Desert Star Knowledge Base

Search the Knowledgebase	Browse by Category
[Advanced Search]

The Care, Service Interval and Product Life of Desert Star Underwater Equipment

Would you like to...

Print this page

With proper care and regular preventative service, Desert Star equipment will operate for many years. This article discusses the system product life, service interval, common failure modes and techniques of field care and maintenance to maximize operational reliability and minimize wear and damage. The attached check list summarizes equipment care requirements.

Service Interval
We recommend that equipment is returned to the factory for service once every three years. It is at these intervals that it generally becomes necessary to replace the rechargeable batteries, re-calibrate depth sensors and inspect the equipment for any wear and corrosion that might cause reliability problems or even catastrophic failure such as flooding. If your use of the equipment is in particular intense and/or the consequences of equipment failure in the field are severe, then the service interval should be shortened and annual inspections should be considered. With proper service, Desert Star underwater equipment can be maintained for very long periods. In fact, at the time of this writing in 2006 we were still servicing AquaMap equipment originally purchased in 1995 (shortly after the system introduction) and under continous use since that time. We recommend that you budget 15% of the system purchase price for annual maintenance.

EnviroTech divers with their AquaMap AM-1 system in Dutch Harbor (Aleutian Islands), 1995. This system is serviced in regular intervals and is still in very active use today (2006).

Product Life & Support
The modular architecture of our product line allows it to evolve economically. That generally means that system support is open ended. In fact, with a single exception (a decompression computer for technical divers), all of the non-custom systems that entered our product line in the first few years of Desert Star's existence in the mid 1990's remain to this date in our active product line and are improved on a regular basis. In addition, we frequently convert original single-customer systems to standard products, thereby promoting their long-term availability and ongoing development for the original sponsor customer as well as the wider user community.

That said, within a product line such as the AquaMap underwater navigation system or the SharkEye underwater cameras, it does sometimes become necessary to retire a particular model in favor of an improved version. For example, our original DS-1 diver navigation sstation was first introduced in 1994 and subsequently improved until around 2002. We made a decision in 2006 to discontinue this model and replace it with the more capable DS-3 station which is designed around a PDA platform and will offer advanced charting to the diver. In the case of a a product retirement, there is generally an improved replacement. So, while you may ultimately be faced with a swap of hardware, the new product will maintain and enhance your existing capabilities. You may wish to inquire about the maturity and life cycle position of systems and individual products prior to making your purchase or maintenance decision.

Caring for your Desert Star System
Now let's take a look at how Desert Star underwater systems typically encounter wear and failure - and what care techniques you can use to prolong product life and minimize the service cost. However, even with the best of care you will experience wear and the occasional failure. If your service costs average below 10% of purchase price per year, you are doing well. If you go above 20% per year, then improved care might really reduce costs.

For this example we will use parts of a system recently returned by a customer for service. This system was first sold in the 1997-1999 time frame, experienced significant use and when returned in 2006 still contained many of the original components.

Corrosion Damage
Underwater housings from Desert Star are made from Delrin plastic, hard-anodized aluminum or titanium with use of some other materials such as stainless steel fasteners or PVC sonar transducer components mixed in. We currently use hard anodized aluminum for most products rated in the 300m-1000m depth range, but also for shallower water applications. It does have the advantage of high strength, good economy and the ability to absorb substantial drops without damage. Yet, despite the hard anodize finish, aluminum is still subject to corrosion damage. Therefore, aluminum is suitable only for limited immersion profile systems> Examples are AquaMap and PILOT systems which generally spend a few hour to a few weeks underwater per deployment.

Corroded aluminum is identified by presence of a white powder (aluminum oxide) and pitting in the affected area. This is generally only of cosmetic consequence unless the damage occurs around O-ring areas and other sealing surfaces. In these cases, the seal may be compromised leading to flooding. To minimize corrosion, soak your aluminum stations in fresh water after each use - or at least rinse them off with fresh water, paying particular attention to the location around the end caps, connectors, viewports etc. where seals are located.

If you anticipate very intensive use but only in shallow water (up to about 300m), ask us to quote a Delrin plastic housing. That will avoid corrosion damage - but you may also experience greater danger of housing damage due to drops and impact.

This RBS-1 end-cap had to be replaced because corrosion in the area of a connector seal may have ultimately compromised the housing.

Damage to Plastic Components
The typical failure mode for plastic components is cracking due to impact events such as drops. While the Delrin and PVC plastic components used by Desert Star are highly impact resistant, we still see occasional damage. The most typical and illustrative case is a fracture of the threaded PVC base of our 34kHz end-cap mounted sonar transducer employed on the RBS-1 and RBS-2 baseline stations. An aluminum cage does effectively protects the transducer against drops and impacts with flat surfaces, but the spacing between the cage rods means that sharper tools can still hit the transducer and cause damage. Damage is most likely in cases such as this where a relatively small plastic part is mounted to a much more massive housing.

Protect plastic parts against impact through appropriate protection and use. Avoid scratching and impact of optical components such as viewports and lens windows. However, don't be overly concerned. At this time, we might see one or two broken sonar transducers per year - and perhaps a similar number of damaged DiveTracker Sport PVC housings (out of hundreds or thousands in the field).

PVC sonar transducer from a RBS1 station with broken-off threaded stem.

Damaged Lexan or Acrylic Viewport

Underwater connectors and cables
Many Desert Star products use rubber molded underwater connectors. These connectors are very rugged and simple to operate. Connector wear and damage generally falls into three categories.

1. Connectors normally wear out with use. Eventually, contacts will not work properly and intermittant connections might appear. The manufacturer generally specifies a life time of 500 mating cycles or above. However, the connectors must be lubricated with a thin film of silicone grease before mating. Failure to do so can cause damage to the rubber seals - and a potential failure of just a few mating cycles.

2. Cables with connector terminations tend to fail after a certain number of flex cycles near the connector. The internal wires will fatique and an open develops. We see this failure mode most commonly in he sonar trasducer cables of diver stations. You can reduce the stress by spreading the flex over a longer area of the cable through the use of tape, plastic reinforcements etc. However, it's probably best to just consider underwater cables consumables - they are not that expensive anyway. Another common cable failure mode is cuts to the outer neoprene jacket. Minimize squeezing, avoid sharp objects etc.

Desert Star will recommend connector replacement if connectors appear worn or the brass base is showing significant signs of corrosion.

Sonar Transducer Failures
Sonar transducers are subject to substantial stress as the small internal ceramic element vibrates with great force to convert electric into acoustic energy. If the transducer is operated in air rather than in water, the emitted energy cannot dissipate and reflects back into the sonar transducer itself. To avoid premature failure, do not operate sonar transducers for extended periods (many minutes and more) while in the air. Damage is more likely in our high-powered 'H' equipment where stresses are greater. However, over time transducer damage may also occur in regular powered equipment.

Marginal sonar transducer should be decomissioned because failure in the field may not always be obvious, but rather result in marginal performance.

This sonar transducer was decomissioned due to intermittant behaviour.

O-Rings
O-rings are used to seal most underwater housings. O-rings are highly reliable, as long as they are kept clean, lubricated with a slight film of silicone and the O-ring seating area is not damaged. Your main concern with O-rings will be in housings that are opened such as to replace batteries. Our DiveTracker Sport and Scout stations and the ARC-1 acoustic release are examples. Do your work in a dry, well lit environment. Inspect the O-ring closely, remove all debris and apply a thin film of silicone grease. Do not use an O-ring that shows any signa of damage such as abrasions or cuts.

The rubber in old O-rings might potentially grow brittle and crack. Therefore, we replace most O-rings during service as a matter of course.

Electronics
Electronics normally operate reliably for many years. Then, after a number of years component failures start to increase. However, premature component failures are always a possibility in electronics as well. We do update our electronics in regular intervals to improve performance, reliability or replace components that have become obsolete and are no longer available. If an electronics board is exhibiting a failure, we may recommend component or board replacement depending on its age, serviceability and overall condition.

All five electronics modules in this customer's 6-8 year old system operated fine and can continue service. However, the electronics have since been superceded by three new revisions and parts availability is limited. In future service, we would recommend replacement of the entire module if a component failure has occured.