D&S segment sales improved by 29% to $77.2 million for the fourth quarter of 2010, compared with $59.8 million for the same quarter in the prior year. The increase in sales was largely due to improved volume across most product lines, especially in China. We continue to see strong order trends in all market segments led by our industrial gas customers. D&S gross profit margin declined to 28% in the quarter compared with 32% a year ago largely due to higher material costs and warranty expense.
BioMedical segment sales improved 50% to $39.6 million for the fourth quarter of 2010, compared with $26.4 million for the same quarter in the prior year. This increase is largely due to the acquisition of Covidien's oxygen therapy business, which closed in late November 2009. BioMedical gross profit margin increased to 45% in the quarter compared with 33% for the same period in 2009. Favorable volume and mix in the current quarter and higher restructuring-related costs in the prior year quarter impacted margins including higher cost of sales due to the write-up of inventory to fair value in the Covidien transaction. BioMedical's fourth quarter gross profit margin was higher than the profit margins in all prior quarters in 2010, as the prior quarters included significant restructuring and acquisition-related costs.
Global markets are expected to continue their recovery during 2011 with the return of significant project work in our E&C business and continued growth in LNG-related orders in our D&S business. Order rates improved throughout 2010, and this is expected to continue in 2011. Based on our current backlog and order expectations, 2011 net sales are expected to be in a range of $710 to $750 million. Diluted earnings per share for 2011 are expected to be in a range of $1.50 to $1.70 per share based on approximately 29.5 million weighted average shares outstanding. Included in our 2011 earnings estimates are approximately $0.20 per diluted share for anticipated restructuring charges for the recently completed SeQual acquisition and trailing costs associated with the shutdown of the Plainfield, Indiana facility acquired from Covidien. Excluding these charges, earnings would be expected to fall in a range of $1.70 to $1.90 per share.