Pipeline Spheres

Expandable elastometer spheres for pipeline services have been around for years. The first use of the spheres was for product separation of Shell Oil Company's 14-in Woodriver to Chicago Pipeline in the late 1950's. Since then, the sphere has found many uses in the oil and gas industry.

Spheres are easy to handle and have a long service life because they can be re-inflated to compensate for wear. (View our sphere inflation instructions.) They negotiate irregular bends and turns as well as short-or-long radius 90 ells. Spheres can go from smaller lateral lines into larger mainline pipelines; they require little energy for movement, usually less than 2psig of differential pressure; they are safe, due to absence of spark-producing metal parts; and they traverse both oversize and undersize piping.

Sphere launching and receiving systems also lend themselves more readily to automatic launching of spheres held in a multiple sphere launcher.

Sphere are considered a sealing type pig, and are made of various elastomers, such as neoprene, nitrile, and polyurethanes. Although most sphere are inflatable, they may also be solid. Solid-foam spheres can be manufactured with a brush coating for cleaning purposes, and soluble spheres are available for applications where concerns may exist for the sphere becoming lodged in the pipeline.

The inflatable design has a hollow inside. The sphere is inflated with either water or water and glycol, through a valve, or valves, molded into the sphere. Depending on the sphere material selected, spheres are inflated to 1% to 2% over the nominal pipeline inside diameter. Most operators will establish their own sizing for proper interference fit. A good rule of thumb for sizing spheres is, not less than 1/8" nor more than 1/2 " over measured pipeline diameter.

Material Selection

Pipeline spheres are exposed to a wide range of fluids and gases in today's environment. Proper material selection is important for the proper sphere performance, and long life, as well as economics. Listed below are the more-common elastomers that sphere are manufactured from today. However, there are also additional materials and compounds available to fit unusual conditions.

Condensate removal of wet gas systems

One of the most-common sphering applications is the removal of liquids and condensate from natural gas gathering systems. This process is for corrosion control, as well as maintaining line efficiency.

Operational sphering has proven to be a successful method of handling two-phase flow, when liquid-gas ratios and operating conditions vary. Retrograde condensation, which normally occurs with temperature and pressure reductions, can also create liquid accumulation, or slugs.

Spheres are launched at periodic intervals, to sweep the lines and bring liquids into a slug catcher. In some gathering systems there are various-diameter lateral lines going in to the main line. Spheres are launched in the lateral lines, and sweep the liquids to the main line. These spheres will jump out of the lateral lines into the main line tee, and be swept into the receiver by the main-line sphere.

It is recommended all lateral lines be 1/2 the diameter of the main line, plus one size (i.e. 24-in main line and 14- in lateral line).

Hydrostatic testing pipelines

When hydrostatically testing pipelines with compressed air, the volumes and pressures required to run a scraper fast enough to avoid by-passing air are beyond the capacity of large compressors.

In these applications, spheres provide multiple advantage. They provide a tight seal and, because they can be run in both directions, they greatly reduce the formations of air locks.

Because of is good sealing characteristics in water, neoprene spheres are recommend.

Batch inhibition

Running a batch of inhibitors between two spheres is another application . This process is often used in offshore pipelines.

Internal coating pipelines

It is not uncommon to use spheres for internal coating of pipelines. The internal coating is batched between two spheres, and several passes are required to get the proper coating thickness.

This works efficiently in 20-in and smaller lines. In larger lines, the sphere will have a tendency to sag and a non-uniform coating will result.

Because better sealing characteristics, neoprene spheres are normally used for internal coating purposes.

Product conversion

Many pipelines in chemical plants, refineries, and other industrial applications, are designed to run various products in the same line. Since no pig will wipe the wall completely clean of all product remaining in the line, spheres will also work in this application also. Some refineries will actually push the end of a product batch down to a barge or tanker with a sphere. The sphere will be moved back to its launching point using nitrogen, and will evacuate the line of product.

Sphere/pig detector

Each launcher and receiver should be equipped with a sphere/pig detector, to indicate the sphere has been launched or received. The most-common design is the intrusive type that has a plunger or trigger protruding into the line and is actuated, by the sphere passage. Non-intrusive detectors, which are magnetically actuated, are also available.

Detectors are equipped with visual indicators, electrical switches, or a combination of both, to indicate the passage of a sphere. Electrical indicators are used to actuate valves, sound alarms, and actuate lights to indicate the location of the sphere.

BJ Pipeline Cleaners

BJ Pipeline Cleaners polyurethane spheres are ideal from removing liquids from wet gas systems, product separation, hydrostatic line testing and wax control in crude oil pipelines.

Pipeline spheres are manufactured of high quality polyurethane for lasting service in the worst conditions. The polyurethane compound will with stand high-pressure gas service and sour crude oil environments.

Inflatable spheres, 12" & larger are designed with two (2) filling holes to as-sure that you can remove all the air inside the sphere. Spheres 12" and larger size have oversize filling holes to reduce the filling time.