When a client wants a blockage in his pipe, where a valve or other blocking device does not exist, EA can perform a Cryo-Plugging job. Also known as Line Freezing, Pipe Freezing, Freeze Stops, and Freeze Plugging, Cryo-Plugs are a non-intrusive method of developing temporary piping isolations. Pipe Plugs require no special welding or setup costs often associated with Line Stop Fittings. Internal piping fluid develops solid, dependable and workable freeze plugs
EA Services assembles a chamber (much like a barrel, split in half the long way, with cut-outs in the barrel-head and bottom, the size of the pipe to be plugged.) around the pipe, fastening the two chamber halves together with seals or sealant, along the split-line and where the chamber wraps around the pipe.
Hoses are then run from a liquid nitrogen source (minus 320° F) and the nitrogen cryogenic refrigerant is trickled into the barrel, slowly cooling the pipe and components. Once chilled down, the nitrogen flow volume is increased and the water inside the pipe turns to a block of ice, caught tightly to the inside of the pipe.
An interesting plus to getting a small area of the pipe so cold is that it shrinks in diameter, within the Cryo-Plug chamber. In this chamber area, the pipe goes from normal diameter at the ends, to smaller diameter in the middle - in other words, it looks something like an hour glass. The ice plug forms within this hour-glassed area, so it has larger ends, with a narrower middle. That effectively locks the ice plug inside the pipe, preventing it from moving in either direction as long as the cold is maintained.
The client can then depressurize the downstream side of the ice plug (Cryo-Plug) and perform his work.
Upon completion of the client's work, we refill the downstream piping, equalize pressure on both sides of the Cryo-Plug, turn off the nitrogen and let everything thaw out.
All of this can be done with no welding and no special permanent fittings of any type - quite an important feature in many instances.
Advantages of a Cryo-Plugging Freeze Isolation
- Piping modifications performed without complete building or system drain downs
- Save time & money. Avoid replacing costly chemically treated fluids
- Avoid the possible disposal of waste water or toxic fluids
- Cryo-Plug Freezes are a non-intrusive method of developing temporary piping isolations
- Internal piping fluid develops solid, safe and workable freeze plugs
Types of Pipe
Steel pipe is the type most frequently plugged using this process. All types of metal pipes are easily Cryo-Plugged. Almost all of the plastic pipes can also be serviced with Cryo-Plugging, after taking a few special precautions. Even concrete, asbestos-cement and composite pipes can be worked. If you have any questions or doubts, call EA Tech Support.
Cryo-Plugging can be performed on a many types of pipes, including:
- Carbon Steel
- Stainless Steel
- Cast & Ductile Iron
- Coated & Lined Pipe
- 1/2" to 42" OD
- Vertical, Horizontal, Inclined
- Out of Round
Typical Applications and Industries
- Fire Protection Systems-Modification and Service
- Valve / Pump Replacement
- Pressure Testing - Leak Testing
- HVAC / Chiller Modifications, Replacement and Service
- Oil-Filled Electrical Cable Pipe Repairs
- Chemical & Petrochemical Plants
- Fossil Fuel Power Plants
- Nuclear Power Plants
- Hospital & Institutions
- Industrial & Commercial Production Facilities
- Telecommunications Industry
- Water & Sewage Treatment
- Malls & Shopping Centers
- Hotels & Apartment Complexes
- Paper Mills
- Office Buildings
- Fire Protection Systems
Fluids that can be Cryo-Plug Frozen
- Waste Water
- Chill Water
- Brine Solutions
- Fuel Oils
- Glycol Solutions
- Heavy Hydrocarbons and Oils
- Contact your EA Services Representative for your specific application
This one is not a magic cure-all. Following are some of the key limitations to watch for:
- Pipe contents flowing at any rate are very hard or impossible to freeze.
- Pipe contents that are not water-based need to be investigated prior to a commitment to use Cryo-Plugging.
- Pipe that is vertically oriented may be difficult to Cryo-Plug.
- Pipe contents that are warmer than 90°F (32C) will take a long time to freeze.
- Pipes that are branched off from an active high-flow header will be difficult to freeze within a few feet of the header.
- Pipes with a diameter greater than 42-inch will require very special methods.
- Plugs that must be held (kept frozen) more than 24 hours can be expensive.
- Cryo-Plug locations that are on a dead-leg or near to a blockage, such as a valve in the closed position require special methods.
- Cryo-Plugging work that is more than a few hundred feet away from a convenient place from which to dispense liquid nitrogen from its container-tanks ("dewars").
EA's method of temporarily plugging a water or product-filled pipe by the engineered cryogenic super-cooling of a slug of the pipe contents to its solid form ("ice") sometimes causes customers new to this concept to be concerned because of other experiences they have had with the accidental freezing of pipes. Their most frequently asked questions, and the answers to those questions follow.
Why do accidentally frozen pipes break?
Pipes only break when a slug of ice forms inside the pipe near to a dead-end or closed valve. As the ice slug forms, it seals off the pipe I.D., and then expands longitudinally, along the center axis of the pipe, pushing on the trapped water. This push causes the pressure to rise in the entrapped unfrozen water area until it reaches a pressure-level that the pipe can no longer hold. The pipe then breaks. Highly involved testing has shown that radial expansion of the ice plug does not come close to exerting enough stress on normal piping systems to cause failure.
So why won't EA's process cause an expansion break?
EA doesn't Cryo-Plug up against a dead-end, or we install pressure relief equipment to monitor and control the pipe internal pressure.
Don't the extremely cold temperatures cause damage to my pipe or alter it in some bad way metallurgically?
No. In fact there are types of steel that are "heat treated" to improve their per¬formance properties by cryogenically quenching them. For piping and pipeline metals, no permanent damage or deformation occurs with EA Cryo-Plugging.
It's just a chunk of ice. Why won't it blow out when we cut the pipe?
First, ice has an amazingly high adhesion to steel (you've witnessed that if you've ever tried to chip ice from steel surfaces in the winter). This, combined with friction of the long ice plug inside the irregular surface of the pipe would be enough to assure the plug isn't going anywhere. Additionally, EA Cryo-Plugs lock themselves in place due to a phenomenon known as "hour-glassing". As the Cryo-Plug begins forming, the pipe cylinder being chilled temporarily elastically reduces in diameter at a localized area inside our Cryo-Chamber. The Cryo-Plug then conforms to this shape, having large ends on either side of a narrower middle. This dimensional change of the pipe is small and only lasts as long as EA maintains the Cryo-Plug, but it is one of the reasons why Cryo-Plugging can be used to hold back thousands of pounds of line pressure.
How much pressure will the Cryo-Plug hold?
How much pressure will your pipe hold? A "high pressure" Cryo-Plug will hold even when pressure behind it is raised to cause stresses greater than 100% SMYS of the pipe. Our plugs can be hydrotested to whatever pressure you require, prior to depressurizing your downstream system.
If this is so safe, why won't EA Cryo-Plug over a joint weld or simple dent?
EA is a safety-driven company. We know that Cryo-Plugging is a well engineered procedure with large safety factors built into it. We don't want to use up any safety factor unnecessarily. Welds, dents, gouges, scrapes, corrosion pits and the like often hide dangerously weakened spots in pipe -- these are the spots where leaks occur. That's why EA's pre-job inspection of your pipe is so thorough. We will work with customers that absolutely must Cryo-Plug over a joint or known defect, but it won't be easy and one of the many other EA pipe plugging options should be considered.
What aspect of Cryo-Plugging makes pipe defects a concern?
Although Cryo-Plugging may temporarily increase the tensile and yield strength of your pipe, the pipe is quite brittle inside the Cryo-Plugging equipment during the procedure. If your pipe is damaged enough so that it's just about to fail at room temperature, while it's being worked on there is an unknown degree of hazard.
So what are the mechanical hazards?
Impact, water hammer, pounding on or jerking the pipe around at the Cryo-Plugging location. Again, these are not quantifiable hazards but it's obvious that temporarily super-cooled pipe shouldn't be abused with impacting stresses. This is why EA insists on things like: (a) locating the Cryo-Plug back away from your work location; (b) absolute securing of the pipe if it's going to be opened or cut, and; (c) separate bell holes for the Cryo-Plug(s) and your work site if the job is on underground piping.
Why such an involved job procedure and rigorous safety monitoring?
It's that safety-driven EA philosophy again. Perfect execution of a job equals perfect and safe results. EA knows the hazards of handling cryogenic liquefied refrigerants and we take prudent precautions to assure a safe jobsite. That's why we insist on such a large safety perimeter on a jobsite. We're concerned about your safety too.