Blast performance depends on more than the explosive. The way the hole is designed and how energy is managed in the column can be the difference between clean fragmentation and inconsistent results.
Stemming plugs provide more consistent hole confinement. Options that focus on collar confinement keep the top sealed longer. At the same time, other options focus on in-column control. The right choice depends on what will deliver the biggest benefit on your site, whether that is reducing flyrock, improving collar breakage, managing wet holes or voids, or optimising powder factor and vibration.
We compare Varistem and HELIXPLUG stemming solutions based on cost, hole-diameter, mechanism, explosive compatibility, and results to help you make an informed blasting choice.
Varistem plug prices vary based on hole-diameter. You’ll find that pricing starts approximately US$1 for smaller sizes and goes up to around US$16.13 for the largest. This size-based pricing allows you to select plugs that match the actual hole-diameter, helping maintain consistent and predictable cost per hole across patterns with varying diameters.
The pricing for HELIXPLUG is provided on a quotation basis. You won’t find an MSRP list online. The product is sold in box quantities, with pricing effectively per plug but quoted per box/carton.
Varistem offers size-based unit pricing, making it easy to budget per hole across mixed patterns. In contrast, HELIXPLUG is sold via quotation in box quantities, with pricing varying by size and not publicly listed.
Varistem stemming plugs accommodate blasthole diameters ranging from 1.75″ to 10″ (approximately 45 to 251 mm) across their BP size range. This allows you to choose a plug that fits the actual drilled hole size.
HELIXPLUG is available in sizes designed to fit blasthole diameters from about 76 to 152 mm. Each size is intended to wedge securely within a specific diameter range, providing a reliable fit for most standard production holes. However, it does not currently cover very small (sub-3″ or 76.2 mm) or large-diameter (above 6″ or 152mm) holes. It is best suited for mid-range blast patterns.
Varistem offers broad diameter coverage, fitting blastholes from 1.75″ to 10″, making it suitable for everything from narrow development holes to large production blasts. HELIXPLUG stemming is optimised for mid-range hole sizes between roughly 3″ and 6″, providing a secure fit for standard blast patterns but lacking options for very small or large-diameter applications.
Varistem is compatible with a wide range of commercial explosives, including ANFO, emulsions, water gels, and heavy ANFO. The choice of explosive still depends on specific hole conditions, such as using ANFO in dry holes and switching to water-resistant products in wet or flooded conditions, along with your site’s standard blasting practices.
HELIXPLUG is suitable for use with all standard explosive types, including ANFO, emulsions, water gels, and packaged explosives. Because it functions as an inert, mechanical barrier, it does not react with the explosive material. This allows it to be used effectively in both dry and wet holes.
Both Varistem and HELIXPLUG are compatible with common commercial explosives, including ANFO, emulsions, and water gels. Varistem is typically used to enhance collar confinement across standard loading conditions. The HELIXPLUG, however, offers flexibility by enabling deck separation and bridging over wet zones, allowing dry explosives to be used above water-affected sections.
Varistem is installed point-down using a loading pole so it rests directly atop the explosive column. After placement, standard stemming material is added above it. When the blast is initiated, the initial shockwave drives the plug upward into the stemming, where its flexible, tear-resistant body wedges into place, creating a temporary pressure seal within the blasthole. This short-lived seal helps direct more explosive energy into the surrounding rock before the advancing flame front destroys the plug.
The HELIXPLUG is a stemming-and-decking plug. It is installed at a specific depth where it wedges securely against the borehole walls, without the need for inflation or activation. Once in place, it supports stemming or explosive material above it.
During detonation, the HELIXPLUG and the air gap it maintains act as a compressible barrier, redirecting more explosive energy into the surrounding rock. Its conical shape helps reduce upward gas escape and enhances radial energy distribution, improving fragmentation and blast efficiency.
The Varistem stemming plug enhances collar confinement by reacting to the blast’s shockwave. The stemming plug is driven upward to create a temporary seal, boosting energy retention at the top of the hole. In contrast, HELIXPLUG is a pre-positioned mechanical plug used to create stable air decks or deck separations within the blast column, and it can act as a stemming plug, providing a versatile option for in-column control.
Varistem reports independently verified results. At one underground platinum mine, the Varistem stemming plug was credited with improving advance per blast from 2.46 m to 2.82 m (about 15%), and the case study associated this with an estimated R1.19 billion in annual net benefit linked to improved ore recovery.
Across other sites, reports note flyrock reductions of up to 80%, an 87% improvement in cast, crusher throughput gains of more than 14%, more than US$10 million per year in added value, about US$1.45 million in savings from reduced waste, and loading rate improvements of up to 8%.
Field trials of the HELIXPLUG have shown promising performance improvements. Sites using HELIXPLUG reported up to 30% finer fragmentation, reducing oversize material and improving diggability. These performance claims are manufacturer-reported and are not independently verified.
Varistem demonstrates independently verified gains in safety, fragmentation, and downstream productivity. HELIXPLUG also shows strong potential in optimising fragmentation, but only provides data directly from the manufacturer. Both products enhance blast outcomes, with Varistem focused on collar confinement and offering flexibility for advanced blast designs.
Choose Varistem as a practical, cost-effective stemming solution that enhances collar confinement without increasing consumable expenses. Available in sizes from 1.75″ to 10″, it’s well-suited for small to mid-diameter production holes and helps crews maintain consistent collar performance across blasts. It’s best used when your primary objective is to retain explosive energy at the collar.
Choose HELIXPLUG when your blasting conditions call for more than just collar confinement. It’s ideal for situations that require air-decking and deck separation. HELIXPLUG enables precise placement of air gaps within the column, allowing you to reduce explosive use without compromising fragmentation.
If your operation demands flexibility and control within the blast hole, HELIXPLUG offers a reliable solution for enhancing performance beyond the collar.
Varistem and HELIXPLUG solve different problems in the blasthole, so your choice depends on what you need to control. Varistem is the straightforward choice when your priority is improved collar confinement and predictable, size-based costing across mixed patterns.
HELIXPLUG is better suited to blast designs that require in-column control, such as air-decking and deck separation, particularly where conditions are challenging, and the goal is to optimise explosive use and manage performance in more complex holes.
Contact us for a quote to see how your blasting team can benefit from Varistem.
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