JC TOWER Quality Control
The manufacture and fabrication of tower must follow relevant codes and documents such as:
Technical Specification of the Tender Document
General Specification for Tower Fabrication in the drawing
Relevant national codes and standards
1) Material procurement control
All the material used for the tower must be procured from eligible suppliers and at the same time they must meet the requirements of existing national standards as well as the requirements specified in the drawings.
The original quality certificate must be presented before the material is accepted.
2) Progress quality control z Raw
material quality control:
⑴ The store keeper shall check the appearance quality according to the material procurement schedule and original quality certificate.
Checking items：
a. No such defects as fissure doubleskin or pockmark.
b. The specification thickness and quality meet the requirement of GB700‐88 andGB/T1591‐94.
⑵ Application for chemical analysis and physical experimentation.
⑶ The physical‐chemical lab will conduct relevant testing to find out whether the material is eligible. If the material pass the test, the lab will inform the store keeper to use the material in production; if not, the material will be rejected according to underproof control process. z Blanking quality control
⑴ Check each workpiece according to the operation card; the unqualified ones shall be rejected back following the underproof control process.
⑵ Requirement: the cut edge shall be even and smooth without burrs. For parts with groove, the Ferric oxide slag and oxide layer shall be removed to guarantee welding quality.
⑶ When the workpiece is eligible, the operation card and handover sheet shall be signed and the workpiece can go to the next procedure. z Hole perforation quality control
⑴ Check a sample workpiece according to the operation card; if the sample is eligible, other workpiece can be checked accordingly. The unqualified ones shall be rejected back following the underproof control process.
⑵ Checking items：
a. Appearance quality：no burrs near the hole，no fissure around the cutting edge，no fissure/pochmark/ferric oxide or damage larger than 1.0mm on the surface. All the marking signs should be clear and well arranged and the seal mark shall be 0.5~1.0mm thick. The letters or numerals used should be uniform.
b. The thickness requirement must be satisfied.
⑶ Technical requirement：
a. Tolerance between adjacent flange holes±1.0mm，tolerance of the hole with the flangeedge≤1.0mm
b. For other parts, the overall size tolerance±2.0mm, tolerance between adjacentholes±1.0mm.
⑷ When the workpiece is eligible, the operation card and handover sheet shall be signed and the workpiece can go to the next procedure. z Quality control of welding pipeGenerally speaking, the most widely used tower body material is straight line welding pipe, thus its quality will directly influence the quality of the whole tower.
⑴ Blanking control：The cut plate edge shall be smooth and even without burrs. For the plate with groove,further milling treatment is needed to get rid of heat deformation. The overall size tolerance is ±2.0mm.
⑵ Pre‐bending： Before bending, 2400T press machine is deployed to pre‐bend the plate edge to avoid possible straight edge of the pipe.
⑶ Bending：There are special moulds for each type of straight line welding pipe to guarantee the precision. After the bending there is a rectification procedure guided with the sample pipe.The tolerance is ±1mm.
⑷ Sewing up：Automatic pipe sewing machine and gas protection welding machine can realize continuous and uniform pipe pre‐welding.
⑸ Interior welding For thick wall pipe, in order to decrease the seam width and improve the welding quality X‐shape groove is adopted. Equipped with 3 welding wires, the welding machine can finish interior pipe welding work at the same time. Hence avoiding seam indentation and bubbles.
⑹ Exterior welding Four‐wired submerged arc welding machine can weld thick plate with large groove at one time. Internal pipe defects can be avoided and pipe deformation can be minimized.
⑺ Non‐destructive flaw testing ：Each seam will be inspected by X‐ray testing and ultrasonic testing to ensure the welding quality can reach the requirement of Grade Ⅰ、Ⅱ. z Quality control of angle steel：
⑴Check each kind of angle steel according to the operation card; the unqualified ones shall be rejected back following the underproof control process.
⑵ Checking items：
a. Appearance quality：no burrs near the hole，no fissure/doubleskin around the cutting edge，no bending at the angle steel ends, no obvious pochmark and other mechanical damage like dent/press mark/scratch etc on the surface. If any, the depth shall be within 0.3mm.
b. Using vernier caliper and tape measure to check the thickness and overall size of the angle steel as well as the distance between holes. All the taken data must comply with the requirement of the process card. ⑶ Other requirements：
a.Straightness ratio ≤L/1000（L:the length of the angle part）。
b.The external corner of the angle shall be arc shape.
c.The bending edge shall be even and smooth without significant folds/dents or other damages. After bending the minimum edge thk shall not be less than 70% of the original thk.
d. All the marking signs should be clear and well arranged and the seal mark shall be 0.5～1.0mm thick. The letters or numerals used should be uniform.
⑷ When the workpiece is eligible, the operation card and handover sheet shall be signed and the workpiece can go to the next procedure. z Quality control for rectification：
⑴ Each pipe shall be measured according to the process card.
Checking items：
a. Straightness ratio≤L/1000（L: pipe length）。
b. Length: tolerance within ±2.0mm.
c. End roundness ratio within ±2.0mm，other place ±3.0mm.
d. Pipe edge deviation ≤0.15t (t:plate thk) and ≤2.0mm.
e. Pipe diameter tolerance 0～‐2mm.
f. There shall not be significant press scratch on the surface after rectification, and the depth shall not exceed 0.5mm.
⑵ After welding, hot rectification method will be used to improve the straightness and flatness .Flatness shall meet L/1000(L:length of the connection plate)，straightness≤L/1500（L:length of the component）。
⑶ When the workpiece is eligible, the operation card and handover sheet shall be signed and the workpiece can go to the next procedure. z
Quality control for rivet welding：
⑴ Checking the welding position, and angle of the welded parts to make sure that it is in compliance with the drawings.
⑵ Checking items：
a. Whether the marking signs is covered.
b.Size and angle of all connecting points
c. Perpendicularity of the flanged.
d.The centripetal angle of tower boots and connection plate.
e.The size of positioned welding. The thickness should be 1/2～2/3 of the plate thk and the
length be about 25mm.
⑶ When the workpiece is eligible, the quality supervisor should sign and the handover sheet shall be signed and the workpiece can go to the next procedure. z Quality control of the connection welding：
⑴ Check shall follow the leg size marked on the drawings.
Checking items：
a. Leg size checking .
b.Ultrasonic flaw testing shall be deployed to detect the longitudinal seams and circular
seams. When the plate thickness exceeds 6mm, X‐ray is to be used.
c.Appearance check of the seam：
Besides the leg size requirement, seam appearance shall satisfy the following criteria like uniform welding wave, no crack/flash/penetration/arc crater/bubble/welding spatter/flux layer / splash/overmask etc.
⑵ When the workpiece is eligible, the handover sheet shall be signed and the workpiece can go to the next procedure.
3) Trial Assembly：
⑴ Each tower must be pre‐assembled in the plant. Three sects of the tower will be one assembly unit, each time add two sects successively. Every component should be in position and forced installation is forbidden. Meanwhile trial assembly record should be prepared.
⑵ Quality supervisor and relevant technician shall organize tower acceptance after the assembly.
Checking items：
a. Tower bottom width, anchor bolt diameter and the anchor bolt hole distribution circle
diameter b Height of the tower
c. Clearance between cross arms, cross arm length
d. Diameter for conductor hoisting holes, specification for conductor hoisting plate
e.Size of the hole positioned in the outside of the cross arm connection plate
f.whether the assembly totally complies to the drawings.
g.Check the condition of the flanges component joints. If the damage is beyond theallowable limit, remedial measures shall be taken.
⑶ Prepare the trial assembly record according to 《Regulations of Trial Assembly》.
4) Galvanization
⑴Appearance quality： The surface shall be practically smooth; there are no such defects as over acid treatment, un‐galvanized spot, flash etc.
⑵ Coating thk: galvanized parts thk≤5mm, min average zinc thk≥65μmgalvanized parts thk≥5mm, min average zinc thk≥86μm ⑶ Checking method：For angle steel： 3 points on each side all together 12 For connection plate：6 points on each side all together 12
⑷ Prepare zinc coating thk testing paper after the test.
5) Finishing and packing
⑴ Tower packing：the flanges and connection plate shall be wrapped with cushion feltcloth.
⑵ The angle steel shall be bundled and marked with: tower type, height, weight, bundle No,etc.
⑶ The bolts and nuts will be put in the steel drum. The anchor bolts and plates will be put in the wooden box.
⑷ The packing shall be secure as well as orderly and nice looking.
6) Quality records：
All the quality records shall be timely and carefully finished and there shall be duty person who will be responsible for the collection, sorting and storage of all these documents.
