Reasons for the rupture of reverse osmosis membranes

Membrane rupture in organic tubular membranes usually occurs under the following circumstances: First, the flow rate entering the membrane cross-section is too high; such a high flow rate leads to excessive flow velocities on the membrane surface, resulting in displacement between the membrane layer and the underlying non-woven fabric. Especially when the system is first started, if a high-pressure pump without variable frequency control is used, the flow rate to the membrane increases suddenly, causing significant damage to the membrane. Secondly, the pressure drop across the membrane is too high; if the pressure across a single membrane often exceeds 0.15 MPa in an instant, this kind of displacement will also occur. Also, check for water hammer and backpressure when parking, among other things. Since organic tubular membranes are characterized by low strength between the membrane layer and the substrate layer, it is necessary to avoid sudden changes in parameters such as fluid flow rate and pressure during operation. I hope this helps you.

I’m sorry; I mistakenly wrote “tubular membrane” instead of “roll-type membrane” just now. Membrane rupture in organic roll-type membranes generally occurs under the following circumstances: First, the flow rate entering the membrane cross-section is too high; such a high flow rate leads to excessive flow velocities on the membrane surface, resulting in displacement between the membrane layer and the underlying non-woven fabric. Especially when the system is first started, if a high-pressure pump without variable frequency control is used, the flow rate to the membrane increases suddenly, causing significant damage to the membrane. Secondly, the pressure drop across the membrane is too high; if the pressure across a single membrane often exceeds 0.15 MPa in an instant, this kind of displacement will also occur. Also, check for water hammer and backpressure when parking, among other things. Since organic spiral-wound membranes are characterized by low strength between the membrane layer and the substrate, it is necessary to avoid sudden changes in parameters such as fluid flow rate and pressure during operation. I hope this helps you.

First of all, thank you for your answer. We use high-pressure pumps with variable frequency control, and low-pressure flushing is carried out to discharge air both after shutdown and before startup

I also checked that the pressure difference before and after operation of the reverse osmosis membrane remained within the allowable range

During normal operation, the reverse osmosis membrane can suddenly cause the adapter to break – what is the reason?

Is the pressure difference between sections too high? If it is, and exceeds 0.4 MPa, the adapter may break, and even the membrane could rupture.

The pressure difference is not large, below 0.20 MPa

Is the ruptured membrane located at the front part of the membrane shell or at its end (in the direction of water flow)? What kind of breaking method do you mean by blasting? Does it mean that the fiberglass wrap on the outside has cracked, allowing the white diaphragm to be seen? What does the pressure on the freshwater side show? Your operating pressure is “below 2.5 Pa” – is there a missing ‘M’? 2.5 MPa is about right. Are you using this for seawater desalination? Can water be produced with such a low operating pressure? It would be best to send a picture for a look. The preliminary estimate is that it is either due to an excessive pressure difference across a single membrane or the backpressure on the pure water side.

I kindly ask the moderator to move this post to the membrane separation section; I will keep an eye on it. Thank you.

Blasting – explosive destruction (damage); is that what it means? Judging from the technique described by the poster, such things shouldn’t happen. Under normal operating conditions, while the adapter breaks and the fiberglass shell of the membrane core cracks, the membrane is often not damaged (with normal flux and retention rates). The adapter breaks due to uneven stress (uneven contact surfaces, lack of adapter support on the end caps, etc.) ； The fiberglass shell cracks due to high flow rates; uneven stress on the adapter can also cause the fiberglass shell to crack. Furthermore, the large sealing ring was not installed as required, resulting in significant vibration of the diaphragm core inside the container, which in turn can cause damage to the adapter and the fiberglass shell.

Our company uses seawater membranes to concentrate ammonium chloride wastewater; after six months of operation, the fiberglass shell surrounding the membrane core cracked. The conductivity of the fresh water produced was similar to or higher than that of the inlet water, and the desalination efficiency decreased. We determined that the membrane had cracked, and after replacing it, the conductivity of the water produced was lower

Our company uses self-cleaning pre-treatment systems that include safety filters, ultraviolet sterilization units, and ultrafiltration membranes. Low-pressure flushing is also employed during startup and shutdown processes, and high-pressure pumps with variable frequency control are used as well. So how can membrane rupture or adapter breakage occur during operation?

A membrane rupture cannot be assumed just based on a decrease in membrane conductivity and damage to the adapter’s fiberglass casing. Since the membrane has been replaced, an membrane core should be dissected to check whether the conductivity of the membrane sheet has decreased. If the membrane conductivity decreases, it is not possible to determine whether this decline in membrane conductivity is caused by the same issue as the damage to the adapter’s fiberglass casing; in such cases, the conductivity of the entire membrane may be poor. If the diaphragm has good conductivity, it is possible that the cause is the same as that of damage to the fiberglass shell of the adapter; in this case, many diaphragm cores should still be intact, as damage due to mechanical reasons would not affect them all.

Based on what the poster has described, the possibility of backpressure on the water generation side occurring instantly is quite high! Please answer: Is the ruptured membrane located at the front part of the membrane shell or at its end (in the direction of water flow)? ”

Cracks of varying degrees appeared at the front, middle, and back ends of the membrane shell; only in some cases remained the conductivity of the produced water unchanged, while in others it was higher

Cracks of varying degrees appeared at the front, middle, and back ends of the membrane shell; in some cases the conductivity of the produced water remained unchanged, while in others it was higher, which most likely indicates that mechanical force caused damage to the membrane. Since chemical damage does not result in uneven conductivity, such as some cells producing water with constant conductivity while others produce water with higher conductivity, a careful examination will reveal the cause of the damage.

You can also look for reasons from another perspective: you are using seawater desalination membranes for the concentration of ammonium chloride. If the concentration of the incoming water is unstable or if the operation process is not proper, this can result in an excessively high concentration of ammonium chloride on the concentration side. Such a high concentration causes crystallization to occur on the surface of the membrane layers, and these crystals cause significant damage to both the base layer and the filtration layer of the membrane. When the material concentration decreases, the crystals disappear again. So such problems are difficult to detect.

Is it a problem with the pump, or was it an excessively high flow rate that caused damage to the membrane?

Mechanical damage is a likely possibility; it is recommended that the poster upload photos of the membrane, so that it will be easier for everyone to identify the cause of the problem. Generally, a high conductivity of the produced water does not necessarily mean that there is a problem with all the membranes; the main issue with the adapter is uneven stress, as the operating pressure is not particularly high.

Membrane rupture is often an accident, caused by a sudden increase in inlet pressure or by pressure buildup due to the valves at the product water side not opening in time. Membrane burst is also a type of high-pressure protection for reverse osmosis systems.