Solids Erosion - Target T vs LR Elbow

[Nosey]

Mature oil & gas fields inevitably produce sand along with the hydrocarbons and water. These sand particles result in a multitude of problems, one of which is erosion of 90° elbows. Standard practice is to install "Target Tees" at these point.

The blind on the tee generally has a lead (or other soft metal) insert to "absorb the impact of the particles". Over time the dead leg of the tee accumulates sand and this prevents erosion of the pipe fitting itself.

Recently I have heard extensive debate on the usefulnes of Target Tees and whether or not Long Radius Elbows should be employed instead.

Whilst LR elbows are subjected to the same amount of erosion as short radius elbows the depth of penetration is less due to the larger surface area [SPE 38842 - Solid Particle Erosion in LR Elbows and straight pipe, 1997, McLaury et al]

I have come across both LR and Target Tees in severe sand duty, but have neither has established itself over the other with the exception that LR Elbows are easier to monitor with UT.

Obviously the flow regime will have a large effect upon the rate of erosion. At the moment I am looking solely at single phase (erosion) pipework.

Does anybody out there have experience (old war stories) on this matter or comments?

 

[zdas04]

Nosey,
Long Radius elbows have a bend radius (at the centerline)that is 1.5 times the pipe diameter. Short radius elbows have a tighter bend. I've never seen a short radius elbow in Oil & Gas field operations (I've heard that they are common in plants and refineries, but I've never worked in that environment)

Often times people try to control errosion with sweeps which have a bend radius on the order of 6-8 pipe diameters. I've looked at a lot of data on the effectiveness of sweeps in controlling errosion, and it looks to me like once again we want "wishing to make it so". They get eaten out nearly as often as target tees and are a whole bunch harder to replace.

The bull plug in a target tee can be replaced easily, often without taking the well down. I like bull plugs instead of bushings because the fitting they screw into often stays intact while the energy of the sand is often expended inside the bull plug. With a bushing, the wear point is the tee at the point where the bushing stopped.

David