• Nadirsha Shahabudeen

An Article on Equipments & Piping Insulation

Piping and equipment shall be insulated according to the insulation class, operating temperature and insulation thickness stated in the P&ID and Data sheets. All insulation shall be covered with weather protection designed and installed to prevent ingress of water during normal operation throughout the design life. Insulation adjacent to flanges in piping and equipment shall be terminated to allow removal of bolts without damage to insulation. Minimum free space from the flange to the nearest part of the insulation shall be equal to the bolt length +25 mm. The termination of the weather protection shall be waterproof. When a rigid type of insulation is used, provision shall be made for longitudinal expansion and contraction.

Vessel insulation

Insulation of all vessels shall be supported on rings with a distance of 900 mm c/c installed on the vessel. Rings shall also be provided around nozzles above DN 200 mm. Block insulation shall be fastened with mechanically tightened metal bands or with bonding adhesive. Insulation on vessel heads shall be fastened with bands spaced not more than 300 mm centres. The bands shall be fixed to the fixing ring installed on the vessel. Vessels of diameter 1500 mm and smaller shall be insulated as piping.

Removable insulation of flanges and valves

Removable insulation for flanges and valves, like tailor made jackets or preformed insulation boxes, shall be suitable for quick removal and reinstallation. All tailor made jackets shall fit the actual valve/flange/equipment and secure adequate overlap to incoming insulated pipes.

Hot Service Insulation

Guidance for the choice of insulation thickness for heat conservation and personnel protection is for cellular glass given in table 2. If a specific temperature has to be maintained, the thickness of the insulation material in question has to be specified in each case.

The following equipment shall not be insulated for heat conservation class 1 except for steam services or when otherwise specified:

1. Vessel manway covers, nozzles and flanges.

2. Exchanger nozzles and flanges.

3. Valves and piping flanges.

4. Control valves, line valves and fittings, which are to be removed periodically.

5. Expansion and rotation joints, slide valves and similar equipment.

6. Steam traps.

Flanges operating at temperatures above 450 OC shall be insulated and protected with sheet metal jacketing.

Block insulation for vessels / cellular glass

Block insulation for vessels:

1. Insulation for vessel heads shall be curved blocks or standard flat blocks cut to fit.

2. For single layer and outer layer of multi layer insulation, banding shall be placed approximately 30 mm on each side of all butt joints with intermediate bands at a maximum of 300 mm centres. The inside layer of multi layer installations shall be banded at a maximum 450 mm centres.

Blanket insulation on vessels / ceramic fibres / mineral wool

Blanket insulation on vessels:

1. The last piece of insulation in each layer shall have a snug fit to make all joints tight. Contraction joints are not required for resilient insulation materials.

2. The meeting edges of blankets shall be tied together with stainless tie wire.

Prefabricated pipe section insulation / cellular glass / mineral wool

Prefabricated insulation shall be applied as follows:

1. Insulation pipe sections shall be tightly butted together and secured to pipe with stainless steel bands.

2. Insulation shall be secured with bands over the outer layer at each side of radial joints and at the centre of each section.

3. Spacing of bands for the inner layer of multi layer insulation need only be sufficient to hold sections in place until the outer layer is secured.

4. To cover elbows and other irregular surfaces, sections may be cut and fitted in the field

Guidelines for acoustic insulation

The acoustic pipe insulation classes can be met by various combinations of insulation materials and jacketing systems. Within the same installation one should try to limit the number of pipe insulation systems by choosing alternatives that provides combinations of sufficient personnel protection, heat insulation, cold medium conservation, fire protection and noise insulation when and as required. Valves and flanges shall be insulated when specified.

Cold Service Insulation


If a specific temperature has to be maintained for process reasons, the thickness of the insulation has to be specified in each case.

Vessel insulation

Where required, man ways shall be provided with removable covers of the same insulation thickness as the shell insulation. Covers shall be secured to the shell insulation and sealed to provide vapour tight joints.

Piping insulation

Valves and fittings shall be insulated with pre formed pipe insulation. Sections shall be cut from standard blocks, fitted and wired in place. Alternatively, tailor made jackets may be used. Flanges shall be insulated with the same insulation thickness as the thickness on adjoining pipe run, vessel, machinery or fitting. In order to avoid frost formation or condensation on pipe supports, insulated prefabricated pipe supports shall be used.

Block insulation for vessels

Block insulation for vessels:

1. All block edges shall be smeared with a thin coat of joint sealer when single layer insulation and the outer layer of a multi layer insulation are applied. The remaining joints shall be left dry, except where vapour seals or contraction joints are required,

2. Termination of insulation on all layers, including contact surfaces where removable insulation covers are installed, shall be vapour sealed.

Piping insulation

Prefabricated insulation of cellular glass shall be applied as follows:

1. All joints of single layer and outer layer of a multi layer insulation shall be applied with butt edges smeared with joint sealer before installation.

2. Anti-abrasive compound shall be applied to the inner bore and allowed to dry before application. Anti abrasive compound when required, is preferred factory applied.

3. Bands or glass fibre reinforced tape shall be used to secure each layer of insulation, including the outer layer. Bands or tape shall be installed on 275 mm centres, and at least 25 mm back from butt joints. Wire shall not be used.

4. Prefabricated flange and fitting covers shall be applied in the same manner as pipe insulation, except that non-removable joints shall be cemented with adhesive.

Pre insulation for piping.

Pre insulation shall be applied as follows:

1. The concept shall give a compact construction without any spaces or voids.

2. Insulation ends shall be water proof.

3. For heat tracing a groove (duct) suitable for the heat tracing cable shall run along and close to the pipe inside the insulation.

Guidance for insulation thickness

Thickness of insulation for piping and equipment shall be:

1. 40 mm up to and including nominal diameter 200 mm.

2. 50 mm above 200 mm and flat surface.

Thickness of insulation for piping and equipment shall be:

1. 30 mm up to and including nominal diameter 80 mm.

2. 40 mm above 80 mm and flat surface.

**The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.

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