Watlow FIREROD^® Renal Dialysis Machine Case History

Application

Renal dialysis machines purify the blood in patients whose kidneys have failed. During the kidney dialysis procedure, it’s critical that body temperature is regulated in order to prevent the occurrence of thermal shock. A renal dialysis machine implements a three-step thermal process that typically includes a 90°C (194°F) disinfection cycle, followed by a 37°C (98.6°F) cycle to clean the blood and a 90°C (194°F) system cleaning cycle at the end of usage each day.

Problem

To ensure temperature stability and meet safety requirements, the application required an in-line immersion heater that wouldn’t touch the perimeter of the plastic water transport tube. If the plastic tubing were to make contact with the heater, the tube would melt. Also, for the patient's safety, medical products require a low leakage current. To comply with UL® safety requirement 60601-1, a Class 1 medical device must have a leakage current of less than 300 micro amperes.

Solution

Watlow's engineering team collaborated with the customer to create a heater solution that met all temperature and medical device requirements. A 1/8-inch (3 mm) thick flange was attached to a 0.625-inch (16 mm) diameter by 7-inch (18 cm) long FIREROD^® heater. The flange allowed the FIREROD to remain concentric with the plastic tube. To meet leakage specifications, a Type LL, special low leakage FIREROD heater capable of maintaining leakage below 15 micro amperes (0.0000015 amps) was used.