Robotics revenues decreased $7.2 million, or 14%, in the third quarter 2021 compared to the third quarter 2020. The decrease in revenues year over year was due to fewer vessel days as well as a reduction in trenching activity compared to the third quarter 2020. Vessel days during the third quarter 2021 decreased to 358 compared to 450 during the third quarter 2020, with fewer days working seabed clearance. Vessel days during the third quarter 2021 included 77 spot vessel days performing ROV support work for a telecom project offshore Guyana and 99 spot vessel days performing seabed clearance work , compared to 196 spot vessel days performing seabed clearance work and 95 spot vessel days performing other projects during the third quarter 2020. Chartered vessel utilization increased to 99% during the third quarter 2021 compared to 95% during the third quarter 2020. Total ROV, trencher and ROVDrill utilization was 43% in the third quarter 2021 compared to 37% in the third quarter 2020, with 90 trenching days in the third quarter 2021 compared to 154 days in the third quarter 2020. Robotics income from operations declined $2.0 million in the third quarter 2021 compared to the third quarter 2020 due to lower revenues year over year.
Production Facilities
Production Facilities revenues increased $4.3 million, or 31%, in the third quarter 2021 compared to the previous quarter primarily due to higher oil and gas production and prices during the third quarter 2021. Production Facilities revenues increased $4.4 million, or 31%, in the third quarter 2021 compared to the third quarter 2020 due to higher oil and gas production and prices and higher revenues from the HFRS during the third quarter 2021.
Selling, General and Administrative and Other
Selling, General and Administrative
Selling, general and administrative expenses were $13.3 million, or 7.4% of revenue, in the third quarter 2021 compared to $13.4 million, or 8.3% of revenue, in the previous quarter.
Other Income and Expenses
Other expense, net was $4.0 million in the third quarter 2021 compared to other income, net of $1.0 million in the previous quarter. Other expense, net includes unrealized foreign currency losses related to the British pound, which weakened approximately 3% during the third quarter 2021.
Cash Flows
Operating cash flows were $28.7 million in the third quarter 2021 compared to $52.7 million in the previous quarter and $52.6 million in the third quarter 2020. The decrease in operating cash flows quarter over quarter was primarily due to increases working capital outflows, offset in part by tax refunds of $12.4 million related to the CARES Act received during the third quarter 2021. The decrease in operating cash flows year over year was due to lower earnings, offset in part by working capital inflows, which include the tax refund related to the CARES Act received during the third quarter 2021.
Capital expenditures totaled $0.6 million in the third quarter 2021 compared to $5.4 million in the previous quarter and $1.6 million in the third quarter 2020. Free cash flow was $28.1 million in the third quarter 2021 compared to $47.2 million in the previous quarter and $51.4 million in the third quarter 2020. The decreases in free cash flow quarter over quarter and year over year were due primarily to lower operating cash flows in the third quarter 2021. (Free cash flow is a non-GAAP measure. See reconciliation below.)
Financial Condition and Liquidity
Cash and cash equivalents were $237.5 million at September 30, 2021 and excluded $71.3 million of restricted cash pledged as collateral on a short-term project-related letter of credit. During the third quarter 2021, we terminated our previous credit agreement, which was scheduled to expire December 31, 2021, and entered into an $80.0 million asset-based revolving credit facility (“ABL facility”). Available capacity under our ABL facility was $69.6 million at September 30, 2021. Long-term debt decreased to $304.5 million at September 30, 2021 from $335.7 million at June 30, 2021 following our repayment of the term loan associated with our previous credit agreement. Negative net debt at September 30, 2021 was $4.3 million.
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