The island of Oahu produces most of the economic output in the state of Hawaii. Despite its wonderful geographic location, the island has not been immune to the hardships of the recent economic recession, but has generally weathered the storm. This has been due to investment in infrastructure and residential property projects by the State of Hawaii, the Federal government, as well as the Department of Defence.
A key contributor in these projects has been the Hawala quarry. This has been in existence since the late 1940s, and is one of the biggest quarries on the island, now owned by Hawaiian Cement.
Long proud history supporting the construction industry
Hawaiian Cement, part of the Knife River Corporation, leases seven quarries on three of the main Hawaiian Islands, employing 200 people in a variety of roles. The business now operates in four divisions: cement, aggregate, ready-mix concrete and coloured concrete products, and has nine offices throughout the state. Within the aggregate division, Hawaiian Cement ranks among the three biggest aggregate suppliers in Hawaii, with the Halawa quarry being one of the largest on the island of Oahu.
Modern production began in the 1960s and, until recently, some of the equipment installed in the Halawa quarry dated back to those years. Fifty years on, the expectations of the customer base have dramatically veered towards obtaining high quality sand particle shape – demands that outdated technology could not satisfy.
Strength derived through particle shape
Particle shape has become increasingly important in the cement industry, as it is the key factor influencing sand quality and therefore concrete strength. The tighter the sand particles sit together, the fewer the number of voids, and the less water is needed. This allows for sturdier concrete, thus directly influencing the strength and durability of built roads and maximising the return on investment of a construction project. The cubicity of the sand is also essential, with the desired shape producing strength; this contrasts with round or elongated particles that can have a higher number of voids and therefore result in spongy and weaker concrete.
Although the shape of some natural sand available suited Hawaiian Cement’s expected quality standard, this particular type of sand is very scarce on the island. Additionally, the use of the Hawaiian naturally occurring sand is limited by legislation due to environmental factors. Hawaiian Cement had to therefore source it from outside the island, in this case from British Columbia, Canada. However, the need for a self-produced material, which would not harm the islands natural resources, spurred the need for developing an on-site solution to produce the required materials for concrete production.
The solution from Sandvik
Hawaiian Cement chose a CV229 impact crusher from Sandvik Construction after a demonstration of the machine in the field. This demonstration was supported by analysis of crushed particles in Sandvik’s laboratories in Sweden and Wisconsin and material flow studies through Sandvik’s Plant Designer software. Additionally, the machine is installed with a HP85 rotor, which has the lowest number of wear parts within a closed rotor of its size on the market. As Jason Macy, Vice President of Operations, Hawaiian Cement explains, “We liked the simplicity of the Sandvik crusher. Other VSIs in the market we looked into had many more parts than the Sandvik crusher.” This simplicity makes it easier to run in terms of manpower needed and a reduction in the number of spare parts stocked; both key factors in the smooth and continuous running of a complex operation.
Introduced in 2002, Sandvik’s line of autogenous crushers, of which the CV229 is one of the more recent developments, utilise a rock-lined rotor to accelerate material. This is then impacted in a highly energised rock-lined crushing chamber and it impacts with material falling through the biflow system. The crushers incorporate the Sandvik Hurricane™ rotor, which became a major breakthrough in VSI autogenous rotor design due to its decreased vibration levels and wear part design, which results in increased crusher bearing life combined with reduced maintenance. Standard Sandvik VSI crushers are fitted with a timed trapped two-key system, which ensures the safety of maintenance personnel combined with electrical isolation. Also supplied and fitted as standard are a vibration detection switch and a pre-start alarm siren.
These and other features have enabled the CV229 to deliver a very impressive performance. “Since its installation in December 2012, the machine has produced 200 000 tons, at an average rate of 40 000 tons per month. Considering the rotor wear, there is at least another 200 000 tons that can be crushed before the parts need to be replaced,” says Kevin Bohanon, Sales Manager for Sandvik Construction in the USA. Steve Pegler, Sales Manager at Elrus, Sandvik Construction’s distributor of stationary crushers in the State of Hawaii, as well as the North West of the USA, Western Canada and Ontario, explains how the high production rates at lower costs can also benefit non Sandvik crushers: “Sandvik offers a Rotor Retrofit Program, which makes it possible for customers with various makes of autogenous VSI crushers to achieve the benefits Hawaiian Cement is seeing on their CV229.”
Don Matsumura, General Manager at the Halawa quarry explained future development at the quarry; “Our goal is to get rid of importing the BC sand and produce our own number 4 product (-40 mm) with the CV229. This machine asks lots of questions of us, like the feed it needs and the moisture it can handle. We need to figure out how the rest of the plant has to work to keep up with the production rate of this new crusher. The cost of the BC sand alone, however, validates the capital expenditure as the savings the CV229 will give us comparatively in terms of production. The low parts wear further validate this investment. Changes of parts on the older models were made every month. With this one, no changes have been needed for five months.”
Adapted from press release from Sandvik
Read the article online at: https://www.worldcement.com/the-americas/17042014/updated_quarry_equipment_helps_hawaii_cement_improve_production_16/