Relational Investors SC 13D/A SPX / RELATIONAL INVESTORS ownership change

Exhibit B

JOINT FILING AGREEMENT

In accordance with Rule 13d-l(k) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the common stock, $10.00 par value, of SPX Corporation and further agree that this Joint Filing Agreement be included as an Exhibit to such joint filing.  In evidence thereof, the undersigned hereby execute this Agreement this 25th day of March, 2013.

RELATIONAL INVESTORS MID-CAP FUND I, L.P.
RELATIONAL INVESTORS MID-CAP FUND II, L.P.
RELATIONAL FUND PARTNERS, L.P.
RELATIONAL COAST PARTNERS, L.P.
RELATIONAL INVESTORS IX, L.P.
RELATIONAL INVESTORS XV, L.P.
RELATIONAL INVESTORS XVI, L.P.
RELATIONAL INVESTORS XX, L.P.
RELATIONAL INVESTORS XXIII, L.P.

By:	RELATIONAL INVESTORS, LLC
	as general partner to each,

	By:	/s/ Ralph V. Whitworth
		Ralph V. Whitworth, Principal
RELATIONAL INVESTORS, LLC
	By:	/s/ Ralph V. Whitworth
		Ralph V. Whitworth, Principal
/s/ Ralph V. Whitworth
Ralph V. Whitworth
/s/ David H. Batchelder
David H. Batchelder