When I started working as a tubular membrane supplier a little over eight years ago, I used to think operating pressure was a straightforward metric—turn a dial, get more throughput, right? Early on, I’d get calls from clients who’d crank up pressure in their systems because they heard higher pressure meant better membrane performance. Then we’d troubleshoot a week later when their membranes were fouling faster, or flow rates dropped off suddenly. Those early lessons taught me that operating pressure isn’t a one-note lever to pull—it’s a balancing act that makes or breaks tubular membrane efficiency, and getting it wrong can cost a plant thousands in downtime and replacement parts. Tubular Membrane
First, let’s ground this in what tubular membranes actually are, for anyone new to the space. Unlike hollow fiber or spiral wound membranes, tubular membranes are housed in rigid, pipe-like tubes (usually 6 to 25 millimeters in diameter, perfect for handling high-solids feeds that would clog other membrane types, like wastewater with grit or oily runoff, or food and beverage processing streams with suspended solids). The feed flows through the inside of the tube, and permeate (the filtered fluid) passes through the membrane wall to the outside, where it’s collected. The operating pressure here refers to two key pressures: the transmembrane pressure (TMP), which is the difference between the feed side and permeate side pressure, and the cross-flow velocity (CFV) related to pressure drops along the tube length. Most people mix these two up, and that’s where the biggest mistakes happen.
Let’s start with the basics: how pressure drives filtration. The whole point of membrane filtration is to push small molecules through a porous barrier while blocking larger particles. For tubular systems, the ideal TMP range is typically 10 to 30 psi for most standard applications, though that shifts a bit depending on membrane material (PVDF, ceramic, or polypropylene) and feed type. At low pressures, below that sweet spot, the driving force isn’t strong enough to push permeate through the membrane’s pores consistently. I had a client a couple years back running a food processing line with tomato pulp, where they initially ran TMP at 5 psi, thinking that would be gentler on the membrane. But their permeate flow was 30% lower than our system’s projected output, and even worse, the product had higher residual suspended solids because the low pressure couldn’t overcome the feed’s viscosity to force the solution through the pores. They had to add a booster pump, bringing TMP up to 18 psi, and within a week their flow hit the target, and product quality improved. That’s the low-pressure limit in action: insufficient driving force = reduced efficiency, both in flow rate and filtrate purity.
But here’s the thing that surprises new clients: increasing pressure beyond that optimal TMP range doesn’t just stop improving efficiency—it starts hurting it fast. The problem is called membrane compaction, and it’s one of the most common issues we see when clients over-pressurize their systems. Tubular membranes have tiny, uniform pores; when you apply too much pressure, the membrane material (even rigid ceramic or reinforced polymer) deforms, squeezing those pores smaller or even closing them entirely. I remember a municipal wastewater treatment client who, in an effort to meet a tighter discharge permit, cranked TMP up to 45 psi, thinking more pressure would mean cleaner water. Within three months, their permeate flow had dropped by 40%, and when we inspected their membranes, the pore structure was permanently distorted—they had to replace the entire 120-tube array, which cost them over $120,000 in downtime and parts. Membrane compaction isn’t reversible, and it’s a direct result of operating pressure exceeding the membrane’s structural limit. For most commercial tubular membranes, the maximum safe operating pressure is around 50 psi, depending on the material, but we always advise clients to stay 10 to 15 psi below that to avoid long-term damage.
Even if you don’t cause permanent compaction, overpressure leads to fouling, which is a bigger, more common drag on long-term efficiency. Fouling is when particles, organic matter, or minerals stick to the membrane surface or get lodged in the pores, blocking flow. Here’s how pressure plays into that: at pressures above the optimal TMP, the shear force from cross-flow (the feed moving along the membrane tube) isn’t enough to keep particles from being pushed into the pores. Higher pressure increases the convective flow toward the membrane surface, so more solids are forced into the pores instead of being swept away. I work with a craft brewery that uses our tubular membranes to filter spent yeast from their beer. Early on, they ran TMP at 28 psi, which is just at the upper end of our recommended range. After two weeks, their cleaning cycles (which they use to flush built-up fouling from the membranes) went from every 72 hours to every 36 hours, and each clean took twice as long as before. When we adjusted their TMP down to 20 psi, their cross-flow shear rate increased slightly (because the pressure drop along the tube worked with the cross-flow), so the yeast solids were swept away from the membrane surface instead of getting forced into the pores. Their cleaning intervals went back to 70 hours, their permeate flow stabilized, and they reduced their cleaning chemical use by 25% in the first month. That’s the hidden cost of overpressure: higher short-term flow comes at the expense of faster fouling, which kills long-term efficiency.
Wait, but what about the difference between feed-side pressure and permeate-side pressure? A lot of clients focus only on raising the feed pump pressure, but neglect the permeate side. If you have a constant permeate-side pressure, increasing feed-side pressure does boost TMP, but if you throttle the permeate valve to keep permeate pressure low, you can get a higher TMP that’s actually below the membrane’s structural limit. I had a chemical processing client who was struggling because their feed pump was maxing out, so they thought they needed a bigger pump. Instead, we adjusted their permeate collection pressure: they’d been running permeate at 10 psi, so even with a feed pressure of 25 psi, their TMP was only 15 psi. When we dropped permeate pressure to 2 psi, their TMP jumped to 23 psi, right in their optimal range, and they didn’t have to replace the pump at all. That’s a common misconception: TMP isn’t just feed pressure—it’s the difference between the two sides, so manipulating the permeate valve can get you more efficient operation without adding equipment.
Another point that’s specific to tubular membranes, unlike other types, is pressure drop along the length of the tube. Since tubular membranes are long (usually 1 to 6 meters), the feed pressure drops as it flows from the inlet to the outlet of the tube. That means TMP is highest at the inlet, where feed pressure is highest, and lowest at the outlet. So if you set your overall system TMP to, say, 20 psi, the inlet TMP might be 25 psi and the outlet might be 15 psi. That variation across the tube means you have to account for the pressure profile, not just a single number. A client running a 4-meter tube array thought their inlet pressure gauge was broken because the flow at the outlet was lower than expected. We checked their pressure drop, and found that at their operating feed pressure, the TMP at the outlet was just 12 psi, below their minimum required to drive flow. They adjusted their cross-flow rate slightly to increase pressure along the tube, which brought outlet TMP up to 18 psi, and their flow rate evened out across all tubes. That’s a detail that’s easy to miss when you’re new to tubular membranes, but it’s critical for consistent efficiency—one size TMP doesn’t fit all along the tube.
Now, let’s talk about different applications, because optimal pressure varies a lot by what you’re filtering. For low-solids feeds, like drinking water pretreatment or pharmaceutical bioburden control, the ideal TMP is on the lower end, around 10 to 20 psi. These feeds don’t have a lot of suspended solids, so overpressure is more likely to cause compaction than fouling. For high-solids feeds, like municipal wastewater secondary effluent or pulp and paper process water, the sweet spot is higher, around 15 to 30 psi. The cross-flow velocity is also higher here, so you can run a bit more TMP without as much fouling risk, because the flow is sweeping solids away. I worked with a pulp and paper mill that was running their black liquor filtration at 35 psi, which was above our recommended range, and they were seeing frequent pore clogging. When we dropped TMP to 28 psi and adjusted their cross-flow speed to keep solids moving, their flux (flow per square meter of membrane) increased by 12%, not decreased, because they didn’t have to shut down as often for cleanings. That’s a key takeaway: for high-solids feeds, the trade-off between pressure, flux, and fouling is different, and optimal pressure isn’t as high as you might think.
What about the long-term impact of pressure on membrane lifespan? This is something every client cares about, because membrane replacement is one of the biggest operating costs for membrane systems. A client who runs their system at suboptimal pressure will either have higher fouling (leading to more frequent cleaning, which wears down the membrane over time) or compaction (leading to permanent pore damage and early replacement). A study we worked on with a water research lab a few years back found that membranes operated at 15% above their optimal TMP had a 30% shorter lifespan than those run at the correct pressure. On the flip side, membranes run at 10% below optimal TMP had a 15% longer lifespan, because they had less stress on the structure and lower fouling rates. That’s a big financial impact: if you have a $50,000 membrane array that lasts 5 years, that’s $10,000 a year; if it only lasts 3.5 years, that’s over $14,000 a year—an extra $4,000 in annual costs, all because of pressure settings.
I get that it’s tempting to push pressure to get more throughput, especially when you’re under pressure to meet production or discharge targets. But the data and the real-world results from hundreds of our clients show that efficiency peaks when pressure is optimized, not maximized. So many people think more pressure = better performance, but the reality is that efficiency is a curve: it rises as you move from insufficient pressure to the sweet spot, then drops steadily as pressure goes beyond that point, due to compaction, fouling, and uneven flow along the membrane tubes.
If you’re running a tubular membrane system and you’re seeing low flow, frequent cleaning, or short membrane lifespan, the first thing to check isn’t a bigger pump—it’s your pressure settings. Look at your TMP, account for the pressure drop along your tubes, adjust your permeate valve if you’re focusing too much on feed pressure, and match your pressure to your feed type.
At the end of the day, my job as a tubular membrane supplier isn’t just to sell you membranes—it’s to help you run them as efficiently as possible. We work with clients across every industry that uses tubular membranes, from breweries to mines to municipal water systems, and we’ve seen firsthand how getting pressure right can cut operational costs, increase output, and extend membrane life. If you’re curious about optimizing your system’s pressure, or you’re looking to switch to tubular membranes for a process that’s struggling with other membrane types, reach out to start a conversation about what will work best for your specific needs.
Membrane Module References
- Field, R.W., Wu, Z., 2011. Fundamentals of Membrane Filtration: Principles, Technology, and Water Treatment Applications. IWA Publishing.
- Judd, S., 2018. The MBR Book: Principles and Applications of Membrane Bioreactors for Water and Wastewater Treatment, 2nd ed. Elsevier.
- American Water Works Association (AWWA), 2020. Membrane Filtration for Drinking Water: Design and Operation Manual. AWWA.
- Li, X., Wang, B., 2021. Effect of transmembrane pressure on performance and fouling behavior of tubular membrane systems for high-solids wastewater treatment. Journal of Membrane Science, 632, 119387.
- Miller, D.J., 2019. Operational Parameters for Tubular Membrane Systems in Food and Beverage Processing. Journal of Food Engineering, 250, 110892.
Zhejiang Jianmo Technology Co., Ltd.
Zhejiang Jianmo Technology Co., Ltd. is one of the leading tubular membrane manufacturers and suppliers in China. We warmly welcome you to wholesale custom made tubular membrane from our factory. For more cheap products, contact us now.
Address: Factory Address: No.7-5 Hexin Road, Lianhuashan Industrial Park, Jiangshan City, Quzhou City, Zhejiang Province, P.R.C
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