Globe valves are used mainly for steam or other media where a throttling service is required. The seat design gives an advantage for doing this by utilising its globe shape as it comes down to connect with the seat effectively cutting the flow gradually up until it seals completely on the seat face. This however does cause a larger pressure drop than say a gate valve and causes turbulence in the line.
The size, pressure class and material selection of all globe valves are the responsibility of the user or system designer. Process Systems may offer suggestions in this area, however the selection process is solely the responsibility of the end user or plant operator.
Globe valves are unidirectional whereby they are only designed to take the flow in one direction, under the disc. There is an arrow of direction cast into the valve body but can easily be checked by looking into one end of the valve and see whether you are looking at the under side of the seat or above the seat. It is recommended that the valve be mounted vertically only whereby the handwheel operation will be at the top of the valve. THis ensures that no premature wear or damage will occur to the valve. The main installation points are below
Remove any packing or debris from the valve
Ensure the inside of the valve is free from water or moisture (can expand when subject to heat on startup)
Ensure the valve is supported (can be damaged by long runs of unsupported pipe clamping in on the valve)
Ensure you have room to operate the valve
Do a complete dry cycle of the valve from closed to open then back again
Tighten flange bolts gradually in a diagonal pattern
Gradually raise the internal pressure to ensure the flanges and bolts are installed correctly and the valve is sealed
Raise internal pressure to operating levels and check again
Our Globe valves are clockwise close (anti-clockwise to open).
Do not overtighten on the seat to close. If media is still leaking through the seat may be damaged
Even though they are great for controlling flow try not to leave the disc in the middle of the flow for extended periods of time. This will cause the seat to wear prematurely and in steam applications where continuous throttling is less than 10% open, excessive vibration, noise and wire draw across the seat causing a leak path which at times may not be visual to the naked eye.
Do not exceed 100% of the maximum pressure rating of the valve at any time during its operation. Pressure spikes or fluctuations beyond the valve’s pressure rating are solely the responsibility of the operator and can cause considerable harm or even death if not adhered to.
A regular maintenance and inspection schedule will ensure you get the best life and operation out of your globe valve. Some things to consider are below (not exhaustive).
Regular inspection of the valve. Pay particular attention to the gland to ensure there is no obvious wear or the valve is leaking
If the valve is not operated regularly it is a good idea to cycle the valve to ensure the disc is not bedding itself in the seat
Grease the crossbar by using a grease gun on the grease nipple provided. Lubricate the spindle if needed
Slightly tighten the gland bolts if the packing needs adjustment. Do not overtighten otherwise the gland will be damaged. If it is still leaking through here the gland packing may need to be replaced
Please be aware if the valve is to be removed from the line for inspection to ensure that there is no pressure in the line and it has cooled to room temperature. Once it is removed a complete inspection can be carried out including inspection of the globe (disc) and the seat. Any scale build up at the bottom of the valve can be removed.