Chapter two on the topic of how to detect and recognize the causes of mechanical seal troubles, after the post dedicated to the problems related to lubrication. Mechanical seals can undergo a series of different kind of wear. An irregular wear can be the consequence of an excessive wear on bearings and in presence of vibrations.
Small amounts of tough particles in the fluids can also lead to corrosion on mechanical seals: by sedimenting on the seal’s surface, these particles act like cutting tools in a grinding machine, damaging contact surfaces. An intermittent spotted wear on the seal surface can also relate to an imperfect linearity of the seal surface itself, due to defective mechanical construction of the seal, or even due to a wrong mounting.
Mismatched materials and fluids
The right choice of seal’s materials is essential to ensure a long mechanical seal working lifetime, enabled by the compatibility between the seal’s material and the pumped fluids. A wrong matching can lead to swelling problems in elastomers, boosted by the high temperatures and the long exposure periods involved. Corrosion on mechanical seals can also be provoked by the incompatibility between materials and fluids, deteriorating the seal surfaces.
Installation and connections
The correct installation is also a key factor to preserve the conditions of a mechanical seal. Pictured here are two examples of damages related to a wrong installation of the seal, leading to cut or damaged OR and breakage of the seal ring.
Also the working pressure of the pump must be comprised in the range of design values of the mechanical seal. In case of excessive pressure, the seal can be damaged irreversibly. At last, pay attention to the rotation verse of the pump, to avoid a breakage of the spring. This breakages can happen with a wrong electrical connection of the engine, a pump installed in parallel without a check valve, or also with a return flow when the pump is off.
A cogeneration plant is usually equipped with an endothermic engine driving a generator to produce electricity. Cogeneration stands for power and heat generation at the same time, also leveraging thermal energy produced by the engine. This is possible thanks to heat recovery achieved by a shell and tube heat exchanger on the exhaust fumes circuit.
Exhaust coming as waste from the endothermic engine in cogeneration have very high amounts of energy, making thermal recovery really advantageous instead of dissipating the heat. Here exhaust are at very high temperatures, typically between up to 550 and 650° C depending on the kind of engine and fuel employed.
For cogeneration heat recovery applications, shell and tube heat exchangers are suitable with straight pipes to allow cleaning operations, because exhaust can contain particles from combustion requiring some periodical cleaning maintenance. Construction material is usually stainless steel, especially for pipes and headers being in direct contact with exhausts. Diesel oil, biogas and methane exhaust can indeed contain acid elements exposing the components to corrosion, an even higher risk in case of high temperature conditions of cogeneration plants.
Working with high temperatures, heat recovery cogeneration applications thus also require special construction tricks: aimed to avoid failures due to thermal expansion, with unwanted side effects such as leaks, all the tubes are welded and pressed on headers, while the shell, which allows water flow employed for thermal recovery, is equipped with a thermal expansion joint to compensate the expansion gap between the shell, with water at temperature of approximately 90°, and the tube.
Mechanical seals employed in machinery with rotating components can be affected by a series of wear issues. The main cause of mechanical seal problems is related to the correct lubrication of the seal itself. These are the main signs and causes of a scarce or wrong lubrication in mechanical seals aiming to a proper troubleshooting.
Dry running happens when there is no liquid at all around the mechanical seal. The absence of the liquid film generates friction between the faces of the seal, with a dramatical increasing of the temperature. The typical damage of dry running is the presence of burned elastomeric parts. The damage happens when the O-ring is in direct contact with the over-heated mechanical seal ring.
A scarce lubrication can happen when the pumped fluid has a very low viscosity, or when temperature at atmospheric pressure is higher than boiling point, or if there is some air in the circuit. In these cases, the heat caused by the friction can concentrate on small areas on the seal surface, with the result of even extreme heating conditions. Local alternation of heating and cooling of the mechanical seal surfaces can cause small radial cracks due to the thermal shock.
Absent or scarce flow
It happens when the pump circuit is working with the inlet valve closed. Heat generated by the friction on the shaft seal can generate very high temperatures. The temperature increase can thus damage elastomeric parts of the mechanical seal. In addition, it increases the risk of dry running on the surface of the mechanical seal.
Further mechanical seals problems can also be related to installation issues, failure in components or a wrong selection in materials matching. We will dedicate another article to analyze in depth the troubleshooting of these cases.
A new video is up on our YouTube Tempco channel (subtitles option available), dedicated to the kind of plates H and L in plate heat exchangers. H and L plates stands for high and low efficiency, referred to the thermal exchange rate achievable. Thermal transfer efficiency in a plate heat exchanger is indeed a result of the turbulence rate of fluids, depending upon the kind of Chevron angle in the plates corrugation design.
The Chevron angle in H plates is a dull angle, so that when overlapping the plates, rotated by 180° on each other, there will be many contact points leading to a very high thermal transfer rate. By the way, pressure drop will also increase.
That’s the reason why L plates are also available, having a more acute angle in the herringbone design of the corrugation. This goes with less contact points in the plates overlap, reduced pressure drop and also a lower efficiency in thermal exchange.
L plates are suitable for heat transfer applications using viscous fluids, not requiring very high thermal exchange rates. H plates are suitable to obtain high thermal exchange efficiency with high pressure drop allowed, thus having pressure of a recirculation pump.
How to choose H or L plates in a heat exchanger? The selection is easily done by introducing the design values in a software to calculate a heat exchanger, values such as maximum pressure drop allowed, kind of fluids involved and their inlet/outlet temperatures. The software then determine the kind of plates, often suggesting the right mix between H and L plates in order to achieve the best compromise of heat transfer efficiency and pressure drop for the specific application.
Here we are introducing one of the anticipated and most immediate innovations that are driving Tempco into 2019, a new and redesigned image and logo for our company. The decision to come up with a new logo is due to the fact that personally, after so many years of activity accompanied by the old cherished one, I was really longing for something totally brand new for Tempco, representing a new course projecting Tempco into the web 4.0 and most of all heading to the lean efficiency paradigms of Industry 4.0.
The meaning of the new logo is strictly related to the concept of control of what is called secondary energy. Dropped out of the old binomial of heat and cold associated with red and blue colors, the new Tempco logo embraces a widened concept of energy, with a symbol that represents the control of a variable energy flow, being the color’s shade.
The idea explores a completely new way to face the concept of ‘Solid temperature’, remaining as our Tempco pay-off. The new logo showcases indeed a regular wave that can be linked to a heat or fluid flow, that becomes solid folding on itself. Making it in our vision a very effective, unique and original technical symbol.
And you, what do you think of the new Tempco logo?
We wanted to make this 2019 a new year full of news, starting with a series of tutorial videos aimed to explain in a simple way the main working characteristics of some machinery employed in thermal energy management, such as heat exchangers and heat pumps.
I wanted to be featured in first person, and yes, the one you’ll see in these videos (in Italian language but with subtitles) it’s me, Valter Biolchi, owner and manager of Tempco and behind this Tempco Blog as well.
I wanted to dedicate the first video to the topic of plate heat exchangers, a kind of machinery that I’ve always considered as the most flexible and efficient in terms of heat transfer above all. Heat exchangers ensure indeed higher thermal transfer rates compared to shell and tube heat exchangers. This is due to the fact that fluids are moving inside the exchanger with a turbulent flow, even when the fluids have very low speeds.
The turbulent flow is obtained thanks to the design of the plates, which are then coupled each-other rotated by 180° in order to create tiny flowing channels with 2,5 – 3 mm width, depending on the kind of heat exchanger, forcing the fluids through the plates in a continuously interrupted and non-linear flow.
Another advantage offered by plate heat exchangers is the compact design and smaller size achievable with this kind of solutions, and most of all the possibility to obtain crossing temperatures between warm and cold fluids.
Let’ start the New year on the sign of continuity within innovation… We further go on indeed on the topic of cooling in data center, that we have already covered in our last year’s post. And we welcome you in the 2019 with a new Tempco logo, to be properly focused on in a future post of our blog.
Talking about cooling in data centers, we recently found an interesting article online that explains how the power increase in data center’s racks is becoming a problem for traditional air cooling systems, promoting the growth of liquid cooling, a topic we’ve already faced in the past months. A Gartner statement reported affirms that the air cooling is no more able to achieve the necessary heat dissipation in data centers where the electrical consumption is increasing by 16 up to 20 kilowatt for each rack. An increase in energy intensity that affects all data centers around the world, with liquid cooling solutions growing at a rate of 25%.
The higher efficiency ensured by liquid cooling solutions is naturally due to the fact that fluids can carry heat better than air, offering an efficiency in heat transfer 50 to 1.000 times higher. Liquid cooling offers a range of solutions, including water and special non-conductive fluids, and also the new groundbreaking innovations in nanofluids, special thermal fluids on which R&D around the world is very committed, able to increase conductivity and heat transfer capacity of common thermal fluids by the addition of metallic nanoparticles.
In liquid cooling for data centers, heat exchangers can be installed on the rear of the racks or by direct contact with hardware components, properly using non conductive fluids. A trailblazing and growing application is the direct immersion of racks in dielectric fluids, or even the construction of underwater data centers, such as the Natick project of Microsoft or the data center Green Mountain as well.
The trend raises new challenges for IT staff, traditionally scared by possible leaks of water and fluids in the presence of electrical devices. Elsewhere, the increase in computational power required from data centers is forcing to find new cooling solutions for servers and racks, employing water and liquids that are developed offering high security and protection for electrical components. A cultural change is thus necessary for IT administrators, with training programs aimed to prepare them to the technical transformation happening in the cooling systems for IT infrastructures.
We would like to wish you all Happy Holidays, a Warm and Merry Christmas and a Joyful and Thrilling New 2019, from all the Tempco team!
Looking forward for all the new and challenging applications related to thermal energy management, and to the many news and innovations we’re working on… soon to be revelead! But in the meantime, Merry Christmas and Happy New Year to Everyone!
Cooling in data centers is often achieved by direct expansion chillers. This kind of systems, in addition to being highly energy-intensive, employ refrigerants that are pollutants, and thus more and more banned or limited by regulations. The increase in the computational power, due to the global adoption of artificial intelligence, big data analytics and cloud computing, machine learning and blockchain, has an effect increasing the impact of data centers upon the global warming.
If actually the increase of working temperatures of computers is reducing the need of mechanical cooling in data centers, regulations are pushing to a drastic reduction in the employ of refrigerants, responsible of greenhouse gas emissions.
Different HFC (hydro-fluorocarbon) refrigerants are employed in data centers, the most commonly being the R13a (in big plants) and the R410A (in small-medium size data centers). Their control imposed by regulations around the world is making their prices getting higher, pushing operators to find out new technologies and green cooling strategies for data centers.
Among green solutions for data centers, there is the employ of TCOIL dimple jacket exchangers for liquid cooling of the servers. Possibly also leveraging cold water available in the environment (as achieved in the Green Mountain installation in Norway). Getting rid of chillers, in addition to eliminating the use of HFC refrigerants, also would allow low energy consumption in data center operations.
Free cooling is another green cooling strategy for data centers, that stands out, as well as dimple jacket exchangers, for cooling efficiency and sustainability. The free cooling employs cold environmental air where it’s available, representing an efficient solution combined with cold water cooled systems. Moreover, the option of an adiabatic boost, which extends the dissipation efficiency of the free cooling systems, makes this green cooling solutions feasible in a wider range of geographical areas.
The new electrical heating units dedicated to chemical, industrial and pharma fields meet the need of these sectors to regulate the temperatures in their processes, with increasing precision and programming functionalities.
In addition the pharma sector requires a constant monitoring of all process’ steps, thus including a continuous monitoring of temperatures and cycle times of all the heating/cooling/temperature maintaining cycles.
These requirements must be fulfilled providing compact machinery, ensuring easy and fast installation and commissioning. Tempco’s solutions portfolio offers a broad constructive range of power capacities, with different temperature control levels.
On the side of equipments we held our decisions, at the beginning not always accepted but nowadays representing a very appreciated and required standard:
Stainless steel heating armored resistances
Stainless steel internal pipings
Stainless steel plate heat exchangers
Process and utilities connections on the upper side, making installation easier
Electrical panel in watertight box with thermoregulation unit interface and remote set point
ALL-IN execution complete with fairing, allowing a ‘clean’ installation without external components
TEMPCO researches and develops systems and solutions for cooling, heating, control temperature and heat exchange in different industrial processes.