IMPORTANT: Since we first supplied these balls in 1986 there has been a notable diminution
of the requirement for rubber coated balls. This means that it is no longer viable for us
(or others - one USA competitor has pulled out) to supply from stock a wide range of products.
In general, we now make to order, with a lead time of not less than 4 weeks. This may shift
the emphasis to uncoated balls, where the lead time is typically 7 days.
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Function: To act as fluid diverters so that active ingredients such as acids or proppants are
diverted from a high flow area of perforations to a low flow area so that the low flow area gets
the treatment. Used with coil tubing and in other downhole squeeze applications.
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Materials: Benoil's consist of a core based on epoxy resins with suitable light- and heavy-weight
fillers to achieve the desired specific gravity. Balls may then be overmoulded with either
nitrile or fluorocarbon (eg FCR) rubber. Not all diverter balls are so covered however. Nitrile
coated balls are suitable for use to approximately 100°C or for short periods to 120°C. FCR
coated balls are suitable for use to approximately 180°C - the limitation is not in the FCR but
in the epoxy core.
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Other materials could be used, such as phenolics or nylons etc, but the volume required has
never warranted our manufacture.
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There are many possible epoxy resin combinations. The standard series are based on room temperature
curing systems. We can also use a hot cure resin which takes longer to process and is more
difficult to handle. The latter has a higher Deflection Temperature under Load (up to 140°C
rather than 96°C), a higher recommendable operating temperature, and a better compressive
strength. Because the balls are highly filled systems, their values are not those of the unfilled
resins; and because the composition is different for each ball size (in the coated series) and
for each specific gravity, we have not undertaken the determination of exact values. We have
used the hot cure system for the FCR coated balls, and could use it for uncoated balls, if the
application justifies it. Please ask.
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Identification: We formerly colour coded to identify SG fractions, but when these were refined
to 0.05 this became impossible as the range expanded. We have renumbered this section as it
has been expanded.
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We can make to any required practical specification on request, subject to determination. We now
list SG values to 1.95; we could produce higher values if ever required. If rubber overmoulding
is required, this adds considerably to time (and cost), whereas we can produce, and have produced,
uncoated balls within a few days. We will produce only a few if requested, but at proportionate
cost. The largest so far produced is a 3" diameter uncoated drop ball of SG 1.2; the lightest is
a nitrile coated ball of SG 0.8 and the densest a Viton coated ball of SG 1.8.
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Testing: The pressure test to which sample balls have been subjected involved loading 125kg on
to 3 cores sandwiched between 2 metal plates at ambient temperature for 24 hours. The contact
area was estimated, and thus a pressure was estimated at greater than 10000psi. The balls showed
no deformation damage other than a slight flattening at the contact point. However, it has also
been claimed that, when squeezed against an orifice, the ring of deformation damage on a coated
ball caused by a pressure of 3000+psi was enough to prevent perfect sealing when back- floated
and then refloated into place. These are not incompatible results and uncoated cores not
subjected to the heat and pressure used in moulding are, probably, stronger.
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Not only that, but the forces in the two tests are not exerted in the same way and it is possible
to show theoretically that greater damage is likely for a ball squeezed against an orifice.
Indeed, because of this difference, it is not merely the compressive strength which matters; ball
cohesion also reflects the tensile strength, though not in simple fashion. Further, the size and
nature of the orifice considerably affect the likelihood of damage to a ball. We therefore
recommend that, where possible in use, a substantial safety margin be allowed for after due
calculation of the geometry of the system. If this understanding is relevant in your well
development, please ask and we will try to indicate the optimum system.
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Sizes: We list the finished ball diameter in inches and its specific gravity. While all ball
sizes have a full range of SG in the uncoated form, this is not so for coated balls. The amount
and density of the rubber coating prevents the creation of the lower SG balls with any strength
in the smaller sizes; borderline vales are marked *** and incur a premium.
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Prices: These are given in the paper catalogue for quantities of 200 upward in units of 25 or
50 packed to order, otherwise in 100s. If you want fewer than 200, that is possible; a single
special uncoated ball has been made, as have 3 or 4; the price in such cases has to cover all
the relevant costs.
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