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                                                                     EXHIBIT 4.6

                          FIRST SUPPLEMENTAL INDENTURE



                  THIS FIRST SUPPLEMENTAL INDENTURE (this " First Supplemental
Indenture"), dated as of June 4, 2001, among Dresser Entech, Inc., and Ring-O
Valve, Incorporated (each, a "Guaranteeing Subsidiary" and collectively, the
"Guaranteeing Subsidiaries"), subsidiaries of Dresser, Inc. (or its permitted
successor), a Delaware corporation (the "Company"), the Company, the other
Guarantors (as defined in the Indenture referred to herein) and State Street
Bank and Trust Company, as trustee under the indenture referred to below (the
"Trustee").

                                   WITNESSETH:

                  WHEREAS, the Company has heretofore executed and delivered to
the Trustee an indenture (the "Indenture"), dated as of April 10, 2001 providing
for the issuance of an aggregate principal amount of up to $300,000,000 million
of 9 3/8% Senior Subordinated Notes due 2011 (the "Notes");

                  WHEREAS, the Indenture provides that under certain
circumstances each Guaranteeing Subsidiary shall execute and deliver to the
Trustee a supplemental indenture pursuant to which each Guaranteeing Subsidiary
shall unconditionally guarantee all of the Company's Obligations under the Notes
and the Indenture on the terms and conditions set forth herein (the
"Guarantee"); and

                  WHEREAS, pursuant to Section 9.01 of the Indenture, the
Trustee is authorized to execute and deliver this First Supplemental Indenture.

                  NOW THEREFORE, in consideration of the foregoing and for other
good and valuable consideration, the receipt of which is hereby acknowledged,
each Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

                  1. CAPITALIZED TERMS. Capitalized terms used herein without
definition shall have the meanings assigned to them in the Indenture.

                  2. AGREEMENT TO GUARANTEE. Each Guaranteeing Subsidiary hereby
agrees as follows:

                     (a)     Along with all Guarantors named in the Indenture,
                             to jointly and severally Guarantee to each Holder
                             of a Note authenticated and delivered by the
                             Trustee and to the Trustee and its successors and
                             assigns, irrespective of the validity and
                             enforceability of the Indenture, the Notes or the
                             obligations of the Company hereunder or thereunder,
                             that:


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                             (i) the principal of and interest on the Notes will
                     be promptly paid in full when due, whether at maturity, by
                     acceleration, redemption or otherwise, and interest on the
                     overdue principal of and interest on the Notes, if any, if
                     lawful, and all other obligations of the Company to the
                     Holders or the Trustee hereunder or thereunder will be
                     promptly paid in full or performed, all in accordance with
                     the terms hereof and thereof; and

                             (ii) in case of any extension of time of payment or
                     renewal of any Notes or any of such other obligations, that
                     same will be promptly paid in full when due or performed in
                     accordance with the terms of the extension or renewal,
                     whether at stated maturity, by acceleration or otherwise.
                     Failing payment when due of any amount so guaranteed or any
                     performance so guaranteed for whatever reason, the
                     Guarantors shall be jointly and severally obligated to pay
                     the same immediately.

                     (b)     The obligations hereunder shall be unconditional,
                             irrespective of the validity, regularity or
                             enforceability of the Notes or the Indenture, the
                             absence of any action to enforce the same, any
                             waiver or consent by any Holder of the Notes with
                             respect to any provisions hereof or thereof, the
                             recovery of any judgment against the Company, any
                             action to enforce the same or any other
                             circumstance which might otherwise constitute a
                             legal or equitable discharge or defense of a
                             guarantor.

                     (c)     The following is hereby waived: diligence,
                             presentment, demand of payment, filing of claims
                             with a court in the event of insolvency or
                             bankruptcy of the Company, any right to require a
                             proceeding first against the Company, protest,
                             notice and all demands whatsoever.

                     (d)     This Guarantee shall not be discharged except by
                             complete performance of the obligations contained
                             in the Notes and the Indenture or pursuant to
                             Section 6 hereof.

                     (e)     If any Holder or the Trustee is required by any
                             court or otherwise to return to the Company, the
                             Guarantors, or any custodian, Trustee, liquidator
                             or other similar official acting in relation to
                             either the Company or the Guarantors, any amount
                             paid by either to the Trustee or such Holder, this
                             Guarantee, to the extent theretofore discharged,
                             shall be reinstated in full force and effect.

                     (f)     No Guaranteeing Subsidiary shall be entitled to any
                             right of subrogation in relation to the Holders in
                             respect of any obligations guaranteed hereby until
                             payment in full of all obligations guaranteed
                             hereby.


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                     (g)     As between the Guarantors, on the one hand, and the
                             Holders and the Trustee, on the other hand, (x) the
                             maturity of the obligations guaranteed hereby may
                             be accelerated as provided in Article 6 of the
                             Indenture for the purposes of this Guarantee,
                             notwithstanding any stay, injunction or other
                             prohibition preventing such acceleration in respect
                             of the obligations guaranteed hereby, and (y) in
                             the event of any declaration of acceleration of
                             such obligations as provided in Article 6 of the
                             Indenture, such obligations (whether or not due and
                             payable) shall forthwith become due and payable by
                             the Guarantors for the purpose of this Guarantee.

                     (h)     The Guarantors shall have the right to seek
                             contribution from any non-paying Guarantor so long
                             as the exercise of such right does not impair the
                             rights of the Holders under the Guarantee.

                     (i)     Pursuant to Section 11.03 of the Indenture, after
                             giving effect to any maximum amount and any other
                             contingent and fixed liabilities that are relevant
                             under any applicable Bankruptcy or fraudulent
                             conveyance laws (including, without limitation, all
                             Senior Debt of such Guarantor), and after giving
                             effect to any collections from, rights to receive
                             contribution from or payments made by or on behalf
                             of any other Guarantor in respect of the
                             obligations of such other Guarantor under Article
                             11 of the Indenture shall result in the obligations
                             of such Guarantor under its Guarantee not
                             constituting a fraudulent transfer or conveyance.

                  3. SUBORDINATION. The Obligations of each Guaranteeing
Subsidiary under its Guarantee pursuant to this First Supplemental Indenture
shall be junior and subordinated to the Senior Debt of such Guaranteeing
Subsidiary on the same basis as the Notes are junior and subordinated to the
Senior Debt of the Company. For the purposes of the foregoing sentence, the
Trustee and the Holders shall have the right to receive and/or retain payments
by such Guaranteeing Subsidiary only at such time as they may receive and/or
retain payments in respect of the Notes pursuant to the Indenture, including
Article 10 thereof.

                  4. EXECUTION AND DELIVERY. Each Guaranteeing Subsidiary agrees
that the Guarantees shall remain in full force and effect notwithstanding any
failure to endorse on each Note a notation of such Guarantee.

                  5. Guaranteeing Subsidiary May Consolidate, Etc. on Certain
Terms.

                     (a)     No Guaranteeing Subsidiary may consolidate with or
                             merge with or into (whether or not such Guarantor
                             is the surviving Person) another corporation,
                             Person or entity whether or not affiliated with
                             such Guarantor unless:


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                             (i) subject to Section 11.05 of the Indenture, the
                     Person formed by or surviving any such consolidation or
                     merger (if other than a Guarantor or the Company) shall be
                     a corporation organized and validly existing under the laws
                     of the United States or any state thereof or the District
                     of Columbia, and unconditionally assumes all the
                     obligations of such Guarantor, pursuant to a supplemental
                     indenture in form and substance reasonably satisfactory to
                     the Trustee, under the Notes, the Indenture and the
                     Guarantee on the terms set forth herein or therein;

                             (ii) immediately after giving effect to such
                     transaction, no Default or Event of Default exists; and

                             (iii) the Company would be permitted, immediately
                     after giving effect to such transaction, to incur at least
                     $1.00 of additional Indebtedness (other than Permitted
                     Indebtedness) pursuant to Section 4.09 of the Indenture.

                     (b)     In case of any such consolidation, merger, sale or
                             conveyance and upon the assumption by the successor
                             Person, by supplemental indenture, executed and
                             delivered to the Trustee and satisfactory in form
                             to the Trustee, of the Guarantee endorsed upon the
                             Notes and the due and punctual performance of all
                             of the covenants and conditions of the Indenture to
                             be performed by the Guarantor, such successor
                             Person shall succeed to and be substituted for the
                             Guarantor with the same effect as if it had been
                             named herein as a Guarantor. Such successor Person
                             thereupon may cause to be signed any or all of the
                             Guarantees to be endorsed upon all of the Notes
                             issuable hereunder which theretofore shall not have
                             been signed by the Company and delivered to the
                             Trustee. All the Guarantees so issued shall in all
                             respects have the same legal rank and benefit under
                             the Indenture as the Guarantees theretofore and
                             thereafter issued in accordance with the terms of
                             the Indenture as though all of such Guarantees had
                             been issued at the date of the execution hereof.

                     (c)     Except as set forth in Articles 4 and 5 of the
                             Indenture, and notwithstanding clauses(a)(iii)
                             above, nothing contained in the Indenture or in any
                             of the Notes shall prevent any consolidation or
                             merger of a Guarantor with or into the Company or
                             another Guarantor, or shall prevent any sale or
                             conveyance of the property of a Guarantor as an
                             entirety or substantially as an entirety to the
                             Company or another Guarantor.

                  6. RELEASES. In the event of a sale or other disposition of
all of the assets of any Guarantor, by way of merger, consolidation or
otherwise, or a sale or other disposition of all to the capital stock of any
Guarantor, then such Guarantor (in the event of a sale or other disposition, by
way of merger, consolidation or otherwise, of all of the capital stock of such


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Guarantor) or the corporation acquiring the property (in the event of a sale or
other disposition of all or substantially all of the assets of such Guarantor)
will be released and relieved of any obligations under its Guarantee; provided
that the Net Cash Proceeds of such sale or other disposition are applied in
accordance with the applicable provisions of the Indenture, including without
limitation Section 4.10 of the Indenture. Upon delivery by the Company to the
Trustee of an Officers' Certificate and an Opinion of Counsel to the effect that
such sale or other disposition was made by the Company in accordance with the
applicable provisions of the Indenture, including without limitation Section
4.10 of the Indenture, the Trustee shall execute any documents reasonably
required in order to evidence the release of any Guarantor from its obligations
under its Guarantee.

                  Any Guarantor not released from its obligations under its
Guarantee shall remain liable for the full amount of principal of and interest
on the Notes and for the other obligations of any Guarantor under the Indenture
as provided in Article 11 of the Indenture.

                  7. NO RECOURSE AGAINST OTHERS. No past, present or future
director, officer, employee, incorporator, stockholder or agent of any
Guaranteeing Subsidiary, as such, shall have any liability for any obligations
of the Company or any Guaranteeing Subsidiary under the Notes, any Guarantees,
the Indenture or this First Supplemental Indenture or for any claim based on, in
respect of, or by reason of, such obligations or their creation. Each Holder of
the Notes by accepting a Note waives and releases all such liability. The waiver
and release are part of the consideration for issuance of the Notes. Such waiver
may not be effective to waive liabilities under the federal securities laws and
it is the view of the Commission that such a waiver is against public policy.

                  8. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF
NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS FIRST SUPPLEMENTAL INDENTURE
WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT
THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED
THEREBY.

                  9. COUNTERPARTS. The parties may sign any number of copies of
this First Supplemental Indenture. Each signed copy shall be an original, but
all of them together represent the same agreement.

                  10. EFFECT OF HEADINGS. The Section headings herein are for
convenience only and shall not affect the construction hereof.

                  11. THE TRUSTEE. The Trustee shall not be responsible in any
manner whatsoever for or in respect of the validity or sufficiency of this First
Supplemental Indenture or for or in respect of the recitals contained herein,
all of which recitals are made solely by each Guaranteeing Subsidiary and the
Company. IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed and attested, all as of the date
first above written.


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Dated:  June 4, 2001


                                DRESSER ENTECH, INC.



                                By: /s/ Frank P. Pittman
                                   --------------------------------------
                                Name: Frank P. Pittman
                                Title: Vice President and Asst. Secretary

                                RING-O VALVE,  INCORPORATED


                                By: /s/ Frank P. Pittman
                                   --------------------------------------
                                Name: Frank P. Pittman
                                Title: Vice President and Asst. Secretary


                                STATE STREET BANK AND TRUST COMPANY, as Trustee


                                By: /s/ Philip G. Kane Jr.
                                   -----------------------------------------
                                Name: Philip G. Kane Jr.
                                Title: Vice President