Nakakita control valves have been adopted as optimum products of high quality for services ranging from high temperature & high pressure to cryogenic temperature & vacuum in al1 types of industrial facilities such as nuclear power, thermal power, iron and steel making, chemical plants and ships.
The valves are designed with high level technical standards. The production of valves in series has been established on the basis of high reliability of individual valves which has been confirmed by verification tests conducted by the highly competent technical staff using the latest facilities.
Every production process is thoroughly controlled by competent Nakakita staff well trained for quality control. They are assisted by fully rationalized facilities including NC machines and by carefully maintained measuring instruments. From general purpose valves to special ones, Nakakita assures stable and reliable quality. (IS09001). Every valve is designed with due consideration given to maintenance pursuing further ease in maintenance is now in production in series.
The nationwide network of after-sale service promises quick and satisfactory services after delivery, including supply of parts and field service. After sales management of the products is exercised by each serial number. Nakakita is certified to produce high pressure gas valves for services of 500K and under, and of ranges from high temperature down to ultra-low temperature, by the Minister of International Trade and Industry in accordance with the High Pressure Gas Control Act. Nakakita has many actual results in various high pressure gas facilities including LNG facilities.
Valve body assembly
The pressure containing part consisting of the valve body, bonnet and trim is called the valve body assembly. The pressure-temperature rating for the materials is determined by the applicable standard. As to the type and size, the optimum selection is made according to customers’ specifications.
The valve plug, seat ring, cage, guide bushing, valve stem, etc. are called the trim, and its combination is determined according to customers’ specifications including the fluid properties and pressure drop.
The flow characteristic which indicates the relationship between the valve travel and the flow rate is determined by properly selecting the shape of the throttle portion consisting of the valve plug and seat ring.
The gland packing is required to prevent leakage of the fluid as well as to possess low-friction property and durability. It has a vital role in the noemal operation of the control valve.
The actuator controls the travel of the valve, via the valve stem, by the balance between the operating air pressure applied to the diaphragm chamber and the compressive force of the counter spring. The signal (standard; 20 to 100kpa) from a pneumatic indicating controller is normally guided into the diaphragm chamber. For further responsiveness, a positioner is installed. When the electric signal (4 to 20 or 10 to 50 mA DC) is used, an E/P positioner is applied.