Exhibit 3.15


                AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                               J.B. SMITH MFG CO.



TO THE SECRETARY OF STATE OF THE STATE OF OKLAHOMA:

         J.B. Smith Mfg Co. (the "Corporation"), a corporation organized and
existing under and by virtue of the Oklahoma General Corporation Act (the
"Act"), for the purposes of amending and restating its certificate of
incorporation, does hereby submit the following:

A.       The name of the Corporation is J.B. Smith Mfg Co. The name under which
         the Corporation was originally incorporated is Preferred Pipe Products,
         Inc.

B.       The original Certificate of Incorporation of the Corporation was filed
         with the Secretary of State of Oklahoma on March 3, 1989 (as amended
         from time to time, the "Certificate of Incorporation").

C.       This Amended and Restated Certificate of Incorporation was duly adopted
         in accordance with the provisions of Section 1080 of the Act after
         being adopted and approved by the directors and shareholders.

D.       The Certificate of Incorporation is hereby restated to read in its
         entirety as follows:

                                    ARTICLE I
                                      Name

         The name of this Corporation is:  J.B. Smith Mfg Co.

                                   ARTICLE II
                           Registered Office and Agent

         The address of the registered office of the Corporation in the State of
Oklahoma is 115 S.W. 89th Street, Oklahoma City, OK 73139-8511. The
Corporation's registered agent at such address is Corporation Service Company.

                                   ARTICLE III
                                    Duration

         The duration of the Corporation is perpetual.




                                   ARTICLE IV
                                    Purposes

         The purpose of this Corporation is to engage in any lawful act or
activity for which corporations may be organized under the Act.

                                    ARTICLE V
                               Authorized Capital

         The total number of shares of capital stock which the Corporation has
authority to issue is one thousand (1,000), all of which is designated as Common
Stock par value $1.00 per share.

                                   ARTICLE VI
                           Attributes of Capital Stock

         Each share of Common Stock shall be equal to each other share of Common
Stock and, when issued, shall be fully paid and nonassessable, and the private
property of shareholders shall not be liable for corporate debts. The holders of
Common Stock of the Corporation shall each be entitled to share in any dividends
of the Corporation ratably, if, as, and when declared by the Board of Directors.

         Each holder of record of Common Stock shall have one vote for each
share of Common Stock outstanding in his name on the books of the Corporation
and shall be entitled to vote said stock.

         In the event of any voluntary or involuntary liquidation, distribution,
or winding up of the Corporation, the holders of shares of Common Stock shall be
entitled to receive all of the assets of the Corporation available for
distribution to its shareholders, ratably in proportion to the number of shares
of Common Stock held by them.

                                   ARTICLE VII
                               Board Of Directors

         The number of directors of this Corporation shall be as specified in by
the By-Laws, and such number may from time to time be increased or decreased
under the By-Laws or any amendment, or change thereof, upon resolution of the
Board of Directors. Directors and officers need not be shareholders. In case of
vacancies in the Board of Directors, including vacancies occurring by reason of
an increase in the number of Directors, a majority of the remaining members of
the Board, even though less than a quorum, may elect directors to fill such
vacancies to hold office until the next annual meeting of the shareholders.

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                                  ARTICLE VIII
                                 Indemnification

         Any person who was or is a party or is threatened to be made a party to
any threatened, pending, or completed action, suit, or proceeding, whether
civil, criminal, administrative, or investigative (whether or not by or in the
right of the Corporation) by reason of the fact that he is or was a director,
officer, incorporator, employee, or agent of the Corporation, or is or was
serving at the request of the Corporation as a director, officer, incorporator,
employee, or agent of another corporation, partnership, joint venture, trust, or
other enterprise (including an employee benefit plan), shall be entitled to be
indemnified by the Corporation to the full extent then permitted by law against
expenses (including attorneys' fees), judgments, fines (including excise taxes
assessed on a person with respect to an employee benefit plan), and amounts paid
in settlement incurred by him in connection with such action, suit, or
proceeding; provided, however, that the Corporation shall not indemnify any such
person in relation to matters as to which he shall be adjudged in such action,
suit or proceeding to be liable for gross negligence or willful misconduct, or
to have not acted in good faith and in a manner he reasonably believed to be in
or not opposed to the best interests of the Corporation. Such right of
indemnification shall inure whether or not the claim asserted is based on
matters which antedate the adoption of this Article VIII. Such right of
indemnification shall continue as to a person who has ceased to be a director,
officer, incorporator, employee, or agent and shall inure to the benefit of the
heirs and personal representatives of such a person. The indemnification
provided by this Article VIII shall not be deemed exclusive of any other rights
which may be provided now or in the future under any provisions currently in
effect or hereafter adopted by the By-Laws, by any agreement, by vote of
stockholders, by resolution of disinterested directors, by provision of law, or
otherwise.

                                   ARTICLE VIV
                             Exculpatory Provisions

         No director of the Corporation shall be liable to the Corporation or
any of its shareholders for monetary damages for breach of fiduciary duty as a
director, except for liability (i) for any breach of the director's duty of
loyalty to the Corporation or its stockholders, (ii) for acts or omissions not
in good faith or which involve intentional misconduct or a knowing violation of
law, (iii) under Section 1053 of the Oklahoma General Corporation Act, or (iv)
for any transaction from which the director derived an improper personal
benefit.


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         IN WITNESS WHEREOF, the Corporation has caused this Certificate to be
signed by its Chief Executive Officer and attested to by its assistant secretary
this 4th day of August, 2004.

                                                    J.B. Smith Mfg Co. an
                                                         Oklahoma Corporation


                                                    By: /s/ Dale B. Smith
                                                        ------------------------
                                                        Dale B. Smith
                                                        Chief Executive Officer


ATTEST:

/s/ Darrell Jean
- ------------------------------------
Darrell Jean
Assistant Secretary