FAQ

Is liquid Nitrogen a dangerous substance?

Liquid nitrogen is a colorless clear liquid resembling water.At atmospheric pressure, liquid nitrogen boils at  −196 °C; −321 °F and is a cryogenic fluid which can cause rapid freezing on contact with living tissue, which may lead to frostbite. As it boils off nitrogen liquid becomes nitrogen gas. Our atmosphere is made up of 78.08% nitrogen. This gas is non flammable. CPS technicians are highly trained in Liquid Nitrogen safety, and our strict procedural policies demand safe practices for all attending a Pipefreezing service.

Why do frozen pipes accidentally break?                                                                                                                                                                         
Pipes only break when a slug of ice forms inside the pipe near to a dead-end or closed valve. As the ice plug forms, it seals off the pipe, 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 trapped water area until it reaches a pressure-level that the pipe can no longer hold. The pipe then breaks. Testing has shown that radial expansion of the ice plug does not even come close to exerting enough stress on normal piping to cause failure.

CPS controls the expansion forces by making sure that there are no blockages on either side of the freeze or we install pressure relief equipment to monitor and control the pipe internal pressure.

Do the extremely cold temperatures of liquid nitrogen cause damage to a pipe or alter it in some way?                                                                                                                                                              

No. The freezing process is used to harden steel in some tooling applications. For piping and pipeline metals, no damage or deterioration occurs.

Why won't it blow out when we cut the pipe?

First, ice has a high adhesion rate to steel. 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, Pipe Freeze Plugs lock themselves in place due to shrinkage of the pipe diameter. As the Pipe Freeze Plug begins forming, the pipe cylinder being chilled temporarily reduces in diameter at a localized area inside our Chamber. The Pipe Freeze 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 Canadian Pipe Freezing Services maintains the Pipe Freeze Plug, but it is one of the reasons why Pipe Freezing can be used to hold back thousands of pounds of line pressure.

How much pressure will the Pipe Freeze Plug hold?

A Pipe Freeze Plug will hold greater than 100% SMYS of the pipe. Simply stating, a freeze plug can hold back more pressure than the pipe could withstand.

So what are the mechanical hazards?                                                                                                                                                                                 Water hammer, pounding on or jerking the pipe around at the pipe freeze location is monitored because   super-cooled pipe shouldn't be abused with impacts or stresses. This is why Canadian Pipe Freezing Services insists on things like: locating the Pipe Freeze Plug back away from your work location, absolute securing of the pipe if it's going to be opened or cut.

If this is so safe, why won't CPS pipe freeze over a joint weld or simple dent?

CPS is a safety-driven company. We know that Pipe freezing  is a well engineered procedure with large safety factors built into it.. Welds, scrapes, gouges, dents, and corrosion pits, often hide dangerously weakened spots in pipe -- these are the spots where leaks occur. That's why CPS's pre-job inspection of your pipe is so thorough. We will work with customers that absolutely must pipe freeze over a joint or known defect, but it won't be easy and one of the many other CPS pipe plugging options should be considered.