It appears that there is no difference between a Bleed Ring and a Drip Ring. The vast majority of companies call them bleed rings because they allow bleeding pressure or mount pressure gauges or other sensors into a piping system.
A bleed ring is a ring section with one or more radial pipe connections designed to fit between standard flanges within the bolt circle, using conventional gasket material. The ring normally comes with a 1/2 inch socket weld or 3/4 inch tapped for connecting with valves and instruments. The face of the ring can also be made to matched with any flange type, and has different sizes based on the ASME flange rating of the process piping.
Bleed Rings can provide a beneficial way of draining piping, taking samples, attaching instruments or even bleeding of a valve. They can also be used with a valve and/or blind flange, this allows you to reduce and dispose of the pressure for your valve before you remove the flange. This is usually done with a replacement for a leaky valve.
The bleed ring can come in any material or size, and is designed for connecting valves and instruments. The face of the bleed ring can be manufactured to match with any flange type. The standard sizes for a bleed ring are NPS 1 to NPS 24 and ASME Pressure Classes 150 through 1500. It comes in many different materials such as carbon steel, stainless steel etc.
DIMENSIONS BLEED RINGS - NPS 1 TO NPS 12 ACCORDING TO ASME 31.3, B16.5, B16.20
BLEED RING MOUNTED BETWEEN TWO VALVES