Place the bypass valve at the highest level than the control valve to reduce the risk of bypass line becoming plugged. For other arrangements e. Control valves, block and by-pass valves shall be sized on the PID. Control valves shall be accessible from grade or platforms unless otherwise approved for good process or economic reasons on an individual item basis. Control valves shall be located in sight of instruments or indicators showing the variables they control.
Unless otherwise approved by Owner, control valves shall be located high enough to permit valve stem removal, but not higher than mm above grade or platform. In a recent thread see thread Why is there a pressure drop when the control valve was opened?
BigInch gave a link to the Fisher Design Manual. If any reference anywhere has something sensible to say on this subject it will be the Fisher book. The vast majority of control valves I've seen are located near low points in a piping circuit.
Often a pipe up in a pipe rack is diverted to belt buckle height for a control valve. This allows easy access to the valve; e. In these situations, I would always use a concentric reducer because 1 they really are "the standard", 2 they are cheaper, 3 they are more readily available, 4 less chance for error, and 5 the pressure drop will be less than an eccentric orifice. The only situations where I would use eccentric reducers are for slurry systems and where it is imperative to totally drain ALL condensed fluid.
In both these situations, eccentric reducers can avoid small "dead spots" that exist behind concentric reducers. The only place I'd use flat side up eccentric reducers would be in pump suction line to avoid accumulation of gas pockets. To Mr. Katmar - guilty as charged. I admit being one of those that took part in the heated confabulation mentioned by Katmar about reducers on centrifugal pump suction lines.
The general recommendations, from a process point of view, to avoid adversely altering the CV characteristics and capacity are: 1. Avoid arrangements that can result in a nozzle-effect into the CV 2. Avoid closed-coupled inlet block valves reduced from line size 3. The length of the reduction is usually equal to the average of the larger and smaller pipe diameters. Reducers are usually concentric but eccentric reducers are used when required to maintain the same top-or bottom-of-pipe level.
In Concentric Reducer the reduction of the pipe size is achieved by decreasing the diameter of the fitting at a constant rate over a specified length, maintaining symmetry around the fitting. Concentric Reducers are used to join pipe or tube sections of different diameters on the same axis. They provide an in-line conical transition between pressurized pipes of differing diameters. Thus, concentric reducers connect pipes of unequal size but have a common centerline. In horizontal gas, steam, or vapor piping, eccentric reducer are required to be installed with flat side down which allows condensed water or fluid to drain at low points.
Eccentric reducers with the flat side up are used for all pump suction lines excluding pumps handling slurry on horizontal lines. This way one can avoid air getting trapped inside the pipeline during initial venting through pump casing and will help in avoiding Cavitation. Depending on end connections of this fitting with a straight pipe, reducers are grouped as follows:. The applicable pressure rating, dimensional and material standards for butt welding reducers are the same as those applicable to butt welding elbows.
Standards are the same as those applicable to socket welding elbows. Available only in the concentric type and are in the form of coupling having one end to fit bigger pipe and another end to fit smaller pipe.
ASME B Material standards including pressure ratings are the same as of screwed elbows. Their pressure rating, use, material, and dimensional standards are the same as those applicable to flanged elbows. Regardless of reduction, their face to face dimensions is governed by the larger pipe size. Pipe reducers are made of various material like Carbon Steel, Alloy, or Stainless steel and much more like non-ferrous materials.
0コメント