Springs special designs

Users are warned that an ordinary spring loaded safety relief valve will not open at its set pressure if back pressure builds up in the space between the valve and rupture disk. A specially designed valve is required, such as a diaphragm valve or a valve equipped with a bellows above the disk. 

Rupture discs are specially designed to rupture at a specified relief set pressure. They usually consist of a calibrated sheet of metal designed to rupture at a well-specified pressure. They are used alone, in series, or in parallel to spring-loaded relief devices. They can be made from a variety of materials, including exotic corrosion-resistant materials. 

Burette clamps are specially designed to hold the burette vertically. Springs hold the burette at two points about 5 cm apart - again check for the presence of a rubber or plastic cushion at the points of contact - to prevent slipping and lateral movement. Since the burette clamp slides down the rod of the support stand, then provided the support stand is vertical, the burette will be vertical. 

Seat leakage is specified for conventional direct spring operated metal-to-metal seated valves by API RP 527. The important factor in understanding the allowable seat leak is that it is stated at 90% of set point. Therefore, unless special seat lapping is specified or soft seat designs used, a valve operating with a 10% differential between operating and set pressures may be expected to leak. 

This phenomenon is attributed to the absence on the end surfaces of the shear and compressive stresses that are needed in order to maintain a state of simple shear. As a result, the stresses throughout the block are affected (in contrast to a conventional end effect that would have a negligible effect far from the ends). One consequence is that high internal stresses can develop, sufficient in principle to cause failure. It is clear that the effect of the special conditions obtaining at the ends should be taken into consideration in the rational design of rubber springs. 

Others such as Macas et al. (1998) successfully adapted the Biomek 2000 (Beckman Coulter), a commonly used liquid handling robot, to prepare microarray slides using a specially constructed print head and quill pins. Up to 28 microscope slides could be placed on a work surface for printing. Biomek s HDRT head was adapted to accept microarray quill pins held between two parallel plates with holes drilled on 9-mm centers to dip into 96-well source plates. The quill pins were spring-loaded similar to the design... 

Usually the size of the body and bonnet are determined by the design of the special spring (pressure and material). 

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