In this module, you’ll gain an understanding of the key considerations when selecting pumps for temperature control, focusing on three common liquids: ammonia, propylene glycol, and hot water.

Regular pumps are designed to meet general specifications, but in temperature control applications, they often face challenging conditions that exceed these limits, such as extreme temperatures and high-viscosity or dense liquids.

Let’s start with ammonia in refrigeration applications. Ammonia is often the preferred coolant in chiller units, especially when sustainability and efficiency are the main focus. Thanks to its zero-ozone depletion potential and high heat absorption capacity, ammonia offers excellent cooling performance.

However, these cooling properties demand more robust pumps that can withstand harsher conditions. While most pumps are built to handle liquids down to -10 degrees Celsius, ammonia can reach temperatures as low as -40 degrees Celsius. Using a standard pump in these conditions can lead to hazardous leaks, blockages, or even system failures.

To safely handle ammonia, pumps need to be optimised with special features. These should include Magnetic Drives to prevent leaks and rubber gaskets or O-rings made from materials like Ethylene Propylene Diene Monomer (EPDM) to maintain elasticity at low temperatures.

Another challenge is ice formation. Ice can form on the pump exterior during standstill, blocking the motor-pump coupling. Proper insulation with mats and heat tracing is essential to prevent this issue.

Now let’s look at propylene glycol in cooling applications. Propylene glycol is a cost-effective, non-hazardous coolant that remains liquid even below zero degrees Celsius, offering effective freeze and burst protection. It ensures safety in sensitive applications, inhibits corrosion, and is environmentally friendly, making it a versatile choice for efficient and safe cooling systems.

However, propylene glycol has a high viscosity—up to 100 times thicker than tap water. This means pumps need to be equipped with oversized motors to handle the additional load.

Leaks can also be problematic, as they may cause crystallisation, which can damage the shaft seal surface. To address this issue, opting for harder surfaces for the shaft seal can be an effective solution. In certain specific cases, using pumps with a double shaft seal can provide additional protection against liquid leakage.

Now let’s look at hot water in heating applications. In industrial processes like sawmills, pumps often need to handle hot water up to 140 degrees Celsius. Standard shaft seals typically fail at around 120 degrees Celsius, which means regular pumps aren’t sufficient for this kind of high-temperature application.

To manage these extreme conditions, pumps must have single shaft seals designed to keep hot water away from the seal, or double shaft seals that are actively cooled.

Another solution is to use air-cooled tops to insulate the seal chamber or circulate cooling water through the shaft seal chamber to maintain a safe operating temperature.

Let’s recap.

• Ammonia offers excellent cooling properties but requires specialised shaft seals, O-rings, and insulation to prevent leaks and ice formation.

• Propylene glycol is non-hazardous with strong freeze protection and corrosion resistance, but its high viscosity requires oversized motors and specialised shaft seals.

• Hot water is used in high-temperature heating processes, demanding pumps with advanced seal designs to handle extreme heat safely. When selecting pumps for temperature control, it’s essential to consider the specific demands of each application—whether it’s refrigeration, cooling, or heating.

By choosing pumps that are designed to handle the unique challenges of each liquid, you can ensure optimal performance, efficiency, and safety.