Oil and gas production handbook An introduction to oil and gas production

The tubing hanger (also 
called a donut) is used to 
position the tubing correctly in 
the well. Sealing also allows 
Christmas tree removal with 
pressure in the casing. 
 
Master gate valve. The 
master gate valve is a high 
quality valve. It provides full 
opening, which means that it 
opens to the same inside 
diameter as the tubing so that 
specialized tools may be run 
through it. It must be capable 
of holding the full pressure of 
the well safely for all 
anticipated purposes. This 
valve is usually left fully open 
and is not used to control flow. 
 
Pressure gauge. The 
minimum instrumentation is a 
pressure gauge placed above 
the master gate valve before 
the wing valve. In addition, 
other instruments such as a 
temperature gauge are 
normally fitted. 
 
Wing valve. The wing valve can be a gate or ball valve. When shutting in 
the well, the wing gate or valve is normally used so that the tubing pressure 
can be easily read. 
 
Swab valve. The swab valve is used to gain access to the well for wireline 
operations, intervention and other workover procedures (see below). On top 
of it is a tree adapter and cap that mates with a range of equipment. 
 

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