Spare Parts - Emerson Sempell S Series Operating Instructions Manual

SEMPELL SERIES S, TYPES SO, SC, SB, SOH FULL-LIFT SAFETY VALVES
OPERATING INSTRUCTIONS
7 METHODS TO PRODUCE SUPERFINISHED
SEALING SURFACES
ATTENTION
Lapping is a precision operation and must
be carried out by trained personnel. Various
operating areas ask for various operating
methods.
7.1 Lapping area production
7.1.1 Disc (3)
Parts with flat seats are normally machine
lapped.
Procedure
Allow boron carbide lapping emulsion
(a mixture of grade 800 lapping powder and
lapping oil) to drip onto the constantly rotating
lapping machine wheel. Load the items to
be lapped into a suitable locator that is set
eccentrically to the table.
The lapping operation takes 15 to 20 minutes
depending on the quality of the prepared
sealing surface. Afterwards the parts will be
polished. In case of parts made of material
1.4980 the parts will additionally polished on
a tin plate with a diamond suspension; grain
size 2 - 3. A sight control and a test with an
interference glass follow to check whether the
surface is plane and not convex or concave.
7.1.2 Valve seat (2.1)
The preferred method is hand operated
machine lapping in case the valve seat is fixed
in the body (screwed in, welded in or in another
connection). Thereby it is important that the
required force is constantly and steadily
transferred through a spring.
Procedure
Grinding and/or lapping foils of different grain
sizes are pasted onto a plain carrier wheel of
the machine. The prepared seating areas with
3.2 Ra roughness are alternately lapped with
grain sizes of 200-600-1000. After lapping with
200 grain size, there should be no visible tool
marks. The change takes place at intervals
of about 1 minute. Lapping is carried out with
oscillating movements. Finally the seating area
is cleaned and visually inspected.
7.2 Lapping area site
As a rule, there is no lapping machine available
so only a manual method or the method
described in section 7.1.2 can be used.
7.2.1 Disc (3)
Depending upon the size, lap the parts on glass
plates or discs or rings made of grey cast iron.
Lapping abrasive: Tetra Bor lapping paste
(grade 120 to 1200).
Procedure
Up to a size of about 200 mm diameters lap
the parts on the plates. In case of greater
diameters, use the part to be lapped as a pad
and move the discs or rings. Thinly distribute
the lapping abrasive on one side and up a
grain size > 400 additionally sprinkle it with oil
drops. Oscillatingly move the valve part or the
lapping wheel with constant hand pressure.
This operation takes several minutes. Remove
the paste with a cold cleaning and repeat the
procedure using progressively finer lapping
paste. Finally a sight control follows.
Up to a size of about 200 mm diameter lap the
discs with a mobile manual lapping machine
according to section 7.1.2.
7.2.2 Valve seat (2.1)
Procedure see section 7.1.2.
ATTENTION
Check body seats regularly to verify that the seat
surfaces are still rectangular to the body center.
If this is not the case, restore squareness by using
a flat grinding machine.

8 SPARE PARTS

• Disc (3)
• Disc holder (7)
• Bellows (8)
• Guide (10)
• Gaskets (23 - 26)
• Piston ring, slide ring (38)
• Gaskets (43) (47)
Please specify valve type and job no.
(see nameplate) in your order.
9 DECLARATION TO EC-DIRECTIVE
The declaration of conformity can be found in
the documentation.
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