A 50/50 propylene glycol and water mix protects a chiller loop to about -33 °C. Most food plant chillers in Oman run warmer than that and work better on a 30 to 40% mix. This article covers how to choose the strength, mix and test the loop, and order food grade propylene glycol from Barka.
A 50/50 propylene glycol and water mix protects a food plant chiller loop to about -33 °C. Most chillers in Muscat and across Oman run much warmer than that and work better on a weaker blend. Use 50/50 where the loop serves blast freezers, cold stores or low-temperature brine duty. For a typical process chiller, a 30 to 40% mix usually gives enough freeze protection and moves heat faster. We supply food grade propylene glycol IP from Barka Industrial Area, Oman.
What a 50/50 propylene glycol and water mix does in a food plant
Propylene glycol (1,2-propanediol, CAS 57-55-6, C3H8O2) lowers the freezing point of water, so the coolant in your chiller loop stays liquid below 0 °C. It is generally recognised as safe (GRAS) for food use under FDA 21 CFR 184.1666. That makes it the standard choice for loops where coolant could reach the product by accident through a leaking plate heat exchanger, tank jacket or coil.
Ethylene glycol and automotive antifreeze do not belong in these loops. Ethylene glycol must not be used where it could leak into potable water or food processing systems. Food grade means the fluid is acceptable for incidental contact. It does not mean the fluid is safe to drink.
A 50 wt% blend is non-flammable and boils at about 106 °C (222 °F), typical. Pure propylene glycol has a closed-cup flash point of about 103 to 104 °C, typical.
Propylene glycol freeze point chart
The table shows typical freezing points of propylene glycol and water solutions by mass. Use it to pick a starting strength for your glycol chiller concentration.
| Propylene glycol in water (% by mass) | Freezing point (typical) |
|---|---|
| 10% | -3 °C |
| 20% | -8 °C |
| 30% | -14 °C |
| 40% | -22 °C |
| 50% | -34 °C |
| 60% | -48 °C |
Ready-made 50/50 premixes are usually quoted at about -33 °C (-28 °F), and 30/70 premixes at about -13 °C (9 °F), typical. The chart is by mass and most plants mix by volume, so treat these figures as a guide. Confirm the strength of your own loop with a refractometer.
Stronger mixes carry less heat. Specific heat falls from 1.000 for water to 0.935 at 30% and 0.850 Btu/lb·°F at 50%. At 0 °F, a 50% propylene glycol solution is about twice as viscous as 50% ethylene glycol. As glycol strength rises, your pumps work harder and the chiller delivers less cooling. Derate chiller capacity with the manufacturer's glycol correction factors.
Is 50/50 right for your chiller in Oman's heat?
Choose the strength from the coldest fluid temperature the loop will see. The outside air temperature does not decide it. Food and beverage chillers commonly run 30 to 35% propylene glycol by volume with a reservoir setpoint near -3 to -2 °C (26 to 28 °F). One industry guide keeps the freeze point 10 to 15 °F (about 6 to 8 °C) below the coldest loop temperature. Another sets it 20 to 25 °F below the chiller setpoint, because the refrigerant runs 10 to 15 °F colder than the glycol. If you are unsure, use the wider margin.
A dairy, bottling or bakery chiller in Muscat or Sohar holding +2 to -5 °C is usually covered by a 30 to 40% mix. Keep 50/50 for blast freezers, cold stores and low-temperature duty. Too little glycol can freeze the loop and rupture the evaporator. Too much glycol cuts heat transfer for protection you never use. Do not run glycol solutions close to their freezing point, because slush forms.
Summer heat also changes the loop. In a hot plant room, open reservoirs lose water to evaporation, which pushes the strength up. Leaks and drain-downs that crews top up with plain water push it down. Top up with premix at the loop's own strength, not with plain water, and test after every large top-up.
Food grade (IP/USP) or inhibited propylene glycol
IP and USP are pharmacopoeia grades. Plain food grade propylene glycol of the USP type contains no additives. Inhibited propylene glycol contains a corrosion-inhibitor package for steel, copper and brass. Many inhibited heat-transfer fluids are not food grade and must not be used for food contact or potable-water protection.
Use food grade glycol wherever a leak could reach the product. Use inhibited fluid only in fully isolated loops. Do not mix the two in one system, and flush the loop before you switch. Black iron, galvanised and other ferrous loops need a rust inhibitor in the glycol solution, so check your pipework before you fill. Avoid galvanised (zinc) surfaces with inhibited blends. Safety data sheets also list zinc as incompatible with propylene glycol.
| Item | Our product |
|---|---|
| Product | PROPYLENE GLYCOL IP food grade |
| Part number | RXSOL-19-1615-025 |
| CAS number | 57-55-6 |
| Application | Freezing tanks for ice pops (popsicle machines) |
| Appearance | Clear liquid |
| Colour (APHA) | 10 Max. |
| Distillation range | 184 - 189 °C |
| Specific gravity | 1.035 - 1.040 |
| Water (% w/w) | 0.2 Max. |
| Purity as C3H8O2 by GLC (% w/w) | 99.5 Min. |
| MSDS | On request |
How to mix 50/50 propylene glycol and water, how much to order and how to test it
Mix the glycol with deionised, distilled or RO water, not tap water. Chlorides can pit stainless steel, and hardness leaves scale on heat-exchange surfaces. If your plant runs an RO unit for process water, that is the easiest source.
For a 50/50 mix by volume, half the loop volume is concentrate. A 1,000 litre loop takes 500 litres of propylene glycol and 500 litres of treated water. Pure propylene glycol has a density of about 1.036 g/mL, so 500 litres of concentrate weighs about 518 kg. A 35% loop of the same size takes 350 litres of glycol. Count the volume of the pipework, jackets and buffer tank as well as the reservoir, and order a little extra for top-ups.
Blend the mix in a clean tank before charging and circulate it fully. Check the strength before you bring the chiller down to setpoint. After that, check the loop concentration at least once a year with a glycol refractometer or hydrometer, and more often in summer. If the loop reads weak, add concentrate. If it reads strong, add treated water.
Healthy glycol is neutral to slightly alkaline. If the pH drifts toward acidic, the fluid is due for replacement. Inhibited fluid in a clean closed loop commonly lasts 3 to 5 years. Plain food grade fluid has a shorter cycle that depends on test results, so log every pH and strength reading. Keep spent glycol out of storm drains and hand it to a licensed waste contractor in line with your environmental permit.
Storage, handling and documents for your food safety file
Propylene glycol is hygroscopic, which means it absorbs moisture from the air. Keep drums tightly closed in a cool, dry, shaded store, away from strong oxidisers, strong acids and strong bases. Use opened drums quickly. Prolonged heating in air slowly oxidises propylene glycol to aldehydes and acids, which matters in a warehouse that gets very hot in an Omani summer. Stainless steel, carbon steel, polyethylene and polypropylene are suitable container materials.
USP-grade propylene glycol needs no hazard classification under GHS criteria, but your HACCP team will still want documents on file. Ask us for the MSDS with your quote. If your auditor needs other documents, such as a certificate of analysis showing assay, water and diethylene glycol limits, or a Halal statement, tell us and we will confirm what is available for your batch. Typical USP/EP specifications call for an assay of at least 99.5%, water of no more than 0.2% and diethylene glycol of no more than 0.10%.
Where to buy food grade propylene glycol in Muscat and Oman
Muscat Chemical (Muscat & Barka for Business Trading) is based in Barka Industrial Area, Sultanate of Oman. Send us your loop volume and target strength, and we will confirm the drum quantity, packing and delivery date in the quote.
The same product is also listed on Sohar Chemical for buyers around Sohar port and the Batinah coast and on OmanChem for orders across the Sultanate. For other solvents and plant chemicals, see the Muscat Chemical product range.
Call +968 77333599 or email muscatchem@gmail.com. To request a quote for food grade propylene glycol, use our quote request form or send your loop details on WhatsApp +968 77333599.
Frequently asked questions
What is the freezing point of 50/50 propylene glycol and water?
A 50/50 propylene glycol and water premix typically freezes at about -33 °C (-28 °F). Freeze point charts by mass give -34 °C at 50%. Do not run the loop close to that temperature, because slush forms before the fluid freezes solid.
Is a 50/50 propylene glycol mix too strong for a food plant chiller?
Often it is. Food and beverage chillers commonly run 30 to 35% propylene glycol by volume with a setpoint near -3 to -2 °C. A 50% loop moves heat noticeably slower than a 35% loop, so keep 50/50 for blast freezers, cold stores and low-temperature duty.
Can I use ethylene glycol or automotive antifreeze, or mix USP and inhibited propylene glycol?
No. Ethylene glycol must not be used where it could leak into food or potable water. Use food grade propylene glycol wherever a leak could reach the product, and use inhibited fluid only in fully isolated loops. Do not mix the two in one system, and flush the loop before you switch.
What water should I mix with propylene glycol: tap, distilled or deionised?
Use deionised, distilled or RO water. Tap water can carry chlorides that pit stainless steel and hardness that leaves scale on heat-exchange surfaces. Top up with premix at the loop's own strength, not with plain water.
Where can I buy food grade propylene glycol in Oman?
Muscat Chemical is based in Barka Industrial Area and lists propylene glycol IP food grade (part number RXSOL-19-1615-025). Send your loop volume and target strength on WhatsApp +968 77333599 for a quote, and we will confirm packing and delivery in the quote.