1900 Series - Maintenance Manual

X. Parts InspectionNozzle Inspection CriteriaNozzle should be replaced if:• Dimension from seat to first thread, after remachiningand lapping, is less than D min.(see Table 1).• Threads are damaged from pitting and/or corrosion.• Top of flang and intersecting surface are damagedfrom galling and/or tearing.• Seat width is outside specification (see Tables 7a,7b or 7c).Nozzle Seat WidthUsing a measuring magnifying glass (see LappedNozzle Seat Widths), determine whether the seatingsurface must be machined before lapping. If the seatcan be lapped flat without exceeding the requiredseat width (see Tables 7a, 7b or 7c), it does notrequire machining. To reduce the seat width, the 5ºangle surface must be machined. The nozzle mustbe replaced if the D dimension is reduced below theminimum (see Table 1).ATTENTION!!Flange thickness changes the center-to-facedimension. Ensure the minimum dimension for orificeD through P is .656" (16.67 mm), and for Q throughW is .797" (20.24 mm).Nozzle Bore InspectionAll 1900 Series SRV nozzles manufactured afterAugust 1978 have increased bore diameters. Originaland new nozzles are interchangeable, but the ratedcapacities are different (see Table 2).1900 TM Series SRV StandardDisc Inspection AreasThe standard 1900 TM Series disc (see Figure 20) canbe machined until the N dimension is reduced to itsminimum size (see Table 3). The T dimension is providedto ensure the disc has not been machined beyond itslimits. If re-machining reduces the thickness of the disc(T min.), the entire disc holder assembly drops withrespect to the seating plane of the nozzle. This creates asignificant change in the huddle chamber configurationand results in significantly more simmer before opening.1900 TM Series Thermodisc ®Replacement CriteriaThe Thermodisc ® must be replaced if:• Seat defects and damage cannot be lapped outwithout reducing the A dimension below those listedin Table 4 (see Figure 21).ATTENTION!!The A dimension on orifice D through H is difficult tomeasure. If the .006" (0.15 mm) minimum thicknessof the thermal lip cannot be measured, replace theThermodisc ® .5 0 ACBL5°FHNMAKLBDED minJ45 0 D minNozzleBorePNozzle BoreNozzleBoreFigure 19a: MetalSeated NozzleFigure 19b: O-RingSeal NozzleFigure 19: Metal Seated and O-Ring NozzlesFigure 19c: Soft-SeatO-Ring Nozzle1900 Series Safety Valve (July/2010) | 21