Chapter One: General Information Introduction
17
Chapter One: General Information
Introduction
The MKS Type 253B Exhaust Throttle Valve is a butterfly valve designed to regulate (and in the
case of a sealing valve, to shutoff) the removal of gas from a vacuum chamber when used with a
MKS controller.
The 253 valve can be used with the Type 651, 652, 152G, or 252 (revision D or later) controllers.
If you are retrofitting the 253B valve into an existing system with hex connector cables, an
adapter cable is required (refer to Table 5, page 20).
The 253 valve is normally mounted to a Roots blower, diffusion, turbo, cryo, or other high
vacuum pump. The valve’s butterfly is positioned to modulate the gas flow (pumping speed as
seen by the chamber), thereby controlling pressure within the vacuum chamber. A special feature
of the valve is a nonlinear actuator placed between the butterfly shaft and the motor drive shaft
whose function is to generate a linear valve transfer characteristic
1
.
Practically speaking, the
MKS controller will need little gain and phase lead adjustment as it operates the valve from the
full closed to the full open position. This is of extreme importance when systems are
automatically programmed to change flows and pressures as a process is carried out within the
chamber.
1
U.S. Patent No. 4,327,894
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