In no circumstances can the inlet diameter be reduced below the stated size.
While the outlet diameter and side run off diameter can be reduced if necessary, there is no advantage and it can result in reduced capacity.
Increasing the size of the outlet diameter and side run off diameter is permitted up to 1.5-inch for the valve models MS/LC and SS6 and up to 3-inches for valve models MS/STD and SS10, but no increase in flow will result.
Where smaller inlet connections already exist, the change of pipe size must be made using welding reducers or longer tapers and not by bushing or other means involving sharp changes in diameter.
The Belfield valve can be used for practically any decanting operations within the limits of its capacity, pressure and temperature limitations. It should be noted that this is a decanting valve, and not a separation valve. It will not be of any value for systems where pre-separation of the phases has not occurred.
Applications may be broadly classified as:
Discharge to atmosphere
This is the most common application involving discharge of the heavier phase to drain or a second vessel under gravity where all vessels in the discharge side are at
atmospheric pressure. The lighter phase may be recovered through the side run off of the valve or via some other run off from the main vessel.
Float Detection Application
It is possible to detect if the valve is OPEN or CLOSED remotely if required by ordering the valve with a ‘magnetic’ proximity device built into the top of the valve. This requires the valve to be modified with a stainless steel bolted top if it’s an MS/STD or MS/LC. Stainless bodied valves are manufactured in this style of top as standard.
This device will require 24vdc power by others and can be used in a hazardous area. There is a magnet attached to the top of the float and when it is in the proximity of the sensor a switched signal is generated indicating valve float up/down. This is a cost added to the standard valve.
Pumping applications present no real difficulty. It is, however, necessary to work with a great deal more information and in general no recommendation can be made without viewing detailed pipe drawings and flow sheets. However, certain guidelines can be given.
On general pumping circuits and discharge from pressurised vessels, Belfield valves can be used, where first one phase and then the other are pumped or pressurised from a common storage vessel either to, two other vessels or one phase to drain and the second to storage.
The general guidelines for sump pump applications apply and the automation system is the same. There are however, significant differences. Continue reading for an example.
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If the heavy phase is running to drain or to storage with no back pressure on the valve, then the valve will try to discharge 10,000 G/H (453M3) and will close prematurely due to lack of flow at the inlet. A suitable size orifice plate on the outlet, restricting the flow from the valve to about 4500 G/H (19.53 M3) will prevent problems. Under no circumstances work with check valves.
• If it is not possible to install the valve close to the pump and/or if the side run off is used to discharge the lighter phase, then a bleed back into the vessel on the pump suction will be necessary because the pump, line and valve will be full of light phase, unless the pump is allowed to discharge all of the light phase. This is unusual since most pumps have mechanical seals which must not run dry.
• Always remember the valve size must be based on the net head available. That is the difference between the pressure at the pump and the resistance and/or “lift” of the liquid after the valve.
• Finally, always determine the head generated under “no flow conditions” if the pump is centrifugal since this could exceed the safe design pressure of the valve, despite the fact that the head under “flowing conditions” is quite satisfactory.