H2S system

[ash9144]

We have an H2S delivery system feeding from a one ton cylinder. It is all small flow rates 10 lb/hr max and small bore 1/2" pipe and tubing. We had issues with a regulator, one of which was needing to apply steam to get needed rate, so we upgraded materials and removed the regulator to operate at roughly 250 psig. The feed is off the gas draw off. We thought removing the regulator would eliminate the need to heat the high pressure gas but it has not. The flow becomes erratic and can't meet set point unless the steam is applied to the piping externally. There are no indications of two phase flow and all components should be able to provide the needed flow. I am at a total loss as to why we can't maintain such a low flow with 250 psig supply gas through 1/2" tubing. Any one have any thoughts?
Thanks