Water Hammer in Condensate Transport Piping
Water hammer in condensate transport piping is usually caused by the interaction of low temperature condensate and high temperature steam. These often form from the dual presence of condensate and flash steam in the piping.
This pattern occurs at junctures where condensate transport lines with large pressure differentials meet, or near points where a condensate transport line meets a flash tank. At these junctures, high-pressure flash steam flows into the low-pressure condensate transport piping and water hammer occurs.
Condensate cannot be removed to solve this type of water hammer because the piping's very function is the transport of condensate. There are thus no direct countermeasures against water hammer in this type of piping, only remedies to lessen its effects.
Mechanism & Countermeasures
Water hammer in condensate transport piping occurs in many patterns, which are fundamentally all caused by the sudden condensation of steam. The three most common patterns are discussed below.
Chugging
When two transport lines converge, high-temperature flash steam can come in contact with low-temperature condensate. If no large pockets of steam occur, the steam will rapidly condense and cause small-scale, rapidly cyclical impacts known as chugging. The name is derived from the noise produced, which sounds something like an engine chugging. The force of the impact is not great, but the resulting noise becomes a problem.
From backflow
Water hammer from backflow is caused by a pulsating flow of low temperature condensate in condensate transport piping, and is often seen in factories.
Water Hammer caused by backflow of steam from condensate transport piping
Water hammer caused by backflow of steam from flash tank
A countermeasure against this is the installation of a check valve to prevent the backflow of steam. However, the effectiveness of this countermeasure is reduced if the location or the type of check valve are incorrect.
From the formation of 'large pockets of steam'
This is the most frequently encountered form of water hammer in condensate transport piping. It occurs at points where piping carrying high temperature flash steam and piping carrying low temperature condensate converge. Unlike water hammer resulting from backflow, steam and condensate do not flow in opposite directions to cause water hammer. In this case the problem is caused by the formation of large 'pockets of steam'.
Just like water hammer caused by backflow, water hammer impacts may occur far away or upstream from the convergence point of transport piping. If such is the case, pinpointing the cause can become quite difficult.
Countermeasures for each of these three main patterns of water hammer have several points in common:
- They ensure that pockets of steam remain small.
- They intercept the steam (e.g. flash steam) that is the cause of the trouble, or connect it to a different line.
- Wherever possible, they avoid contact between horizontal piping runs of high temperature steam and low temperature condensate.
Note: When water hammer occurs in condensate transport piping, the piping itself is sometimes the cause. This makes it very difficult to predict the occurrence or location of water hammer in advance. Countermeasures are thus often investigated only after the problem arises. On top of this, when the cause of water hammer is equipment that is far away or seasonally operated, a more extensive and long-term investigation may be required.
