Ziegra Ice Pigging Systems

Ice pigging

What is Pigging?

Pushing a piston like object through a pipe to clean the pipe walls is known as ‘pigging’. This technique is widely used in the hydrocarbon recovery and processing industries and is beginning to be adopted in others such as food and pharmaceutical production.

Pigging can do more than just cleaning; it can be used to enhance product recovery from a pipeline and can be strategically used to separate different products in the same duct. Conventional pigs can only be used in relatively simple geometries. Specifically, pigs can be ‘pushed’ through uniform pipes with constant diameter, but find it difficult to negotiate bends or minor changes in cross sectional area/shape.

Clever mechanical design and use of compliant materials to act as piston rings, has extended the use of conventional pigs to ducts with minor cross sectional area change (typically no more than 20%), however they cannot be used in complex topologies or when the geometry changes rapidly with position. This means that pigs cannot be used in relatively simple situations such as branching ductwork, pipes with valves, pipes containing intruding instrumentation or heat exchangers.

When topology constraints makes conventional pigging impossible it may still be possible to achieve some of the benefits of pigging by ‘flushing’ the system with a suitable fluid. As the flushing shear rates at the containment walls are modest compared to those achieved by a solid pig scrapping the surfaces, flushing tends to be less effective than pigging in cleaning duties.

What is required is an adaptable material that flows like a fluid, squeezing through complex geometries, but behaves as though it were a solid.

What is an ice pig

The ice pig is a mass of crushed ice that is pumped into the piping. Ice particles are abrasive and so they clean the inside of the pipe as they go. Liquid ice is easy to pump and is self-lubricating; it behaves like a semisolid, penetrating and filling the most complex of topologies. Unlike conventional pigs, ice “pigs” can negotiate bends or minor changes in pipe work.

However it is not quite as simple as crushing ice and pumping it in, special ice systems had to be developed to freeze water into a slurry and stir it as it forms, keeping the ice crystals small. A freezing-point depressant, stops the crystals freezing together and forming into a solid plug. Various delivery and control technologies had to be developed to insert the pig intact into the pipework, without water separation occuring.

Once a quantity of ice has been pushed into the pipe to form a “pig”, water pressure then pushes it through the pipeline. Over the past 5 years the technology has been extended and applied to a variety of industries and applications.

For example it has been used in the food manufacturing industry to displace valuable food material from process equipment. This has many benefits including product recovery (actually recovering product and selling this rather than throwing it away), reduced effluent treatment (with less product being thrown away there is less demand for land fill and less demand on the water companies to clean up effluent), and reduced need for harsh cleaning chemicals.

Other areas where the technology is being used includes the paints and coating industries (to clean out their pipes), the potable water supply industry (to remove loose fine sands from their drinking water supply pipes), even the nuclear industry is investigating the use of the methodology to remove difficult materials from ducts whilst keeping the effluent volumes to a minimum.

Fig 1

The slurry is made inside the machine in the ice making cylinder. Brine is introduced into the bottom of the yellow cylinder and as crystals form they are transported up the cylinder body by the rotating auger and ejected from the top.

By controlling the geometry and speed of the auger, crystals of a certain size can be ‘grown’ and a slurry of the correct ice fraction can be obtained.

It is important that the ice crystals are of the right shape and size for pigging, you could not for instance simply ‘crush’ ice and add to a brine and get the same results

Fig. 2 image left shows the back of an ice pig (ice is white) when it is followed by water (water has been dyed red).

Both the ice pig and the water have been through a piston pump, into a 1 inch diameter duct, through two 90 degree bends, one 180 degree bed and then expanded out into the 3 inch plastic pipe which is viewed in the picture.

A typical Ice Pigging delivery system may consist of:

• A Ziegra StreamIce machine to generate the ice slurry
• A fully insulated, mechanically agitated storage vessel for ice slurry
• A pumping group (with over-pressure protection) capable to deliver thick ice slurry at a required flowrate or pressure
• A range of bespoke sensors and instrumentation
• A control system ranging from simple manual operations through to full PLC control with automated valves

In addition the following can be supplied with the delivery system:

• FPD making facility – process equipment designed to make the water based solution, used to generate ice slurry to the correct concentration, quickly and reliably
• Water delivery system – linked to the Ice Pigging delivery system, water can be used to accurately propel the ice slurry though the pipe after injection without having to rely on mains water pressure

Fig 3. below shows a typical large capacity ice pigging plant A system consisting of a large (5,000litre) slurry ice machine, a tank/pig delivery system, controls and a brine production unit.

The machine feeds ice by gravity into the tank, so is raised on a platform above complete with handrails.

Fig. 4 below. Containerised system Systems are bespoke and are designed to fit specific spaces within a production environment while remaining easy to maintain. Systems can be skid mounting for mobility, designed to fit inside standard shipping containers for multi site portability or even mounted on HGV trailers.

Machine, tank, delivery and controls are matched to the customers desired operating parameters and cleaning regimes.
Systems are turnkey including survey, design, installation, commissioning and training/documentation.

Fig. 5 An ice pig emerges from a pipe system during trials at a meat factory

Fig. 6 The pig after passing through the pipework above.

Ice pigging

Ziegra Ice Machines (UK) Ltd

Tel: 0844 8808055


	Fig 1 The slurry is made inside the machine in the ice making cylinder. Brine is introduced into the bottom of the yellow cylinder and as crystals form they are transported up the cylinder body by the rotating auger and ejected from the top. By controlling the geometry and speed of the auger, crystals of a certain size can be ‘grown’ and a slurry of the correct ice fraction can be obtained. It is important that the ice crystals are of the right shape and size for pigging, you could not for instance simply ‘crush’ ice and add to a brine and get the same results

	Fig. 2 image left shows the back of an ice pig (ice is white) when it is followed by water (water has been dyed red). Both the ice pig and the water have been through a piston pump, into a 1 inch diameter duct, through two 90 degree bends, one 180 degree bed and then expanded out into the 3 inch plastic pipe which is viewed in the picture.

A typical Ice Pigging delivery system may consist of: • A Ziegra StreamIce machine to generate the ice slurry • A fully insulated, mechanically agitated storage vessel for ice slurry • A pumping group (with over-pressure protection) capable to deliver thick ice slurry at a required flowrate or pressure • A range of bespoke sensors and instrumentation • A control system ranging from simple manual operations through to full PLC control with automated valves In addition the following can be supplied with the delivery system: • FPD making facility – process equipment designed to make the water based solution, used to generate ice slurry to the correct concentration, quickly and reliably • Water delivery system – linked to the Ice Pigging delivery system, water can be used to accurately propel the ice slurry though the pipe after injection without having to rely on mains water pressure

Fig 3. below shows a typical large capacity ice pigging plant A system consisting of a large (5,000litre) slurry ice machine, a tank/pig delivery system, controls and a brine production unit. The machine feeds ice by gravity into the tank, so is raised on a platform above complete with handrails.