Over the past couple of years, the IEC 60601-1 movement over a threshold test has been a hot topic for medical cart designers, and for good reason. Medical carts can be very heavy, and carts weighing more than 45kg (99 lbs.) need to comply with the threshold test in the IEC standard.
When a cart fails to roll over a threshold easily, the operator is exposed to the strain of lifting the cart over the obstacle or, worse, continuing to push the cart until an unstable/tip-over situation occurs. Both of these scenarios present a risk of injury and potential property damage.
Evolution of the IEC 60601-1 Standard
Prior to adoption of the 60601-1 3rd edition standards, threshold testing was not required. However, the 3rd edition standard added a stringent threshold test that some would say was nearly impossible to pass:
- The height of the obstruction was raised to 20mm
- The cart had to go up and over the obstruction
- You needed to repeat the test 10 times in a row
- The speed of movement was controlled and slow (.4m/s)
This test called for a very slow, conservative walking pace, so as you approached the threshold this slow speed often caused the cart to stop when it encountered the threshold. The natural thing to do then was to take a small step back and give the cart a good shove up and over the obstruction; something the test didn’t allow for.
With publication of Amendment 1, the threshold test was changed. The revised Subclause 18.104.22.168.3 doubled the speed to .8m/s and halved the height of the threshold to 10mm, which greatly reduced the difficulty for a cart to pass the test.
Setting Up and Performing the Threshold Test
Using some common materials, the test is easily set up and performed. The most challenging part of running it is maintaining the correct speed.
- A flat hard floor
- Masking tape
- Tape measure
- Metronome or a smartphone with a metronome app
- Threshold secured to the floor (see IEC standard for exact threshold dimensions. A 3/8”-thick sheet of plywood against a wall is often substituted and can be used to gauge in the lab whether a cart will go up and over)
- A second observer with a stopwatch (optional)
- Instructions for using the cart (you need to know how the designers intended it to be transported, i.e., what direction to push it or pull it)
Starting at the threshold, lay your tape measure out on the floor perpendicular to the threshold. Place a piece of masking tape on the floor every .8 meters. You’ll probably need a minimum of 8m of total space to perform the test.
Set up your metronome or smartphone app to make one click/beat every second, and then use the second hand on your watch to verify the accuracy of the metronome.
Practice walking back and forth at .8m/second, making sure each of your steps is on the masking tape and in cadence with the metronome. Now you should be able to move the medical cart at .8m/second over the threshold. You can also have a second observer use a stopwatch to measure the time it takes to travel from the last piece of masking tape to the threshold. It should be between .89 seconds and 1.14 seconds (speed tolerance is ±.1m/second).
You can adjust the distance between the marks on the floor and the speed of the metronome clicks for a more comfortable stride. For example, .4 meters between marks and 120 beats per minute equals .8m/second.
Running the IEC 60601-1 Test
- Following the cart’s instructions for use, load the cart and secure items to it in the typical transport configuration
- Move the cart so it contacts the 10mm threshold at a speed of .8 m/second
- Repeat 10 times
In order for the cart to pass, it must go up and over the threshold without damaging the cart or creating any tip-over risk.
To see this test in action, watch this video:
Have questions about 60601-1 Standards? Contact us and we’ll be happy to share our knowledge with you.