Special Application
If solid particles are contained in the fluid, valves are provided with Tungsten Carbide (WC) coated metal seats to avoid the erosion of soft seats.
Some processes require valves able to be operated and to assure leakage rates within specified limits at high temperatures. In this cases Dafram provides a special valve design including extended bonnet (recommended for use at temperatures 50°), gaskets and seals and material selection suitable for high temperature service. For application where soft seats would be unsuitable, Tungsten Carbide (WC) or Chromium Carbide (CrC) coated metal seats are used.
 
Some gas treatment processes require valves able to be operated and to assure leakage rates within specified limits at low temperatures. In this case Dafram provides a special valve design including extended bonnet (recommended for use at temperatures below minus 50°), gaskets and seals and material selection suitable for cryogenic service.
 
Materials for pressure-containing parts of valves used in H2S-containing environments in oil and gas production, shall meet the requirements of ISO 15156 (NACE) if sour service is specified. HIC and SSCC corrosion test certificates can be provided on request.
High Alloy, Duplex (22Cr – 2 Ni) and Superduplex (25 Cr – 5 Ni) can be supplied according to corrosion resistance requirements as per special material standards (i.e. Norsok MDS D46 and D44 for Duplex, D56 and D54 for Superduplex, or similar standards). In addition Electroless Nickel Plating (ENP) and 316L SS or Alloy 625 weld overlay are frequently used to enhance corrosion resistance of balls, seats, stems, seat pockets and stem sealing areas, in corrosive service.
Ball valves are often required as “emission free valves” that is able to comply with the up dated regulations which state very low rates of emission from the valve to the atmosphere. In this case special valve stem sealing design including high body and stem surface finishing and suitable seals is available.
Anti explosive decompression O-rings or Lip seals are used to eliminate the possibility of O-ring explosion due to the sudden decompression of gas absorbed into the molecular structure of elastomeric sealing elements.
Carbon Dioxide, Chlorine, Oxygen
Valves working with particular fluids, must meet some special requirements according to Dafram special procedures. To avoid risk of explosive decompression in Carbon Dioxide (CO2) service special O-rings or Lip-seals are used. Valves to be used with Chlorine need special features and a full degreasing and decontamination. Valves for Oxygen service requires also special features to eliminate the risk of ignition.
On customer request Dafram is able to design and manufacture special valve pattern such as three-way trunnion mounted ball valves or valves incorporating different special design features.
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