Installation Instructions For Rubber Bellows

A. Pre-Installation Check

1. SELECTION

Prior to installation, check that you have the right bellows for the particular duty. Rubber bellows have temperature and pressure limitations. Maximum allowable pressures need to be derated at temperatures above 70˚C.See Fabricated Products data sheets for allowable pressures and temperatures. All rubber bellows will extend under pressure. These pressure thrust forces can be very substantial at pressures above 2.0 bar and 100mm n.b. size unless the pipe work can be sufficiently anchored a tied bellows should be fitted (see fig.1).

2. MATING FLANGES

We strictly recommend that the rubber bellows are mated up against full bore weld neck flanges only (see fig.5.). If installed in this manner no additional gaskets are required. We advise against using slip on or screwed flanges as mating flanges as these can damage the rubber bellows. Once the sealing face has been damaged the medium will penetrate the reinforcement layers and destroy the integrity of the bellows. If it is unavoidable to use this type of mating flange, a gasket must be used (this should be a hard gasket such as Klingerite and be at least 3mm thick). The gasket should reach the internal bore of the rubber bellows (see fig.4.). Another option is to fill the gap of the slip on flange with weld and grind it flush (see fig.3.).

3. MISALIGNMENT

Check that the two mating flanges are parallel and that they are in line (maximum allowed offset is 5mm in any direction). The gap between flanges should be within +/- 5mm of the bellows neutral length (see fig.7.). Ensure that the pipework is adequately supported. The bellows must not support pipes or plant.

C. TAKING CARE OF RUBBER BELLOWS

1. PAINT

Do not paint rubber bellows. The paint will attack the rubber. (This also applies to paint splatter).

2. WELDING

Protect the rubber from weld spatter. When welding, always ensure that the bellows is bridged using a continuity strap

3. LAGGING

Do not lag rubber bellows on heating systems. The increased temperature will reduce the life of the bellows.

4. TIE BAR CHECK

Once the system is filled but not under pressure, check that the tie bars are still tight (pipework on springs may have dropped due to the weight of the water). Retighten the bars if slack. Note: tie bars should never be slackened off to reduce noise or vibration transmission, major damage to equipment may occur.

5. WATER TREATMENT

Most bellows use an EPDM inner liner. EPDM is a proven material in heating and chilled water systems. It is resistant to glycol and to most chemicals used in water treatment, when used in normal concentrations. As suppliers of water treatment chemicals are reluctant to giveinformation about their formulations, we cannot approve any specific chemical.

D. BEST PRACTICE

The following are only recommendations but if followed they will ensure the maximum service life of the rubber bellows.

System - when the bellows are installed on rotating equipment such as pumps to absorb noise and vibration, the pipework either side of the bellows should be guided. This ensures that the bellows moves and not the pipework (see fig. 8) thus acting as an acoustic break.

E. STORAGE

Rubber joints should be stored in a fairly cool dry place protected from sunlight. They should be stored flat on the flange with no sunlight on them.

B. INSTALLATION

1. BOLTS

Bolts should be inserted from the bellows side (see fig.5.). On some larger sizes this may not be possible. In that case a bolt of the exact length needs to be selected. An alternative is to use studding cut to length and fitted with a nut at both sides (see fig.6.). This is important, as the bellows will increase in diameter under pressure. Even if there is space between the bolt and bellows in an unpressurized state, they may foul when pressurized. Bolts of the right diameter must be used to ensure correct alignment.

2. ALIGNMENT

Take care when inserting the bellows into the gap between the two mating flanges. Sharp edges can damage the sealing face of the bellows. Before tightening the bolts, ensure that the bellows fit evenly in its flange groove and does not get pinched between flanges. The sealing face of the bellows must be concentric with the sealing face of the mating flanges.

3. TIGHTENING THE BOLTS

Great care has to be taken with the tightening of the flange bolts. Remember that you are tightening against a rubber face. As with gaskets, over tightening will cause the joints to leak and it will damage the bellows. “Tighter is definitely not better!” Tighten opposite bolts to get an even pressure all round (check the gap between the flanges). Rubber will set and the bolts will have to be retightened after 24 hours.

4. TIE BARS

Once the bellows is fitted, ensure that the tie bars are tight. If necessary adjust nuts at either end. All tie bars should be at equal length. When three or more tie bars are fitted it may be necessary to remove one tie bar to aid installation. Ensure that washers are reassembled in the right order and orientation. A lock nut must be refitted.

5.ANCHORING

Rubber bellows must be anchored to ensure their correct performance. Tied rubber bellows should be selected for sizes above 100mm and where pressures exceed 2.5 bar.