A box filter and a vacuum purifier both filter oil, but one uses filter frames with cloth and the other uses filter elements, and the two consumables accounts are not the same account. Averaging the two costs together tends to produce a conclusion that fits neither. This article takes the configurations of the LY-200 and the ZYD-100 and splits the cost structure of the cloth and of the elements side by side.
Different filtering methods, different cost structures
The LY-200 is a box filter with a flow rate of 4800 L/h, fitted with 40 sets of 300×300 filter frames and rated at 11 kW. The cloth is held in the frames and the solids are caught on the surface of the fabric by the pressure of the filtration. The consumable is the cloth, replaced one piece at a time, cheap per piece, and the consumption grows directly with the volume treated and the level of contamination.
The ZYD-100 is a two stage vacuum purifier with a flow rate of 6000 L/h, a filtration accuracy of ≤1 μm and a cleanliness of NAS 1638 class 5, and the standard configuration is five 150-500-5 fine filter elements in parallel. The consumable is the element, replaced one at a time, dearer per piece, but how often it has to be changed depends on how well the pressure drop is managed.
The account splits into three parts
Whether it is cloth or element, the account can be split into the purchase, the work of the change and the additional consumption, and putting the two side by side part by part shows where they differ.
| Cost item | Cloth (box filter) | Element (vacuum purifier) |
|---|---|---|
| Purchase price | Counted per piece, low unit price | Counted per element, high unit price |
| Replacement interval | Directly related to the volume treated and the level of contamination | Related to the pressure drop management and to the accuracy required |
| Work involved in the change | The frames have to be washed and the cloth fitted again | Removing and refitting the end cover, fitting the new element, resetting the pressure drop |
| Additional consumption | Water and cleaning agent for washing, disposal of the residue in the frames | Sealing rings, oil used for wetting, wear on the tools |
When each one is changed
- Cloth: replaced when it is damaged, when the cloth blocks and the flow falls, or when the residue in the frames can no longer be washed out.
- Element: replaced when the pressure drop approaches the alarm value or when the filtration accuracy no longer holds, and the pressure alarm value of the 150-500-5 is 0.35 MPa.
- The coarse elements 150-250-50 and 110-250-50 and the second stage element 110-400-20 are upstream consumables and are scheduled according to the level of contamination.
- Check the sealing ring whenever the element is changed; fitting the old sealing ring again eats into the saving on the change.
- Keep the quantity and the reason for every change in one ledger, and only then is the consumables account worth anything.
- Do not mix the two: spreading the cloth cost of the box filter over the running cost of the vacuum purifier gives a wrong result.
Beyond the cost there is the result
The cost of the consumables is only half of the story; the other half is the benefit that comes with the filtration accuracy. The filtration accuracy of ≤1 μm, the cleanliness of NAS 1638 class 5 and the water content of ≤3 ppm (GB/T 7600) of the ZYD-100 belong to work on insulating oil, where the cleanliness is clearly specified; the box press filter suits oil whose main contaminant is solid dirt and whose accuracy requirement is more relaxed.
The right order of decisions is therefore this: first work out which filtering method the oil and the target indicators call for, and only then work out the consumables account for that method. Doing it the other way round, comparing the prices first and choosing the machine afterwards, ends with cheap consumables being asked to deliver an accuracy they cannot reach, and neither the money nor the result is achieved.
Writing this into the spare parts plan is more useful than comparing the prices afterwards: estimate the cloth by area and by the frequency of the changes, and the elements by number and by the interval between the changes, keep the two kinds of consumption in their own ledgers, and then the quantity and the reason are both clear when the order is placed.
The consumables account has to be worked out in its own way: cloth is compared by unit price, elements by life, and the two are not on the same sheet.
