Tips on deciphering error codes, servicing, and performing preventive maintenance on this challenging sterilizer system.

Like much of the equipment we biomeds service, the Steris System 1 sterilizer can present quite a challenge. I must confess that I have never attended the System 1 service school, and I am not an expert, but with the service manual in hand and an open phone line to Steris—not to mention an OR staff bearing down my back—I have managed to achieve some success.

My hope is that by sharing some of my experiences on the System 1, I will assist other biomed techs in their approach to servicing the unit. I will also mention some valuable service tips that I have picked up along the way, and I will conclude with my recommendations for preventive maintenance of the unit. I recognize that experiences may differ, and all service suggestions and recommendations reflect only my opinion.

Problems and Solutions
During the System 1’s sterilize and diagnostic cycles, error codes are generated that point the technician in the direction of a failure. However, the error codes cannot be accepted at face value, and require interpretation. Here is an example that occurred with one of our units. The error code “water temp < 43°C” was generated (the machine specifications state that water inlet temperatures of 43°–48°C are required). Seeing this error code, one might come to the conclusion that the water temperature was actually out of spec. Not so fast. A look at the first few steps of a properly functioning sterilize cycle should help us determine the problem:

  1. The chamber seal inflates by the activation of the air compressor. The chamber seal reaches the desired pressure of 40 (+/- 2.5) psi, and the air compressor deactivates.
  2. Supply-inlet water runs through the unit and out to the drain to verify that its temperature is within specification.
  3. When the supply-inlet water temperature is sensed to be within its acceptable limits, the water begins to fill the unit’s sterilize chamber.

In step 1, the air compressor can normally be heard turning on and then off as the chamber seal reaches pressure. Regarding our error code of “water temp <43°C,” however, the compressor never cut off. It could be heard continuing to run. Nevertheless, the unit began to check the water temperature. There was one slight problem: the supply-inlet water never flowed, because the chamber seal never achieved the desired pressure. Consequently, the thermistor never measured the water temperature but, in fact, measured the air temperature at a perfect 27°C. This is significantly less than 43°C, and hence the error code was generated. The solution? Replacing the leaking chamber seal solved the problem.

Another scenario occurred with the same error code. In this failure, the air compressor and chamber seal worked exactly as they should have. Even so, the water did not flow to verify proper temperature.

Once again, the air temperature was measured, and the error code was generated. I am aware of two possible causes for this lack of water flow. First, it is possible that the prefilters A and/or B were dirty enough to totally block flow. Second, it is possible that there was a problem in the float block, which could inhibit water flow.

The float block is mounted adjacent to the sterilize chamber and is used as an indicator of the chamber water level. This is done via the float switch (LS3). Without water in the float block, LS3 should read closed, indicating an unfilled chamber. Conversely, when the float block is full, LS3 should read open, indicating that the chamber level is full. Further, if the system controller thinks the sterilizer chamber is full, the water inlet will not allow flow. Therefore, a problem with the float block—or with the interpretation of its status—can result in the water inlet valve never opening. In our failure, the float block system was determined to be working correctly. The solution? Replacing prefilters A and B solved the problem.

Occasionally during a cycle, water will pour out the front of the unit (definitely a failure mode, and a good opportunity to refine one’s housekeeping skills). There are some common problems that can cause this to occur. Excessive buildup of water under the equipment tray will push the tray up and off the seal, causing the water to spill out the front. With a correctly functioning unit, after each cycle there is an accumulation of 50–100 cc of water under the tray. Proper maintenance requires the operator to remove this water before it becomes a problem. If there were to be more water than this after a cycle, it would indicate excessive leakage. Its cause is often simply a problem with the equipment tray (either a hairline crack, or broken/loose hose fittings). One should inspect the tray carefully, especially at the rounded areas. A second common leakage point is at the lid vent hole, which is glued to the bottom rear of the lid. It seems to be somewhat fragile and will develop cracks. Unfortunately, if this is the case, the entire lid requires replacement.

Another cause for a water spill is air trapped in the chamber. In a correctly functioning unit, when water enters the chamber, the air in the chamber is displaced, and passes to the float block, through the float block check valves (ck2 and ck3), and out to the drain. If ck2 and/or ck3 fail, then the air is trapped in the chamber and will break the lid seal, causing a spill. Problems with ck2 and ck3 are common, but fortunately, they are not too difficult to access and replace.

Any article discussing common failures of the System 1 would be sorely lacking without some mention of those infamous pinch valves (drain pinch valve [V5] and circulation pinch valve [V6]). The pinch valves are soft rubber tubes, approximately the length and diameter of an average forefinger. By applying air pressure to the outside of the rubber tube via the air compressor, the pinch valve is squeezed closed, or pinched off. During pinch off, water is blocked from flowing through the valve. By means of these valves, the fluid path is directed as required. If not replaced periodically, these rubber valves will develop small holes or tears and will not pinch properly. A variety of faults are possible with the failure of one or both of these valves, and I will describe one such failure: “chamber level low.”

During the circulation portion of the cycle, if the chamber loses enough fluid to cause the float block switch to drop and become closed, a “chamber level low” error can occur. In encountering a unit with this error code, I observed two symptoms. First, during the circulation portion of the cycle, the air compressor never stopped running. This indicated a leak somewhere in the pneumatic system. Simultaneously, water was exiting the unit’s drain port, until the chamber was empty. In a correctly functioning unit, during circulation, V5 should be closed in order to block the water path to drain. Given that this is accomplished by means of the air compressor, V5 was strongly suspect. In fact, upon inspection, it was found to have a tear. This allowed air to be infused into the circulation path to the chamber. Also, with the failure of V5 to become fully closed, the path to the drain remained open. Solution? Replacing V5 solved the problem.

Service Tips and Suggestions
The following are tips and suggestions probably not found in the service manual. Some of them are obvious.

  • Do not be afraid of turning over the unit and removing the bottom cover. As a matter of fact, get used to it. It is a good idea to get some assistance. When turning it over, lift up the right side of the unit first, letting the excess water spill out to the left. This will protect the electronics, which are on the right side.
  • When servicing either the circulation pump, pinch valves V5 and V6, or the drain check valve (CK8), gain access by removing the bottom cover.
  • When servicing the high-pressure pump, gain access from the top (which is more difficult).
  • When replacing the high-pressure pump, also replace the high-pressure sense switch (LS6).
  • When removing the float block, it is extremely useful to drill a couple of small holes in the side of the cover, to allow a screwdriver to gain access to the hose clamps. Otherwise, the whole machine needs to be disconnected, turned over, and the bottom cover removed. These access holes will not cause any problems, and will save much time and energy. They can even be capped.
  • When replacing the sterile water filter, soak it for 2–3 minutes in water prior to installing. Otherwise, the unit may fail the diagnostic cycle two or three times before passing (not helpful when you are attempting to repair a unit).
  • Excessive water under the equipment tray (ie, >50–100 cc) is most often caused by a cracked or broken tray. The second most likely cause is a cracked lid vent hole.
  • For a slow fill-time problem, try replacing prefilters A and B, as well as the sterile water filter.
  • If large bubbles are observed entering the chamber during fill, pinch valves V5 and/or V6 are defective. The cycle may still pass, but have replacements available.
  • When replacing one defective pinch valve, replace them both.
  • Error code “low heat rate” will often be caused by a tripped heat sensor switch, which is mounted to System 1’s internal water heater. This can occur if the incoming water temperature is excessively high. Remove the bottom cover, and check the switch. Reset if necessary. If the incoming water temperature is too high, it will need to be adjusted. At Union Memorial, Baltimore, we have 50-gal hot water heaters mounted in the ceiling. This hot water is mixed with house cold water and fed into the System 1s.
  • Make sure system 1’s internal heater coil resistance is 10 ohms.
  • Always take care to protect the printer from spilled water, or risk ruining the printer board. (Believe me, I know.)

Recommendations for PM
My experience indicates that replacing the following parts on an annual basis will keep real failure calls to a minimum (maybe even nonexistent).

  • drain and circulation pinch valves (V5 and V6)
  • drain check valve (ck8) rebuild kit
  • float-block check valves (CK1, CK2, and CK3,) with O-rings
  • chamber seal
  • water filters A and B, sterile water filter, and the air filter
  • sterilant aspirator

The total cost on these parts is approximately $1,000.

Additionally, while the bottom cover is removed, check for signs of water leakage. Check the lid vent hole for cracks. Finally, check the functioning of the gas spring cylinder, which holds the lid open, and replace it if necessary. Reassemble the unit, reattach the plumbing, and test the unit by running both a diagnostic and regular sterilize cycle. Then go tell the wonderfully patient nurse manager that all is well because you have just completed a big-time PM on the System 1!

Learning how to service the Steris System 1 has been both challenging and gratifying. Recently, my boss asked me whether or not I thought that the hospital needed to purchase newer units. With much satisfaction, I was able to respond that as long as we can continue to get parts, we can keep the System 1s up and running well.

Robert Resnicoff, CBET, studied biomedical engineering technology at Catonsville Community College in Catonsville, Md, and has worked at Union Memorial Hospital, Baltimore for the past 21 years.

Suggested Reading
Steris System 1 Processor Model 89A1/90B1 Service Manual (P/N 612001). Mentor, Ohio: Steris Corp; 1994.

Steris System 1 Operator Manual (P/N 612025). Mentor, Ohio: Steris Corp; 1994.