Cast Carbon Steel Globe Valves | AB-05
Ref: AB-05
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BONNET
Bonnet design is circular for all ratings. In all cases bonnet flange thickness is designed to work under most severe conditions according to ASME B16.34.Body bonnet connection is usually male-female designed up to 900 class valves. For class 1500 and 2500 pressure seal design is preferable. On request other connections such as RTJ seal may be supplied. Auxiliary connection bosses are provided according to ASME B16.34 for instrumentation, drain, or measure purposes. Bonnet machining is carefully checked to ensure disc travel to be perpendicular to the bore line, so that operating problems are avoided. Stem nut seating must be parallel to bonnet connection. Stuffing box must be extremely smooth machined to provide perfect tightness without applying too much strength on the eye bolts. Life loaded stuffing box may be fitted for special applications using Belleville springs to improve durability and reliability of the packing seal.
DISC
The disc seats on the seat ring to tight the valve. Disc is designed to revolve free over the stem to avoid rubbing against the seat ring while closing and prevent galling at the closure. Plug sealing surface is at least 13% Cr, integral or overlaid. Usually plug works opposite to the pressure line. For big size valves, or big ratings, to achieve a smaller torque on line, the design is changed to make plug work parallel to the pressure line. In this cases opening is in two steps. In the first one the pressure equalizes on both sides of the plug, and in the second one the valve opens. For pipelines with a lot of turbulence, or for valves in vertical position, the plug is guided in the seat ring. Special manufactures such as parabolycal or percentual plug, or SOFT SEATED may be produced for special applications. Sealing surfaces are carefully machined so that long life, small torque, and no leakage are achieved.
SEATS
For carbon steel valves seat ring is manufactured from forged steel. The sealing surface is sprayed welded with the material required by customer. Renewable threaded seat is used for NPS 10" and smaller valves, welded seat design is used for NPS 12" and bigger. For stainless steel valves usually integral seat is used, overlaid, or not. Other constructions are available under request. Seat surfaces are carefully machined to provide tightness. Special attention must be taken with the seat ring thread to avoid seizing. Special care is taken to provide hardness difference between seat and wedge according to BS 1873. For this reason seat rings are heat treated.
BODY
The valve body is manufactured of cast steel, or forged steel, depending on the customer's requirements. In any case ANSI B16.34 pressure-temperature ratings and BS 1873, or B5-5352 minimum wall thickness are strictly fulfilled. Globe valves are unidirectional and may be installed in both vertical and horizontal position. All ratings valves have circular sections to make minimum stresses, under severe working conditions,. These sections are carefully calculated in order to prevent stress concentrations. Sealing ring seating is carefully machined and inspected to prevent leakage between seat ring and body. Seating surface must be 1,6 AARH at least. Machining on seat sealing is controlled to ensure perfect sealing and interchange ability with spare parts. Special care is taken to ensure, body end flanges, and bonnet flange to be parallel and perpendicular to prevent operating problems in line and during testing. Flange facing is spiral smooth finish 125-250 AARH standard machining. Other facings are available under request. Auxiliary connection bosses are provided according to ASME B16.34 for instrumentation, drain, or measure purposes. Flange dimensions fulfil with ASME B16.5. Other flange types may be produced under request.
STEM
Stem is made of one piece forged steel. The diameter of the stem fulfil with BS-1873.Stem connexion is T type. T head is properly designed to allow the plug adapt to the stem in any assembling position (vertical or horizontal). In some cases a washer is assembled to help the plug adapt to the stem. Stem connexion is designed to prevent the stem being disengaged from the plug using a stem nut and one split washer. Back seat sealing face is carefully machined to provide tightness on pressurized pipe line with valve fully opened. For this reason the surface finish of the packing seal must be smooth enough. Machining of ACME threads is smooth enough to obtain a low operating torque.
GLAND ASSEMBLY
The gland flange and the gland bushing push the packing rings to make them seal the stuffing box and the stem. Gland bushing is shoulder type to prevent over strength over the packing. Gland flange is designed with enough resistance to work on the most severe conditions. Gland flange and gland bushing are self adjusting to each other to ensure perpendicular pressure on the packing.
BACK SEAT
All of our valves have back seat design according to BS 1873. Carbon steel valves are fitted with renewable back seat 13% Cr minimum. For stainless steel valves, the back seat is directly machined on the body. Overlaid surface is possible under request.
STEM NUT
Stem nut is made of different materials such as ASTM A439 D2, Ni-Resist, or Aluminium bronze. Depending on the size and class of the valves rolling bearings are fitted on both sides of the stem nut, in order to make torque operation minimum.