- Record Type:OSHA Instruction
- Current Directive Number:STD 03-12-003
- Old Directive Number:PUB 8-1.8
- Title:Guidelines on the Stability of Well Servicing Derricks
- Information Date:
OSHA Instruction PUB 8-1.8 July 15, 1991 Directorate of Technical Support
Subject: Guielines on the Stability of Well Servicing Derricks
A. PURPOSE. This instruction provides guidelines to Federal OSHA and Plan States compliance officers, 7(c)(1) consultants, employers, and employees on the stability of well servicing derricks.
B. SCOPE. This instruction applies OSHA-wide.
C. ACTION. Regional Administrators and Area Directors shall provide copies of the attached Guideline on the Stability of Well Servicing Derricks to the appropriate Federal an State personnel and ensure that copies are available for distribution to the public upon request.
D. FEDERAL PROGRAM CHANGE. This instruction describes a change in the Federal program for which a state response is not required. Each Regional Administrator, however, shall:
- 1. Ensure that this change is promptly forwarded to each State designee.
- 2. Explain the technical content of this change to the State as requested.
- 3. Inform the State designees that they are encouraged to make available the Guidelines to State Plan personnel and appropriate employers.
E. STATE CONSULTATION PROJECTS.
- 1. Regional Administrators shall forward a copy of this instruction to each consultation project manager and explain the technical content when requested.
- 2. Consultation Project Managers shall ensure that the information in the Guidelines is provided to appropriate employers and ensure that the copies are available for distribution to the public upon request.
F. BACKGROUND. There have been several fatalitites as a result of derrick collapses caused by the failure of temporary anchors in the oilwell drilling and servicing industry. Since OSHA has no applicable standards, in many of these incidences, our field office have attempted to cite under the General Duty clause, section 5(a)(1) of the OSHact. This action, however, may not be adequate in addressing the problem. Therefore, to assist OSHA compliance officers, State compliance and consultation personnel, employers, and employees, in the recognition of the hazard of derrick collapse due to the failure of temporary stability systems, OSHA contracted Sigma Associates, Ltd. to develop guidelines detailing the type of temporary stability systems, type of soils and its holding capacity, methods of installing guywire anchors, integrity determination of the system, actual pull testing, and acceptable parameters in liew of actual pull testing (Appendix A).
Gerard F. Scannel Assistant Secretary
Distribution: National, Regional and Area Offices All Compliance Officers State Plan Designees 7(c)(1) Consultation Project Managers NIOSH Regional Program Directors
This work was prepared under a contract to the U.S. Department of Labor, Occupational Safety and Health Administration, Directorate of Technical Support, Washington, D.C. Any mention of company or trade name is by reference only and graphic material presented is for illustration and is not an endorsement of any company or specific product by the U.S. Department of Labor or OSHA.
TABLE OF CONTENTS ___________________________________________________________________________
- Section 1: Purpose & Scope .................................... A-5
- Section 2: Industry Practices and Concensus Standards.......... A-5
- Section 3: Anchor Types ....................................... A-7
Section 4: Evaluation Criteria for Anchors and Appropriate Stability Systems .................................. A-10
- Section 5: Temporary Guywire Anchors .......................... A-16
- Section 6: Alternatives to Pull Testing ....................... A-22
- Section 7: Bibliography ...................................... A-23
- Section 8: Acknowledgements ................................... A-23
- Appendix B Rig Stability Checklist ............................ A-25
SECTION 1: PURPOSE & SCOPE
PURPOSE: The purpose of this document is ________________________________________
1) to discuss and recommend reasonable safety guidelines to guard against and minimize injury to workers and thereby provide for the protection of life, limb and property, by recommending procedures, practices, equipment and requirements;
2) to provide direction to persons concerned with, or responsible for the assuring of work-over rig stability; and
3) to assist governments and other regulatory agencies in the development of appropriate minimum safety guidelines.
SCOPE: To provide a representative basis for determining the availability, capability, dependability, reliability of Stability Systems on Land Based Work-Over Rigs and the recommended practices and procedures for their safe use.
INDUSTRY PRACTICES AND CONSENSUS STANDARDS
ASSOCIATION OF OILWELL SERVICING
ASSOCIATION OF DRILLING CONTRACTORS,
AMERICAN PETROLEUM INSTITUTE, OIL AND
GAS WELL SERVICING, STATE OF WYOMING _________________________________________
A typical double derrick with load guys in place in Figure 2-1. The sub-structure is in place and the unit properly configured to begin installation of the guying system. From this configuration determination can then be made as to the proper selection, location, configuration and holding capacity of guy anchors. Load guys should meet manufacturers recommendations. In the absence of manufacturers recommendations, the minimum wire rope diameter should not be less than that which is recommended by a representative of a major, oil field recognized, wire rope manufacturer.
*FOR FIGURE 2-1, DERRICK WITH LOAD GUYS
SEE PAGE A-5 OF PRINTED COPY OF PUB 8-1.8
FIGURE 2-2. API, AOSC, AND IADC RECOMMENDED GUYING PATTERN FOR FIGURE 2-2, SEE PRINTED COPY OF PUB 8-1.8.
FIGURE 2-3. TYPICAL INSTALLATION FROM A PLAN VIEW PERSPECTIVE FOR FIGURE 2-3, SEE PRINTED COPY OF PUB 8-1.8.
The diagram illustrated in Figure 2-2 is typical of the recommendations set forth by the American Petroleum Institute, The International Association of Drilling Contractors and The Association of Oilwell Servicing Contractors. It should be noted that API (The American Petroleum Institute) is in the process of re-assessing some of these criteria. This information will be addressed later in this document.
The Figure 2-3 shows a typical location preparation plan. The load bearing area (cross hatched area on diagram) should consist of, as a minimum, compacted sand or gravel which requires picking for removal. The area should be level and drained and provide a minimum 8000 psf bearing capacity (API Spec. 4E).
The rig location area may grade away from the well bore along centerline II at a maximum drop of 1:20. The cross grades, parallel to centerline I, should be level. The area shall provide a minimum bearing capacity of 6000 psf.
Provisions should be made to allow for maneuverability of vehicles required to be in the area. Drainage of the entire area is required. Your attention is directed to pages 4-9 and 4-10 of Section 4 which provides typical information on the "Safe Bearing Capacity of Soils".
When setting guying systems, special attention should be given to determining the elevation difference between the well ground level and the anchor ground level. i.e.: An anchor located 10" above well ground level, 100' from the well head, would require the same holding capacity as if it were 110' from the well on level terrain. Likewise, an anchor 15' below well ground level, 80' from the well head would require the same holding capacity as though it were 70' from the well head. ( Wyoming Standard, Figure 6, "Anchor Elevation Adjustment Chart", p. 34)
A "Rig Stability Checklist is presented in Appendix A as an aid during inspections of well servicing derricks.
SECTION 3: ANCHOR TYPES There are three basic types of temporary guywire anchors commercially available, the helical or screw anchor, the expandable anchor and the pivoting anchor.
A screw anchor consists of one or more helix sections, an anchor rod and an eye-nut (see Figure 3-1.) This type of anchor develops its holding power in the same manner as a screw in wood. A moderate turning force is converted into rather substantial resistance to pull (holding power). By increasing the diameter of the helical sections and by increasing the number of these sections the holding power of the anchor can be substantially increased. As with any anchor, however, holding capacity remains a function of soil class, soil condition (disturbed or undisturbed), moisture content and anchor depth.
ADVANTAGES OF THE SCREW ANCHOR.
The screw anchor does not require pre-drilled holes for installation thus minimizing soil disturbance.
FIGURE 3-1. SCREW (HELIX) ANCHOR FOR FIGURE 3-1, SEE PRINTED COPY OF PUB 8-1.8.
TABLE 3-1. HELIX SIZE (INCHES) FOR TABLE 3-1, SEE PRINTED COPY OF PUB 8-1.8
Also, the torque applied during installation can be used to obtain an estimate of the anchor's holding power. Manufacturers have established, through testing, the approximate installation torque required in each soil class along with the approximate holding strength developed. Table 3-1, above, is taken from sales literature provided by McGraw-Edison and illustrates the range of holding strength available from this class of anchor.
Considerable variety exists in the design of expandable anchors. In general, these anchors can be characterized as requiring a pre-bored hole in which the unexpanded anchor is placed. The anchor is then expanded so that portions of the anchor extend into undisturbed soil. The hole is then filled. Figures 3-2 and 3-3 are illustrative of two types of expanding anchors.
The Expanding plate anchor is a device with several pre-formed plates connected to a central bracket by means of levers. Once the anchor is placed in the hole it is "tamped", this forces the central bracket down. As the bracket lowers, it forces the plates out into the undisturbed soil around the anchor.
FIGURE 3-2. EXPANDING PLATE ANCHOR FOR FIGURE 3-2, SEE PRINTED COPY OF PUB 8-1.8.
TABLE 3-2. EXPANDING ANCHORS - HOLDING STRENGTH (LBS) FOR TABLE 3-2, SEE PRINTED COPY OF PUB 8-1.8.
FIGURE 3-3. FLAT PLATE ANCHOR FOR FIGURE 3-3, SEE PRINTED COPY OF PUB 8-1.8.
The flat plate anchor is stamped from metal plate then folded into a reduced profile for insertion into the ground. The flukes are expanded into undisturbed soil, again by tamping or impact, to provide the holding power for this type of anchor. A base plate supports the extended flukes providing added strength and stability.
Representative holding strengths for various sizes and models of expandable anchors are reflected in Table 3-2.
Both of these expanding anchor types suffer from the same disadvantages. A power earth auger is required to pre-drill the holes in which these anchors are inserted. Further, there is no certain method of determining when the anchor is fully extended.
The final type of anchor is the pivoting anchor, Figure 3-4. This type of anchor consists of a plate connected to the anchor rod by means of a hinge or pivot. The anchor plate is positioned parallel to the anchor rod for insertion into the ground. Insertion is accomplished by driving the anchor into the ground with a pneumatic or hydraulic hammer. When the anchor has reached the desired depth an upward load is imparted to the anchor rod. This causes the anchor plate to rotate into the loaded position (perpendicular to the anchor rod).
FIGURE 3-4. PIVOTING ANCHOR FOR FIGURE 3-4, SEE PRINTED COPY OF PUB 8-1.8.
Advantages to this type of anchor include: no pre-drilling of holes which saves labor; no disturbed soil which increases holding power and if the device used to set the anchor is instrumented each anchor is load tested as it is set. Foresight Products, Inc indicates that the anchors in their Manta Ray Line have holding capacities up to 20,000 pounds in normal soils.
SECTION 4: EVALUATION CRITERIA FOR ANCHORS AND APPROPRIATE STABILITY SYSTEMS
EVALUATION CRITERIA - STABILITY SYSTEM SELECTION
There are several States which have statutorily addressed the installation of Guy Anchors. The State of Michigan, for example, references the American Petroleum Institute Specification, API SPEC 4E. Alaska requires that Derricks be effectively guyed, braced, or otherwise engineered to resist overturning in accordance with generally recognized safe practices in the industry. (Industry practices are discussed in Section 1).
The State of Wyoming, on the other hand, has established specific guidelines for making field determinations as to the adequacy of a guy anchor system and its installation. These criterion apply to permanent anchors only. The State of Wyoming does not permit the use of temporary anchors.
FIGURE 4-1. WYOMING WIND GUYWIRE ANCHOR PATTERN. FOR FIGURE 4-1, SEE PRINTED COPY OF PUB 8-1.8.
FIGURE 4-2. DISTANCE VERSUS HOLDING CAPACITY. FOR FIGURE 4-2, SEE PRINTED COPY OF PUB 8-1.8.
We have taken the Wyoming guidelines and tailored them so they would be applicable for use as an evaluation procedure in "Field Determinations" of appropriate guy anchor systems. Through the use of this criterion, field judgment can be made and acceptable anchor systems determined.
This process will, from this point forward, be referred to as the "WYGUY" method.
The following drawings and charts (extracted from Wyoming OSH Regulations) with supporting explanation are intended to assist you in understanding the "WYGUY" system and its implementation.
The chart, Figure 4-1, is oriented into four quadrants. For discussion purposes the top of the chart will be considered North. The quadrants then, proceeding clockwise, will be: Northeast, Southeast, Southwest, and Northwest.
The "Well Head" is located at the center of the Chart. This will be considered the base reference point for positioning of the guy anchors. The holding capacity of the anchors will then be determined by the zone in which they are located. ie: A, B, C, or D.
It should be pointed out that zone determination is a function of angle and distance. Zone "D" will be discussed first for only Single Derricks may be located in this zone and they will require a minimum 10,000 pound anchor, anywhere in the zone. (This is not the case in other zones which will be discussed later.) Zone "D" ranges through all four quadrants. Your attention is directed to the Northeast Quadrant. The zones parameters begin at the 22.5 degree radial and end at the 67.5 degree radial using line segment OE as the zero radial . The nearest point of Zone "D" to the Well Head is 35 feet and is located on the 45.0 degree radial. (see Southwest Quadrant). The far point of Zone "D" on the 45.0 degree radial is 50 feet. (see Northeast Quadrant).
TABLE 4-1. SOIL CLASSFICATION DATA (Note 1) FOR TABLE 4-1, SEE PRINTED COPY OF PUB 8-1.8.
FOR CONTINUITY WE WILL ALWAYS USE LINE SEGMENTS OE AND OW AS THE ZERO RADIAL.
The near parallel baseline of Zone "D" to the cross lines NS and EW is 25 feet. (see Northwest and Southeast Quadrants). The far baseline of Zone "D" to the cross lines is 35 feet. (see Northwest and Southeast Quadrants). The vertical distance from the cross lines to the end of the base line is 60 feet and 85 feet to the end of the far line. The area located within this geometrically angled rectangle, within each quadrant, is the area comprising Zone "D".
ONLY SINGLE DERRICKS, WITH A MINIMUM 10,000 POUND HOLDING CAPACITY PER ANCHOR (MINIMUM 4), MAY BE GUYED IN ZONE "D".
The minimum anchor holding capacity required for any other location and/or other than single derricks will be determined by Zone and horizontal distance from the "Well Head".
Zone "A" is located between the 35.0 degree and 55.0 degree radial in each quadrant with line "WOE" serving as zero degrees. Zone "B" is located between the 30.0 and the 35.0 degree radial as well as the 55.0 and 60.0 degree radials. Zone "C" is located between the 22.5 and 30.0 degree radials, also between the 60.0 and the 67.5 degree radials.
It should be noted that once the anchor location has been determined then the anchor's holding capacity must be determined by using the "Distance versus Holding Capacity" Chart. (Figure 4-2). The chart consists of a grid on which are superimposed three curved lines representing Zones A, B, and C respectively. The horizontal legend represents the horizontal distance from the "Well Head" in feet. The vertical legend is the minimum required holding capacity for each anchor (minimum 4).
Using the chart: An anchor in Zone "A" located a horizontal distance of 70 feet from the "Well Head" would require an anchor of what minimum holding capacity? On the chart move along the horizontal legend from left to right until you reach 70 feet. At this juncture proceed vertical until you intersect the curved line for Zone "A", now follow the intersecting horizontal line, left toward the vertical legend. We have now determined that the minimum holding capacity for the anchor, at this precise location, is 20,000 pounds.
Using the same horizontal distance we can determine that the minimum required holding capacity for an anchor located in Zone "C" would be 26,800 pounds.
IF ANY ANCHOR IS LOCATED WITHIN ZONE "C" THE MINIMUM ANGLE FOR ALL ANCHORS IS 22.5 DEGREES.
If one or more anchors is located in Zone "B" and the remainder of the anchors located in Zone "A", the minimum angle for all anchors shall be 30.0 degrees.
ANCHOR PLACEMENT DETERMINATION (FIELD EVALUATION)
To determine if already installed guy anchors are within acceptable angular parameters the following "Bench Reference Test" may be conducted:
- Standing at the "Well Head", with the well bore immediately to your back, proceed North (in direction monkey board is facing) 24 paces. (The pace length is not as important as the numerical relationship of the units and the consistency of the unit length. The method will work with any unit of length as long as the same unit is used throughout.) Place a stake or other marker at this location (Bench Reference). Turn West 90 degrees and proceed forward 10 paces. At this location turn your body so that the front portion of your anatomy is approximately parallel to the radial of the guy anchor. If the northwest guy anchor is forward of your right shoulder and the southeast guy anchor is aft to the rear of your left shoulder, it can then be presumed that the radial angles are within acceptable parameters. Repeat the procedure from the bench reference, this time to the east, proceed ten paces. In this orientation the northeast anchor should be forward of the left shoulder and the southwest anchor should be aft of the right shoulder.
- The stepping-off of 24 paces applies to Zone C anchors and for a check of Zone A anchors, you would step off 14 paces in a northerly direction and ten paces in a westerly direction. For Zone B anchors, you would go 17 paces north and ten paces west.
TABLE 4-2. SAFE BEARING CAPACITY OF SOILS* (pounds per square foot) ____________________________________________________________________________
Solid ledge of hard rock, such as granite, 50,000 trap, etc. Sound shale and other medium rock 20,000 requiring blasting for removal Hard pan, cemented sand and gravel 16,000 difficult to remove by picking Soft rock, disintegrated ledge; in natural 10,000 ledge, difficult to remove by picking Compact sand and gravel requiring 8,000 picking for removal Hard clay requiring picking for removal 8,000 Gravel, coarse sand, in natural thick beds 8,000 Loose medium, and coarse sand, fine 3,000 compact sand Medium clay, stiff but capable of being 4,000 spaded Fine loose sand 2,000 Soft clay less than 2,000
- *Values taken from Marks Mechanical Engineers' Handbook, McGraw-Hill Book Co., Inc., New York, Sixth Edition (1958)
This procedure may; also be used to determine the approximate, guy anchor placement, location for the placement of temporary anchors.
The tables 4-1 and 4-2 are to be used in determining SOIL CLASSIFICATION DATA and SOIL BEARING CAPACITIES.
The first draft of the new API (American Petroleum Institute), RP (Recommended Practice), "Recommended Practice for Maintenance and Use of Drilling and Well Servicing Structures" includes the simplified chart, Figure 4-3. Please note that:
- 1. Zone "A" is restricted to single masts and pole masts only.
- 2. Pole units are restricted to zones "A" and "B".
- 3. Anchor capacities shown on the following page assume the following:
- * Adequate foundation support for mat and carrier * Crown-to-Carrier internal load guys * Maximum Hook Load per Mast Rating or Maximum Wind Load (70 MPH) * Full Rod and Tubing Set Back, Note: Pole Mast has no set back.
FIGURE 4-3. ANCHOR SPACING AND CAPACITY CRITERIA FOR FIGURE 4-3, SEE PRINTED COPY OF PUB 8-1.8
The criteria chart, Figure 4-3, provides simplified anchor location and placement data. Zone locations are determined directly by distance and angle from the center line of the well bore. The following chart is to be used to determine the required minimum holding capacity of each anchor. Cross referencing, with the recommendations set forth in the Wyoming data, is required when one or more of the anchors is in a different zone. ie: If two anchors are in zone "B" and two anchors are in zone "C" then all anchors must have the holding capacity as set forth for zone "B".
From the data in Table 4-3, we can determine the anchor locations, the required anchor holding capacity and the required geometric configuration of the anchors. Installation and erection is covered in Section 5.
TABLE 4-3. ANCHOR CAPACITY (TONS) FOR TABLE 4-3, SEE PRINTED COPY OF PUB 8-1.8.
In keeping with the concept, which embraces the acceptance of new and innovative approaches, that are based on sound engineering principals, the following alternative, recommended installation guideline, is presented.
FIGURE 4-4. ALTERNATE APPROACH FOR FIGURE 4-4, SEE PRINTED COPY OF PUB 8-1.8.
SECTION 5: TEMPORARY GUYWIRE ANCHORS
SYSTEM INSTALLATION PROCEDURES: MINIMUM CONSIDERATIONS
After the location has been selected and the site prepared, erection of the "DERRICK" and its stabilization system can proceed. Presently the API, AOSC and IADC recommend the following basic procedure, with reference to Figure 5-1:
The guys are listed: "A", the crown to ground guys; "B", the racking board to ground guys and "C", additional racking board guys. "D" are intermediate guys, installed, ONLY IF RECOMMENDED BY THE MANUFACTURER.
GUY "A" Crown to Ground "Guys" (4 required), minimum guywire diameter 5/8 inch (Rig manufacturers manual should be consulted to determine if a larger size guywire is required). Where terrain permits "X" (see Figure 1) should be greater than "Y" and "Z" shall be equal to or less than 1.5 "Y" but shall never be less than "Y". This should be accepted as a Cardinal principal. Tensioning shall be approximate 1000 pounds. In the absence of a dynamometer or other type measuring device, reduction in the guywire catenary (sag) to approximately six (6) inches will be representative of 1000 pounds pull.
FIGURE 5-1. RECOMMENDED GUYING PATTERN: GENERAL CONDITIONS FOR FIGURE 5-1, SEE PRINTED COPY OF PUB 8-1.8.
WHEN THE TWO (2) "A" GUYWIRES ON THE "Z" AXIS ARE USED FOR LOAD GUYWIRES THEY SHALL BE A MINIMUM DIAMETER OF 3/4 INCH, 6X19 or 6X37 CLASS, REGULAR LAY, IMPROVED PLOW STEEL (IPS), INDEPENDENT WIRE ROPE CORE (IWRC) WIRE ROPE OR BETTER.
THE MINIMUM "Z" DISTANCE SHALL NOT BE LESS THAN SIXTY (60) FEET.
GUY "B" Racking Board (monkey board) to ground "Guys" (2 required), minimum diameter 9/16 inch. [The rig manufacturers manual should be consulted to determine if a larger size guywire is required]. "B" guywires should terminate at the "A" ground anchor on the "Y" axis. Tensioning shall approximate 500 pounds. In the absence of the instruments listed in A, reduction in the guywire catenary (sag) to approximately twelve (12) to eighteen (18) inches, preferably 12 inches would be approximate 500 pounds of pull.
GUY "C" Additional Racking Board (monkey board) "Guys" (2) are recommended when wind is expected to exceed 25 miles per hour. They shall be installed when winds are expected to exceed the design magnitude (usually shown on the name plate rating) or when wind screens are installed on the derrick. The minimum guywire diameter recommendation is 9/16 inch. [Rig manufacturers manual should be consulted to determine if a larger size guywire is required]. Guywire shall be installed perpendicular to the longitudinal axis of the carrier and "X" distance from the centerline. Tensioning shall approximate 1000 pounds. In the absence of the instruments listed in "A", reduction in the guywire catenary (sag) to about 6 inches will be approximate 1000 pounds of pull.
GUY "D" Two (2) or four (4) intermediate mast to ground "Guys" may be installed (ONLY IF RECOMMENDED BY THE MANUFACTURER; consult Rig manufacturers manual for specific recommendations). If installed, the minimum guywire diameter is 5/8 inch and they shall be installed to 1000 pounds tension (See "A" for method of installation). They should attach to the "A" ground anchors. See profile view of installation diagram, Figure 5-1, for approximate location of guywires.
PRECAUTIONS AND PROCEDURES FOR LOW TEMPERATURES
The American Petroleum Institute in its specification 4E, "Drilling and Well Servicing Structures," provides the following caveat on cold weather operations:
- A survey of 13 drilling contractors operation 193 drilling rigs in northern Canada and Alaska indicated that there is a wide range of experience and operating practices under extremely low temperature conditions. While there is very little precise information available, there have been a sizeable number of failures in portable masts while in the lowering or raising process in winter. Thus the exposure to low temperature failures focuses on mast lowering and raising operations. Based on reports, however, this operation has been accomplished successfully in temperatures as low as -50 degrees F. While the risk may be considerably greater because of the change in physical characteristics of steel at low temperatures, operators may carry on "normal" operations even at extremely low temperatures. This may be accomplished by a program of closely controlled inspection procedures and careful handling and operation. This should reduce damage and impact loading during raising and lowering operations. At the present, there seems to be no widely accepted or soundly supported basis for establishing a critical temperature for limiting the use of these oilfield structures. Experience in the operation of trucks and other heavy equipment exposed to impact forces indicates that -40 degrees F may be the threshold of the temperature range at which the risk of structural failure may increase rapidly. Precautionary measures should be more rigidly practiced at this point. The following recommended practices are included for reference:
- * To the extent possible, schedule mast raising and lowering operations to take place at the "warmest" time of day; take advantage of any sunlight or predictable atmospheric conditions. Take into account wind velocity factors.
- * Make use of any practical, available means to warm sections of the mast, such as using high pressure steam to heat the points of attachment between the mast and its base; also timber bonfires, and the like.
- * Take up and loosen mast raising lines several times to assure the free movement of all parts.
- * Warm up engines and check the proper functioning of all machinery to assure that there will be no malfunctions which would result in sudden braking or jarring of the mast. Mast travel, once begun, must be slow, smooth, and continuous.
FIGURE 5-2 USE OF GUYWIRE SAG TO ESTIMATE WIRE PRETENSION FOR FIGURE 5-2, SEE PRINTED COPY OF PUB 8-1.8
- * Inspection and repair are extremely critical under low temperature condition. Mast should be maintained in excellent condition.
- * In making field welds, the temperature of structural members should preferably be above zero degrees F. In the immediate weld areas, steel should be preheated, warm to the hand, before starting welding or cutting operations.
As was referenced earlier in this document, API, in its pending RP for drilling and servicing structures discusses line tensioning as a function of distance. The sag that is permissible, also used to determine adequate tension, will vary with the distance the
FIGURE 5-3. RECOMMENDED GUYING PATTERN FOR FIGURE 5-3, SEE PRINTED COPY OF PUB 8-1.8
anchor is located from the well head. The chart below, Figure 5-2, discusses this sag.
If maintained to these tolerances the sags will indicate a pretension of 1000 pounds for crown to ground guywires and 500 pounds for tubing board guywires. this is based on the use of 5/8 inch, 6x19, or 6x37 class, regular lay, ips, IWRC wire rope, installed according to the rigging guidelines set forth in chart depicted in Figure 5-5
With the new Recommended Practice there are also slight changes in the long existing rectangular guying pattern. The following Diagram, Figure 5-3, is an illustration of the current API thinking.
Figure 4-3 and Table 4-3 should be examined again to facilitate installation continuity.
FIGURE 5-4. ANCHOR SPACING AND CAPACITY CRITERIA FOR FIGURE 5-4, SEE PRINTED COPY OF PUB 8-1.8
TABLE 5-1. ANCHOR CAPACITY (TONS) (same as Table 4-3) FOR TABLE 5-1, SEE PRINTED COPY OF PUB 8-1.8.
INSTALLATION DATA CRITICAL TO RIG STABILITY
- 1. Zone "A" is restricted to single masts and pole masts only.
- 2. Pole units are restricted to zones "A" and "B". 3. Anchor capacities shown on the following page assume the following:
- * Adequate foundation support for mat and carrier. * Crown-to-Carrier internal load guys. * Maximum Hook Load per Mast Rating or Maximum Wind Load (70 MPH).
- * Full Rod and Tubing Set Back, Note: Pole Mast has no set back.
The "Criteria Chart", Figure 4-3 and Table 4-3, provides simplified anchor location and placement data. Zone locations are determined directly by distance and angle from the center line of the well bore. The chart is to be used to determine the required minimum holding capacity of each anchor. When one or more of the anchors is in a different zone, i.e.: If two anchors are in zone "B" and two anchors are in zone "C" then all anchors must have the holding capacity as set forth for zone "B".(Most restrictive.)
INSTALLATION OF WIRE ROPE CLIPS(1)
All clips must be drop-forged steel; malleable iron clips must never be used. Wire Rope Clips, of the proper type, have the advantage of allowing thorough examination and ease of field installation. Properly installed wire rope clips will develop 80% of the rope strength. This 80% efficiency can only be assured if thimbles are used. A combined clamp and thimble unit is also capable of developing 80% of the wire rope strength.
Double Saddle or Fist Grip clips are preferable to the U-Bolt clips, Table 5-2. It is impossible to install them incorrectly and they cause less damage to the wire rope.
TABLE 5-2. U-BOLT CLIPS FOR TABLE 5-2, SEE PRINTED COPY OF PUB 8-1.8
The drawing on the following page, Figure 5-4, (SAME AS FIGURE 4-4) is another illustration of the continuing evolution of Rig Stability System engineering and design. It represents the latest API thinking relative to planing and preparing a Rig Stability System.
FIGURE 5-5. ALTERNATE ANCHOR SPACING AND CAPACITY CRITERIA
SECTION 6: ALTERNATIVES TO PULL TESTING
Before we can begin to discuss alternatives to pull testing we must first understand the procedure for pull testing. The following is taken from the pending API, RP.
a. The direction of pull should be applied to the anchor in the plane of the anchor and the wellhead at an angle which approximates the guy wire angle b. The test pull should be applied for at least two (2) minutes after all anchor movement has stopped.
c. Devices used to measure and/or record the amount of pull should be calibrated annually by a qualified independent equipment service company and current records of calibration should be maintained by the party responsible for the pull test equipment.
d. Permanent anchors should be tested by devices equipped with chart recorders to provide a permanent record of the pull test.
CAUTION: SOLE EMPHASIS SHOULD NOT BE PLACED ON PULL TESTING OR ALTERNATIVES TO PULL TESTING AS THIS MEASURES ONLY ONE COMPONENT OF THE RIG STABILITY SYSTEM.
The rig contractor should be responsible for the following: a. Insuring that anchor capacities are verified and that anchor spacing and capacity is suitable for the mast guying pattern and anticipated loading.
b. Records of pull testing or records of other methods used to verify temporary anchor capacity should be retained by the rig contractor until the job is complete and the guy wires have been removed from the anchors. The records should indicate the capacity of each anchor, the date of verification, name and phone number of the party responsible for verification, and the soil condition at the time of verification.
c. Maintaining all guywires and end terminations in good working condition.
d. Inspecting and re-inspecting the guying systems for damage and deterioration. Records should be maintained of these inspections.
e. Inspecting surface ground conditions, assuring that water drains away from the anchor locations. Avoiding pooling in the vicinity of the anchors.
f. Properly aligning the rig in relation to the well head and anchor zone location.
g. Placing high visibility markers on all guy lines.
ALTERNATIVES TO PULL TESTING:
Temporary Anchors, installed in accordance with the manufacturer's specifications, may be deemed to be representatively pull tested, if upon inspection the following is observed:
a. Anchors are of the proper, manufacturer's rated, capacity for the zone in which they are installed.
b. Records indicate that the anchors have been installed in conformance with manufacturer's recommendations.
c. The wire rope guys are of the proper diameter for the section of the derrick to which they are attached and conform to Section 5, Figure 5-3.
d. End terminations conform to the requirements as set forth in Section 5, Table 5-3.
e. The guy line catenary (sag) conforms with the requirements as set forth in Section 5, Figure 5-2.
OUT OF AN ABUNDANCE OF CAUTION IT IS EXTREMELY IMPORTANT TO POINT OUT THAT THE PREVENTION OF RIG UPSET IS DIRECTLY DEPENDENT ON THE TOTAL INTEGRITY OF THE RIG STABILIZATION SYSTEM. THE SYSTEM INCLUDES ALL OF ITS COMPONENTS AND IS ONLY AS SOUND AS ITS WEAKEST MEMBER.
Our research has concluded, that the latest State-of-the-Art in RIG STABILIZATION is to be found in the pending American Petroleum Institute, Recommended Practice for MAINTENANCE and USE of DRILLING and WELL SERVICING STRUCTURES.
SECTION 7: BIBLIOGRAPHY
American Petroleum Institute (API). RECOMMENDED PRACTICE FOR MAINTENANCE AND USE OF DRILLING AND WELL SERVICING STRUCTURES. (Pending Recommended Practice[RP]) API: Washington, D.C.
International Association of Drilling Contractors (IADC). LESSONS IN WELL SERVICING AND WORKOVER LESSON 6: PRODUCTION RIG EQUIPMENT. IADC:
State of Wyoming. OCCUPATIONAL HEALTH AND SAFETY RULES and REGULATIONS FOR OIL AND GAS WELL SERVICING. Laramie.
Department of Civil Engineering, University of Wyoming. PROJECT REPORT: COOPER COVE GUYLINE ANCHOR STUDY (Conducted for the Rocky Mountain Oil and Gas Association). Laramie, Wyoming
SECTION 8: ACKNOWLEDGEMENTS
This document was developed by A.J. Scardino, Jr. of Sigma Associates, Pass Christian, Mississippi with contributions by Donald Godlewski, Marie M. Rogers, and Loislyn B. Scardino of Sigma Associates, and Larry Angelo of Welltech, Inc. Houston Texas. Comments, review, and editing by OSHA staff.
APPENIDIX A: RIG STABILITY CHECKLIST FOR APPENDIX A, SEE PRINTED COPY OF PUB 8-1.8
APPENIDIX A: RIG STABILITY CHECKLIST FOR APPENDIX A, SEE PRINTED COPY OF PUB 8-1.8