UPDATE 2-Invensys keeps forecast but poor orders hit shares

* Still expects year to be ahead

* H1 revenue, op profit broadly in line

* Analysts say Operations Management orders raise concerns

* Shares down as much as 10 percent

(Adds CEO comments, analyst reaction, shares)

By Paul Sandle

LONDON, Nov 5 (Reuters) - British engineer Invensys Plc (ISYS.L) revealed a sharp fall in orders for its Operations Management (IOM) unit, sending its shares down as much as 10 percent to their lowest in a month.

Reporting a 15 percent drop in first-half operating profit to 102 million pounds, the group said on Thursday orders for its IOM unit from oil and gas producers and large industrial companies had fallen 23 percent year-on-year.

"We expect disappointment to centre on IOM after what has been a surprisingly weak second quarter in terms of orders," Nomura analyst Lisa Randall said in a note.