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Product FAQ - Answers to common questions

Questions About Traps

Is it OK to insulate steam traps?

The operating principle of some types of steam traps relies on fluctuations in temperature, so those types of traps must not be insulated. Mechanical types (float and bucket) may be insulated without any problem. Thermostatic types will not operate properly if insulated. For thermodynamic types, insulating measures should be limited to rain-proofing.

Is it OK to submerse trap outlets?

Trap outlets should not be submerged as a general rule. If submerged, there is the danger that a vacuum will form inside the trap or at the trap inlet when the equipment is shut down, causing water to be sucked back up. This is not a problem if only water is sucked up, but if particulate matter such as dirt or sand is also sucked up, it can result in problems. If for some reason the outlet must be submerged, make a small air-intake hole in the piping to prevent the formation of a vacuum.

Is it OK to have a rise in the trap outlet piping?

If the condensate is pressurized, this pressure (self-pressure) will allow the condensate to flow upward through rising piping. For example, the self-pressure of condensate at 1 barg will theoretically allow it to flow upward through a rise of approximately 10 m. However, and this is not limited to rises in piping, if the trap backpressure increases, the risk of the following must be considered:

  • Reduced discharge capacity due to a decrease in trap operating differential pressure
  • Tendency for failure of traps with low allowable backpressures (e.g. disc type)

In addition, as condensate will pool in vertical sections of piping during equipment shutdown, some arrangement for blowing out this condensate must be considered if such pooling is undesirable.

What is the safety factor for trap selection?

The mechanism of operation for traps differs depending on the trap operation type. Some traps are extremely responsive, whereas others are extremely slow to respond. The recommended safety factors are determined based on the different operation types. Another parameter used in determining the various safety factors is the speed with which equipment startup occurs. If rapid startup times are required, a larger safety factor must be considered.

What is the possible trap operating pressure?

Traps have a specified maximum operating pressure. They may not be used at pressures exceeding this value. Mechanical traps are broken down minutely into categories of maximum operating pressures. The maximum operating pressure is found in the numbers displayed at the end of each model of almost all TLV Free Float® traps (units: bar). If this pressure is exceeded, the operation principle will cause the valve-closing force to become greater than the valve-opening force, and the trap will cease to operate (= valve will no longer open).

Questions About Pressure Reducing Valves and Control Valves

Is a safety factor necessary in pressure reducing valve selection?

There is no need to take into account a safety factor if selecting from within the designated flow rate.

What is the difference between the MC-COS series and the CV series?

The MC-COS series is specialized for steam use. The CV series may be used on a variety of fluids in addition to steam, such as air and water. The MC-COS series is mainly used for the control of steam pressure, while the CV series is used for the control of pressure, temperature, flow rate, etc. When combined with its specialized controller, the MC-COS series features extremely high-precision, rapid control. The CV series, used in combination with a multi-purpose controller/sensor, features extreme versatility for use on a wide variety of applications.

Is it necessary to install a strainer in front of a pressure reducing valve?

All TLV pilot-type reducing valves have an integral screen in the pilot section. In the COS series (with built-in separator and trap), there is an integral main valve screen. The COS-R series, however, does not have an integral main valve screen, so installation of a strainer with a minimum of a 60 mesh is recommended. In addition, in the COS series, if there is noticeable clogging of the integral screen due to dirt or scale, use the COS in conjunction with a strainer.

General Questions About Steam

Why is a separator used?

Separators are installed in steam or air piping and are used to separate out and remove moisture entrained in the steam or air. TLV’s DC-A and DC-S series features a cyclone style separator and Free Float® trap combined into one unit.

What is the difference between an air vent for steam and an air vent for water?

An air vent for steam is used to discharge air from a system in which both steam and air are found. An air vent for water is used to remove air from water piping systems. The air vent for steam employs thermostatic trap technology, which operates based on temperature differences. The air vent for water employs Free Float® trap technology, which makes use of buoyancy. Thus, though they are both called ‘air vents,’ they cannot be used interchangeably; the air vent for steam must not be used on water systems, and vice versa.

What is ‘stall?’

‘Stall’ occurs when a lack of trap operating differential pressure (the difference between the pressure in front of the trap and the pressure behind the trap) causes condensate to no longer be discharged from the trap and instead to pool inside the heat exchanger. It is sometimes due to the relationship between the load and heat transfer surface area of the equipment whose temperature is being controlled.

What is ‘steam locking?’

‘Steam locking’ occurs when the flow of condensate into the trap is hindered by the steam layer in front of the trap, and the discharge of condensate is delayed. Steam locking has a tendency to occur in equipment such as that with a rotating body and on which a siphon pipe is used (cylinder dryers, roll heaters). There are steam traps with an optional ‘lock release valve’ designed to eliminate such steam locking.

What are dampeners and siphon pipes used for?

Dampeners are used to minimize the effects of pulsations or sudden surges on equipment such as pressure gauges. They restrict the pathway by means of a throttling mechanism similar to that of a needle valve. Siphon pipes are filled with fluid to prevent high temperature fluids from coming into direct contact with pressure gauges and transmitters, while at the same time preventing the radiant transmission of heat from the surface to the instrumentation.

Are there check valves that can be used on vertical piping?

TLV’s CK series of check valves features a spring and disc valve configuration that allows for installation in either vertical or horizontal orientations. There are other types of check valves, such as swing or lift, but these types rely on gravity for valve opening and closing, which limits them to use only on horizontal installations.

Questions About Condensate Recovery

Are check valves needed at trap outlets?

Trap outlets are piped independently, and no check valve is required if the outlet is piped to atmosphere. For applications in which trap outlets are piped to a condensate return line, if some equipment may still be running while others are shutdown there is a chance that condensate will flow back up through the trap. A check valve must be installed to prevent this backflow.

What is two-phase flow design for condensate return lines?

As the name implies, condensate return lines are pipelines through which condensate flows. Flash steam often accompanies hot condensate, however, and in this case flash steam (gas phase) and condensate (liquid phase) are found mixed together inside the piping. Two-phase flow piping design takes into account this mixture of gas and liquid. As the specific volume of steam is 100’s to over 1,000 times that of condensate, condensate return piping is more like steam piping than water piping. However, consideration must be given to flow rates that prevent the occurrence of condensate-induced (liquid phase) water hammer.

What is the motive medium for Powertrap®?

Motive medium at a pressure higher than the backpressure is introduced into the body of the Powertrap®, and this pressure forces the discharge of condensate from the Powertrap®. The motive medium acts as the driving force, in the same manner as the piston in a child’s water pistol.

Is it OK to connect the outlets of traps with different pressures to the same return line?

It depends on the conditions. Condensate will flash into flash steam when it travels from high pressure to low pressure. This results in a two-phase flow of flash steam and condensate inside the condensate return line. Such conditions require that this flash steam be taken into account when sizing the condensate return line (selecting proper pipe diameter). Careful consideration must be given if high pressure condensate is to be added to a return line designed to receive only low pressure condensate.

Questions About Air and Drain Traps

What is the difference between air and drain traps?

Air traps are used to remove condensate from the ends of air piping, from receiver tanks, etc. Some models have larger orifices to facilitate the removal of high viscosity condensate with entrained oil or scale. As corrosion resistance is not of particular importance, trap bodies are typically constructed of cast iron.

Drain traps, as defined by TLV, are traps which are available in two forms - for air or non-flammable, non-toxic gas applications. Drain traps are used to remove condensate from air or non-flammable, non-toxic gas systems requiring a tight seal. For this reason, TLV drain traps employ 3-point seating to provide a tight seal even under low condensate load conditions. Products constructed of materials suitable for use on high pressure lines are also available.

What is the difference between metal valve seats and rubber valve seats?

The most important feature of rubber valve seats in comparison with metal valve seats is their superior sealing ability under low condensate load conditions. Rubber valve seats are therefore ideal for applications in which a trap is necessary but the amount of condensate is extremely small. However, even under the same maximum operating pressure rubber valve seats also feature small discharge capacities, low maximum operating temperatures and a limited number of fluids with which they can be used.

I’m using an air trap, but why is condensate not being removed as expected?

Is the trap designed for use with a pressure-balancing line? If the displacement of the air inside the trap by the inflowing condensate is not taking place as it should, condensate can no longer flow into the trap and the discharge of condensate from the trap will cease completely. A pressure-balancing line will prevent this from occurring. The air inside the trap is released through the pressure-balancing line when condensate flows into the trap, allowing the condensate to be discharged smoothly.

General Questions About Air Systems

Why does water drip from air equipment during hot, humid weather?

If the condensate that forms inside the piping is not removed properly, the operation of air-using equipment such as receiver tanks, after-coolers and piping may be hindered. In particular, during periods of high humidity and high temperatures condensate flow rates increase, which can lead to these types of problems.

Is there a valve for use on air applications?

TLV ball butterfly valves are a soft-seat type, employing a Fluorine Resin (PTFE) valve seat, making them suitable for use on air applications. These products are not listed in our promotional materials or website so please contact us directly for further information. The bellows-sealed valve series are of a metal-seat type with a metal valve seat and valve body, which from the standpoint of sealing ability are not particularly suited for use on air applications.