To build on the responses above, it might be useful to break it down into a few areas, I'd recommend:
Design stage, step 1, specifying what you want - this is where some companies write a URS and have a multi functional team feed into it. It's potentially long winded but where I've worked on projects where this has been skipped or done badly, they almost always find design issues later. The point of the URS (user requirement specification) is to clearly set out for the supplier what it is you want and what it needs to comply with. So for production they may want to specify the number of operators, the line speed etc. You will probably need to specify the grade of metal, that belts are quick release, that there are no trap points and easily cleanable.
A lot of companies have a standard template for these which you then must adapt to the machine. There are some good references which you can go to for fundamental hygienic design principles. Your engineering team will probably have copies. Two sources I'd use are the EHEDG (while it's Europe focused, the design principles are superb).
EHEDG: Guideline Catalogue
While I can't seem to find an up to date copy, perhaps it's been superceded now, but the second source I'd use is the list compiled by the EDTF in the US which is a great starting point for a URS, here's an article on it:
Sanitary design principles for meat processing - New Food Magazine
They're not as prescriptive as the EHEDG but they are good and this is at the point you're asking for the suppliers to comply. Also check out any retailers codes of practice or certification schemes you work with. Many will specify lots of other requirements which are often borne out of bitter experience.
DO specifically write in the URS what is important to you. Don't just say "comply with EHEDG" as most suppliers will just assume they do.
Design stage, step 2 - getting the supplier to commit to it. Again another stage often missed and to the detriment of cost and quality. An FDS or functional design specification is how the supplier will comply with your URS. There may be some compromises here. There may be an area you can't use blue plastic, only white which isn't ideal for example or you've specified 316 Stainless, they can use 304 but that's ok. This is where you both agree to the design and the principles of it before a single piece of metal is cut. If the machine is standard and used elsewhere, go see it if you can. Make sure you know about cleaning issues and if the other machine is used in the same way (I have a bitter story on that...)
Step 3. Early PDI. I really recommend getting in early before the kit is finished to do a PDI (pre delivery inspection), not the week before. Follow up later if needed with another visit but you want to leave time to enable changes if needed. Again this should be cross functional.
Step 4. Plan install and trials. Clear plan with the cross functional team on installation. Don't leave it to the day. Have a plan of how the kit will get in, if you have to break hygiene barriers, how will you reinstate the hygiene status of the area. How will you monitor etc. Once in, what time do you have for trials? Again don't underestimate how long cleaning validation may take, especially if using multiple allergens.
Step 5. Install and regular on / off track. Whoever is project managing the whole thing should keep the team informed of any dates slipping on any part of the process.
Step 6. Validation. Make sure the machine is fully validated for whatever purpose, don't forget that cleaning validation will be needed if it's new to site and food contact for most equipment.
Step 7. Post install review. What went well, what could be improved etc.
I'm guessing the ask from the team is what info needs to go into the design stage 1 and the PDI. But it would also be useful to share what activities need to take place from Technical on install to do so safely and to validate as well for them to build into the plan.