level control

I've been in instrumentation for 23 years but I've never heard of a bridle in a prressurized vessel.

The common meaning for a bridle is that thing that you put on a horse so that you can control it. The other is a set of two wires/string/cables that holds an object in position while being pulled.

Can someone enlighten me please?

Hi Vulcan,

I'm with you - never heard of it before in this context. Hopefully, "guest" will respond.

Mike

I've seen the term before, specifically in some of our steam drums in the waste heat recovery section. It really is just the two flanges that the level transmitter(s) sit on. The question doesn't make sense to me though, can you attach a drawing showing what you mean?

A bridle, not in, but on a pressure vessel is an outside chamber usually 4" pipe that can be isolated from the vessel with valves top and bottom. It can contain a level glass, taps for level transmitters and taps for pressure transmitter and level switches. On steam drums, it allows for cooler environment for instrumentation and convience of isolation of instrumentation without shuting down operating equipment. It can be used for calibration of inplace instruments by raising and lowering the level in the bridal using and outside source for liquid,i.e. water hose to botton drain valve with vent open.

That is what I was talking about, thanks JasBond.

Ah yes, okay. We call it a stilling tube, which pretty much says what its purpose is. It's found in pressurized vessels but can also be seen in un-pressurized vessels.

In a number of condensate collection tanks in our factory, the fluid inside the tank is very turbulent. If you put a differential pressure level transmitter directly on it, the signal will be very jumpy. Increasing the damping parameter helps but slows down the response of the control system. Installing a stilling tube lessens the variations resulting in a cleaner signal, hence, better control.

I should have added: It also acts as a stilling well in a tank with agitators and allows for a cleaner environment for displacer, ultrasonic or radar installations. In dirty service blowdown of sediment and reduction of rag(floating debris or foam) is allowed.

I think our friend speaks about a bridle to be assembled to a pressure vessel not in the vessel itself. To minimize the number of openings for the nozzles required for level gauges and level controllers, we prefer to design the vessel with two nozzles to be assembled with a bridle, where we can attach a level gauge and can erect a level switch into the bridle.