User Manual
Tool Catcher
OPS-4428 Rev A
4
3 Technical
Description
3.1 Description
The IRIS Tool Catcher is designed to prevent tool strings from falling
downhole in the event of a breakage in the wire after the rope socket has
struck the stuffing box. The unique IRIS fingers will catch in the recess of the
fishing neck and lock the tool string in position. The Tool string can be
released by applying hydraulic pressure to the piston to open the fingers –
note that this will occur even with significant tool string weight so operators
must guard against the dropping of the string when hydraulic pressure is
applied.
There are twelve independent fingers mounted on a pivot joint that are spring
closed. The upward movement of the tool string will naturally open the fingers
against the spring, and they will then collapse into the recess below the fishing
neck. When the tool direction is reversed the sharp angle at the base of the
fishing neck prevents the fingers from opening allowing the whole tool string
weight to be supported.
There is a second set of IRIS fingers mounted in the reverse direction and the
top of the tool catcher. This group acts as a stop for the tool string to ensure
that the lower set of fingers is correctly positioned to catch the fishing neck
upset. The upper set is also mounted on a shock absorber so that any upward
momentum is dissipated with minimum shock loading to the wire and the tool
string. The fact that we are using IRIS fingers as an upward stop has the
additional benefit that the tool string can now be loaded through the tool
catcher from the top, which greatly simplifies the set up operation. Note that
the tool string cannot be withdrawn from the top unless the top set of fingers
are being held open with a suitable, locally manufactured, tubular sleeve (not
supplied).
The Tool catcher is moved into the release position by applying hydraulic
pressure to the piston, which will move upwards and force the fingers into the
open position. With the piston fully extended the fingers are open to allow full
bore access to the tool string.
Note:
The second set of iris fingers can be removed and replaced with a
spacer ring (supplied) if a longer fish neck is to be used. Care must be taken
that the fingers can only catch in the correct recess when the tool strings
stops and the top of the riser.