Harn R/O Systems Blog

8 Simple Steps for Performing a Successful Membrane Installation

Posted by Julie Nemeth-Harn on Mar 22, 2021 9:15:00 AM

Membranes are loaded from the feed end of the pressure vessel. To better understand the installation procedure, the following definitions are helpful:

Related Blog: Pretreatment: The Last Line of Defense for Your R/O Membranes

Membrane Installation Components

End cap assembly: There are two (2) end-caps per pressure vessel. One end-cap is on the feed end of the pressure vessel while the other end-cap is installed on the brine end of the same vessel. The brine end end-cap also contains the permeate port.

Membrane adapter: There are two (2) membrane adapters (also called stub tube adapters) per pressure vessel. These devices connect the membrane product water tube to the end-cap assembly at each end of the pressure vessel.

end adapters

There are six (6) membrane inter-connectors per 7 membrane pressure vessel. The interconnectors connect the product water tubes between each adjacent membrane element.

membrane interconnector

Brine Seal: Each membrane element requires a brine seal (sometimes called a chevron seal). The brine seal fits in a groove at the feed end of the element with the open section of the seal facing the incoming feed water. The brine seal will expand under normal operation, effectively sealing against the inside wall of the pressure vessel and thus stop feed water by-passing around the outside of the element, thus forcing all the feed water through the membrane brine channel.

brine seal on ro membrane element, brail seal on a membmerane


Pressure Vessel Preparation/Membrane Installation

  1. The pressure vessels are all properly mounted in their respective positions. Refer to the pressure vessel manufacturer’s instructions in the appendix to identify all vessel components. Inspect all O-rings on the end caps for proper fit. Lubricate all O-rings with glycerin. Following the instructions in the manufacturer’s manual, install the downstream end-caps (concentrate/brine end).

  2. Install the large PVC thrust cone into the feed end of the pressure vessel.

  3. Unwrap the membrane elements and place them on a clean surface to drain the preservative – usually sodium meta-bisulfite solution. Latex gloves should be worn when handling the elements and all surroundings should be kept in a clean state.

  4. First, all membranes should have brine seals on one end which becomes the feed end. The brine seals should be lubricated with glycerin.

  5. On the downstream end of the first membrane, install one of the membrane adapters (stub tube adapters). Lubricate all O-rings. The membrane adapter will push into the product water tube of the membrane. Next, push the thrust cone and membrane element into the feed end of the pressure vessel, pushing the membrane element in about halfway.

  6. Next, push the interconnector into the feed end of the first membrane loaded. The next membrane will push onto the first membrane connecting the two membranes with the inter connector. Push the second membrane into the pressure vessel making sure it is kept aligned until half of the second membrane is inside the pressure vessel.

  7. Repeat this procedure to push the last membrane into the pressure vessel. On the feed end of the last membrane install another membrane adapter (stub tube adapter). This adapter will connect the membrane to the end cap assembly of the feed end of the pressure vessel. Push all membranes from the feed end until the lead end membrane adapter seats into the downstream (brine/concentrate) end-cap. Should seating the adapter in the end-cap prove difficult, try tapping the downstream end cap to help align it with the adapter.

  8. Finally, install the feed end end-cap assembly. Refer to the manufacturers’ manual for complete installation instructions regarding the pressure vessels and membranes.

    NOTE: Be careful not to roll any of the O-rings. Rolled, broken, or nicked O-rings will result in raw feed water entering the permeate tube of the membrane, which will reduce permeate water quality. 

Nanofiltration Unit Description and Specs


Topics: membrane treatment system, membrane treatment, water treatment, water quality