Instruction Manual for F1300/1600 Mud Pump
36
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The purpose of preheating is to expand the area being repaired so that as the cooling process
takes place, the welded area and the preheated area will cool more uniformly. Heat cracking during
eliminating weld also prevents hard spots from forming between the base metal and the welding by
eliminating a thermal shock as the weld is being applied. This hard spot will, of course, be a good
place for fatigue cracks to occur.
The welding procedure is the same as that mentioned above.
3.11 Repair Valve Cover Bore
When making repairs to washouts in the valve pot cover bore, it is extremely important that the
surface where the valve cover seats is either “machined” or “ground” perfectly flat and 90°to the axis
of the threads. As shown in Fig. 23, the valve pot cover gasket (1) seats into the counterbore at top of
valve cover deck, and as the cover makes up metal to the valve deck, the gasket is confined within its
counterbore obviously, any high spots on the valve cover deck from weld repairs, or any low spot from
over-grinding of the repairs can result in a clearance between top of the valve cover deck and bottom
of the valve cover, through which the valve cover gasket can be extruded and washout under pressure.
The high or low spot can also cause valve covers to make up in a “cocked” position and result in
severe thread damage (cracks) due to the axis of the two mating threads being out of square.
Fig .23
3.12 Change of Dampener Bladder
Procedures of change for dampener bladder (Refer to Fig 10):
1)
Sure that the pressure in the system has been drained out completely (see 1.7 Dampener
assembly).
2)
Disassemble the cover (5) by screwing three bolts into the “jack screw” holes. If the stud is
demounted from studded assembly, clean the studs and screw holes after the nuts have been taken
down. Screwing the studs using special wrench or normal wrench with two nuts at the same time,
tightening them with the torque 800N.m (580ft-lbs).
3)
Take off the bladder.
Insert a bar without edges and burrs into the gap between bladder and shell, then compress it flat
with pressure and takes it off from the top hole.
4)
Check the bladder if there is any damage. If the bladder is destroyed by piercing, check if there
are some blow-ups or impurities, clean them thoroughly at once.
