Pressure leaks in hydraulic systems limits

Could anybody inform where I can consult limit values acceptable for leaks in a wellhead, downhole tubulars or other off-shore equipment? We know that the conections are never quite dry, but this kind of issue can take inoperable subsurface safety valves, casing pressure, environmental pollution, loss of production and, in extreme cases, blowouts, so , the question is how much is acceptable? Can I calculate it for define the time that must be cured or alleviated?

Thanks in advance,