When to Change Your (Dairy) Membranes - Caloris Engineering LLC

Facilities Managers: Are you wondering when to change your dairy membranes? In this article, we’ll walk you through the signs and symptoms that let you know it’s time.

Feed Quality

Feed quality is a huge factor in the life of your membranes. You will want to look for the following:

Entrained air feeds oxygen to bacteria and also contributes to flux loss. Look for leaky seals.
Temperature — for whey, and whole and skim milk, you will have more microbial growth at 120 degrees F. Temperatures below 70 degrees F are ideal.
Pre-treatment can be essential — make sure you know the prefiltration specs for your unique situation.
UF Permeate
- Check for cloudiness and repair/seal membranes if present. Cloudiness indicates you are losing protein.
RO Permeate
- Same as above regarding cloudiness
- Also, clean the CIP storage tanks and lines regularly (every 1-2 days) to remove organics and avoid microbial issues.

CIP Considerations

See our previous article on CIP Best Practices.

Clean Water Flux Test

This test determines the effectiveness of your CIP. The test should be done at the conclusion of every CIP cycle. Record permeation rate of the system at base temperature and pressure. Normalize temperatures and pressures outside of the baseline. Additional washes may be needed if not within 5% of the previous test. When you graph these tests, there should be a stable line.

Records Are Your Friend

Records are very important. On install, record dates, lot numbers, manufacturer information and plant location. Record daily CIP logs and production logs. Maintain a record of your clean water flux tests (see above).

Visual Checks

Take permeate samples regularly and check for signs of leakage. RO permeate should be clear and colorless. MF/UF/NF permeate will normally have color but should not appear cloudy.

Analytical Checks

RO Polishers — regularly record permeate conductivity. For new membranes, this typically would be 10-30 micro-mhos.
RO conductivity is usually a lot higher (~100-1,000 micro-mhos). Record when new and use that as your baseline. Results are dependent on the ash content in your feed.
NF — test the permeate for sugar content to determine if leaks are present.
UF — test the permeate for protein. There should be less than 1% loss for new membranes. For membranes 6 months or older, approximately 2-4% loss. Change out your membranes before it gets to 4%.

Find Your Sweet Spot

The below graphs illustrate a hypothetical situation — your results will depend on your product.

Chart the cost of your membranes over the membrane lifetime.

Next, chart protein loss over the membrane lifetime.

Where the two graphs intersect is the sweet spot — that’s when you should change your membranes in order to get the biggest bang for your buck.