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Everything listed under: Water Hammer

  • Test Your Knowledge: Which Device Is It?

    Which of the following helps minimize water hammer, helps drains condensate, and minimizes temperature swings?

    1. Inverted Bucket Steam Trap
    2. Vacuum Breaker
    3. Fluid Air Coil
    4. Mechanical Condensate Pump
    5. Pilot Operated Regulating Valve

    And the answer is...


    2. Vacuum Breaker

    A Vacuum Breaker is a simple, reliable device that allows air to enter a steam piping system when a vacuum is induced. When a steam system shuts down, the remaining steam condenses into water, which takes up a much smaller volume than the original steam. This creates a vacuum, which can lead to water hammer and tube damage if not relieved of in a timely way. 

    Check out this video which shows the proper use of a vacuum breaker in a steam system.


    Here are our top 4 reasons for including a vacuum breaker in your system:

    1. It helps allow for complete condensate drainage under all operating conditions: on/off or modulating applications. 
    2. It helps minimize water hammer. 
    3. It helps minimize temperature swings and uneven temperatures. 
    4. It helps minimize product waste.

    All heat transfer components, whether shell-and-tube exchanger, plate-and-frame exchanger, air heating coil or any other device, require vacuum breakers. As the video shows, because the condensate piping after our coil is clear glass, you can watch condensate backing up into the coil without a vacuum breaker.  Once the vacuum breaker is allowed to operate, the coil can remain free of condensate under all operating conditions, which eliminates many issues that can shorten equipment service life and/or cause operation problems.

    The footage for that video was taken in our Steam Training Room located in Minnetonka, Minnesota, where we have regular training classes.  We utilize a steam boiler, glass piping, and functional glass-bodied steam traps to describe and demonstrate a variety of steam basics and advanced concepts in the 4 main areas of a steam system: Generation, Distribution, Utilization, and Condensate Return.

    Contact us for more information on the proper use of vacuum breakers or sign up for our Steam Energy Conservation seminars to learn more. 

     


  • Water Hammer Problem: Here Are The Top Solutions from the TRAP Magazine Challenge

    Condensed from Armstrong TRAP Magazine

    PROBLEM:

     With the steam line pressure running from 125 lbs. to 150 lbs. there will always be sufficient differential for the traps to discharge to the return line. But this is not an ordinary condensate return line -- with the condensate temperature fairly close to the steam pressure in the return line. The return line is handling the discharge from condensate pumps which are assumed to be taking condensate from low pressure traps and boosting the pressure so that it will flow back to the boiler room. The return line, is therefore, probably running full of condensate at the temperature of anywhere from 180˚F to 210˚F. Very likely it will be a lot lower than the temperature of the flash and condensate from the drip trap. Under these conditions water hammer could be quite a problem.

    What do you think? If you agree that water hammer is likely, what do you suggest as an alterative hookup to the one shown in the accompanying sketch? Please give full reasons for your conclusions. The engineer that offers the best practical solution will receive an award post haste to compensate for their effort.

    ANSWERS:

    Ninety-three percent of those replying said there would be water hammer. In fact, several engineers proved with calculations that flash steam would form in sufficient quantities when the high temperature trap discharge met the lower pressure to make water hammer almost inevitable. The TRAP Magazine judges agreed that under the conditions stated in the problem, water hammer would very probably occur, even though some readers reported that under somewhat similar conditions they had no problem.

    Suggested solutions fell into the following categories:

    1. Discharge the trap to atmosphere. This was eliminated as being unnecessarily wasteful. 

    2. Discharge the trap to a receiver. 

    3. Discharge the trap to a heat exchanger. 

    4. Discharge the trap to a flash tank.

    Solutions 2, 3, and 4, while perfectly valid means of avoiding water hammer, generally would be more expensive and complicated than the situation calls for.

    Again, it’s recognized that there are circumstances where any one of these solutions could be considered ideal, but the solution named as best must apply generally.

    5. External radiation. These included long drip legs ahead of the trap, long return lines from the trap, fin type radiation, tempering coils, etc. Such systems did not get the nod because of the needless expense, as well as the waste of heat.

    6. Ejectors. Solutions employing ejector ran a very close second to the winner.

    Reader T. Mackie, Head Plumber, Royal Alexandra Hotel, Winnipeg, Manitoba, exemplifies this school: “It is my belief there will be water hammer and to overcome this difficulty it would be my suggestion to install an ‘ejector’ such as Penberthy XL96” of the proper size and installed as illustrated in the accompanying sketch (Figure 2).

    “The high pressure discharge from the trap while passing through the ejector will pick up water from low pressure return and so will reduce the temperature of the high pressure discharge to nearer the low pressure temperature and in this way avoid water hammer.”

    The advantages of such a system are obvious. It is simple and inexpensive. It works. It wastes no heat.

    7. Special means of admitting the high pressure discharge into the 50 psi return header.

    THE WINNER:

    This category contained the winner. W.F. Gundlack, C.E., Twin Cities Arsenal, Federal Cartridge Corporation, New Brighton, MN, came up with a hookup remarkable in its simplicity. Figure 3 demonstrates this. In the opinion of the TRAP Magazine judges, admitting the flash steam in the direction of the flow of the condensate in the manner shown will be sufficient to prevent water hammer. Mr. Gudlack also offered the installation of tempering coils (Figure 4) in conjunction with the curved nipple as an even surer cure for water hammer, but this should not be necessary in most cases. The award therefore goes to W.F. Gundlack on the basis of providing the simplest, most practical and proven solution. 

    NEAR MISSES:

    J.M. Parish, Mechanical Engineer, Dow Chemical Company, Freeport, TX was close to the winning solution when he stated “...inject the trap discharge into the condensate line though a properly designed nozzle,” but did not include enough detail.

    A similar solution employing the same method of admitting the flash steam but using perforated piping (Figure 5) was advanced by readers, P.F. Krol, Cranford, NJ and J.M. Perish, Freeport, TX. In this system, flash steam is admitted more gradually and over a greater area, though still at right angles to the condensate flow, which may cause some turbulence.

    TIPS ON IMPROVING PIPING PRACTICES

    With the water hammer problem out of the way, several engineers went on to improve the general piping from that which was originally shown, particularly in consideration of the fact that this is an outdoor installation and freezing is a definite consideration.

    The TRAP Magazine presented an unmodified customer’s drawing and was criticized about some omissions. Figure 6 therefore rights this situation by revising the original to conform with the “American Standard Code for Pressure Piping”.

    1. Drip pocket.

    2. Shut off valve as close as possible to steam main and at high point on outdoor installation.

    3. For free blow to atmosphere also getting sediment out of dirt pockets.

    4. Permit shut off for trap inspection or removal; necessary if bypass is used, otherwise convenient.

    5. Strainer -- not necessary on larger Armstrong inverted bucket traps.

    6. Test valve -- optional.

    7. When valve (3) is opened for manual blowdown, there will be a pressure drop in the line to the trap which may cause trap prime to flash and make the trap lose its seal. Such traps should be protected by installing an Armstrong Internal Check Valve, (7) or by a swing check valve between the trap and valve.

    8. Pop Drain protects trap against freezing, automatically drains trap when the steam pressure is below 8-9 psi. Check valve (7) should not be used with pop drain, although strainer (5) with blow down valve is essential. Check valve (9) may also be omitted.

    9. This check valve prevents backflow into the trap.

    10. Permit shutoff for trap inspection or removal; necessary if bypass is used, otherwise convenient.

    11. Bypass valve

    12. Shutoff valve as close as possible to return header and at high point on outdoor installation. 

    One reader questioned the use of a bypass on an outdoor installation. Many would subscribe to omitting the bypass particularly when using Armstrong traps which seldom need attention. If a bypass is used, provision for draining it to prevent freezing is recommended.


  • What Is Water Hammer?

    Note: This article contains some background knowledge on the cause and effect of water hammer and was originally posted by DFT)

    Water hammer is a shockwave that moves through the fluid (liquid) contained in a piping system. This shockwave occurs when a fluid already in motion is suddenly stopped, ceasing to move through the pipe.

    The abrupt stop creates a pressure surge that moves through the fluid, affecting everything within the closed pipe system. Though the pressure dissipates fairly quickly, the resulting damage can be long-lasting and widespread — potentially causing damage to various system parts and components, such as expansion joints, gasketed pipe joints, pressure sensors, flowmeters, and the pipe walls. This pressure commonly results in a thumping or banging noise akin to hammering, hence the term “water hammer.”

    Though some degree of water hammer is inevitable in any type of piping system, leaving it unmitigated can result in serious system-wide issues, and even complete failure.

    The Effects of Hydraulic Shock

    The resulting shockwave — the increase in fluid pressure that occurs when a fluid’s movement through the pipe suddenly stops — is referred to as hydraulic shock. The most common cause of hydraulic shock is either a valve closing too quickly or a pump shutting down suddenly.

    When a valve closes too quickly, the fluid after the valve will elastically stretch because of the momentum of that fluid until the fluid’s momentum stops. The fluid will then inevitably try to return to its normal, unstressed state — much like a stretched rubber band snaps back once released. This action, however, will also cause the fluid to travel back through the pipe. The fluid that flows back will hit the closed valve, sometimes with a very strong force, which can be extremely destructive.

    Water hammer, also known as liquid hammer, is very common and can occur in both residential and industrial settings. In homes, any action involving water can trigger water hammer. This includes taking a shower, washing clothes, and running the dishwasher. In industrial settings, water hammer can be caused by improper valve selection, unsuitable valve locations (swing check valves in vertical pipe runs), and poor maintenance.

    Choosing the Right Valves to Combat Water Hammer

    The types of valves being used in a piping system can play a major role in whether or not water hammer occurs. For example, swing check valves — one of the oldest designs available — are the most commonly used style in piping systems. With these valves, the flow of the fluid opens the valve, and the fluid’s reverse flow closes it. But as popular as they are, these valves often result in water hammer since the opening and closing mechanisms have no way to control the pressure surge.

    Tilting disc check valves are also commonly used in piping systems. These function in a similar way to swing check valves; the flowing fluid opens the valve, and when the flow reverses, the valve closes — sometimes resulting in water hammer.

    The use of silent (in-line) check valves, however, can help prevent the occurrence of water hammer. A relatively new style of check valve, these feature a unique design that allows the flow to open the valve, while internal springs help close the valve before the flow reverses — thereby reducing or even eliminating the occurrence of water hammer and its various effects.  In-Line (Silent) Check Valves can be successfully installed in either vertical or horizontal pipe runs.

    Learn More

    Contact Campbell-Sevey for recommendations on how to prevent water hammer and keep your system running smoothly and efficiently. 


  • DFT® Introduces the TLW® a Tapped Lug Wafer Check Valve Built for Safety

    DFT recently announced the release of their new tapped lug, wafer style, check valve, the model TLW. Here is an overview of the features and a TLW spec sheet you can download

    With its one-piece solid body construction and tight seal, this non-slam, center-guided TLW check valve is designed to prevent leak paths and has the optimal safety feature of no exposed studs in the clamping area, which could impact the integrity of the valve in the event of a fire or corrosive environment.

    Prevents Leak Paths, No Exposed Studs

    This valve was originally designed for use in applications of the refining and chemical industry where exposure to fire, corrosion, and other harsh chemicals justifies the need to conceal studs, but is well-suited to any industry requiring no exposed studs.

    Its tight seal and one-piece body prevents operating fluid leakage, allowing for safer more reliable operations.

    These TLW axial flow check valves are lightweight and compact, meeting API 594 face-to-face dimensions. They can be installed in either a horizontal or vertical position, and used in liquid, gas, and steam pipelines.

    They are built for a long life service life and low maintenance. For valves 10 inches or larger, tapped holes are included in the body, allowing lifting lugs to assist with installation.

    Preventing Hydraulic Shock with TLW® Check Valves

    As with all DFT axial flow check valves, the TLW has the ability to eliminate water hammer or hydraulic shock, the result of the generation of pressure waves in a pipeline, which occurs when the flow of the fluid is stopped by a sudden valve closure.

    This pressure wave then travels back and forth through the pipeline, which can cause serious damage to pumps and piping systems. Such failures can be extremely costly, time consuming, and dangerous, especially if the pipeline is carrying toxic chemicals or high temperature fluids such as steam.

    The TLW check valves eliminate the problem of water hammer by using silent, spring-assisted technology. Unlike traditional check valves, TLW valves do not rely on the velocity of operating fluid or gravity for valve closure. The disc is closed by the spring assist on the valve as the forward velocity of the fluid slows.

    This coupled with the relatively short distance the disc must travel, by the time the forward velocity of the liquid reaches zero, the valve disc would already have reached the seat, and the valve will have already closed. Reverse flow is eliminated, and therefore the forces necessary to produce water hammer on the upstream and downstream sides of the valve are substantially diminished.

    For optimal durability, the bodies of these valves are typically made of carbon steel or stainless steel. The disc, stem, bushing, and seat are made of stainless steel.

    The valve is also equipped with a Nitronic® 60 stem and an Inconel® X-750 spring. These valves are available in sizes ranging from 2 inches to 24 inches and, as mentioned earlier, the larger models come with tapped holes for lift-assist lugs.

    The TLW valves also feature a threaded lug design and raised face (RF) wafer ends, which assist in eliminating leaks. Well-suited for a wide range of applications, TLW check valves help ensure safe operation in fluid pipelines.

    Learn More

    The team at Campbell-Sevey can provide you more details regarding check valves and control valves and evaluate whether they are the best fit for your system.  For more information download the TLW spec sheet or give us a call.

    Content from this article originally posted by DFT. 

     


  • Minimizing Water Hammer with Wafer-Style Axial Flow Check Valves

    In 2015, a wastewater treatment facility began reviewing alternatives to its existing design in an effort to resolve a water hammer issue and considered the use of wafer style axial flow check valves. Axial flow check valves were considered due to the ability to minimize and/or reduce the effects of water hammer based on the difference between an axial flow and dual disc trim. 

    To understand the improved performance of an axial flow check valve in minimizing water hammer, you must consider the fundamental difference in the trim design. Just as ball valves, globe valves, gate valves, etc. have different flow characteristics, so do check valves. Check valves can be classified into two basic categories, swing checks and axial flow. In the case of axial flow check valves the trim moves parallel to the axis of the flow path. Only non-slam silent check valves are designed this way. 

    A comprehensive case study was put together detailing how the wastewater treatment facility resolved the following hammer problems:

    • Check valve spring failure every 2-3 months
    • Repair and replacement of check valve every 3-4 months
    • Increased routine for tightening loosened flanging due to hydraulic shock in system
    • Retuning of instrumentation due to hydraulic shock in system
    • Loss of capacity due to increased maintenance routine

    Download the case study to learn more about DFT Check Valves or contact the team at Campbell-Sevey.

  • Test Your Knowledge: Steam Line Water Hammer

     

    Steam line water hammer can best be prevented by...

    A. keeping steam pipes drained and insulated

    B. replacing all 90 degree elbows with capped tees

    C. always opening steam valves rapidly

    D. keeping steam temperature below saturation point

     

     

    The answer is...

    A. keeping steam pipes drained and insulated

     

    One type of water hammer is Differential Shock

    Steam flow over accumulated condensate can create waves that grow as they are pushed downstream. If the steam is moving fast enough and the condensate is sufficiently abundant, the waves will grow until they block the pipe completely. This traveling slug of condensate can accelerate and grow in size, stopping only when something intervenes or they're suddenly diverted by equipment or a bend in the piping. This can be a dangerous situation and can lead to catastrophic valve or fitting failure.

    Differential Shock can best be prevented by reducing condensate accumulation wherever possible, both by draining the condensate from steam lines at regular intervals and at every change in elevation, and by minimizing the condensing rate with proper insulation.
     

     

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