm needed for this type of work. Moreover, he is actually ripe for this task. Indeed, much of the success achieved during our steam trap program can be attributed to Randy's initiative.”
While recently promoted steam trap mechanic R. Hardison was attending an Armstrong seminar on steam energy conservation, a local Armstrong representative promoted a two-week training program for about a quarter of the 460 maintenance department employees. mill in Plymouth.
The maintenance and repair department, as B. Kasper explains, is considered an extremely important department of the plant. “Due to the continuous nature of production in our plant, maintenance and repairs are of key importance to ensure profitable operations. We sensed how important it would be for as many of our employees as possible to gain the necessary knowledge at the steam trap seminar.”
Meanwhile, participants in the representatives' seminars on steam energy management actively absorbed this knowledge. “The seminar participants know that each of them is faced with the task of helping to save money, and here we realized the potential for savings in our own steam and condensate system,” notes B. Kasper.
Armed with new knowledge of how their plant's steam traps worked, the first thing they discovered was that many of the steam traps installed were incorrectly sized. The condensate return lines were too small in diameter, which led to a large amount of work to replace them. Many steam traps have been installed in hard to reach places. “I think,” notes R. Hardison, “they should be accessible so that anyone can check and test both the traps and the entire system.”
Improving accounting helps save information.
When the major steam trap inspection and repair program began in March 1987, the old maintenance record correction system was converted to a computer system. The leading role in transforming the system was taken by R. Hardison, who was entrusted with responsibility for its modernization.
“The large number of steam traps in our plant led us to the idea that to simplify accounting, we needed to enter this information into a computer. In addition, we were impressed by the effectiveness and simplicity of Armstrong's Preventative Maintenance Program,” notes R. Hardison.
As progress reports emerged on the Weyerhaeuser steam trap program, cost savings began to emerge. “We have found that our steam trap program pays for itself,” explains R. Hardison. “Condensate return increased from 50 to 63%. We now operate on 4 steam boilers instead of 11, as was the case just three years ago. Plus, we now receive 3% more condensate from the entire plant system than before.”
To save time and increase productivity, Randy Hardison converted a regular factory truck into a dedicated steam trap maintenance and repair vehicle.
“Energy Tamers” are important allies.
Maintenance employees are not the only ones involved in steam energy management. Other workers have also become aware of the importance of energy conservation thanks to the emergence of “energy tamers.” “Whenever someone notices a steam leak, they contact me and we put together a committee of energy tamers,” explains R. Hardison. “The movement of “energy tamers” arose several years ago at another Weyerheuser plant, but has already been picked up here. During these meetings, I will usually talk about how the steam/condensate system works and how to test steam traps, as well as help the committee resolve problems related to steam leaks.”
In addition to leading Energy Tamer committee meetings, Hardison organized a series of his own seminars called “Let's Talk Steam Traps.” Every couple of months, approximately 25 to 35 workers will gather for his one-hour lunch-break training seminars. At these lunch-and-lunch seminars, which are mandatory for all plant employees, Hardison gives an overview of how steam traps work. All seminar participants receive a special participant's cap, as well as a copy of R. Hardison's original comedy, which causes a pleasant surprise.
Priority attention is reflected in financial results.
Inspector of the maintenance and repair department B. Kasper believes:
“I can advise the following to everyone who is involved in the management of steam-condensate systems:
First, assign one person complete responsibility for steam trap maintenance and repair and ensure that this responsibility is their first priority.
- Second, provide the person with the appropriate training, tools, and equipment.
In our case, these rules are respected and we receive an increase in the annual profit of the company thanks to a renewed attitude towards steam energy management. “Of course,” B. Kasper immediately adds, “the key factor in increasing profits is knowledge. Knowing where your steam and condensate system may be losing money helps you understand the different ways you can implement steam saving programs. And Armstrong has proven that it is a reliable partner, delivering the products and knowledge we need.”
Http://www.energycontrol.spb.ru/Appek.nsf/(sitetree)/DEEA11C767B81A7EC325708B004A90E9?OpenDocument
When designing steam-condensate systems, one of the main tasks is the correct organization of condensate drainage. The presence of condensate in steam systems leads to water hammer, a decrease in thermal power and a deterioration in the quality of steam supplied to consumers. In addition, wet steam causes premature corrosion of pipelines and failure of control and shut-off valves. To remove condensate from steam lines, special devices called steam traps. There are several different types of steam traps, the choice of which depends on the individual characteristics of the section of the steam pipeline or the type of heat exchange equipment on which it is installed. The condensate trap must allow condensate to pass through, while preventing any passing steam from entering the condensate return line.
Steam traps can be divided into three groups: mechanical, thermostatic and thermodynamic.
Mechanical steam traps The operating principle of such condensate traps is based on the difference in density of liquid (condensate) and gas (in this case, steam). Here are the following two types of mechanical steam traps:
Float-type condensate drain with spherical float. The most common type of mechanical steam trap is the float type with a spherical float. This condensate trap has a high throughput capacity. Removes condensation immediately after formation. Contains a built-in bimetallic air release valve. Internal components are made of stainless steel. If there is no condensate, the float is lowered and the valve is closed. As condensate enters the float chamber, the float begins to float and opens the valve that releases the condensate. As steam enters, the condensate level decreases and the float moves down, closing the outlet valve. This type of steam trap is recommended for removing condensate from heaters, heat exchangers, dryers, digesters and other equipment in heated rooms. Susceptible to freezing.
Float trap with an overturned glass. This steam trap operates cyclically. For its normal operation, the water seal must be filled. If there is no condensate, the float is lowered and the valve is open. Condensate entering the housing exits through the outlet valve into the condensate line. When steam enters the space under the float, the float floats and closes the outlet valve. After the steam condenses, the float lowers and opens the outlet valve. Susceptible to freezing.
Thermostatic steam traps The operating principle of these steam traps is based on the temperature difference between steam and condensate. Here are the following two types of thermostatic steam traps:
Capsule steam traps. A thermostatic capsule is used as a shut-off valve. This steam trap allows condensate and air to pass through, preventing the passage of steam. Can be used as an automatic air vent in steam systems. The use of different types of thermostats allows you to select a condensate drain so that the condensate is discharged cooled. Recommended for draining steam lines in heated rooms, as well as for digesters, sterilizers and other heat exchange equipment.
Bimetallic steam traps. A bimetallic valve is used as a shut-off device. This condensate trap, like the capsule one, allows condensate and air to pass through, preventing the passage of steam. Can be used as an automatic air vent in steam systems. Resistant to negative temperatures and water hammer. Recommended for draining steam lines outdoors, as well as for digesters, sterilizers and other heat exchange equipment. Thermodynamic steam traps The operating principle of these steam traps is based on the difference in the speed of passage of steam and condensate in the gap between the disk and the seat. When condensate passes through, the speed is low and the disc is in the upper position. As steam enters the trap, the speed increases, the static pressure under the disc drops, and the disc drops onto the seat. The steam above the disk, thanks to the larger contact area, keeps the disk in the closed position. As the steam condenses, the pressure above the disk decreases, and the disk rises again, allowing the condensate to pass through. The thermodynamic steam trap is the least efficient of all the types listed. Can be used for draining steam lines outdoors in cases where condensate is not returned.
Selecting a steam trap When choosing a steam trap, the following factors must be taken into account: - It is necessary to decide on type of steam trap. The choice of type depends on the installation location and the type of consumer behind which the condensate trap is installed. The choice of steam trap type is influenced by steam parameters and system features: changes in loads, cyclic operating modes, water hammer, etc. - The next step is size determination. The diameter of the steam trap is selected based on the throughput of the steam trap and the pressure drop across it. As a rule, difficulties arise in determining the pressure drop, since pressure gauges are usually not installed on the condensate return line. Therefore, when calculating throughput, it is customary to use safety factors. Table 1. Recommendations for selecting steam traps.
T. Gutsulyak, A. Kirilyuk
Due to the constant rise in the cost of energy resources, all industrial sectors are busy searching for alternative sources of increasing energy efficiency. Water vapor, as a means of transferring thermal energy, is becoming increasingly popular
In addition to heat exchangers, condensate traps play an important role in the effective extraction of heat from steam. Their main task - extracting as much heat as possible from water vapor - is quite difficult and depends not only on the presence of the condensate traps themselves in the system, but also on how correctly they are selected. In order to choose the right steam trap for a specific production process, it is necessary to have a good knowledge and understanding of the principles of its operation and the specifics of the use of steam in this process.
Purpose of steam traps
The condensate trap must prevent the heat transfer coefficient from decreasing. The decrease occurs due to the formation of condensate at the steam consumer or in the steam pipeline. The task of this equipment is to remove condensate, while preventing “flight” and release of steam.
Steam, losing the heat necessary for heat exchange processes, gives it to the walls of the pipeline, turning into condensate. If it is not diverted, the “quality” of the steam deteriorates, cavitation and water hammer occur. The best option is when the steam trap is capable of removing condensate, as well as air and other non-condensed gases.
There is no one-size-fits-all steam trap that is suitable for all applications and applications. All types of condensate traps differ in their operating principle, while having their own disadvantages and advantages. There is always a better solution for a specific steam and condensate application. The choice of steam trap depends on
temperature, pressure and amount of condensate formed.
Rice. 1. Main types:
a) - mechanical (float); b) - thermodynamic; c) - thermostatic
There are three fundamentally different types: mechanical, thermostatic and thermodynamic.
Operating principle mechanical based on the difference in density between steam and condensate. The valve is actuated by a ball float or an inverted glass float. Mechanical steam traps provide continuous removal of condensate at steam temperature, so this type of device is well suited for heat exchangers with large heat exchange surfaces and intensive formation of large volumes of condensate.
Thermostatic steam traps determine the temperature difference between steam and condensate. The sensitive element and actuator in this case is a thermostat. Before the condensate is removed, it must be cooled to a temperature below the dry saturated steam temperature.
Based on the operating principle thermodynamic steam trap lies the difference in the speed of passage of steam and condensate in the gap between the disk and the seat. When condensate passes through, due to the low speed, the disk rises and allows condensate to pass through. As steam enters the thermodynamic steam trap, the speed increases, causing the static pressure to drop, and the disc lowers onto the seat. The steam above the disk, due to its larger contact area, keeps the disk in the closed position. As the steam condenses, the pressure above the disk drops, and the disk begins to rise again, allowing the condensate to pass through.
Table 1. Types of steam traps
Table 2. Comparison of steam traps and their types
Selecting a steam trap
To correctly select the nominal diameter of the condensate drain You must first determine the inlet pressure, see fig. 3.
If the steam trap is installed after a steam-consuming installation, the inlet pressure is 15% lower than the pressure at the inlet to the installation.
For an approximate calculation of back pressure, we assume that each meter of pipeline rise equals 0.11 bar of back pressure.
Pressure drop = Inlet pressure - Back pressure.
The amount of condensate can be calculated using the technical documentation of the manufacturer of steam-consuming equipment, taking into account the safety factor for condensate consumption. On the main steam pipelines, in heat exchangers and similar equipment, the throughput reserve should be set to 2.5 - 3 times greater than the calculated one. In other cases, the reserve is 1.5 - 2 times greater.
After calculating the safety factor for condensate flow, the diameter of the condensate trap is selected according to the diagram
throughput (see Fig. 2), which is provided by the manufacturing plant.
Below, as an example, are the AYVAZ SK-51 throughput diagrams (data and recommendations provided by AYVAZ UKRAINE).
Rice. 2. Capacity diagram of SK-51 (1/2”-3/4”-1”)
Example of using a chart (see Fig. 2): the condensate flow rate for the condensate drain is set to 180 kg/hour.
The condensate is discharged from the heat exchanger at a pressure of 6 bar and a back pressure of 0.2 bar. Pressure drop 6 - 0.2 = 5.8 bar.
Condensate flow 180 x 3 = 540 kg/hour.
Safety factor: 3.
To drain 540 kg/hour of condensate at a drop of 5.8 bar, along the blue line in the diagram marked with the number 10 (the throughput in this case is 700 kg/hour), we select a condensate drain with a diameter of 1” (DN25). The number 10 indicates the size of the exhaust valve opening. As can be seen from the diagram (Fig. 2), condensate traps with a diameter of 1/2" and 3/4" cannot be selected in this case, because their condensate capacity is lower than required.
Use of flash steam energy
When water is heated at constant pressure, its temperature and heat content increases. This continues until the water boils. Having reached the boiling point, the temperature of the water does not change until the water completely turns into steam. And since it is necessary to make maximum use of the thermal energy of steam, steam traps are used, see Fig. 3.
Rice. 3. Use of condensate and flash steam for heat exchange
Condensate has the same temperature at a given pressure as steam. When the condensate after the steam trap enters the atmospheric pressure zone, it instantly boils and part of it evaporates, because the temperature of the condensate is higher than the boiling point of water at atmospheric pressure.
The steam that is formed when the condensate boils is called secondary boiling steam.
Those. This is steam that is formed as a result of condensate entering the atmosphere or environment with low pressure and temperature.
Calculation of the amount of flash steam:
Where:
Ek
: Enthalpy of condensate entering the steam trap at a given pressure (kJ/kg).
Ev
: Enthalpy of condensate after the steam trap at atmospheric pressure or at the current pressure in the condensate line (kJ/kg).
St
: The latent heat of vaporization at atmospheric pressure or at the current pressure in the condensate line (kJ/kg) of the pipeline is 0.11 bar back pressure.
As can be seen, the greater the pressure difference, the greater the amount of flash steam generated. The type of steam trap used also affects the amount of condensate produced. Mechanical ones remove condensate at a temperature close to the steam saturation temperature. While thermostatic ones remove condensate with a temperature significantly lower than the saturation temperature, while the amount of flash steam decreases.
When selecting flash steam, it is necessary to take into account that:
- To obtain even a small amount of flash steam, a large amount of condensate will be required. It is necessary to pay special attention to the throughput of the condensate trap. You also need to take into account that after the control valves the pressure is usually low.
- The scope of application must correspond to that for the use of flash steam. The amount of flash steam should be equal to or slightly greater than that required to ensure the technical process.
- The area where flash steam is used should not be located far from the equipment from which high-temperature condensate is removed.
For an example of calculating the amount of flash steam in a system where condensate is removed immediately after its formation, see below.
Let's take data from the table of saturated steam: at a pressure of 8 bar, 170.5 ° C, condensate enthalpy = 720.94 kJ/kg. At atmospheric pressure, 100°C, enthalpy of condensate = 419.00 kJ/kg. The enthalpy difference is 301.94 kJ/kg. Latent heat of vaporization at atmospheric pressure = 2,258 kJ/kg. Then the amount of secondary boiling steam will be:
Thus, if the steam consumption in the system is 1000 kg, then the amount of flash steam will be 134 kg.
Features of installation of condensate traps
When installing a condensate drain, make sure that the arrow on its body corresponds to the direction of flow, see Fig. 4, a).
Float-type steam traps must be installed strictly horizontally. Some, in special versions, can be installed vertically. The steam inlet into such condensate traps should be on the bottom side, see Fig. 4, b).
Steam traps should be located below the steam line connection to the equipment. Otherwise, the equipment may flood. In cases where installing condensate drains in this way is impossible, it is necessary to organize forced drainage of condensate, see Fig. 4, c).
Thermodynamic steam traps work in any position. However, a horizontal position is more preferable for installation, see Fig. 4, d).
Rice. 4. Correct installation of the steam trap
Steam traps must not be installed one behind the other under any circumstances. Otherwise, the second one will create pressure, which will negatively affect the operation of the first one, which is already installed, see fig. 5, a).
Filters installed in front of steam traps must be facing left or right. Otherwise, condensation will accumulate at the bottom of the filter, which can lead to water hammer, see fig. 5 B).
Rice. 5. Installation of a condensate trap in the system
The correct selection and use of equipment from the manufacturer AYVAZ is an effective way to increase the level of energy saving in steam systems.
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Views: 4,718A distinction must be made between two areas of steam use and condensate removal:
a) main steam pipelines and;
The fundamental difference is that in area a) transient processes are characterized by significant fluctuations in steam consumption. In the heated state, steam consumption, especially on satellites, is extremely small. In area b), the heat required to warm up the equipment can be comparable to the heat taken to heat the product.
Therefore in the areas:
a) steam traps must cope with loads over a wide range of variations,
Steam traps put forward specific requirements for steam traps:
In the event of a “failure,” the steam trap must remain open;
The steam trap must allow periodic purging of the cooled steam traps.
The main thing when choosing any device is the ability to reliably estimate the expected condensate consumption.
The steam trap belongs to the class of valves; its flow capacity depends on the diameter of the seat and the pressure drop across the seat, i.e. the difference between the steam pressure at the inlet and the condensate back pressure at the outlet.
The following estimates may be useful for different condensate drainage areas.
| No | Name | Condensate flow (kg/h) | Safety factor |
| 1 | Highway | W x L x 0.48 x Δ t x 60 / R x hour | 2-3 |
| 2 | Collector | 0.1 x Qboiler max | 1.5 |
| 3 | Heater | V x ρ x Csp x Δ t / R | 2-3 |
| 4 | Heat exchanger | V x ρ x Csp x Δ t / R | 2-3 |
| 5 | Dryer drum | p x D x L x K | 3-4 |
| 6 | Steam satellite | < 1 кг/ч*м x М | 1 |
| 7 | Autoclave | k x F x Δ t / R | 3 |
Here
W - linear weight of the pipeline (kg/m)
L - steam line length (m)
R - latent heat of vaporization (kJ/kg)
Qboiler - steam boiler productivity (kg/h)
Csp - specific heat capacity (kJ/kg x °C) (Steel = 0.48)
V - volumetric flow rate of the heated medium (m 3 / h)
ρ - density of the heated medium (kg/m 3)
D - drum diameter (m)
K - intensity of condensation formation (40 kg/h x m2)
M - satellite length (m)
k - heat transfer coefficient (kJ/m2 x h x °C)
F - surface area of the steam jacket (m2)
If the nameplate power of a thermal object (heat exchanger, autoclave, etc.) is known, then the condensate flow rate is estimated by directly converting the nameplate data values into condensate flow rate (kW in kg/h), taking into account possible heat losses.
It should be remembered that a condensate trap with an inverted glass will be closed if the pressure drop exceeds the permissible design value. This design feature of the devices is used to organize automatic drainage of heat exchangers when the load drops using an additional condensate trap, when the steam pressure drops and it is not possible to lift the condensate into the condensate pipeline. In this case, one steam trap operates under operating conditions when the drain trap is closed, and when the load drops, the drain trap opens.
| Name of performance characteristics | Types of condensate drains and their symbols | |||||
|---|---|---|---|---|---|---|
| Response nature | periodic | continuous (1) | periodic | continuous | continuous | continuous |
| Life time | Exc. | Chorus. | Unsuccessful | Satisfied | Exc. | Satisfied |
| Wear resistance | Exc. | Chorus. | Unsuccessful | Satisfied | Exc. | Satisfied |
| Corrosion resistance | Exc. | Chorus. | Exc. | Chorus. | Exc. | Satisfied |
| Resistance to water hammer | Exc. | Unsuccessful | Exc. | Unsuccessful | Exc. | Exc. |
| Air and CO2 discharge at steam temperature | Eat | No | No | No | Eat | No |
| Air exhaust at very low pressure (0.2 barg) | Unsuccessful | Exc. | (2) | Chorus. | Exc. | Chorus. |
| Ability to remove starting air flow | Satisfied | Exc. | Unsuccessful | Exc. | Exc. | Exc. |
| Performance under back pressure | Exc. | Exc. | Unsuccessful | Exc. | Exc. | Chorus. |
| Frost resistance | Chorus. (3) | Unsuccessful | Chorus. | Chorus. | Chorus. | Chorus. |
| Possibility of system purging | Exc. | Satisfied | Exc. | Chorus. | Exc. | Chorus. |
| Performance at very low costs | Exc. | Exc. | Unsuccessful | Exc. | Exc. | Chorus. |
| Triggers when condensate enters in one burst | Immediate | Immediate | Delayed | Delayed | Immediate | Delayed |
| Stain resistance | Exc. | Unsuccessful | Unsuccessful | Satisfied | Exc. | Unsuccessful |
| Comparative sizes | Large (4) | Large | Small | Small | Large | Large |
| Performance during the formation of boiling steam | Satisfied | Unsuccessful | Unsuccessful | Unsuccessful | Exc. | Unsuccessful |
| State of mechanical failure (open - closed) | Open | Closed | Open (5) | (6) | Open | Open |
Notes:
- At low flow rates, periodic operation is possible.
- Not recommended for low pressures. The inlet pressure must be at least 2 times the back pressure.
- Do not use condensate drain made of cast iron.
- For all-welded stainless steel structures, the sizes are average.
- If dirty, it may remain in the closed position.
- Depending on the design of the bellows assembly, it can be either open or closed.
To operate at subzero temperatures, appropriate housing materials should be selected. It must be taken into account that thermostatic steam traps have a wide range of operating loads, but in steady state they operate in a “flooded” state. Therefore, in the climatic conditions of Russia, there is always a threat of their defrosting when installed outdoors.
Condensate traps with an inverted stainless steel glass made by Armstrong take into account the peculiarities of operation at subzero temperatures - they are equipped with additional valves to protect against defrosting (automatically open when the pressure in the bottom of the housing drops) and removable housing insulation. In the event of a “failure,” this type of condensate trap always remains open, which is essential for satellites that heat product pipelines in the open air.
The universal connecting head allows the device to be connected to the pipeline at any angle, which is also important for satellites when connecting to a condensate collector.
