ESD Earth Ground Impedence

[tc7]

I am trying to improve a static charge buildup problem I am experiencing with a section of glass tube which is incorporated in a steel pipeline. The fluid is a non-conductive oil and flow velocity is approx 5 ft/sec. We observe arcing when the flow is stopped and pipe begins to drain. I am looking to install grounding rings at each end of the glass section to drain away the charge to an earth ground.
Can anyone advise on what specifications or standards tell me what ground impedence I must have when dealing with static charge ?
Thanks,
Tom