<PAGE>   1


                                                                    Exhibit 10.1

                       FIRST AMENDMENT TO CREDIT AGREEMENT

         THIS FIRST AMENDMENT TO CREDIT AGREEMENT (this "Amendment") dated as of
June 4, 1998, is by and among Daniel Industries, Inc., a Delaware corporation
(the "Borrower"), Bank One, Texas, NA ("Bank One"), Chase Bank of Texas,
National Association (f/k/a Texas Commerce Bank National Association) ("Chase"),
CIBC Inc., Credit Lyonnais New York Branch, and the other lenders from time to
time parties hereto (each a "Lender" and collectively, the "Lenders"), Bank One,
as administrative agent for the Lenders (in such capacity, the "Agent") and
Chase, as co-agent for the Lenders (in such capacity, the "Co-Agent").

                                   WITNESSETH:

         WHEREAS, the Borrower, the Lenders, the Agent and the Co-Agent have
entered into that certain Credit Agreement dated as of November 19, 1997, as
amended by that certain letter agreement dated March 3, 1998 (the "Credit
Agreement"), pursuant to which the Lenders have made and agreed to make Loans to
the Borrower and issued and agreed to issue Letters of Credit for the account of
the Borrower; and

         WHEREAS, the Borrower, the Lenders, the Agent and the Co-Agent desire
to further amend the Credit Agreement as hereinafter set forth;

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein contained, the Borrower, the Lenders, the Agent and the
Co-Agent hereby agree as follows:

         1.       AMENDMENTS TO CREDIT AGREEMENT.

                  (a)      Section 6.13(i) is hereby amended by adding the
                           clause ", any Liens securing Indebtedness permitted
                           by Section 6.14(f) on assets of any such foreign
                           Subsidiary incurring any such Indebtedness" after
                           "Section 6.14(i)" in the second line thereof.

                  (b)      Section 6.14(f) is hereby deleted in its entirety and
                           the following inserted in its place:

                           "(f)     Indebtedness of any foreign Subsidiaries of
                                    the Borrower not otherwise permitted by this
                                    Section 6.14 not to exceed $15,000,000
                                    (excluding Indebtedness under undrawn
                                    letters of credit issued for the account of
                                    any such foreign Subsidiary in the ordinary
                                    course of its business but including
                                    Indebtedness listed on Schedule 6.14, to the
                                    extent applicable) in the aggregate at any
                                    time outstanding;".

         2. REAFFIRMATION OF REPRESENTATIONS AND WARRANTIES. To induce the
Lenders, the Agent and the Co-Agent to enter into this Amendment, the Borrower
hereby reaffirms, as of the




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date hereof, that its representations and warranties contained in the Credit
Agreement are true and correct in all material respects (except to the extent
such representations and warranties (x) are not so true and correct in all
material respects as a result of the transactions expressly permitted under the
Credit Agreement or under the other Credit Documents or (y) relate solely to an
earlier date) and additionally represents and warrants as follows:

                           (i)      The execution and delivery by the Borrower
                                    of this Amendment and the performance by the
                                    Borrower of its obligations under this
                                    Amendment and the Credit Agreement, as
                                    amended hereby, are within the Borrower's
                                    corporate powers, have been duly authorized
                                    by all necessary corporate action of the
                                    Borrower and do not and will not contravene
                                    any applicable provision of any law,
                                    statute, rule or regulation, or any
                                    applicable order, writ, injunction or decree
                                    of any court or governmental
                                    instrumentality, except where such
                                    contravention is not reasonably expected to
                                    have a Material Adverse Effect or conflict
                                    with or result in any breach of any term,
                                    covenant, condition or other provision of,
                                    or constitute a default under (except where
                                    such conflict, breach or default is not
                                    reasonably expected to have a Material
                                    Adverse Effect), or result in the creation
                                    or imposition of (or the obligation to
                                    create or impose) any Lien other than any
                                    Permitted Lien upon any of the property or
                                    assets of the Borrower or any of its
                                    Subsidiaries under the terms of any
                                    contractual obligation to which the Borrower
                                    or any of its Subsidiaries is a party or by
                                    which it or any of its properties or assets
                                    are bound or to which it may be subject, or
                                    violate or conflict with any provision of
                                    the Certificate of Incorporation or Bylaws
                                    of the Borrower;

                           (ii)     The execution and delivery by the Borrower
                                    of this Amendment have received all
                                    necessary governmental approvals or other
                                    consents (if any shall be required);

                           (iii)    This Amendment and the Credit Agreement, as
                                    amended hereby, are legal, valid and binding
                                    obligations of the Borrower enforceable
                                    against the Borrower in accordance with
                                    their terms, subject as to enforcement only
                                    to bankruptcy, insolvency, reorganization,
                                    moratorium or other similar laws affecting
                                    the enforcement of creditors' rights
                                    generally and by general principles of
                                    equity, regardless of whether in a
                                    proceeding in equity or at law;

                           (iv)     There are no lawsuits (including, without
                                    limitation, derivation or injunctive
                                    actions), arbitration proceedings or
                                    governmental proceedings pending or, to the
                                    best knowledge of the Borrower,

 
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                                    threatened, involving the Borrower or any of
                                    its Subsidiaries except as disclosed in
                                    Schedule 5.4 to the Credit Agreement and
                                    except for such lawsuits or other
                                    proceedings which are not reasonably
                                    expected to have a Material Adverse Effect;

                           (v)      No Default or Event of Default has occurred
                                    and is continuing; and

                           (vi)     There have been no amendments to the
                                    Certificate of Incorporation or Bylaws of
                                    the Borrower since November 19, 1997.

         3. REAFFIRMATION OF CREDIT AGREEMENT. This Amendment shall be deemed to
be an amendment to the Credit Agreement, and the Credit Agreement, as amended
hereby, is hereby ratified, approved and confirmed in each and every respect.
All references to the Credit Agreement in the Credit Agreement and the other
Credit Documents (excluding this Amendment) shall hereafter be deemed to refer
to the Credit Agreement, as amended hereby.

         4. DEFINED TERMS. Terms used but not defined herein when defined in the
Credit Agreement shall have the same meanings herein unless the context
otherwise requires.

         5. GOVERNING LAW; SUBMISSION TO JURISDICTION; WAIVER OF JURY TRIAL.

                  (A) THIS AMENDMENT AND THE OTHER CREDIT DOCUMENTS, AND THE
RIGHTS AND DUTIES OF THE PARTIES HERETO AND THERETO, SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE INTERNAL LAWS OF THE STATE OF TEXAS.

                  (B) TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, THE
PARTIES HERETO AGREE THAT ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER,
OR IN CONNECTION WITH, THIS AMENDMENT OR ANY OTHER CREDIT DOCUMENT, OR ANY
COURSE OF CONDUCT, COURSE OF DEALING, STATEMENT (WHETHER VERBAL OR WRITTEN) OR
ACTIONS OF THE LENDERS OR THE BORROWER MAY BE BROUGHT AND MAINTAINED IN THE
COURTS OF THE STATE OF TEXAS SITTING IN HARRIS COUNTY OR THE UNITED STATES
DISTRICT COURT FOR THE SOUTHERN DISTRICT OF TEXAS. TO THE FULLEST EXTENT
PERMITTED BY APPLICABLE LAW, THE BORROWER, THE LENDERS, THE AGENT AND THE
CO-AGENT HEREBY EXPRESSLY AND IRREVOCABLY SUBMIT TO THE JURISDICTION OF THE
COURTS OF THE STATE OF TEXAS AND THE UNITED STATES DISTRICT COURT FOR THE
SOUTHERN DISTRICT OF TEXAS FOR THE PURPOSE OF ANY SUCH LITIGATION AS SET FORTH
ABOVE AND IRREVOCABLY AGREES TO BE BOUND BY ANY JUDGMENT RENDERED THEREBY IN
CONNECTION WITH SUCH LITIGATION. TO THE FULLEST EXTENT PERMITTED BY APPLICABLE
LAW, EACH OF THE BORROWER, THE LENDERS, THE AGENT AND THE CO-AGENT FURTHER
IRREVOCABLY

 
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CONSENTS TO THE SERVICE OF PROCESS, BY REGISTERED MAIL, POSTAGE PREPAID, OR BY
PERSONAL SERVICE WITHIN OR WITHOUT THE STATE OF TEXAS. TO THE FULLEST EXTENT
PERMITTED BY APPLICABLE LAW, EACH OF THE BORROWER, THE LENDERS, THE AGENT AND
THE CO-AGENT HEREBY EXPRESSLY AND IRREVOCABLY WAIVES ANY OBJECTION WHICH IT MAY
HAVE OR HEREAFTER MAY HAVE TO THE LAYING OF VENUE OF ANY SUCH LITIGATION BROUGHT
IN ANY SUCH COURT REFERRED TO ABOVE AND ANY CLAIM THAT ANY SUCH LITIGATION HAS
BEEN BROUGHT IN AN INCONVENIENT FORUM. TO THE EXTENT THAT THE BORROWER, ANY
LENDER, THE AGENT OR THE CO-AGENT HAS OR HEREAFTER MAY ACQUIRE ANY IMMUNITY FROM
JURISDICTION OF ANY COURT OR FROM ANY LEGAL PROCESS (WHETHER THROUGH SERVICE OF
NOTICE, ATTACHMENT PRIOR TO JUDGMENT, ATTACHMENT IN AID OF EXECUTION OR
OTHERWISE) WITH RESPECT TO ITSELF OR ITS PROPERTY, SUCH PERSON HEREBY
IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, SUCH
IMMUNITY IN RESPECT OF ITS OBLIGATIONS UNDER THIS AMENDMENT AND THE OTHER CREDIT
DOCUMENTS.

                  (C) TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, EACH
PARTY HERETO WAIVES ANY RIGHT TO A TRIAL BY JURY IN ANY ACTION OR PROCEEDING TO
ENFORCE OR DEFEND ANY RIGHTS UNDER THIS AMENDMENT, THE CREDIT AGREEMENT, ANY
OTHER CREDIT DOCUMENT OR UNDER ANY AMENDMENT, INSTRUMENT, DOCUMENT OR AGREEMENT
DELIVERED OR WHICH MAY IN THE FUTURE BE DELIVERED IN CONNECTION HEREWITH OR
THEREWITH OR ARISING FROM ANY BANKING RELATIONSHIP EXISTING IN CONNECTION WITH
THIS AMENDMENT, THE CREDIT AGREEMENT, ANY OTHER CREDIT DOCUMENT OR UNDER ANY
AMENDMENT, INSTRUMENT, DOCUMENT OR AGREEMENT DELIVERED OR WHICH MAY IN THE
FUTURE BE DELIVERED IN CONNECTION HEREWITH OR THEREWITH AND AGREES THAT ANY SUCH
ACTION OR PROCEEDING SHALL BE TRIED BEFORE A COURT AND NOT BEFORE A JURY.

         6. COUNTERPARTS. This Amendment may be executed in any number of
counterparts, and by the different parties on different counterpart signature
pages, each of which when executed shall be deemed an original, but all such
counterparts taken together shall constitute one and the same Amendment.

         7. SEVERABILITY. Any provision of this Amendment that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.


 
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         8. HEADINGS. Section headings used in this Amendment are for reference
only and shall not affect the construction of this Amendment.

         9. NOTICE OF ENTIRE AGREEMENT. This Amendment, together with the other
Credit Documents, constitute the entire understanding among the Borrower, the
Lenders, the Agent and the Co-Agent and supersede all earlier or contemporaneous
agreements, whether written or oral, concerning the subject matter of the Credit
Documents. THIS WRITTEN AMENDMENT, TOGETHER WITH THE OTHER CREDIT DOCUMENTS,
REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED
BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE
PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

         IN WITNESS WHEREOF, the parties hereto have entered into this First
Amendment to Credit Agreement as of the date first written above.

                                     BORROWER:

                                     DANIEL INDUSTRIES, INC.,
                                     a Delaware corporation


                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------




 
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                                     LENDERS:

                                     BANK ONE, TEXAS, NA, as Agent and a Lender


                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------



 
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                                     CHASE BANK OF TEXAS, NATIONAL
                                     ASSOCIATION (f/k/a TEXAS COMMERCE
                                     BANK NATIONAL ASSOCIATION), as Co-Agent
                                     and a Lender


                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------




 
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                                     CIBC INC., as a Lender


                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------


 
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                                     CREDIT LYONNAIS NEW YORK BRANCH, as a
                                     Lender


                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------





Approval was obtained from necessary bank group and this signature is not
required.

 
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                           CONSENT AND ACKNOWLEDGMENT

         Each of the undersigned Guarantors, by its signature hereto,
acknowledges and agrees to the terms and conditions of that certain First
Amendment to Credit Agreement (the "Amendment") dated as of June 4, 1998, by and
among Daniel Industries, Inc., a Delaware corporation (the "Borrower"), Bank
One, Texas, NA ("Bank One"), Chase Bank of Texas, National Association (f/k/a
Texas Commerce Bank National Association) ("Chase"), CIBC Inc., Credit Lyonnais
New York Branch, and the other lenders from time to time parties hereto
(collectively, the "Lenders"), Bank One, as administrative agent for the Lenders
(in such capacity, the "Agent") and Chase, as co-agent for the Lenders (in such
capacity, the "Co-Agent"). Each of the undersigned acknowledges and reaffirms
its obligations under its Guaranty dated November 19, 1997 (collectively, the
"Guaranties"), and agrees that the Guaranties shall remain in full force and
effect. Although the undersigned Guarantors have been informed by the Company of
the matters set forth in the Amendment, and the undersigned have acknowledged
and agreed to same, the undersigned understand neither the Agent, the Co-Agent
nor any of the Lenders have any duty to notify any of the Guarantors of, or to
seek any of the Guarantor's acknowledgment or agreement to, the Amendment, and
nothing contained herein shall create such a duty as to any transactions
hereafter.

         Dated as of June 4, 1998.

                                     DANIEL MEASUREMENT AND CONTROL,
                                     INC.
                                     DANIEL VALVE COMPANY
                                     BETTIS CORPORATION
                                     SHAFER VALVE COMPANY



                                     By:
                                        -------------------------------
                                     Name:
                                          -----------------------------
                                     Title:
                                           ----------------------------


 
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