The part of a warranty that most often leads to disagreement is usually not the coverage itself but which items count as wear parts and which count as a fault of the whole machine. Even when the scope is written down clearly, the two parties often still understand it differently, and it ends in each side interpreting it from its own experience. The criteria for the judgement have to be made clear at delivery, not negotiated once a dispute has arisen. What this article sets out is a way of thinking about the judgement; the specific terms and the scope are governed by the contract clauses and the documentation pack.
The part that belongs to the consumable materials
The first criterion for the judgement is whether the failure of the part is determined by the normal course of use itself. Every form of consumption that necessarily occurs with the passage of time, with the running hours or with the quantity of oil processed belongs to the consumable materials and is not covered by the whole-machine warranty. The filter elements are the most typical case: the ZYD-100 uses 150-250-50 and 110-250-50 coarse filter elements, a 110-400-20 secondary filter element, and five 150-500-5 fine filter elements in parallel, with 110-600-5 also used as a fine filter element. When the dirt holding capacity of the element reaches its limit, the differential pressure rises and the filtration accuracy falls, and that process has nothing to do with whether the machine has a manufacturing defect.
Seals and vacuum pump oil belong to the same category. Seals age and harden under repeated dismantling and pressure cycling, and pump oil is consumed and emulsified under high temperature and vacuum; as long as they are changed on schedule, they have done their work. The far-infrared carbon fibre heating tube is treated as a life-limited part: it belongs to the parts replaced on the basis of the service years and is not a structural fault of the machine. The cost of replacing these parts during the warranty period is borne by the customer, but the replacements must be parts of matching specification.
The part that belongs to a fault of the whole machine
The second criterion is whether the failure should not occur at all within the design life and under the specified conditions of use. Anything that meets this test belongs to a fault of the whole machine and is our responsibility during the warranty period. Leaks from the tank, the welds and the pipework at the specified pressure; a pump set that fails to reach its design pumping speed under the specified conditions, so that the working vacuum cannot enter the -0.08 ~ -0.0999 MPa range; failure of the heating and temperature control circuits, so that the oil temperature cannot be held at the set range; failure of an electrical component that causes a shutdown; abnormal operation of the control system, including the overpressure audible and visual alarm shutdown and the failure of the phase loss and phase sequence protections to operate. All of these fall within the category of the whole machine.
- Consumable materials: filter elements, seals, vacuum pump oil, heating tubes and other life-limited parts.
- Faults of the whole machine: leaks from the tank and the pipework, insufficient pump set performance, failure of the heating and temperature control circuits, and faults of the electrical and control systems.
- Basis of the judgement: whether the failure is determined by the use process itself rather than by the quality of manufacture or assembly.
- The specific terms and the scope are governed by the contract clauses and the documentation pack; this article sets out a way of thinking about the judgement.
Three references used in making the judgement
Applied to one particular machine, the judgement normally looks at three things at once. First, the period of use and the volume processed: how many years the seals have been in use and how many batches of filter elements have been replaced are the most direct evidence of the consumable materials. Second, the oil and the duty: whether the viscosity, the water content and the cleanliness of the oil processed fall outside the range of application of the machine. If the oil the customer processes is itself high in water content, high in gas content and heavily contaminated with particles, an early failure of the filter element comes more from the operating conditions than from the machine. Third, the operating state at the moment of failure: whether the machine was run overpressure, whether it worked for long periods in an over-temperature state, and whether the alarm and the protective devices were bypassed to force a start.
Of these three references, the third is the one most easily overlooked. Continuing to run with the temperature control inoperative or with the alarm inhibited means that the machine is working under conditions that have passed the design boundary, and damage that occurs in that state is hard to bring within the warranty afterwards. Stopping the machine first and then calling for service after an abnormality appears is therefore both a safety requirement and the precondition for keeping the warranty rights.
What the customer has to do during the warranty period
A warranty stays valid through the routine actions of both parties. What the customer has to do is not complicated: run the machine in accordance with the nameplate parameters and keep the operating records; change the filter elements and the pump oil on the stated cycle so that the blocked differential pressure and the emulsification do not go on degrading the machine; do not modify the pipework, add a bypass or change the electrical wiring on one's own; stop the machine first and then make the call for service when an abnormality is found; and keep the documentation pack and the equipment number.
| Situation | Likely judgement | How it is handled |
|---|---|---|
| Filter element at the end of its cycle, seals aged, pump oil emulsified | Consumable materials | Replaced to specification and charged to the operating cost |
| Leakage from the pipework at the specified pressure, insufficient pumping speed of the pump set | Fault of the whole machine | Handled by us during the warranty period |
| Damage after operation overpressure or with the alarm inhibited | Outside the warranty | Treated as a repair, with the cost charged separately |
| Early failure caused by operating conditions outside the range of application | Judged on the specific circumstances | Requires verification against the operating records and the condition of the oil |
Drawing the boundary between the wear parts and the whole machine rests not on a single exclusion clause but on the three references that can be checked: the period of use, the volume processed and the operating state.