The Mark 708 was developed to provide the most accurate control available for fractional flow services: whether for pilot plant installations, test stands, R & D facilities or for specialized processes such as dosing, injection and venting applications. With Cv’s ranging from 0.00001 to 4.0 available in 1/4″ through 3/4″ line sizes (0,000009 to 3,4 Kv in sizes DN8 through DN20), the Mark 708 offers design features that will provide enhanced performance to insure precision control on your most critical micro-flow applications.
The rolling diaphragm design ensures that the effective diaphragm area remains relatively constant, regardless of valve stem position. This increases accuracy of the actuator when positioning the valve by ensuring a linear response to input signal changes.
The spring-loaded packing maintains a proper compression, while minimizing excessive friction. This alleviates the need for most field adjusting. The TFE packing is suitable for temperatures to 450°F (232°C), while braided or Graphite/Grafoil may be used for higher temperature requirements
The bolting provides solid construction and secure connection. This bolting adds ease to maintenance, as bonnet/actuator assembly may be removed from the valve body in-line.
The extended orifice and plug guiding are standard and offers improved shutoff and accuracy equivalent to heavy duty trim option of competitors ( not applicable to cv’s below 0.05)
The secondary stem connection eliminates stroke adjustment when changing trim facilitating faster, easier trim changes (not applicable to cv’s below 0.05).