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Level controllers and float valves control the liquid level in a vessel.
Level controller or float valve
You should use a level controller with float chamber if the float cannot be mounted in the vessel. It is mounted in the pipeline and
connected to the vessel by means of balancing lines. Float valves have no float chamber. The float is always mounted in the vessel.
Feed and drain valves
Feed valves (code letter "Z") close as the float rises and prevent overflowing. Drain valves (code letter "A") close as the float sinks
and ensure that the liquid level does not drop below the required level.
Mounting of float-controlled valves
Float valves for installations in vessels are mounted inside the vessel complete with float. Float valves for installation on vessels are
flangemounted on the outer skin of the vessel. Float valves for installation in pipe lines are installed in the feed/drain pipe.
The float lever either projects into the vessel or the float movemen´s is transferred by means of a cable.
Flow direction of float valves
The flow direction determines the mounting arrangement and type of float lever used:
horizontal, flow dir. towards or away from the vessel code letter "w"
vertical, flow direction upwards code letter "o"
vertical, flow direction downwards (code letter "u")
Selecting valve type and nominal diameter
To select the valve type and determine the required nominal diameter you should calculate first the operating performance
parameter Kv based on the maximum operating values and minimum pressure drop Dp. You should choose a valve having a Kvs value
which is 30% greater than the calculated Kv figure.
Selecting the operating pressure range
The maximum operating pressure of your system must be within the operating pressure range of the valve; if not,
the float valve will not close or open.
Pressure inside the vessel
Check whether the vessel in which the float is to be mounted is not pressurised. If the vessel is pressurised a pressure-resistant
ball float has to be fitted. Cylindrical floats may only be used in non-pressurised vessels.
Temperature
If the valve is to be used for temperatures above 80°C or a liquid other than water, the compatibility of the elastomers must be checked.
For hydrocarbons like gasoline, petrol etc., for example, the valves are fitted with FPM elastomers, whilst for higher temperatures they
are fitted with EPDM or, if necessary, with a metallic cone seal.
Adapting the float
Float valves are normally designed for media with the specific gravity of water. By choosing a different float geometry,
by filling the float or by altering the operating pressure range, we can adapt the floats to other media.
Balance and double seat
Single seat non-balanced float valves are used for low pressures. They are relatively insensitive to contamination and dirt deposits.
Single seat balanced valves can be used for larger pressure drops and feature smaller floats.
Double seat valves are specially suitable for large flow rates.
Overflow preventers
A special product are the PTB-approved overflow preventers Types 36S and 36SF. These are mechanical safety devices for flammable liquids.
Seat leakage
Level controllers and float valves are control valves which are not required to provide a leak-proof seal(VDI/VDE Guideline 2174).
For leakproof shutoff, shut-off valves must be used. Normally our valves leave the factory with perfectly leakproof valve seats.
During operation, however, solid particles (e.g. sand, welding nuggets etc.) often cause damage and seat leakage.
Any low leakage requirement must be expressly specified when ordering. Valve leakage can be considerably reduced
by special measures such as lapping the valve seat, using special cone seals and increasing the valve closing force
by changing the lever geometry or increasing the size of the float.
Adjustable filling level
In the case of valves fitted with float rod and adjustable float,
the level in the vessel can be adjusted by sliding the float alon g the rod.
Float rod guide
For float rods a guide must be provided in the vessel to prevent the float oscillating.
Float valves with parallel guide or special designs featuring a top-mounted float do not require a rod guide.
Operation
Make sure that no pressure surges or water hammer occur in the system, which could destroy the float.
In the case of foaming media and the resulting reduction of the specific gravity, a float valve cannot operate reliably.
In this case a foam abatement circuit should be provided.
Maintenance
Float valves and level controllers should be cleaned and serviced at regular intervals.
This rule applies especially to valves which are rarely operated e.g. valves fitted in sprinkler systems.
Thorough cleaning is important in the case of liquids containing substances which easily form deposits
(such as iron, lime, suspended solids etc). Sand and abrasive particles carried along in the liquid can cause rapid wear.
Please ask for specially adapted valves.
Valves free of oil and grease or silicone.
Please pay attention to order and fit only spares free of oil and grease resp. free of silicone.
Guidelines for selection, installation and operation, "Notes on Safety", Operating Instruction MUST be followed
Please consult our engineer if extreme operating conditions apply or whenever you are in doubt.
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installation in tanks
installation at tanks
installation in pipelines
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