It is buying Eberle, a German manufacturer of control devices used in heating and air-conditioning systems, and Schmidt Amaturen, an Austrian supplier of control valves and actuators used in industries such as petrochemicals, power generation, paper and food.
Eberle, a family-owned business, achieved turnover of pounds 56m in 1992 while Schmidt's sales amounted to pounds 12m last year.
Although their profits are not being disclosed, Siebe said they offered considerable scope for improved performance.
Net assets being acquired total pounds 26m.
The deals will give the group access to a wider range of advanced products and will complement its existing activities in the sector. Gestra, a Siebe subsidiary, is Schmidt's largest customer.
Colin Bonsey, Siebe's planning director, said the two businesses were being acquired because of their long- term potential.
They were unlikely to be affected by recession in Continental Europe as they exported a high proportion of their products.
The deals are being financed from the group's own resources. Siebe's net borrowings are estimated by analysts at about pounds 350m.
Barrie Stephens, Siebe's chairman and chief executive, said: 'Eberle and Schmidt strengthen considerably our activities in the temperature, appliance and industrial process control markets . . . and enlarge Siebe's existing presence in these markets presently served by Robertshaw Controls, Ranco and Foxboro.'
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