I. Pipe Thread Connection (Galvanized Steel Pipe, Plastic-lined Galvanized Steel Pipe)

1. Pipe cutting: Based on the on-site survey sketch, draw lines on the selected pipe materials and cut the pipes according to the lines.

When cutting a pipe with a grinding wheel saw, place the pipe on the grinding wheel saw caliper, align it with the marked line and secure it firmly before cutting the pipe. When cutting the pipe, apply even force to the handle and avoid excessive force. After the pipe is cut, remove the iron film and burrs on the cross-section of the pipe opening thoroughly.

When cutting a pipe with a hand saw, the pipe should be fixed in the pressure clamp of the pressure table. Align the saw blade with the marked line and push the saw with both hands. The saw blade should be kept perpendicular to the pipe's axis. The force applied by pushing and pulling the saw should be uniform. The saw cut should be sawn all the way through. Do not twist or break it to prevent deformation of the pipe's cross-section.

Two threading: For the cut pipe, thread the pipe according to the pipe diameter size in several steps. Generally, for pipes with a diameter of 15-32mm, thread twice; for those with a diameter of 40-50mm, thread three times; and for those over 70mm, thread three to four times.

Use a threading machine to thread the pipe. Clamp the pipe on the threading machine's chuck, leaving an appropriate length to hold the chuck tightly. Align the plate threading number, install the die teeth, and match the appropriate position on the scale according to the pipe diameter. Firmly hold the fixed trigger, align the lubricant tube with the thread head, start the machine and push the plate. When the thread is threaded to an appropriate length, gently release the trigger.

b uses a manual threading plate to thread the pipe. First, release the fixing trigger, retract the threading plate to zero degrees, thread the plate in sequence, align the plate with the required scale, tighten the fixing trigger, place the pipe in the pressure table pressure clamp, leave an appropriate length for clamping, gently insert the threading plate into the pipe to ensure it is neither too tight nor too loose, and then push the threading plate with both hands, attaching 2-3 buttons. Stand to the side and pull the thread plate again. Apply force evenly. When the thread is about to be pulled, gently release the trigger, turn on the machine and pull the plate to ensure that the thread has the necessary taper.

3. Fitting pipe fittings: According to the on-site survey sketch, fit the pipe fittings onto the pipe that has been threaded.

When installing pipe fittings, the required pipe fittings should be inserted into the pipe threads to test the tightness (generally, it is advisable to insert three threads by hand). Apply lead oil and wrap hemp around the threads, then insert the pipe fittings. After that, use a pipe wrench to tighten the pipe fittings so that 2-3 threads are exposed. Remove the hemp ends, wipe off the lead oil, number them and place them in the appropriate positions to wait for straightening.

Select the appropriate pipe wrench according to the size of the pipe diameter of the fitting

4. Pipe section straightening: Straighten the pipe sections that have already been fitted with pipe fittings before installation.

Apply lead oil to the threaded parts of the pipe sections where the pipe fittings have been installed. Connect two or several sections. During the connection, do not only focus on the direction of the reserved opening but also take into account the curvature of the pipe material. After mutual alignment, turn the direction of the reserved opening to the appropriate position and keep it straight.

After the connection of pipe section b, before adjusting it, it is necessary to check whether the pipe diameter, the direction of the reserved opening and the reducing position are correct according to the design drawings.

When straightening the c pipe section, it should be placed on a pipe straightening rack or platform. Generally, it is advisable for two people to operate. One person visually inspects the end of the pipe section, while the other uses a hand hammer to tap at the curved part. While tapping, observe continuously until the straightened pipe section has no bends. Mark the connection points of the two pipe sections, remove one or several sections, and then connect another or several sections until the straightening is completed.

For overly rigid bends at the connection points of pipe sections or pipes with larger diameters, heating in an oven or gas welding to 600-800℃ (bright red) can be adopted. Then, place the pipe on a pipe rack and keep rotating it to make it straight by its own weight. Alternatively, place a wooden board at the heated area and gently tap it with a hammer to straighten it. After straightening, keep rotating it before cooling. When the temperature reaches an appropriate level, apply engine oil to the heated area.

All the threads that have been heated and straightened must be marked with a number, removed, re-coated with lead oil and wrapped with hemp, and then the pipe sections should be aligned with the marks and tightened.

For the pipe section with the valve installed, when straightening it, the valve cover should be removed first, the valve area should be padded firmly, and then struck to prevent the valve body from cracking due to vibration.

Galvanized carbon steel pipes are not allowed to be straightened by heating.

When straightening the g pipe section, it is not allowed to damage the section.

Ii. Pipe flange connection (requires disassembly and connection with equipment valves, etc.)

2.1 Where pipe sections are connected by flange plates or pipe sections are connected by flange valves, standard flange plates must be selected in accordance with the design requirements and working pressure.

2.2 The diameter and length of the connecting bolts of the flange plate should comply with the requirements of the specifications. When tightening the flange plate bolts, they should be tightened symmetrically. The exposed threads of the tightened bolts should be 2 to 3 turns and should not exceed half of the bolt diameter.

2.3 Flange connection gaskets: Generally, rubber gaskets with a thickness of 3mm are used for water supply (cold water), while asbestos rubber gaskets with a thickness of 3mm should be used for heating, steam, and domestic hot water pipelines. The gasket should be concentric with the pipe diameter and must not be placed off-center.

Iii. Pipe Welding

3.1 According to the design requirements, steam pipes with a working pressure of over 0.1MPa, heating pipes with a general diameter of over 32mm, and fire protection pipes in high-rise buildings can be connected by electric or gas welding.

3.2 When welding pipes, measures should be taken to prevent wind, rain and snow. The ambient temperature of the welding area should be below -20℃. The weld joint should be preheated, with a preheating temperature of 100-200℃ and a preheating length of 200-250mm.

3.3 Generally, pipe welding is in the form of butt joints and assembly.

3.4 Before welding, the axes of the two pipes should be aligned. First, spot weld the ends of the two pipes firmly. For pipes with a diameter of less than 100mm, spot weld three points; for pipes with a diameter of more than 150mm, it is advisable to spot weld four points.

For pipe materials with a wall thickness of more than 5mm, bevels should be dug at the welded ends of the pipes. If gas welding is used to process the bevels of the pipes, the oxide scale on the surface of the bevels must be removed, and the uneven areas that affect the welding quality should be ground smooth.

3.6 When welding pipes to flange plates, the pipes should first be inserted into the flange plates. Spot weld 2 to 3 points first, then use a square to align and level them before welding. The flange plates should be welded on both sides, and the inner seam must not protrude from the sealing surface of the flange plates.

Iv. Pipe Socket and spigot connection

4.1 Cement twist joints: Generally used for socket and spigot connections of indoor and outdoor cast iron drainage pipes

To reduce the number of mortar joints in the fixation process, for some pipes and pipe fittings, mortar joints can be pre-laid. Before laying the mortar joints, check whether the pipes and pipe fittings have any cracks, sand holes or other defects, and pre-arrange the pipes and pipe fittings. Check if there are any errors in the dimensions and whether the circumferential gaps of the mortar joints at the socket and spsocket are qualified.

When connecting pipe b and pipe fittings, they can be placed on a temporary fixed frame. The pipe and pipe fittings should be inserted in the direction of the socket facing up and the spigot facing down as per the drawing requirements, and the mortar should be tightened.

When making the socket, first use a hemp rod to drive the tightened green hemp slightly thicker than the circumferential gap of the socket or the binding rope into the socket. Generally, two turns are appropriate (about one-third of the depth of the socket), and the length of the green hemp lap joint should be more than 30mm. Then, tamp the hemp firmly, while tamping, align and straighten it, and level the hemp whiskers.

After the hemp is beaten well, the twisting joint mortar (the weight ratio of water to cement is 1 9) Layer by layer, fill the annular gap of the socket. First, use a thin chisel, with one hand filling the mortar and the other hand tamping it down. Then, layer by layer, use a hand hammer and chisel to tamp it down until the mortar gap is fully filled. Use a chisel of thickness that matches the size of the annular gap of the socket to tamp and level the mortar gap. When the chisel strikes the mortar gap, there is a feeling of rebound, which is considered qualified.

When mixing the twisting joint ash, it should be used immediately after mixing. The mixed ash should be used up within one and a half hours. At the same time, the amount of water used should be adjusted appropriately according to the climate conditions.

When prefabricating two sections of pipe or more pipe fittings, the pipes or pipe fittings with the mortar joints first laid should be arranged at the top, and then the mortar joints at the bottom should be laid to reduce their vibration. After twisting the last ash joint, check whether the remaining ash joints are loose. If any are loose, deal with them in time.

The prefabricated pipe sections and fittings should be stacked on a flat surface, laid flat and padded firmly. The joints should be wrapped with wet hemp ropes, watered and maintained to keep them moist. Generally, they can be moved to the site for installation after being placed at room temperature for 48 hours.

During the severe cold season in winter, effective anti-freezing measures should be taken for the mortar joints. An appropriate amount of salt water can be added to the plastering water. The mortar joints that have been rolled must not be frozen. The storage environment temperature should be maintained above 5℃. If conditions permit, steam curing can also be adopted.

4.2 Asbestos cement joint: Generally, asbestos cement joints are used for the laying of indoor and outdoor cast iron water supply pipes, that is, an appropriate amount of asbestos wool is mixed into the cement.

4.3 Lead joints: Generally used for the installation of indoor cast iron water supply pipes in industrial plants, lead joints can be adopted when there are special design requirements or when outdoor cast iron water supply pipes need emergency repair and water is urgently needed at pipe joints

4.4 Rubber ring joint: Generally used for the connection between pipes in the laying and installation of outdoor cast iron water supply pipes. Pipes and pipe fittings still need to be twisted with asbestos cement

V. Pipe Bonding and Connection: (UPVC Pipe, ABS Pipe)

5.1 Pipe bonding should not be carried out in an environment with high humidity. The operation site should be kept away from fire sources and impacts should be prevented. The temperature should be within -20.

5.2 Before bonding pipes and pipe fittings, the inner side of the socket and the outer side of the socket should be wiped clean with clean cotton yarn or dry cloth, and the bonding surface should be kept clean. If the surface is stained with oil, it should be wiped clean with cotton yarn dipped in acetone or other cleaning agents.

When applying adhesive with an oil brush, the inner side of the socket should be applied first, followed by the outer side of the spigot. When applying the socket, the foam should be evenly and appropriately applied from the inside out along the axial direction. No area should be missed or applied too thickly.

After applying adhesive to the socket and spigot, it is advisable to align them with the axis and insert them continuously and forcefully within 20 seconds. The depth of the pipe end inserted into the socket should be marked on the surface of the inserted pipe end according to the measured socket depth. After insertion, rotate the pipe by 90°.

After the insertion is completed, the adhesive squeezed out from the outside of the joint should be wiped clean immediately. Force should be avoided. Let it stand until the interface is solidified. Installation can only continue after the joint is firmly fixed.

5.6 Adhesive joints should not be operated when the ambient temperature is below 0℃ to prevent the adhesive from freezing. Open flames or electric stoves and other facilities must not be used to heat the adhesive.

Vi. Ferrule Connection of Pipes (Aluminum-Plastic Composite Pipe)

6.1 Cut the pipeline in accordance with the pipe diameter required by the design and the length of the pipe section verified on site. Check the pipe opening. If burrs, unevenness or the end face is not perpendicular to the pipe axis are found at the pipe opening, it should be corrected.

6.2 Use a special scraper to bevel the inner layer of polyethylene at the pipe opening, with a bevel Angle of 20-30° and a depth of 1.0-1.5mm. Also, wipe the residual debris from the bevel clean with a clean paper or cloth.

6.3 Use a rounder to round the pipe opening.

6.4 Place the lock nut and C-shaped clamping ring on the pipe, and forcefully insert the pipe core into the pipe until the pipe opening reaches the root of the pipe core.

6.5 Move the C-shaped clamp ring to a distance of 0.5-1.5mm from the pipe opening, and then tighten the lock nut to the pipe fitting body.

Vii. Hot-melt connection of Pipes (Currently, it is mostly used for the installation of PP-R pipes and PB pipes for indoor domestic water supply)

7.1 The hot melt tool can only be operated after the power is connected and the working temperature indicator light is on.

7.2 When cutting pipes, the end face must be perpendicular to the pipe's axis. Pipe cutting is generally done using pipe shears or pipe cutting machines. If necessary, a sharp hacksaw can be used, but after cutting, the burrs and rough edges on the pipe surface should be removed.

7.3 The connection end faces of pipes and pipe fittings must be clean, dry and free of oil.

7.4 Use a caliper and an appropriate pen to measure and mark the depth of the hot melt at the end of the pipe.

7.5 When welding elbows or tees, in accordance with the requirements of the design drawings, attention should be paid to the direction. On the straight line direction of the pipe fittings and pipes, their positions should be marked with auxiliary signs.

7.6 When connecting, insert the pipe end into the hot sleeve without rotation to the marked depth. At the same time, push the pipe fitting onto the heating head without rotation to the specified marked position. The heating time should comply with the provisions of the above table (or as per the regulations of the hot melt tool manufacturer).

7.7 After the heating time is reached, immediately remove the pipe and pipe fitting from both the heating sleeve and the heating head simultaneously, and quickly and evenly insert them into the marked depth in a straight line without rotation to form a uniform flange at the joint.

7.8 Within the processing time specified in the above table, the just-welded joint can still be corrected, but rotation is strictly prohibited.

Viii. Connection of Copper Pipes

In building water supply systems, copper pipes are mainly connected in two ways: ferrule type and welding.

(1) The ferrule connection is convenient and simple to operate. By choosing the right accessories, the connection can be made tight without leakage and can withstand sufficient pressure.

Ferrule connections are divided into two types: non-operating joint type A and operating joint type B.

Type A joint connection: The installation process includes selecting a sleeve that meets the pipe specifications, cutting the pipe to the correct length, removing all burrs, checking whether the pipe end is clean and free of deep scratches or other defects. If the end of the pipe is elliptical, use an appropriate tool to make it round. Then insert the pipe into the sleeve until it does not reach the retaining ring. Tighten the nut by hand and with a wrench until the retaining ring clamps the pipe. At this point, the nut on the sleeve cannot be turned by hand. Now, use two wrenches to tighten the nut to 1/3 to 2/3 turns. This causes the pressure ring to bite into the pipe and slightly deform it.

Operable joint Type B: This joint can simultaneously clamp the inner and outer surfaces of the pipe, thus the joint can not only support but also firmly hold the copper pipe.

The connection method includes confirming that the specifications of the pipe and the sleeve used are correct, then cutting the pipe to the required length with a fine-toothed saw, cleaning the burrs inside and outside, fitting the compression nut and the compression ring into the pipe end, knocking the corresponding flaring tool or punch into the pipe end to expand the pipe opening, and then correctly placing the three-dimensional pipe into the pipe end and the sleeve, and tightening the compression nut. First, twist it by hand, then use a wrench to tighten it for about one turn, and a firm and tight joint can be made.

There are mainly two welding methods: tin welding and copper welding

The main differences between the two lie in the different metal fillers used, the different fluxes used, the different application parts, and the fact that the welding method requires professional personnel to operate.

Brazing

Before connecting the pipes, it is necessary to reconfirm whether the specifications and dimensions of the pipe materials and pipe fittings meet the connection requirements.

2. According to the design drawings, the on-site measured length of the piping was measured, and the cutting was precise. Cutting can be done using a rotary pipe cutter or a hacksaw or electric saw with no less than 13 teeth per centimeter for vertical cutting. After cutting, burrs at the pipe opening should be removed and the entire circle should be formed.