Steam turbines should not be seen as unduly complex mechanical installations, you will generally be provided with a modular unit such as a Siemen’s or MAN MARC machine, these machines are preassembled on skids, for smaller units say 1.5 to 12 mw that could be one skid, whereas larger units up to 40 mW. can be in preassembled modules e.g. Turbine skid, gear box, lube skid and generator.

This is not to say they do not require precise installation and experienced staff, the primary task when installing these units is levels, torque and alignment tolerances, levels can be within 0.076mm or 3 thou.

Technicians from the suppliers should be provided and their associated costs built into the Procurement component of the project with their site overheads accounted for in your estimate and plan, this will to ensure the highly engineered requirements are met and warrantees maintained, you will need these people for the duration of the installation and commissioning.

The most time consuming component of the installation is the piping and commissioning tasks.

Blowing down the pipe installation after primary installation can require up to 50 blow downs to ensure the cleanliness of the pipe system, after about 10 successful blow downs installation of a polished steel disc known as a target is required, this is placed in the line and any particles in the air stream pit the target, passing the system requires close examination of this disc. Debris within the system will damage the turbine and it is critical that the system is thoroughly cleaned. A system blow down can take between 1 and 3 hours

All connections must be free of any stress, bolting of piping systems must not apply any loads to the connections.

The equipment is built to extremely fine tolerances and although the turbines are strong enough for the arduous operating parameters they are prone to damage through rough handling and impact, for this reason care must be taken to ensure the erection equipment used matches the precise handling requirements for the turbine. Steady cranes are critical, if an overhead maintenance crane is to be part of the installation then this equipment should be installed and commissioned for used during the turbine installation as it will provide a firm and solid operating base for the equipment. If this is not possible then cranes should be as secure and as rigidly setup as possible.

Start up. 

1. Locate all items and Check all supplied items against equipment list.
2. Before installation, all parts shall be thoroughly cleaned and all rust, dirt, grit and foreign matter shall be removed. Grease or other protective coatings supplied for protection of the equipment in shipment and/or storage, except prime coating, shall be removed by using suitable solvents or cleaners which will not damage the finish of the equipment.
3. All foundation elevations and bolt locations shall be verified and accepted by the erection contractor prior to the start of installation of equipment.
4. Levelling and alignment of all equipment shall be within the tolerance specified on the drawing or as specified in the manufacturer’s instructions. Where equipment is received as a shop assembly unit, alignment shall be checked and adjusted where necessary.

Civil Structures

1. Check all the levels top of concrete and record the exact RL’s.
2. Check bolt locations to drawings.
3. After Checking against civil drawings note any discrepancies in the mechanical check sheet
4. Once RL’s have been checked get sign off to proceed with the installation.

Soleplates / Baseplates

The primary function of the foundation is to provide a permanent rigid, non-distorting support for the equipment. The support structure must hold the machine in correct alignment under operating conditions; support the weight uniformly and evenly

Concrete foundations must be fully cured before loading.

The concrete surface should be scrabbled to a depth of approximately 10 to 12mm to produce a good bonding surface for the grout to be used under the sole plates and baseplates.

Soleplates are set with a void between it and the foundation. After the soleplate is leveled, an alignment check made, once the alignment is correct the soleplate is grouted to the foundation. This procedure creates a constant level baseline for the equipment.

1. Soleplates and machinery must be erected on prepared foundations and aligned to the prescribed centre lines and elevations as shown on the erection drawings.
2. Soleplates and machinery shall be properly levelled, aligned, set and adjusted on packers and shims.
3. Packers shall be of sufficient size to sustain an effective load bearing area. They shall be of one piece thickness.
4. Shims shall be of the same size as the packer. The maximum thickness of shim shall be used to reduce the number of shims required at any one point to a minimum.
5. Set up sub soles using grub screw chock blocks with pin points to hold position in concrete check the RL’s in all directions and sign off the check sheet, all to be done using a Machine level to ensure all points equal.
6. Form up around sole plates and pour 2 pack impact resistant Epoxy grout to sub soles and allow 12 hours before applying any load to the soles.

The procedure to be followed for grouting in of chock blocks, soleplates or baseplates is the same except for quantity of grout placed.. The resin and hardener serve as the adhesive as well as a supporting. With proper application, an epoxy grout should provide a permanent, reliable installation. sand-cement grouts may provide an acceptable installation, however they are generally lower in strength, have more tendencies to shrink unevenly and are generally more susceptible to chemical attack and deterioration by oils.

1. Check center lines measurements to ensure square

Remove Polystyrene formers from Concrete and expose hold down bolts in the concrete foundation, to provide for some stretch of the anchor bolt between the bottom of the sleeve and the bottom of the nut it is recommended that the void be filled with a pliable material prior to grouting.

1. Recheck for level and recheck center lines

SETTING THE EQUIPMENT

 Once the grout has cured sufficiently to withstand the load, installation of the equipment module or modules on the foundation can proceed.

Ensure the surface of the base plates is completely clean and free of rust before installing the equipment and forming up the final grout, this can be done using a grinding disc or sandblaster

The cleaned surface should be coated with epoxy primer.

Install shim pack having an assortment of shim thicknesses on each plate. The shim pack should be to the specified size, clean, de-burred and rust free. This will provide adjustment during leveling.

With soleplates / baseplate set and leveled, remove all temporary shipping braces and equipment protective closures.

A lifting study must be developed for the heavy lifts to ensure no undue stress is applied to each module during installation. If the turbine is a single module supplied fully assembled the modular skid can be lifted into position for leveling  and alignment checks completed.

For larger capacity units the modules may contain separable units such as skid mount Turbine, skid mount gearbox, skid mount generator.  In some cases lubrication skids are separate to the whole.

The latter multi skid units are clearly more labour intensive due to multiple leveling exercises to set each module in alignment with its counterparts, the need for multiple coupling alignment’s opposed to a check and final alignment of the pre assemble one piece modular units.

For modular units there will be no assembly of the internal working components of the turbine, the methodology needs to be accurate and quality assured but the mechanical assembly and installation should be a series of precise preparation, leveling and alignment only.

After machinery has been placed on baseplate, install and tighten hold down bolts. Check for a “soft foot” by loosening each hold down bolt in turn while measuring with a dial indicator movement between machine foot and soleplate or baseplate. If movement on loosening a nut exceeds approximately 0.05 mm at any mounting point, shim to eliminate.

COUPLING INSTALLATION

 The machinery is now ready to be aligned. Initial cold alignment should be completed prior to grouting. In order to provide maximum flexibility, the cold alignment should be completed with all piping disconnected from the Equipment.

A flexible coupling is used between the turbine and the driven equipment. This type of coupling can be manufactured for use with either straight or tapered shaft ends.  Refer to the manufacturer’s instructions for detailing the coupling installation and alignment.

The cold alignment is achieved using dial indicators, feeler gauges, micrometers or a combination.

The cold alignment must allow for thermal growth and deflections that will occur between installation temperatures and operating temperatures. This growth will be calculated by the machinery manufacturers representative.

Seals.

Ensure all seal joints are bolted a tensioned correctly to secure the packing material, all seal steam lines must be checked for correct installation and be free of debris and have clean free steam movement and be air tight.

CONDENSER

A condenser connected to the turbine exhaust flange must be suspended from the flange or spring-supported, if not the expansion joint must be installed to provide the necessary flexibility for expansion. All other piping connected to the condenser must be have suitable expansion joints.

Grouting

1. If satisfied that all checks have been completed and the process to date is signed off by the clients representative setup for Grouting of all equipment mounts.
2. Grout to be formed up for the equipment frames
3. Use the nominated Grout as specified by the clients representative or the contract installation specification
4. Grouting shall be carried out in accordance with the technical specifications.

TURBINE INSULATION

Insulating a turbine reduces heat loss and noise levels, it also provides Personnel protection from the hot parts

Sheet metal, jacketing insulation that sheathes the turbine casing is to be removable, this will provide access to turbine parts for maintenance, the high temperature zones will have a fibrous insulation fixed and packed to the inside of the sheet metal jacketing to increase the insulating capacity and protect bot the turbine and personnel, lower temperature zones will have loose packed insulation.

Hot Alignment Check

A hot alignment will be done after the equipment has operated under load for several hours and a stable operating temperature achieved. This check will indicate any adjustments necessary to achieve final alignment tolerance.

JACKETED TURBINE PIPING