Varian VHS-6 Instruction Manual download pdf (Page 18)

VHS-4, VHS-6 and VHS-250 Diffusion Pumps

xviii

Pressurization Hazards

Large vacuum pumps and their components are designed for vacuum service. They are not

designed to be pressurized, which can cause them to burst and possibly expel shrapnel at

lethal velocities. Serious accidents have been caused by intentional pressurization of

vacuum systems and their components.

❑ Never pressurize any part of a vacuum system for test or any other purpose.

❑ Always provide pressure relief when designing diffusion pumps into systems and

ensure that pressure relief motion is limited to safe envelopes.

❑ Never permit any of the hazards in the table below to develop.

Pressure Relief Devices

Systems larger than 10”, such as this pump, must be designed with pressure relief devices to

provide safe pressure relief from internal explosions. Always recognize that safety devices

can fail or malfunction; provide redundant protection by installing devices having different

failure modes, failure mechanisms, and failure causes. Be certain that exhaust duct

materials are capable of withstanding the corrosivity, temperature, and pressure of

exhausted products.

Pressurization Hazards

Prohibited Action Result

Do not block inlet or vent of liquid nitrogen trap and lines. LN

trap and/or lines burst

Do not close isolation valves at inlet and discharge of main

water cooling coils when pump is reheated.

Water turns to steam and bursts coils

Do not pressurize the pump body. Body of pump bursts

Do not make a hole through the vacuum wall. Loss of structural integrity of wall

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Varian VHS-6 Instruction Manual Page 18